Yuwu Chi

A one-pot hydrothermal method was proposed for the synthesis of carbon based dots (CDs) with high quantum yield and controllable long-wavelength photoluminescence (PL). The PL mechanisms of the CDs were discussed, and a common model has been proposed. Furthermore, the obtained CDs showed excellent biocompatibility and high PLQYs (more than 20%), and presented great potential bio-applications.

Carbon based dot capped silver nanoparticles for efficient surface-enhanced Raman scattering

Co-reporter:Yongqiang Dong, Qian Wang, Lisi Wan, Xu You and Yuwu Chi

Journal of Materials Chemistry A 2016 vol. 4(Issue 31) pp:7472-7477

Publication Date(Web):14 Jul 2016

DOI:10.1039/C6TC01943A

A simple method has been developed for the preparation of silver nanoparticles/carbon based quantum dot nano-hybrids (AgNPs@CDs). First, the small-sized CDs with abundant oxygen-containing functional groups adsorbed Ag+ ions through ion exchange or coordination reactions. Then, during the reaction with NaBH4, the Ag+ ions were reduced to AgNPs while the oxygen-containing functional groups were partially removed from the CDs. Thus, CDs were coated on the surfaces of the resultant AgNPs, leading to the formation of AgNPs@CDs. The residual oxygen-containing groups on the CDs made the obtained AgNPs@CDs possess excellent dispersivity and long-term stability in water. The synthesized AgNPs@CDs showed high surface-enhanced Raman scattering (SERS) activity and provided a sensitive SERS sensing ability for 4-aminothiophenol, with a wide dynamic range from 1 × 10−10 to 1 × 10−5 M and a low detection limit (S/N = 3) of 5.0 × 10−11 M.

Dual-Emission of Lanthanide Metal–Organic Frameworks Encapsulating Carbon-Based Dots for Ratiometric Detection of Water in Organic Solvents

Co-reporter:Yongqiang Dong, Jianhua Cai, Qingqing Fang, Xu You, and Yuwu Chi

Analytical Chemistry 2016 Volume 88(Issue 3) pp:1748

Publication Date(Web):January 8, 2016

DOI:10.1021/acs.analchem.5b03974

Nitrogen and sulfur codoped carbon-based dots (N,S-CDs) with strong blue light emission are encapsulated into red light-emitting europium metal–organic frameworks (Eu-MOFs) to form two color light-emitting nanohybrids (Eu-MOFs/N,S-CDs). In organic solvents, the encapsulated N,S-CDs are aggregated and confined in the cavities of the Eu-MOFs, exhibiting only a very weak photoluminescence (PL) signal. Therefore, the nanohybrids show red light emission of the Eu-MOFs. Contrarily, when the Eu-MOFs/N,S-CDs are dispersed in water, the encapsulated N,S-CDs are released into solution while the red light emission of the Eu-MOFs is quenched due to the effect of O–H oscillators. The nanohybrids are used as the probe for the water content in organic solvents. Take ethanol as an example; as the water content is increased from 0.2 to 30%, the nanoprobe provides distinguishable PL color change. The ratio of light intensity at 420 nm to that at 623 nm (I420/I623) increases linearly with increasing water content in the range from 0.05 to 4% with a low detection limit of 0.03%.

Strong electrochemiluminescent interactions between carbon nitride nanosheet–reduced graphene oxide nanohybrids and folic acid, and ultrasensitive sensing for folic acid

Co-reporter:Chen Zhou, Yingmei Chen, Pengxiang Shang and Yuwu Chi

Analyst 2016 vol. 141(Issue 11) pp:3379-3388

Publication Date(Web):15 Apr 2016

DOI:10.1039/C6AN00664G

Graphite-like carbon nitride nanosheets (g-C3N4 NSs) have recently emerged as electrochemiluminescent (ECL) nanomaterials and have attracted more and more attention due to their excellent ECL properties and promising applications in ECL sensing. However, the ECL study of g-C3N4 NSs is still in the early stages. Many studies are required to reveal the exact ECL mechanisms of g-C3N4 NSs and thus boost their sensing applications. In this paper, we have investigated ECL interactions between folic acid (FA) and a g-C3N4 NS/S2O82− ECL system at a g-C3N4 NS-reduced graphene oxide (rGO) nanohybrid/glassy carbon electrode in aqueous solutions. Compared with bare g-C3N4 NSs, the nanohybrids of g-C3N4 NS-rGO give a much stable ECL emission due to the prevention of over electrochemical reduction of g-C3N4 by rGO. The stable ECL emission from the g-C3N4 NS-rGO/S2O82− ECL system can be strongly quenched by FA, even in a very low concentration (pM levels). The ECL quenching mechanisms are investigated and discussed in detail. Based on the strong interactions between FA and g-C3N4 NSs, a novel, sensitive, stable and selective ECL sensor has been constructed for the detection of FA, with a wide linear response range from 0.1 to 90 nM, and an excellent detection limit (62 pM). This work not only further clarifies ECL mechanisms of g-C3N4 NSs, but also suggests a promising application of the newly emerging ECL nanomaterial.

Yellow electrochemiluminescence emission from hydrophilic poly[(9,9-di-(2-ethylhexyl)-9H-fluorene-2,7-vinylene)-co-(1-methoxy-4-(2-ethylhe-xyloxy)-2,5-phenylenevinylene)] (PFV) conjugated polymer dots capped with Triton X-100 in aqueous solution

Co-reporter:Fanmin Wu, Yingying Feng, Yuwu Chi

Journal of Electroanalytical Chemistry 2016 Volume 779() pp:47-54

Publication Date(Web):15 October 2016

DOI:10.1016/j.jelechem.2016.05.016

•Hydrophilic PFV CP-dots capped with Triton-X 100 were synthesized•The Hydrophilic PFV CP-dots@TX emitted yellow light with good annihilation ECL, anodic ECL and cathodic ECL activities.•ECL mechanisms of PFV CP-dots@TX in aqueous solution were studied and proposed.We synthesized new, yellow-light emitting, and hydrophilic poly[(9,9-di-(2-ethylhexyl)-9H-fluorene-2,7-vinylene)-co-(1-methoxy-4-(2-ethylhe-xyloxy)-2,5-phenylenevinylene)] conjugated polymer dots capped with nonionic surfactant Triton X-100 (PFV CP-dots@TX), immobilized them on glassy carbon electrodes and studied their electrochemiluminescence (ECL) behaviors and mechanisms in aqueous solutions. The ECL activities of the hydrophilic CP-dots were investigated by applying the glassy carbon working electrode with pulse potential between anodic and cathodic potentials in the absence of coreactant, with sweeping anodic potential in the presence of Tri-n-propylamine (TPrA) as the coreactant, and with sweeping cathodic potential in the presence of peroxydisulfate (S2O82 −) as the coreactant. Experimental results shows that PFV CP-dots@TX have good annihilation ECL activity, anodic ECL activity and cathodic ECL activity. All of the three types of ECL reactions emit yellow light with the maximum wavelength of 573 nm, which is the same as the fluorescence emission spectrum of PFV CP-dots@TX in water. The energies involved in the ECL reactions were analyzed and non-surface state ECL mechanisms were discussed and proposed. The yellow light-emitting, hydrophilic CP-dots are envisioned to be a new type of ECL luminophores that may have promising applications in chemical sensing, biosensing and new optoelectronic devices.

Highly sensitive electrochemiluminescent sensing platform based on graphite carbon nitride nanosheets for detection of pyrophosphate ion in the synovial fluid

Co-reporter:Huifeng Xu, Xi Zhu, Yongqiang Dong, Haishan Wu, Yingmei Chen, Yuwu Chi

Sensors and Actuators B: Chemical 2016 Volume 236() pp:8-15

Publication Date(Web):29 November 2016

DOI:10.1016/j.snb.2016.05.056

Graphite carbon nitride nanosheets (g-C3N4 NSs) are the promising metal-free polymer-like semiconductor nanomaterials, which exhibit excellent electrochemiluminescence (ECL) behavior. The g-C3N4 NSs modified the glass carbon electrode showed the obvious ECL response using 10 mM S2O82− as the co-reactant at the scan rate of 0.1 V/s. The presence of Cu2+ would quench ECL emission due to the photo induced electron transfer (PET). Pyrophosphate anion (PPi), an important anion in several bioenergetics and metabolic processes, can chelate with Cu2+ with a strong affinity. The introduction of PPi could release Cu2+ from Cu2+-g-C3N4 NSs system, resulting in the ECL recovery. The dosage of Cu2+ and the ECL recover time were further investigated. Under the optimized condition PPi can be detected in the range of 2.0–800 nM with the detection limit of 75 pM based on 3ơ/slope. This ECL sensor also possessed good selectivity to PPi, and has been used to detect PPi in the synovial fluid.

