Fluorometric “turn-on” glucose detection is presented that is based on the Fenton reaction which can trigger the generation of Ag nanoclusters (Ag NCs). Oxidation of D-glucose by glucose oxidase generates H2O2. Reactive radicals are formed from the Fenton reaction of H2O2 and Fe2+. These radicals initiate the polymerization of methacrylic acid to form poly(methacrylic acid) which is used as a template to generate fluorescent Ag NCs in situ by illumination with UV light. The increase in Ag NCs fluorescence intensity can be used to quantify glucose concentration. The sensing approach employed here provides a new strategy for the determination of glucose selectively.

Near-infrared (NIR) fluorescence nanomaterials with low toxicity and long wavelength emission play an important role in bioapplications. Herein, a simple and rapid microwave heating method is designed to synthesize fluorescent gold nanoclusters (AuNCs) by using glutathione (GSH) as a reducing agent and stabilizing agent simultaneously. By adjusting the microwave heating time, the as-prepared GSH–AuNCs can show size-dependent tunable fluorescence from the visible region to the NIR region, and even to 800 nm wavelength. Besides, the as-prepared GSH–AuNCs are water-soluble, low toxicity and highly stable, and exhibit multifunctional surface chemistry based on GSH as the protective surface layer. Another attractive feature of the resultant NIR GSH–AuNCs is temperature-dependent fluorescence and they could be used as a nanoprobe to measure the temperature in the range from 0 to 80 °C. Moreover, this process is reversible, which means that the fluorescence intensity of the GSH–AuNCs can be recovered to the initial intensity when the temperature changes reversibly. Finally, the resultant NIR GSH–AuNCs are further conjugated with folic acids (FAs) which helps the AuNCs target HeLa cells. These properties provide FA-conjugated GSH–AuNCs with potential applications as a platform for cancer diagnosis studies in various biological systems.

Multiple functions incorporated in one single component material offer important applications in biosystems. Here we prepared a divalent state of rare earth EuS nanocrystals (NCs), which provides luminescent and magnetic properties, using both 1-Dodecanethiol (DT) and oleylamine (OLA) as reducing agents. The resultant EuS NCs exhibit controllable shapes, uniform size, and bright luminescence with a quantum yield as high as 3.5%. OLA as a surface ligand plays an important role in tunable morphologies, such as nanowires, nanorods, nanospheres et al. Another attractive nature of the EuS NCs is their paramagnetism at room temperature. In order to expand the biological applications, the resultant EuS NCs were modified with amphiphilic block copolymer F127 and transferred from oil to water phase. The excellent biocompatibility of EuS NCs is demonstrated as well as preservation of their luminescence and paramagnetic properties. The EuS NCs offer multifunction and great advantages of bright luminescence, paramagnetic, controllable morphologies, and good biocompatibility promising applications in the field of simultaneous magnetic resonance and fluorescence bioimaging.Keywords: controllable morphologies; dual bioimaging; EuS nanocrystals; fluorescence; magnetism;

This study demonstrates high contrast and sensitivity by designing a dual-emissive hydrogel particle system, whose two emissions respond to pH and temperature strongly and independently. It describes the photoluminescence (PL) response of poly(N-isopropylacrylamide) (PNIPAM)-based core/shell hydrogel nanoparticles with dual emission, which is obtained by emulsion polymerization with potassium persulfate, consisting of the thermo- and pH-responsive copolymers of PNIPAM and poly(acrylic acid) (PAA). A red-emission rare-earth complex and a blue-emission quaternary ammonium tetraphenylethylene derivative (d-TPE) with similar excitation wavelengths are inserted into the core and shell of the hydrogel nanoparticles, respectively. The PL intensities of the nanoparticles exhibit a linear temperature response in the range from 10 to 80 °C with a change as large as a factor of 5. In addition, the blue emission from the shell exhibits a linear pH response between pH 6.5 and 7.6 with a resolution of 0.1 unit, while the red emission from the core is pH-independent. These stimuli-responsive PL nanoparticles have potential applications in biology and chemistry, including bio- and chemosensors, biological imaging, cancer diagnosis, and externally activated release of anticancer drugs.Keywords: bioprobes; dual emission; hydrogels; nanoparticles; pH and temperature responses; photoluminescence