Immobilizing water-soluble graphene quantum dots with gold nanoparticles for a low potential electrochemiluminescence immunosensor

Co-reporter:Yongqiang Dong, Huan Wu, Pengxiang Shang, Xiaoting Zeng and Yuwu Chi

Nanoscale 2015 vol. 7(Issue 39) pp:16366-16371

Publication Date(Web):02 Sep 2015

DOI:10.1039/C5NR04328J

Hydrazide-modified graphene quantum dots (HM-GQDs) obtained by refluxing GQDs with hydrazine hydrate were hybridized with gold nanoparticles (AuNPs) through a redox reaction between HM-GQDs and AuCl4−. The obtained nano-hybrids (HM-GQD–AuNPs) possess the unique electrochemiluminescence (ECL) properties of HM-GQDs and the easy self-assembly with some bio-molecules of AuNPs, which have great potential applications in bio-sensors. HM-GQD–AuNPs were modified on a glassy carbon electrode to develop a novel ECL immunosensor of carcinoembryonic antigen (CEA) as a model target analyte. Due to the increment of electron-transfer resistance after immunoreaction, the ECL intensity decreased as the concentration of CEA was increased. The linear response range was between 0.02 and 80 ng mL−1, and the detection limit was 0.01 ng mL−1.

Encapsulation of Hemin in Metal–Organic Frameworks for Catalyzing the Chemiluminescence Reaction of the H2O2–Luminol System and Detecting Glucose in the Neutral Condition

Co-reporter:Fenqiang Luo, Yaolin Lin, Liyan Zheng, Xiaomei Lin, and Yuwu Chi

ACS Applied Materials & Interfaces 2015 Volume 7(Issue 21) pp:11322

Publication Date(Web):April 30, 2015

DOI:10.1021/acsami.5b01706

Novel metal–organic frameworks (MOFs) based solid catalysts have been synthesized by encapsulating Hemin into the HKUST-1 MOF materials. These have been first applied in the chemiluminescence field with outstanding performance. The functionalized MOFs not only maintain an excellent catalytic activity inheriting from Hemin but also can be cyclically utilized as solid mimic peroxidases in the neutral condition. The synthesized Hemin@HKUST-1 composites have been used to develop practical sensors for H2O2 and glucose with wide response ranges and low detection limits. It was envisioned that catalyst-functionalized MOFs for chemiluminescence sensing would have promising applications in green, selective, and sensitive detection of target analytes in the future.Keywords: catalysis; chemiluminescence; glucose; H2O2; Hemin; HKUST-1;

Anodic, Cathodic, and Annihilation Electrochemiluminescence Emissions from Hydrophilic Conjugated Polymer Dots in Aqueous Medium

Co-reporter:Ruiping Dai, Fanmin Wu, Huifeng Xu, and Yuwu Chi

ACS Applied Materials & Interfaces 2015 Volume 7(Issue 28) pp:15160

Publication Date(Web):June 26, 2015

DOI:10.1021/acsami.5b04305

Hydrophilic poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV) conjugated polymer dots (CP-dots) capped by Triton X-100 were synthesized. For the first time, the electrochemiluminescence (ECL) emission of CP-dots was investigated in aqueous solution. At the glassy carbon/water interface, the CP-dots have excellent and multichannel ECL properties, such as having annihilation ECL activity in the absence of coreactants, and give bright anodic and cathodic ECL emission (590 nm) in the presence of tri-n-propylamine (TPrA) and peroxydisulfate (S2O82–), respectively. The versatile ECL properties of the hydrophilic CP-dots combined with their low cytotoxicity, good biocompatibility, and easy bioconjugation may suggest promising applications of this new type of ECL nanomaterial in novel biosensing and bioimaging, and new types of light-emitting devices.Keywords: annihilation; coreactant; CP-dots; electrochemiluminescence; Triton X-100;

A bio-inspired sensor coupled with a bio-bar code and hybridization chain reaction for Hg2+ assay

Co-reporter:Huifeng Xu, Xi Zhu, Hongzhi Ye, Lishuang Yu, Guonan Chen, Yuwu Chi and Xianxiang Liu

Chemical Communications 2015 vol. 51(Issue 81) pp:15031-15034

Publication Date(Web):18 Aug 2015

DOI:10.1039/C5CC05369B

In this article, a bio-inspired DNA sensor is developed, which is coupled with a bio-bar code and hybridization chain reaction. This bio-inspired sensor has a high sensitivity toward Hg2+, and has been used to assay Hg2+ in the extraction of Bauhinia championi with good satisfaction.

Signal-on electrochemiluminescent aptasensors based on target controlled permeable films

Co-reporter:Lichan Chen, Xiaoting Zeng, Abdul Rahim Ferhan, Yuwu Chi, Dong-Hwan Kim and Guonan Chen

Chemical Communications 2015 vol. 51(Issue 6) pp:1035-1038

Publication Date(Web):24 Nov 2014

DOI:10.1039/C4CC07699K

A novel permeability gate-based electrochemiluminescent (ECL) aptasensor has been constructed by utilizing target-responsive polyelectrolyte–aptamer film deposited on the solid-state ECL electrode to control the rate of diffusion of a coreactant that triggers the ECL.

Installing Logic Gates in Permeability Controllable Polyelectrolyte-Carbon Nitride Films for Detecting Proteases and Nucleases

Co-reporter:Lichan Chen, Xiaoting Zeng, Anirban Dandapat, Yuwu Chi, and Donghwan Kim

Analytical Chemistry 2015 Volume 87(Issue 17) pp:8851

Publication Date(Web):July 31, 2015

DOI:10.1021/acs.analchem.5b01916

Proteases and nucleases are enzymes heavily involved in many important biological processes, such as cancer initiation, progression, and metastasis; hence, they are indicative of potential diagnostic biomarkers. Here, we demonstrate a new label free and sensitive electrochemiluminescent (ECL) sensing strategy for protease and nuclease assays that utilize target-triggered desorption of programmable polyelectrolyte films assembled on graphite-like carbon nitride (g-C3N4) film to regulate the diffusion flux of a coreactant. Furthermore, we have built Boolean logic gates OR and AND into the polyelectrolyte films, capable of simultaneously sensing proteases and nucleases in a complicated system by breaking it into simple functions. The developed intelligent permeability controlled enzyme sensor may prove valuable in future medical diagnostics.

Fast, Sensitive, and Selective Ion-Triggered Disassembly and Release Based on Tris(bipyridine)ruthenium(II)-Functionalized Metal–Organic Frameworks

Co-reporter:Xiaomei Lin, Fenqiang Luo, Liyan Zheng, Gongmin Gao, and Yuwu Chi

Analytical Chemistry 2015 Volume 87(Issue 9) pp:4864

Publication Date(Web):April 24, 2015

DOI:10.1021/acs.analchem.5b00391

Metal–organic frameworks (MOFs) are microporous materials assembled from metal ions and organic linkers. Recently, many studies have been focused on the syntheses of MOFs with permanent porosity for various applications. However, no attention has been paid to controllable disassembly of MOFs and related applications. In this work, for the first time we synthesized novel tris(bipyridine)ruthenium(II)-functionalized MOFs (i.e., RuMOFs) that could be ion-responsively disassembled and release massive guest materials loaded in the frameworks. The synthesized RuMOFs exhibited much stability in aqueous solutions containing H+, and many metal ions, but could be selectively and sensitively disassembled by Hg2+ ions, resulting in the release of large quantities of Ru(bpy)32+. The target-responsive release mechanism was investigated and discussed in detail. On the basis of the ion-responsive disassembly and release, an ultrasensitive electrochemiluminescence sensing method for Hg2+ has been developed with a very low limit of detection (5.3 × 10–13 M). It was envisioned that the RuMOFs and similar target-responsive functional MOF materials would have promising applications in ultrasensitive and highly selective chemical sensing and even in accurately controllable drug delivering and releasing.

Electrochemiluminescence sensor for hexavalent chromium based on the graphene quantum dots/peroxodisulfate system

Co-reporter:Yingmei Chen, Yongqiang Dong, Huan Wu, Congqiang Chen, Yuwu Chi, Guonan Chen

Electrochimica Acta 2015 Volume 151() pp:552-557

Publication Date(Web):1 January 2015

DOI:10.1016/j.electacta.2014.11.068

A electrochemiluminescent (ECL) sensor has been designed to detect hexavalent chromium (Cr(VI)) in environmental water samples based on the fact that Cr(VI) can collisionally quench the ECL signal of graphene quantum dots/peroxodisulfate (GQD/S2O82−) system. After optimizing some important experimental conditions including the concentrations of GQDs and S2O82−, response time, and pH value of solution, the ECL sensor has been finally developed. The ECL sensor exhibits a wide linear response range (50 nM-60 μM), excellent selectivity, and high sensitivity (detection limit of 20 nM, S/N = 3). Furthermore, the developed sensor has been applied in the detection of Cr(VI) in a spiked river water. The result suggests that the sensor can offer a simple, green, low cost, high selectivity and sensitivity detection of Cr(VI).