In this work, a simple, low-cost and one-step microwave approach has been demonstrated for the synthesis of water-soluble carbon dots (C-dots). The average size of the resulting C-dots is about 4 nm. From the photoluminescence (PL) measurements, the C-dots exhibit excellent biocompatibility and intense PL with the high quantum yield (QY) at Ca. 25%. Significantly, the C-dots have excellent biocompatibility and the capacity to specifically target the cells overexpressing the folate receptor (FR). These exciting results indicate the as-prepared C-dots are promising biocompatible probe for cancer diagnosis and treatment.

Developing an approach for targeting and detecting cancer cells has long been a challenge. Herein, the folic acid (FA) conjugated gold nanodots (Au NDs) are designed for specifically targeting and imaging folate receptor (FR) positive cancerous cells. Fluorescent small Au NDs were synthesized using stable Ag NPs with size above 50 nm and GSH as capping agent. This method solves the problems of low stability and difficulty in purification of small Ag NDs as templates. The resulting Au NDs display pink fluorescence with an emission peak at 582 nm. As-prepared Au NDs provide tunable fluorescence with a significant red shift (∼60 nm) with increase in the amount of GSH. In addition, GSH acts as a protecting layer, which could provide original functional groups (thiol, carboxyl and amine) and make Au NDs exhibit outstanding properties such as dispersibility in water, high stability, good biocompatibility and surface bioactivity. These characteristics make them suitable for further conjugation with FA. FA-conjugated Au NDs show the specific target HeLa cancer cells compared with 293T normal cells. These properties provide Au NDs with potential applications in distinguishing FR-positive cancer cells from normal cells.

Good biocompatible fluorescent gold nanoclusters (Au NCs) stabilized by cysteine with blue-green emission were first synthesized through a core etching process. The as-prepared clusters were found to be useful as label-free fluorescent sensors for the detection of the biologically important molecules pyrophosphate (PPi) and alkaline phosphatase (ALP). The approach was based on the competition between cysteine and PPi for coordination of Cu2+. The fluorescence of Au NCs could be quenched by Cu2+. PPi could recover the Cu2+-quenched Au NCs fluorescence selectively, and in this way PPi could be detected (with a detection limit of 2 μM). Upon addition of ALP, PPi was hydrolyzed and Cu2+ was released, which re-quenched the recovered fluorescence. As a result, an assay for ALP activity was established (allowing detection of 0.1 mU mL−1 of ALP). The strategy employed here offers a new way to construct novel nanomaterial-based biosensors.

Robust diamond meshes with excellent superhydrophobic and superoleophilic properties have been fabricated. Superhydrophobicity is observed for water with varying pH from 1 to 14 with good recyclability. Reversible superhydrophobicity and hydrophilicity can be easily controlled. The diamond meshes show highly efficient water–oil separation and water pH droplet transference.

We report, for the first time, the design and synthesis of thermoresponsive (TR) photoluminescent (PL) hydrogel nanoparticles, with a core consisting of poly[styrene-co-(N-isopropylacrylamide)] (PS-co-PNIPAM) and a PNIPAM-co-PAA shell. PAA represents polyacrylic acid which interacts with our emitting molecule 1,2-bis[4-(2-triethylammonioethoxy)phenyl]-1,2-diphenylethene dibromide (d-TPE). The electrostatic interaction between each water-soluble d-TPE molecule and two AA repeat units activates these d-TPE molecules to exhibit strong PL. Our d-TPE doped PS-co-PNIPAM/PNIPAM-co-PAA particles in water display remarkable TR PL: the emission intensity decreased in the course of heating from 2 to 80 °C and recovered during cooling from 80 to 2 °C. Such linear, reversible, and sensitive TR PL is achieved by the use of both PAA and PNIPAM as the shell polymeric chain and by careful optimization of the d-TPE to AA feed molar ratio. Thus, the emission of the d-TPE molecule is affected sensitively by temperature. In addition to such an exceptionally temperature-dependent PL, the presence of CrO42– resulted in the decrease of the emission intensity, which was also temperature-dependent. The present study provides a unified conceptual methodology to engineer functional water-dispersible hydrogel nanoparticles that are stimuli-responsive with the potential to advance various PL-based applications.Keywords: CrO42− sensing; photoluminescent hydrogel nanoparticles; reversible and linear thermoresponses; temperature-dependent photoluminescence; TPE derivatives;

•The galvanic replacement reaction was used to prepare Ag/Au alloy NCs.•As-prepared Ag/Au alloy NCs display near-infrared (NIR) fluorescence.•The luminescence could be tunable from visible red (614 nm) to NIR (716 nm).•Resultant alloy NCs was used as a probe for labeling CAL-27 cells.The fluorescent nanomaterials play an important role in cellular imaging. Although the synthesis of fluorescent metal nanoclusters (NCs) have been developing rapidly, there are many technical issues in preparing metal alloy NCs. Herein, we used a facile galvanic replacement reaction to prepare Ag/Au alloy NCs. The characterizations of UV, PL, HRTEM, EDX and XPS confirm one fact the Ag/Au alloy NCs are carried out. As-prepared Ag/Au alloy NCs display near-infrared (NIR) fluorescence centered at 716 nm and show tunable luminescence from visible red (614 nm) to NIR (716 nm) by controlling the experimental Ag/Au ratios. Moreover, as-prepared Ag/Au alloy NCs are protected by glutathione (GSH) whose some functional groups including thiol, carboxyl and amino groups make the as-prepared alloy NCs exhibit good dispersion in aqueous solution, high physiological stability and favorable biocompatibility. Together with NIR fluorescence, these advantages make alloy NCs be promising candidate in biological labeling.

In this work, we first report the application of fluorescent polymer brushes film as a device for ultrasensitive and selective detection of TNT. As positively charged fluorescent molecules of quaternary ammonium tetraphenylethylene derivatives (d-TPE) were self-assembled on the brushes of poly(acrylic acid) (PAA) by coulomb forces, we obtained a novel fluorescent polymer brushes film with excellent photoluminescent properties, and the emission could be quantitatively and sensitively responsive to 2,4,6-trinitrotoluene (TNT) due to the electron transfer between d-TPE and TNT. The limit of detection of TNT was established to be 0.1 ppb in water. The fluorescent device could also be used repeatedly for TNT detection, which indicated a promising application in trace explosive detection.

Novel opal hydrogels with water-tunable photonic bandgap (PBG) exhibiting responses to external stimuli were self-assembled from polystyrene-co-poly(N,N-dimethylacrylamide) (PS-co-PDMAA) microspheres. The polymeric microspheres with narrow size distribution were successfully prepared in water, consisting of two regions. The inner region is rich in PS which is hard and hydrophobic; the outer region is rich in PDMAA which is soft and hydrophilic. The self-assembly of the PS-co-PDMAA hydrogel microspheres is ready induced by centrifugation and resulted in highly ordered three-dimensional (3D) photonic colloidal crystals (PCCs). With an increase of the amount of water, the PBG of the opal hydrogels shifted from the visible to near-infrared region of the electromagnetic spectrum. The maximum shift of diffraction peak positions could be larger than 500 nm with narrow full width at half maximum (FWHM) in the range of 20 to 40 nm only. The change in color was visible to the naked eye. The remarkable sensitivity to water of the lattice spacing of the opal hydrogels was repeatable after centrifugation. These observations are attributed to a reproducible degree of hydration of the hydrophilic outer region of the polymeric microspheres. Furthermore, the diffraction of the opal hydrogels was particularly sensitive to the presence of thiocyanate (SCN–) ions. The interaction between SCN– ions and DMAA repeat units is argued to block hydrogen bonds between DMAA and water molecules. Our PS-co-PDMAA opal hydrogels could be a practical system for diffraction-based detections.Keywords: photonic bandgap (PBG); photonic colloidal crystals (PCCs); SCN− ion detection; self-assembly; stimuli-responsive opal hydrogels;