Sensing applications of luminescent carbon based dots

Co-reporter:Yongqiang Dong, Jianhua Cai, Xu You and Yuwu Chi

Analyst 2015 vol. 140(Issue 22) pp:7468-7486

Publication Date(Web):03 Sep 2015

DOI:10.1039/C5AN01487E

Carbon based dots (CDs) including carbon quantum dots and graphene quantum dots exhibit unique luminescence properties, such as photoluminescence (PL), chemiluminescence (CL) and electrochemiluminescence (ECL). This review summarizes the sensing application of the CDs taking advantage of their luminescence properties. The working principle, merits, and prospects of CD based sensors are presented.

Tailor-made peptide sensor for detection of matrix metalloproteinase 2 in blood serum

Co-reporter:Huifeng Xu, Hongzhi Ye, Lishuang Yu, Yuwu Chi, Xianxiang Liu and Guonan Chen

Analytical Methods 2015 vol. 7(Issue 13) pp:5371-5374

Publication Date(Web):21 Apr 2015

DOI:10.1039/C5AY00666J

We designed a simple and sensitive peptide electrochemical sensor for detection of MMP-2, with a detection limit of 0.3 ng mL−1. The sensor detected MMP-2 in a serum sample with satisfactory results. It was also used to assay an inhibitor of MMP-2.

Flow injection analysis of thiamazole based on strong Ru(bpy)32+ co-reactant electrochemiluminescence

Co-reporter:Dexian Kong;Qinglu Li;Jiang Jiang;Zheng Xinyu;Zhou Xuechou;Guonan Chen

Luminescence 2015 Volume 30( Issue 1) pp:12-17

Publication Date(Web):

DOI:10.1002/bio.2681

Abstract

Based on the strong electrochemiluminescence (ECL) reaction between thiamazole and tris(2,2′-bipyridine)ruthenium(II) (Ru(bpy)₃²⁺), a sensitive, simple and rapid flow injection analysis method for the determination of thiamazole was developed. When a Pt working electrode was maintained at a potential of +1.50 V (vs Ag/AgCl) in pH 12.0 H₃PO₄–NaOH solution containing thiamazole and Ru(bpy)₃²⁺ at a flow rate of 1.0 mL/min, a linear range of 2.0 × 10⁻⁷–1.0 × 10⁻⁴ mol/L with a detection limit of 5.0 × 10⁻⁸ mol/L was obtained for the detection of thiamazole. The method showed good reproducibility with a relative standard deviation (RSD) of 0.75%. The method has been successfully applied to the determination of thiamazole in spiked animal feeds. In addition, a co-reactant ECL mechanism was proposed for the thiamazole–Ru(bpy)₃²⁺ system. Copyright © 2014 John Wiley & Sons, Ltd.

Photoluminescence, chemiluminescence and anodic electrochemiluminescence of hydrazide-modified graphene quantum dots

Co-reporter:Yongqiang Dong, Ruiping Dai, Tongqing Dong, Yuwu Chi and Guonan Chen

Nanoscale 2014 vol. 6(Issue 19) pp:11240-11245

Publication Date(Web):25 Jul 2014

DOI:10.1039/C4NR02539C

Single-layer graphene quantum dots (SGQDs) were refluxed with hydrazine (N2H4) to prepare hydrazide-modified SGQDs (HM-SGQDs). Compared with SGQDs, partial oxygen-containing groups have been removed from HM-SGQDs. At the same time, a lot of hydrazide groups have been introduced into HM-SGQDs. The introduced hydrazide groups provide HM-SGQDs with a new kind of surface state, and give HM-SGQDs unique photoluminescence (PL) properties such as blue-shifted PL emission and a relatively high PL quantum yield. More importantly, the hydrazide-modification made HM-SGQDs have abundant luminol-like units. Accordingly, HM-SGQDs exhibit unique and excellent chemiluminescence (CL) and anodic electrochemiluminescence (ECL). The hydrazide groups of HM-SGQDs can be chemically oxidized by the dissolved oxygen (O2) in alkaline solutions, producing a strong CL signal. The CL intensity is mainly dependent on the pH value and the concentration of O2, implying the potential applications of HM-SGQDs in pH and O2 sensors. The hydrazide groups of HM-SGQDs can also be electrochemically oxidized in alkaline solutions, producing a strong anodic ECL signal. The ECL intensity can be enhanced sensitively by hydrogen peroxide (H2O2). The enhanced ECL intensity is proportional to the concentration of H2O2 in a wide range of 3 μM to 500 μM. The detection limit of H2O2 was calculated to be about 0.7 μM. The results suggest the great potential applications of HM-SGQDs in the sensors of H2O2 and bio-molecules that are able to produce H2O2 in the presence of enzymes.

Graphene quantum dots, graphene oxide, carbon quantum dots and graphite nanocrystals in coals

Co-reporter:Yongqiang Dong, Jianpeng Lin, Yingmei Chen, Fengfu Fu, Yuwu Chi and Guonan Chen

Nanoscale 2014 vol. 6(Issue 13) pp:7410-7415

Publication Date(Web):29 Apr 2014

DOI:10.1039/C4NR01482K

Six coal samples of different ranks have been used to prepare single-layer graphene quantum dots (S-GQDs). After chemical oxidation and a series of centrifugation separation, every coal could be treated into two fractions, namely, CoalA and CoalB. According to the characterization results of TEM, AFM, XRD, Raman and FTIR, CoalA was revealed to be mainly composed of S-GQDs, which have an average height of about 0.5 nm and an average plane dimension of about 10 nm. The obtained S-GQDs showed excitation-dependent fluorescence and excellent electrochemiluminescence. CoalB was found to be some other carbon-based nanomaterials (CNMs), including agglomerated GQDs, graphene oxide, carbon quantum dots and agglomerated carbon nanocrystals. Generally, low-ranked coals might be more suitable for the preparation of S-GQDs. The production yield of S-GQDs from the six investigated coals decreased from 56.30% to 14.66% when the coal rank increased gradually. In contrast, high-ranked coals had high production yield of CoalB and might be more suitable for preparing other CNMs that were contained in CoalB, although those CNMs were difficult to separate from each other in our experiment.

Graphene Quantum Dots/l-Cysteine Coreactant Electrochemiluminescence System and Its Application in Sensing Lead(II) Ions

Co-reporter:Yongqiang Dong, Wanrong Tian, Shuyan Ren, Ruiping Dai, Yuwu Chi, and Guonan Chen

ACS Applied Materials & Interfaces 2014 Volume 6(Issue 3) pp:1646

Publication Date(Web):January 9, 2014

DOI:10.1021/am404552s

A new coreactant electrochemiluminescence (ECL) system including single-layer graphene quantum dots (GQDs) and l-cysteine (l-Cys) was found to be able to produce strong cathodic ECL signal. The ECL signal of GQD/l-Cys coreactant system was revealed to be mainly dependent on some key factors, including the oxidation of l-Cys, the presence of dissolved oxygen and the reduction of GQDs. Then, a possible ECL mechanism was proposed for the coreactant ECL system. Furthermore, the ECL signal of the GQD/l-Cys system was observed to be quenched by lead(II) ions (Pb2+). After optimization of some important experimental conditions, including concentrations of GQDs and l-Cys, potential scan rate, response time, and pH value, an ECL sensor was developed for the detection of Pb2+. The new methodology can offer a rapid, reliable, and selective detection of Pb2+ with a detection limit of 70 nM and a dynamic range from 100 nM to 10 μM.Keywords: coreactant; electrochemiluminescence; graphene quantum dots; l-cysteine; lead(II);

Encapsulation of Strongly Fluorescent Carbon Quantum Dots in Metal–Organic Frameworks for Enhancing Chemical Sensing

Co-reporter:Xiaomei Lin, Gongmin Gao, Liyan Zheng, Yuwu Chi, and Guonan Chen

Analytical Chemistry 2014 Volume 86(Issue 2) pp:1223

Publication Date(Web):December 16, 2013

DOI:10.1021/ac403536a

Novel highly fluorescent (FL) metal–organic frameworks (MOFs) have been synthesized by encapsulating branched poly-(ethylenimine)-capped carbon quantum dots (BPEI-CQDs) with a high FL quantum yield into the zeolitic imidazolate framework materials (ZIF-8). The as-synthesized FL-functionalized MOFs not only maintain an excellent FL activity and sensing selectivity derived from BPEI-CQDs but also can strongly and selectively accumulate target analytes due to the adsorption property of MOFs. The selective accumulation effect of MOFs can greatly amplify the sensing signal and specificity of the nanosized FL probe. The obtained BPEI-CQDs/ZIF-8 composites have been used to develop an ultrasensitive and highly selective sensor for Cu2+ ion, with a wide response range (2–1000 nM) and a very low detection limit (80 pM), and have been successfully applied in the detection of Cu2+ ions in environmental water samples. It is envisioned that various MOFs incorporated with FL nanostructures with high FL quantum yields and excellent selectivity would be designed and synthesized in similar ways and could be applied in sensing target analytes.