Substrate hydrolysis was utilized to trigger a “top-down” etching process for the generation of fluorescent gold nanoclusters, and the changes in emission intensity of the assay solution provide a facile way for the sensing of enzyme activity.

In this work, we first report a thermo-responsive photoluminescent polymer brushes device as a platform for the selective and sensitive detection of Cr(VI). Positively charged fluorescent molecules of a quaternary ammonium tetraphenylethylene derivative (d-TPE) are immobilized in the thermo-responsive polymer brushes of p(NIPAM-co-AAc) by Coulombic force, which leads to the observation of an immobilized induced emission (IIE) phenomenon. The emission intensity of the d-TPE labelled film is improved hundreds of times compared with a d-TPE aqueous solution. As a result, we obtain a novel thermo-responsive polymer brushes device with excellent photoluminescent properties. The photoluminescence (PL) intensity of the device exhibits a linear and reversible response from 4 to 60 °C and shows a high PL quenching for the sensitive and selective detection of Cr(VI) rather than Cr(III). The limit of detection can reach as low as 0.05 ppm, which indicates a promising sensor device for environmental monitoring, laboratory analysis and various other applications.

Highly fluorescent papain stabilized gold nanoclusters (NCs) have been synthesized through a simple wet chemical route. Papain was used for the first time as an effective capping and reducing agent for these clusters. The optimal conditions for the synthesis of the gold nanoclusters, including the concentrations of papain and NaOH, reaction time and temperature, were investigated. The as-prepared Au clusters show intense red emission at ∼660 nm (QY ∼4.3%) and are uniform in size. The clusters are quite stable and the intense red emission remained unchanged at a buffer pH range of 6–12. The fluorescent Au NCs were then used as a label-free probe for the sensitive detection of Cu2+. A limit of detection of 3 nM was obtained. The sensing strategy is also highly selective against the various potential interference ions.Graphical abstractHighlights► A simple and “green” approach has been developed to synthesize the papain-Au nanoclusters. ► Papain is a commercially available inexpensive protein and could be obtained in large quantities. ► The nanoclusters show intense red emission in both solution and powder forms. ► The red emission remained unchanged after ∼3 months and at a buffer pH range of 6–12. ► The use of these Au clusters for the simple, sensitive, selective, and label-free cupric ion detection has been demonstrated.

Metal copper mesh with superhydrophobic and superoleophilic surface had been successfully fabricated via a facile solution−immersion process. The hierarchical structure was prepared on the commercial copper mesh surface by etching with the nitric acid. After being modified by 1-hexadecanethiol (HDT), the as-prepared mesh indicated both superhydrophobic and superoleophilic property simultaneously. This as-prepared metal mesh could then be applied for oil and water mixture separation. The unusual wettability of the as-prepared mesh was stable in corrosive conditions, such as acidic, basic, and salt solutions. The solution−immersion method was simple, time-saving, and inexpensive and therefore exhibited great potential application.Keywords: copper mesh; corrosive condition; separation; superhydrophobic; superoleophilic