Gold Nanoparticle-Graphite-Like C3N4 Nanosheet Nanohybrids Used for Electrochemiluminescent Immunosensor

Co-reporter:Lichan Chen, Xiaoting Zeng, Peng Si, Yingmei Chen, Yuwu Chi, Dong-Hwan Kim, and Guonan Chen

Analytical Chemistry 2014 Volume 86(Issue 9) pp:4188

Publication Date(Web):April 7, 2014

DOI:10.1021/ac403635f

Two-dimensional graphite-like carbon nitride nanosheets (g-C3N4 NSs) were hybridized with gold nanoparticles (Au NPs) to construct an electrochemiluminescence (ECL) immunosensor. The prepared Au NP-functionalized g-C3N4 NS nanohybrids (Au-g-C3N4 NHs) exhibit strong and stable cathodic ECL activity compared to g-C3N4 NSs due to the important roles of Au NPs in trapping and storing the electrons from the conduction band of g-C3N4 NSs, as well as preventing high energy electron-induced passivation of g-C3N4 NSs. On the basis of the improved ECL stability and ECL peak intensity of the Au-g-C3N4 NHs, a novel ECL immunosensor was developed to detect carcinoembryonic antigen (CEA) as a model target analyte. The ECL immunosensor has a sensitive response to CEA in a linear range of 0.02–80 ng mL–1 with a detection limit of 6.8 pg mL–1. Additionally, the proposed immunosensor shows high specificity, good reproducibility, and long-term stability.

Omeprazole as a strong coreactant in the electrochemiluminescence of Ru(bpy)32+

Co-reporter:Dexian Kong, Bing Lin, Yejian Han, Xinyu Zheng, Xuechou Zhou, Qinglu Li, Yuwu Chi, Guonan Chen

Electrochimica Acta 2014 Volume 123() pp:111-116

Publication Date(Web):20 March 2014

DOI:10.1016/j.electacta.2013.12.182

Omeprazole (OPZ) as a high-efficiency coreactant in the electrochemiluminescence (ECL) of Ru(bpy)32+ on a bare Pt electrode has been studied in this paper. Based on the strong enhancement effect of OPZ on the ECL of Ru(bpy)32+, a simple, rapid and sensitive method for the determination of omeprazole has been established. Under the optimum conditions, the logarithmic ECL enhancement versus the logarithmic concentration of OPZ is linear over a wide concentration range of 2.0 × 10−7 to 5.0 × 10−4 M (r = 0.9945), with a detection limit of 2.0 × 10−8 M (6.9 ng/mL, S/N = 3) in a pH = 11.5 100 mM phosphate buffer solution containing 1.0 × 10−4 M Ru(bpy)32+. To demonstrate its applicability, the proposed method was applied in the determination of OPZ in capsules and the recoveries were ranged from 93.3%-106.7%. These provide a possibility to employ the new ECL method for OPZ detection in pharmaceutical preparations. According to the study of electrochemical behavior, ECL behavior and ECL emission spectrum of Ru(bpy)32+/OPZ system, a possible ECL mechanism was proposed.

“Turn-on” fluorescent detection of cyanide based on polyamine-functionalized carbon quantum dots

Co-reporter:Yongqiang Dong, Ruixue Wang, Wanrong Tian, Yuwu Chi and Guonan Chen

RSC Advances 2014 vol. 4(Issue 8) pp:3701-3705

Publication Date(Web):15 Nov 2013

DOI:10.1039/C3RA45893H

A simple, sensitive, rapid fluorescence (FL) sensor has been developed to detect cyanide ions (CN−) based on the branched polyethylenimine-capped carbon quantum dots (BPEI-GQDs). The amino groups at the surfaces of BPEI-GQDs can selectively and sensitively capture copper ions (Cu2+) to form absorbent cupric amine, which can quench the FL of BPEI-GQDs through an inner filter effect. CN− can combine strongly with Cu2+ to [Cu(CN)x]n− species, preventing Cu2+ from being captured by the amino groups of BPEI-GQDs. As a result, Cu2+ can't quench the FL of BPEI-GQDs anymore in the presence of CN−. In other words, CN− can “turn on” the FL signal of BPEI-GQDs/Cu2+ system, producing a “recovered” FL signal. After optimizing experimental conditions, we demonstrated that this easy methodology could offer a sensitive, selective, simple and rapid method for detection of CN− with a detection limit of 0.65 μM (S/N = 3) and a linear response range of 2 to 200 μM.

Capillary electrophoresis coupled with electrochemiluminescence detection for the separation and determination of thyreostatic drugs in animal feed

Co-reporter:Dexian Kong;Qinglu Li;Lichan Chen;Guonan Chen

Journal of Separation Science 2014 Volume 37( Issue 9-10) pp:1199-1205

Publication Date(Web):

DOI:10.1002/jssc.201301254

A rapid, simple, and practical method for the determination of four of the most used thyreostatic drugs (methimazole, 2-thiouracil, 6-methyl-2-thiouracil, and 6-propyl-2-thiouracil) using CE coupled to electrochemiluminescence detection has been established, based on the electrochemiluminescence enhancement of tris(2,2-bipyridyl)ruthenium(II) with these analytes. Parameters that affect separation and detection were optimized. Under the optimum experimental conditions, the four analytes could be well separated within 11 min at the separation voltage of 16 kV in a running solution containing 20 mM phosphate buffer (pH 9.0) and 1.0 × 10⁻⁴ M Ru(bpy)₃²⁺, with a solution of 20 mM phosphate buffer (pH 12.0) containing 1.0 × 10⁻⁴ M Ru(bpy)₃²⁺ in the electrochemiluminescence detection cell. The detection limits for methimazole, 6-methyl-2-thiouracil, 6-propyl-2-thiouracil, and 2-thiouracil were 0.1, 0.05, 0.05, and 0.01 μM, respectively. The proposed method was applied to analyze these drugs in spiked animal feed samples. The recoveries were 88.2∼99.0 and 86.4∼98.7% for the intraday and interday analyses, respectively. The RSDs were 2.7∼4.8 and 1.8∼5.0% for the intraday and interday analyses, respectively. The results demonstrate that the proposed method has promising applications in the detection of thyreostatic drugs in animal feeds.

Synthesis of Au13(glutathionato)8@β-cyclodextrin nanoclusters and their use as a fluorescent probe for silver ions

Co-reporter:Meilan Wang;Huan Wu;Guonan Chen

Microchimica Acta 2014 Volume 181( Issue 13-14) pp:1573-1580

Publication Date(Web):2014 October

DOI:10.1007/s00604-014-1253-2

Heating and drying of the mixture of glutathione-etched gold nanoparticles (Au-SG) and β-cyclodextrin (β-CD) results in the formation of β-CD-capped and glutathionate-protected Au13 nanoclusters (Au13(SG)8@β-CD). Their particle size, composition, and number of gold atoms and the capping molecules were characterized by scanning electron microscopy, fluorescence, UV–vis absorption, FT-IR spectroscopy and mass spectrometry. The fluorescence of these nanoclusters is specifically enhanced by the addition of Ag(I) ions to the aqueous solution. This effect was exploited to develop a selective and sensitive method for the fluorometric determination of Ag(I) in water in the concentration range between 0.5 nM and 0.1 μM, with a detection limit at 0.3 nM (at a signal-to-noise ratio of 3).

Preparation of graphite-like carbon nitride nanoflake film with strong fluorescent and electrochemiluminescent activity

Co-reporter:Lichan Chen, Danjun Huang, Shuyan Ren, Tongqing Dong, Yuwu Chi and Guonan Chen

Nanoscale 2013 vol. 5(Issue 1) pp:225-230

Publication Date(Web):23 Oct 2012

DOI:10.1039/C2NR32248J

The preparation, characterization, fluorescence (FL) and electrochemiluminescence (ECL) of graphite-like carbon nitride nanoflake particles (g-C3N4 NFPs) and nanoflake films (g-C3N4 NFFs) have been reported. Highly water-dispersible g-C3N4 NFPs with a height of ∼5 to 35 nm and a lateral dimension of ∼40 to 220 nm have been extracted from bulk g-C3N4 materials by chemical oxidation. New, stable and defined g-C3N4 NFFs can be easily obtained by drying NFPs on certain hydrophilic substrates such as glass or electrode surfaces. Both g-C3N4 NFPs and g-C3N4 NFFs have good FL activities, i.e. they can give strong blue light (435 nm) emission under UV light (365 nm) excitation. The as-prepared g-C3N4 NFFs on a glassy carbon electrode exhibit strong non-surface state ECL activity in the presence of reductive–oxidative coreactants, including dissolved oxygen (O2), hydrogen peroxide (H2O2) and peroxydisulfate (S2O82−) and give rise to blue light emission (435 nm), which is the same as the wavelength of FL. The non-surface state ECL mechanisms of the g-C3N4 NFF–coreactant systems have been studied and discussed in detail.

Carbon Quantum Dot-Functionalized Aerogels for NO2 Gas Sensing

Co-reporter:Ruixue Wang, Geli Li, Yongqiang Dong, Yuwu Chi, and Guonan Chen

Analytical Chemistry 2013 Volume 85(Issue 17) pp:8065

Publication Date(Web):August 1, 2013

DOI:10.1021/ac401880h

Silica aerogels functionalized with strongly fluorescent carbon quantum dots were first prepared and used for simple, sensitive, and selective sensing of NO2 gas. In the presence of ethanol, homemade silica aerogels with a large specific surface area of 801.17 m2/g were functionalized with branched polyethylenimine-capped quantum dots (BPEI-CQDs) with fluorescence quantum yield higher than 40%. The prepared porous CQD-aerogel hybrid material could maintain its excellent fluorescence (FL) activity in its solid state. The FL of CQD-aerogel hybrid material could be selectively and sensitively quenched by NO2 gas, suggesting a promising application of the new FL-functionalized aerogels in gas sensing.

Preparation of Protein-like Silver–Cysteine Hybrid Nanowires and Application in Ultrasensitive Immunoassay of Cancer Biomarker

Co-reporter:Wenjuan Chen, Liyan Zheng, Meilan Wang, Yuwu Chi, and Guonan Chen

Analytical Chemistry 2013 Volume 85(Issue 20) pp:9655

Publication Date(Web):September 24, 2013

DOI:10.1021/ac401961f

Novel protein-like silver–cysteine hybrid nanowires (p-SCNWs) have been synthesized by a green, simple, nontemplate, seedless, and one-step aqueous-phase approach. AgNO3 and l-cysteine were dissolved in distilled water, forming Ag–cysteine precipitates and HNO3. Under vigorous stirring, the pH of the solution was rapidly adjusted to 9.0 by addition of concentrated sodium hydroxide solution, leading to quick dissolution of the Ag-cysteine precipitates and sudden appearance of white precipitates of p-SCNWs. The p-SCNWs are monodispersed nanowires with diameter of 100 nm and length of tens of micrometers, and have abundant carboxyl (−COOH) and amine (−NH2) groups at their surfaces, large amounts of peptide-linkages and S-bonding silver ions (Ag+) inside, making them look and act like Ag-hybrid protein nanostructures. The abundant −COOH and −NH2 groups at the surfaces of p-SCNWs have been found to facilitate the reactions between the p-SCNWs and proteins including antibodies. Furthermore, the fact that the p-SCNWs contain large amounts of silver ions enables biofunctionalized p-SCNWs to be excellent signal amplifying chemiluminescence labels for ultrasensitive and highly selective detection of important antigens, such as cancer biomarkers. In this work, the immunoassay of carcinoembryonic antigen (CEA) in human serum was taken as an example to demonstrate the immunoassay applications of antibody-functionalized p-SCNWs. By the novel p-SCNW labels, CEA can be detected in the linear range from 5 to 400 fg/mL with a limit of detection (LOD) of 2.2 fg/mL (at signal-to-noise ratio of 3), which is much lower than that obtained by commercially available enzyme-linked immunosorbent assay (ELISA). Therefore, the synthesized p-SCNWs are envisioned to be an excellent carrier for proteins and related immunoassay strategy would have promising applications in ultrasensitive clinical screening of cancer biomarkers for early diagnostics of cancers.

Etching single-wall carbon nanotubes into green and yellow single-layer graphene quantum dots

Co-reporter:Yongqiang Dong, Hongchang Pang, Shuyan Ren, Congqiang Chen, Yuwu Chi, Ting Yu

Carbon 2013 Volume 64() pp:245-251

Publication Date(Web):November 2013

DOI:10.1016/j.carbon.2013.07.059

Single-walled carbon nanotubes (SWCNTs) have been used to prepare single-layered graphene quantum dots (GQDs) through a simple and green hydrothermal etching method. After the characterization of products and intermediates with scanning electronic microscopy, Raman and FTIR, a possible mechanism has been proposed for the formation of GQDs. The treatment of SWCNTs has resulted in two kinds of GQDs (i.e. GQD1 and GQD2), both of which are monodisperse and single-layered nanosheets with an average lateral dimension of 8 nm and an average height of 0.5 nm. Excited with 365 nm UV light, aqueous solutions of GQDs1 and GQDs2 give green and yellow luminescence, respectively. The differences in optical property between GQDs1 and GQDs2 mainly results from their differences in degree of oxidation.

Electrochemiluminescence emission from carbon quantum dot-sulfite coreactant system

Co-reporter:Yongqiang Dong, Congqiang Chen, Jianpeng Lin, Nana Zhou, Yuwu Chi, Guonan Chen

Carbon 2013 Volume 56() pp:12-17

Publication Date(Web):May 2013

DOI:10.1016/j.carbon.2012.12.086

A new electrochemiluminescence (ECL) system consisting of carbon quantum dots (CQDs) and sulfite SO32- has been reported. In the ECL system, SO32- is a new ECL coreactant that can significantly enhance the cathodic ECL signal of CQDs. When cycling the potential between −1.300 and +1.400 V, SO32- is firstly electrochemically oxidized to sulfur trioxide anion free radical (SO3-) in the anodic polarization process. Then the electrogenerated SO3- is involved in a three-step auto-catalytic reaction in the presence of dissolved oxygen, producing sulfate radical (SO4-). In the subsequent cathodic polarization process, CQDs are electrochemically reduced to negatively charged CQDs (C−). Finally, the electrogenerated C− species react with the SO4- to form excited-state CQDs (C∗), emitting light (575 nm) when they come back to their ground states.

An ionic liquid-mediated electrochemiluminescent sensor for the detection of sulfur dioxide at the ppb level

Co-reporter:Lichan Chen, Yuanjin Zhang, Shuyan Ren, Danjun Huang, Chen Zhou, Yuwu Chi and Guonan Chen

Analyst 2013 vol. 138(Issue 22) pp:7006-7011

Publication Date(Web):02 Sep 2013

DOI:10.1039/C3AN01407J

A novel portable SO2 gas sensor based on ionic liquid (IL) mediated electrochemiluminescence (ECL) for detecting SO2 at the ppb levels has been developed. The sensing system for SO2 detection is based on the strong quenching effect of SO2 on the ECL of the tris(2,2′-bipyridine)ruthenium(II) (Ru(bpy)32+)/O2 coreactant system in the IL film. Over the potential window between −1.0 and +1.3 V, O2 can act as an effective coreactant for Ru(bpy)32+ ECL in ILs, giving a bright ECL emission. The ECL of the Ru(bpy)32+/O2 system can be strongly inhibited by SO2 through the direct quenching of the excited state of the luminophore, i.e. Ru(bpy)32+*, by SO2 molecules. The inhibited ECL intensity is proportional to the concentration of SO2 in the range from 40 to 2000 ppb with a detection limit of 20 ppb. The proposed SO2 ECL sensor can be operated at room temperature and shows high selectivity, good reproducibility and long-term stability in a dry atmosphere.

Reply to comment on “one-step and high yield simultaneous preparation of single- and multi-layer graphene quantum dots from CX-72 carbon black”

Co-reporter:Yongqiang Dong, Chun Xian Guo, Yuwu Chi and Chang Ming Li

Journal of Materials Chemistry A 2012 vol. 22(Issue 40) pp:21777-21778

Publication Date(Web):24 Aug 2012

DOI:10.1039/C2JM34130A

A graphical abstract is available for this content

One-step and high yield simultaneous preparation of single- and multi-layer graphene quantum dots from CX-72 carbon black

Co-reporter:Yongqiang Dong, Congqiang Chen, Xinting Zheng, Lili Gao, Zhiming Cui, Hongbin Yang, Chunxian Guo, Yuwu Chi and Chang Ming Li

Journal of Materials Chemistry A 2012 vol. 22(Issue 18) pp:8764-8766

Publication Date(Web):13 Mar 2012

DOI:10.1039/C2JM30658A

A facile, low cost and high yield method has been developed to prepare single- and multi-layer graphene quantum dots (GQDs) from XC-72 carbon black by chemical oxidation. The single-layer GQDs are demonstrated to be excellent probes for cellular imaging, while the multi-layer GQDs may offer great potential applications in optoelectronic devices.