•The carbon dots were synthesized by a facile one-step hydrothermal approach.•The carbon dots exhibit the excitation-dependent PL behaviors with high quantum yield.•The carbon dots can distinguish FA-receptor-positive cancer cells from normal cells.•The carbon dots with positive charges can link to plasmid DNA and efficiently transfect the therapeutic plasmid into cells.Photoluminescent carbon dots (C-dots), as new members of the quantum sized carbon analogues have attracted significant attention due to their unique size, less toxicity, good compatibility and relatively easy surface modification. In this work, we report a simple, low-cost and one-step hydrothermal carbonization approach to synthesize the positively charged C-dots using PEI and FA. From the photoluminescence (PL) measurements, the as-prepared C-dots exhibit good stability and intense PL with the high quantum yield (QY) at Ca. 42%. Significantly, The as-prepared C-dots integrate the advantages of C-dots and PEI: the presence of C-dots can effectively decrease the cytotoxicity of PEI, the C-dots can be applied in biological system for selective imaging of folate receptor (FR)-positive cancerous cells from normal cells, while the cationic PEI with positive charges can make them link to plasmid DNA and efficiently transfect the therapeutic plasmid into cells. Therefore, the as-prepared with the facile synthesis method can be a promising photoluminescent probe for cancer diagnosis and gene therapy.A simple, low-cost and one-step hydrothermal treatment for the synthesis of positively charged carbon dots from FA and PEI. They exhibit excellent photoluminescence property and can be promising nanomaterials for cancer diagnosis and gene therapy.

Chemical vapor deposited (CVD) polycrystalline diamond films with an ultrahydrophobic surface were fabricated by constructing a hierarchical structure through sputtering a ZnO layer on diamond grains, with a growth step feature. Under optimized conditions, the combined original diamond with a step structure of the ZnO can achieve a water contact angle (WCA) of as high as 141° ± 1°. It is proved that WCA decreases as the roughness of ZnO/PDF reduced. It can be concluded that the step structure of diamond grains and ZnO nuclei size have a great influence on the variation of WCA.Highlights► We report the deposition of ZnO layer on diamond film by RF magnetron sputtering method. ► The water contact angle of ZnO-modified diamond surface can be reached as high as ∼141°. ► The influence of roughness of hydrophobic proposed by different processing are analyzed. ► A theoretical model is given to explain the phenomenon observed.

Robust diamond meshes with excellent superhydrophobic and superoleophilic properties have been fabricated. Superhydrophobicity is observed for water with varying pH from 1 to 14 with good recyclability. Reversible superhydrophobicity and hydrophilicity can be easily controlled. The diamond meshes show highly efficient water–oil separation and water pH droplet transference.

Good biocompatible fluorescent gold nanoclusters (Au NCs) stabilized by cysteine with blue-green emission were first synthesized through a core etching process. The as-prepared clusters were found to be useful as label-free fluorescent sensors for the detection of the biologically important molecules pyrophosphate (PPi) and alkaline phosphatase (ALP). The approach was based on the competition between cysteine and PPi for coordination of Cu2+. The fluorescence of Au NCs could be quenched by Cu2+. PPi could recover the Cu2+-quenched Au NCs fluorescence selectively, and in this way PPi could be detected (with a detection limit of 2 μM). Upon addition of ALP, PPi was hydrolyzed and Cu2+ was released, which re-quenched the recovered fluorescence. As a result, an assay for ALP activity was established (allowing detection of 0.1 mU mL−1 of ALP). The strategy employed here offers a new way to construct novel nanomaterial-based biosensors.

In this work, we first report the application of fluorescent polymer brushes film as a device for ultrasensitive and selective detection of TNT. As positively charged fluorescent molecules of quaternary ammonium tetraphenylethylene derivatives (d-TPE) were self-assembled on the brushes of poly(acrylic acid) (PAA) by coulomb forces, we obtained a novel fluorescent polymer brushes film with excellent photoluminescent properties, and the emission could be quantitatively and sensitively responsive to 2,4,6-trinitrotoluene (TNT) due to the electron transfer between d-TPE and TNT. The limit of detection of TNT was established to be 0.1 ppb in water. The fluorescent device could also be used repeatedly for TNT detection, which indicated a promising application in trace explosive detection.

Substrate hydrolysis was utilized to trigger a “top-down” etching process for the generation of fluorescent gold nanoclusters, and the changes in emission intensity of the assay solution provide a facile way for the sensing of enzyme activity.