Blue luminescent graphene quantum dots and graphene oxide prepared by tuning the carbonization degree of citric acid

Co-reporter:Yongqiang Dong, Jingwei Shao, Congqiang Chen, Hao Li, Ruixue Wang, Yuwu Chi, Xiaomei Lin, Guonan Chen

Carbon 2012 Volume 50(Issue 12) pp:4738-4743

Publication Date(Web):October 2012

DOI:10.1016/j.carbon.2012.06.002

An easy bottom–up method for the preparation of photoluminescent (PL) graphene quantum dots (GQDs) and graphene oxide (GO) has been developed by tuning the carbonization degree of citric acid and dispersing the carbonized products into alkaline solutions. The GQDs are nanosheets ∼15 nm in width, and 0.5–2.0 nm in thickness. They show a relatively strong (9.0%) PL quantum yield and an excitation-independent PL emission activity. In contrast, the GO nanostructures consist of sheets that are hundreds of nanometers in width and ∼1 nm in height. They exhibit a relatively weak (2.2%) PL quantum yield and an excitation-dependent PL emission activity.

Polyamine-functionalized carbon quantum dots for chemical sensing

Co-reporter:Yongqiang Dong, Ruixue Wang, Hao Li, Jingwei Shao, Yuwu Chi, Xiaomei Lin, Guonan Chen

Carbon 2012 Volume 50(Issue 8) pp:2810-2815

Publication Date(Web):July 2012

DOI:10.1016/j.carbon.2012.02.046

Polyamine-functionalized carbon quantum dots (CQDs) with high fluorescence quantum yield (42.5%) have been synthesized by the low temperature (<200 °C) carbonization of citric acid with branched polyethylenimine (BPEI) in one simple step. The obtained BPEI–CQDs are spherical graphite nanocrystals (average 6.2 nm in size) capped with abundant BPEI at their surfaces. It is the first report that CQDs are both amino-functionalized and highly fluorescent, which suggests their promising applications in chemical sensing.

Polyamine-Functionalized Carbon Quantum Dots as Fluorescent Probes for Selective and Sensitive Detection of Copper Ions

Co-reporter:Yongqiang Dong, Ruixue Wang, Geli Li, Congqiang Chen, Yuwu Chi, and Guonan Chen

Analytical Chemistry 2012 Volume 84(Issue 14) pp:6220

Publication Date(Web):June 11, 2012

DOI:10.1021/ac3012126

A novel sensing system has been designed for Cu2+ ion detection based on the quenched fluorescence (FL) signal of branched poly(ethylenimine) (BPEI)-functionalized carbon quantum dots (CQDs). Cu2+ ions can be captured by the amino groups of the BPEI-CQDs to form an absorbent complex at the surface of CQDs, resulting in a strong quenching of the CQDs’ FL via an inner filter effect. Herein, we have demonstrated that this facile methodology can offer a rapid, reliable, and selective detection of Cu2+ with a detection limit as low as 6 nM and a dynamic range from 10 to 1100 nM. Furthermore, the detection results for Cu2+ ions in a river water sample obtained by this sensing system agreed well with that by inductively couple plasma mass spectrometry, suggesting the potential application of this sensing system.

Electrochemiluminescence Imaging-Based High-Throughput Screening Platform for Electrocatalysts Used in Fuel Cells

Co-reporter:Xiaomei Lin, Liyan Zheng, Gongmin Gao, Yuwu Chi, and Guonan Chen

Analytical Chemistry 2012 Volume 84(Issue 18) pp:7700

Publication Date(Web):September 4, 2012

DOI:10.1021/ac300875x

High throughput screening is very important for accelerating the discovery of fuel cell catalysts. In this paper, a novel electrochemiluminescence (ECL, a technology changing electric current into light) imaging-based screening platform for electrocatalysts used in fuel cells has been developed. The ECL imaging-based screening platform consists of bipolar electrode array-bridged electrochemical (EC)/ECL twin cells, by which electrocatalytic reduction currents of O2 can be imaged directly by ECL. The ECL imaging-based screening platform is simple in instrumentation, can image the “current–voltage” dependence directly, reversibly, and sensitively, and may enable the activities of electrocatalysts to be evaluated in a high-throughput way. The developed ECL imaging-based screening platform is envisioned to have promising applications in high throughput combinatorial screening of electrocatalysts for fuel cells.

Graphene Quantum Dot as a Green and Facile Sensor for Free Chlorine in Drinking Water

Co-reporter:Yongqiang Dong, Geli Li, Nana Zhou, Ruixue Wang, Yuwu Chi, and Guonan Chen

Analytical Chemistry 2012 Volume 84(Issue 19) pp:8378

Publication Date(Web):September 10, 2012

DOI:10.1021/ac301945z

Free chlorine was found to be able to destroy the passivated surface of the graphene quantum dots (GQDs) obtained by pyrolyzing citric acid, resulting in significant quenching of their fluorescence (FL) signal. After optimizing some experimental conditions (including response time, concentration of GQDs, and pH value of solution), a green and facile sensing system has been developed for the detection of free residual chlorine in water based on FL quenching of GQDs. The sensing system exhibits many advantages, such as short response time, excellent selectivity, wide linear response range, and high sensitivity. The linear response range of free chlorine (R2 = 0.992) was from 0.05 to 10 μM. The detection limit (S/N = 3) was as low as 0.05 μM, which is much lower than that of the most widely used N-N-diethyl-p-phenylenediamine (DPD) colorimetric method. This sensing system was finally used to detect free residual chlorine in local tap water samples. The result agreed well with that by the DPD colorimetric method, suggesting the potential application of this new, green, sensitive, and facile sensing system in drinking water quality monitoring.

Using stannous ion as an excellent inorganic ECL coreactant for tris(2,2′-bipyridyl) ruthenium(II)

Co-reporter:Liyan Zheng, Binbin Wang, Yuwu Chi, Shiping Song, Chunhai Fan and Guonan Chen

Dalton Transactions 2012 vol. 41(Issue 5) pp:1630-1634

Publication Date(Web):07 Dec 2011

DOI:10.1039/C1DT11415H

It was found that stannous chloride (SnCl2), as a popular inorganic reducing reagent, could obviously enhance the electrochemiluminescence (ECL) of tris(2,2′-bipyridyl) ruthenium(II) (Ru(bpy)32+) in aqueous solution. Some factors affecting the ECL reactions between Ru(bpy)32+ and Sn2+, including pH, concentrations of coreactant, and electrode materials, were investigated by comparison with a classic ECL coreactant tripropylamine (TPA). The Ru(bpy)32+–Sn2+ ECL coreactant system produces stronger and more stable ECL signals, can keep its excellent ECL activity over a wider pH range and has more choices in using electrode materials than the Ru(bpy)32+–TPA ECL coreactant system. The ECL mechanism of the Ru(bpy)32+–Sn2+ coreactant system was also studied in detail.

Recyclable fluorescent gold nanocluster membrane for visual sensing of copper(II) ion in aqueous solution

Co-reporter:Zhijin Lin, Fenqiang Luo, Tongqing Dong, Liyan Zheng, Yaxian Wang, Yuwu Chi and Guonan Chen

Analyst 2012 vol. 137(Issue 10) pp:2394-2399

Publication Date(Web):28 Mar 2012

DOI:10.1039/C2AN35068H

Recently, metal-selective fluorescent chemosensors have attracted intense attention for their simple and real-time tracking of metal ions in environmental samples. However, most of the existing fluorescent sensors are one-off sensors and thus suffer from large amount of reagent consumption, significant experimental cost and raising the risk of environmental pollution. In this paper, we developed a green (low reagent consumption, low-toxicity reagent use), recyclable, and visual sensor for Cu2+ in aqueous solution by using a fluorescent gold nanoclusters membrane (FGM) as the sensing unit, basing on our findings on gold nanoclusters (Au NCs) that the bovine serum albumin (BSA)-coated Au NCs exhibit excellent membrane-forming ability under the isoelectric point of BSA, and thus enable us to obtain a new type of sensing membrane (i.e. FGM) by denaturing Au NCs; the fluorescence of FGM can be significantly quenched by Cu2+ ion, and the quenched fluorescence can be totally recovered by histidine; the as-prepared FGM is very stable and recyclable, which makes it an ideal sensing material.

Ultrasensitive gaseous NH3 sensor based on ionic liquid-mediated signal-on electrochemiluminescence

Co-reporter:Lichan Chen, Danjun Huang, Yuanjin Zhang, Tongqing Dong, Chen Zhou, Shuyan Ren, Yuwu Chi and Guonan Chen

Analyst 2012 vol. 137(Issue 15) pp:3514-3519

Publication Date(Web):23 May 2012

DOI:10.1039/C2AN35218D

This work reports that ammonia (NH3) can be used as an efficient co-reactant for tris(2,2′-bipyridine)ruthenium(II) (Ru(bpy)32+) electrochemiluminescence (ECL) in ionic liquids (ILs), on the basis of which a signal-on ECL sensor for directly detecting gaseous NH3 has been developed. The NH3 ECL sensor has a very high sensitivity, with a detection limit of 10 ppt NH3 (at signal-to-noise ratio of 3) without any preconcentration. The high sensitivity is mainly due to the zero ECL background of Ru(bpy)32+ in the ILs, strong co-reactant ECL activity of NH3, and high solubility of NH3 in imidazolium-based ILs. Additionally, the ECL sensor shows an excellent selectivity against common interfering gases and a wide linear response range from 10 ppt to 10 ppm.

Carbon Dioxide Gas Sensor Based on Ionic Liquid-Induced Electrochemiluminescence

Co-reporter:Lichan Chen, Danjun Huang, Shuyan Ren, Yuwu Chi, and Guonan Chen

Analytical Chemistry 2011 Volume 83(Issue 17) pp:6862

Publication Date(Web):August 1, 2011

DOI:10.1021/ac201067u

Electrochemiluminescence of the luminol–O2 system in an electrolyte-free N,N-dimethylformamide (DMF)–dipropylamine (DPA) cosolution is induced by the formation of a carbamate ionic liquid (IL) from the reaction between CO2 and DPA, on the basis of which a facile ECL sensor for measuring atmospheric CO2 has been developed. This ECL sensing method shows several advantages in the detection of CO2, such as high safety, high selectivity, wide linear response range, and good sensitivity. The gas sensor was found to have a linear response range from 100 ppm to 100 v/v% and a detection limit of 80 ppm (at signal-to-noise ratio of 3). This is the first reported IL-induced ECL sensor for a gas, thus the principle of this type of sensor and the IL-induced ECL mechanism have been demonstrated in detail.

Zinc oxide quantum dots synthesized by electrochemical etching of metallic zinc in organic electrolyte and their electrochemiluminescent properties

Co-reporter:Lichan Chen, Nengna Xu, Haiyan Yang, Chen Zhou, Yuwu Chi

Electrochimica Acta 2011 Volume 56(Issue 3) pp:1387-1391

Publication Date(Web):1 January 2011

DOI:10.1016/j.electacta.2010.10.050

A universal and facile electrochemical etching method for synthesizing nanosized metal oxide semiconductors has been presented by taking the synthesis of ZnO quantum dots (QDs) from metallic zinc as an example. By applying an appropriate potential, metallic zinc was controllably oxidized to Zn2+ ion, the latter (Zn2+) was released into an organic electrolyte and hydrolyzed by trace dissolved water therein, giving rise to ZnO QDs. The electrochemically synthesized ZnO QDs were uniform particles with an average diameter of 5.0 nm, and exhibited good photoluminescent and electrochemiluminescent activities. The effects of applied potential window, amount of water and dissolved oxygen on the formation of ZnO QDs were investigated and discussed in detail. The presently proposed electrochemical etching method not only has provided a facile, low-cost and controllable way to obtain ZnO QDs, but also would be applicable as a universal method in synthesizing other kinds of nanosized metal oxide semiconductors from related metals.

Extraction of Electrochemiluminescent Oxidized Carbon Quantum Dots from Activated Carbon

Co-reporter:Yongqiang Dong, Nana Zhou, Xiaomei Lin, Jianpeng, Lin, Yuwu Chi, and Guonan Chen

Chemistry of Materials 2010 Volume 22(Issue 21) pp:5895

Publication Date(Web):October 12, 2010

DOI:10.1021/cm1018844

A facile method has been developed to extract oxidized carbon quantum dots (QDs) directly from activated carbon (AC) by chemical oxidation. The method has several advantages including low cost, high yield of QDs (>10%), and large-scale production. The as-prepared oxidized carbon QDs are mainly graphitic structure nanocrystals of 3−4 nm in diameter, have abundant carboxyl groups at their surfaces, and exhibit strong electrochemiluminescent (ECL) activity, suggesting promising applications in ECL biosensing and imaging. The ECL properities, including ECL activities in the absence and presence of coreactants, effects of the size and surface passivation on the oxidized carbon QDs ECL were investigated and discussed in detail.

Strong electrochemiluminescence based on electron transfer between Tris(2,2′-bipyridine)ruthenium(III) and SnO NPs@MWCNTs

Co-reporter:Liyan Zheng, Yuwu Chi, Binbin Wang, Limin Han and Guonan Chen

Chemical Communications 2010 vol. 46(Issue 31) pp:5734-5736

Publication Date(Web):29 Jun 2010

DOI:10.1039/C0CC00105H

Strong electrochemiluminescence signals caused by the highly effective electron transfer process between SnO nanoparticles-deposited multiwall carbon nanotubes (SnO NPs@MWCNTs) composite and Ru(bpy)33+ were observed.

Enhanced electrochemiluminescence of luminol-O2 system at gold–hydrophobic ionic liquid|water interface

Co-reporter:Jiefeng Rong, Yuwu Chi, Yuanjin Zhang, Lichan Chen, Guonan Chen

Electrochemistry Communications 2010 Volume 12(Issue 2) pp:270-273

Publication Date(Web):February 2010

DOI:10.1016/j.elecom.2009.12.012

A hydrophobic thiol-functionalized ionic liquid (IL) was synthesized and immobilized tightly on a gold electrode surface via Au–S bond to construct a stable Au–IL|water interface. At the Au–IL|water interface, the electrochemiluminescence (ECL) of luminol-O2 system was investigated. The ECL intensity of luminol-O2 system at the Au–IL|water interface was much larger and more stable than that at Au|water interface. The enhanced ECL mechanism at the Au–IL|water interface was studied and discussed in details.

Biocompatible electrochemiluminescent biosensor for choline based on enzyme/titanate nanotubes/chitosan composite modified electrode

Co-reporter:Hong Dai, Yuwu Chi, Xiaoping Wu, Youmei Wang, Mingdeng Wei, Guonan Chen

Biosensors and Bioelectronics 2010 Volume 25(Issue 6) pp:1414-1419

Publication Date(Web):15 February 2010

DOI:10.1016/j.bios.2009.10.042

A new biocompatible ECL biosensor based on enzyme/titanate nanotubes/chitosan composite film was developed for the determination of analytes in biological samples. In the fabrication of the new ECL biosensor, biocompatible titanate nanotubes (TNTs) and a model enzyme, i.e., choline oxidase (ChOX), were immobilized on a chitosan modified glassy carbon electrode (GCE) via electrostatic adsorption and covalent interaction, respectively. By this ECL biosensor, choline was enzymatically oxidized to hydrogen peroxide and detected by a sensitive luminol ECL system. The use of TNTs not only provided a biocompatible microenvironment for the immobilized enzyme, which resulted in an excellent stability and long lifetime of the ECL biosensor, but also exhibited great enhancement towards luminol ECL and thus led to a significant improvement in sensitivity of ECL biosensor. Satisfactory results were obtained when employing this biosensor in assaying the total choline in milk samples. The work would provide a common platform to develop various sensitive, selective and biocompatible ECL biosensors based on using enzyme/TNTs/CHIT composite films.

Heated Indium Tin Oxide Cell for Studying Ionic Liquid-Mediated Electrochemiluminescence

Co-reporter:Lichan Chen, Yuwu Chi, Xiaoxue Zheng, Yuanjin Zhang and Guonan Chen

Analytical Chemistry 2009 Volume 81(Issue 6) pp:2394

Publication Date(Web):February 11, 2009

DOI:10.1021/ac802302p

A heated indium tin oxide (ITO) electrochemiluminescent (ECL) cell containing an ITO counter electrode, an ITO reference electrode, and a heated ITO working electrode has been fabricated to promote ionic liquid (IL)-mediated ECL reactions and hence improve sensitivities of IL-based ECL sensors. Heating the ITO working electrode was carried out by applying high-frequency ac voltages, and the temperature of the heated ITO working electrode was calibrated by the redox currents of ferrocenemethanol (FcMeOH) in 1-butyl-3-methylimidazolium hexafluorophosphate (BMIPF6) IL. A significant increase (26 times) in ECL intensity of the luminol−O2−BMIPF6 system was observed when heating the ITO working electrode from room temperature to 54 °C. The use of the developed heated ITO ECL cell has been demonstrated to be an important way to improve IL-mediated ECL sensitivity and envisioned to enlarge applications of IL-based ECL sensors.

Spectroelectrochemistry for studying electrochemiluminescence mechanism

Co-reporter:Yongqiang Dong, Yuwu Chi, Liyan zheng, Lan Zhang, Lichan Chen, Guonan Chen

Electrochemistry Communications 2009 Volume 11(Issue 5) pp:983-986

Publication Date(Web):May 2009

DOI:10.1016/j.elecom.2009.02.040

UV–Vis spectroelectrochemistry (SEC) was introduced for the first time into the study of electrochemiluminescence (ECL) mechanisms of nitrogen heterocyclic compounds. Uracil and its two derivatives, 5-fluorouracil and 1-methyl-uracil, were chosen as model molecules in the ECL mechanism study. SEC revealed that the substitution of hydrogen at N(1) and the destruction of conjugate heterocyclic ring were very important for ECL activities of uracils. On the basis, a new ECL mechanism was proposed for the uracils. The successful explanation of ECL mechanism for the model molecules by employing SEC indicates that SEC would play an important role in future ECL mechanism studies.

Electrochemiluminescence for probing interactions between a mimic enzyme and biological molecules

Co-reporter:Qingqing Shu, Yuwu Chi, Liyan Zheng, Yongqiang Dong, Lan Zhang, Guonan Chen

Electrochemistry Communications 2009 Volume 11(Issue 2) pp:387-389

Publication Date(Web):February 2009

DOI:10.1016/j.elecom.2008.11.043

The present work proposed a novel ECL protocol to probe the interactions between mimic enzymes and small biological molecules. Iron(II) phthalocyanine (FePc) and two imidazoles (imidazole and histidine) were chosen as model molecules of mimic enzyme and small biological molecules, respectively. The interactions between FePc and the imidazoles were probed by a sensitive luminol–O2 ECL system. Before complexing with the imidazoles, FePc can inhibit luminol–O2 ECL due to its electrocatalysis towards O2, however, after complexing with the imidazoles, FePc decreases the electrocatalysis, leading to the observation of an enhanced luminol–O2 ECL. Additionally, the proposed protocol enables detection limits of 1.0 × 10−8 mol L−1 and 1.0 × 10−7 mol L−1 to be achieved, respectively, for imidazole and histidine under the physiological pH condition (pH 7.4).

Synthesis of N-4-butylamine acridone and its use as fluorescent probe for ctDNA

Co-reporter:Bin Qiu, Longhua Guo, Zhitao Chen, Yuwu Chi, Lan Zhang, Guonan Chen

Biosensors and Bioelectronics 2009 Volume 24(Issue 5) pp:1281-1285

Publication Date(Web):1 January 2009

DOI:10.1016/j.bios.2008.07.055

A novel N-4-butylamine acridone (BAA), which is an acridone derivative was synthesized and characterized by IR, MS and 1H NMR. The fluorescent characteristics of BAA was investigated in detail and used as the fluorescent probe for detection of calf thymus DNA (ctDNA). It was found that DNA was able to quench the fluorescence of BAA at 426 nm with the excitation at 254 nm. Under optimal conditions, the corresponding linear response range was from 1.0 to 20.0 mg/L and the limit of detections (LOD) was 0.020 mg/L (defined as S/N = 3). Moreover, the interaction between BAA and ctDNA was investigated by fluorescence, absorption and viscosity measurements. The results suggested that the interaction between BAA and ctDNA is groove binding in nature.

Electrochemiluminescent Reaction between Ru(bpy)32+ and Oxygen in Nafion Film

Co-reporter:Liyan Zheng, Yuwu Chi, Qingqing Shu, Yongqiang Dong, Lan Zhang and Guonan Chen

The Journal of Physical Chemistry C 2009 Volume 113(Issue 47) pp:20316-20321

Publication Date(Web):November 3, 2009

DOI:10.1021/jp902239j

For years, dissolved oxygen (O2) has been regarded as a quenching species in Ru(bpy)32+ electrochemiluminescent (ECL) systems; however, in the present study, O2 was found to act as a coreactant for Ru(bpy)32+ ECL in Nafion film, resulting in a strong ECL light emission. ECL experiments were carried out at a Ru(bpy)32+/Nafion film-modified glassy carbon electrode (GCE) immersing in air-saturated phosphate buffer solution (pH 7.4). Scanning in the potential range of +1.5 to −1.0 V resulted in three luminescent processes, including two potential-dependent luminescence peaks (ECL-1 and ECL-2), and one potential-independent persistent luminescence emission (CL-P). Therein, ECL-2 occurring at potential less than −0.5 V was demonstrated to be a new chemiluminescent reactions between O2 and Ru(bpy)32+. In ECL-2, Nafion film plays important roles in stabilizing Ru(bpy)33+ and O2•− radical essentially for producing the new ECL. Unlike previously reported ECL processes, ECL-2 peak potential is dependent on the reduction potential of the coreactant (i.e., O2) rather than the redox potentials of the luminopore, Ru(bpy)32+, which would provide a useful way to probe O2, O2•− radical, and their stabilities in electrochemical reactions.

Electrochemiluminescent Behavior of Tris(2,2-bipyridine) Ruthenium(II)/Triethylamine in Ionic Liquid Solution

Co-reporter:Liyan Zheng ; Yuwu Chi ; Yongqiang Dong ; Lan Zhang ;Guonan Chen

The Journal of Physical Chemistry C 2008 Volume 112(Issue 39) pp:15570-15575

Publication Date(Web):September 6, 2008

DOI:10.1021/jp805609y

The electrochemiluminescence (ECL) behaviors of tris(2,2-bipyridine)ruthenium(II)/triethylamine (Ru(bpy)32+/TEA) in 1-butyl-3-methylimidazolium hexafluorophosphate (BMIPF6) ionic liquid were investigated and compared with those in aqueous solution (pH 7.0 PBS) at a gold electrode. It was found that the Ru(bpy)32+/TEA system gave rise to one small and one large peak ECL peak at anodic process. The small anodic ECL peak observed around +0.90 V is due to the direct electrochemical oxidation of TEA at the gold electrode and further chemiluminescent reaction of its oxidative product with Ru(bpy)32+. The large anodic ECL peak found around +1.35 V results from the reversible electrochemical oxidation of Ru(bpy)32+ coupled with a slow following reaction of TEA with Ru(bpy)33+. The effects of viscosity and ionic strength of ionic liquid on diffusion coefficients, catalytic efficiency, and ECL intensity were investigated and discussed to reveal the ECL mechanism of Ru(bpy)32+/TEA system in the ionic liquid of BMIPF6.

Enhanced electrogenerated chemiluminescence behavior of C3N4 QDs@ C3N4 nanosheet and its signal-on aptasensing for platelet derived growth factor

Co-reporter:Huifeng Xu, Shijing Liang, Xi Zhu, Xiuqin Wu, Yongqiang Dong, Haishan Wu, Wenxia Zhang, Yuwu Chi

Biosensors and Bioelectronics (15 June 2017) Volume 92() pp:

Publication Date(Web):15 June 2017

DOI:10.1016/j.bios.2016.10.026

•C3N4 QDs@C3N4 nanosheet nanocomposite was prepared by a simple oxidation method.•It exhibits stronger and more stable ECL response owning to more surface defect.•A signal-on ECL aptasensor for PDGF-BB was fabricated using the nanocomposite.•This work opens up the application of g-C3N4 nanocomposite in signal-on aptasensing.A novel g-C3N4 nanosheets embedded with C3N4 QDs nanocomposites (QD@CNNS) was prepared by simple oxidation using hydrogen peroxide and UV light irradiation. This nanocomposite exhibits more stable and stronger electrochemiluminescent (ECL) behavior compared with CNNS. Coupling this nanocomposite with Fc-labeled aptamer, a signal-on aptasensor for platelet derived growth factor BB (PDGF-BB) is fabricated. Initially, the Fc-labeled aptamer binds onto QD@CNNS via π-π conjugation and electrostatic interaction, quenching ECL emission from QD@CNNS. The introduction of target efficiently recovers the ECL signal by the formation of PDGF-BB/aptamer complex. The ECL intensity is proportion to the concentration of PDGF-BB in the range of 0.02–80 nM with a detection limit of 0.013 nM. This work demonstrates a simple synthesis method to obtain QD@CNNS with excellent ECL behavior, and opens up the application of g-C3N4 nanocomposite in signal-on aptasensing.

Signal-on electrochemiluminescent aptasensors based on target controlled permeable films

Co-reporter:Lichan Chen, Xiaoting Zeng, Abdul Rahim Ferhan, Yuwu Chi, Dong-Hwan Kim and Guonan Chen

Chemical Communications 2015 - vol. 51(Issue 6) pp:NaN1038-1038

Publication Date(Web):2014/11/24