The endoplasmic reticulum (ER) has a central role in the fine-tuning of environmental and internal stimuli. We herein report a ratiometric fluorescent probe, α-Naph, capable of determining basal H2O2 in the ER. The probe specifically responds to H2O2. The limit of detection of the probe is as low as 38 nM, making it a feasible sensor to image intracellular basal H2O2. In addition, utilizing its ratiometric property, we are able to measure the concentration of H2O2 in the ER quantitatively, eliminating the error caused by the probe concentration and environment. The intracellular concentration of H2O2 in the ER is calculated to be 0.692 μM under normal conditions and 1.26 μM under the stimulation of phorbol myristate acetate.

The endoplasmic reticulum (ER) has a central role in the fine-tuning of environmental and internal stimuli. We herein report a ratiometric fluorescent probe, α-Naph, capable of determining basal H2O2 in the ER. The probe specifically responds to H2O2. The limit of detection of the probe is as low as 38 nM, making it a feasible sensor to image intracellular basal H2O2. In addition, utilizing its ratiometric property, we are able to measure the concentration of H2O2 in the ER quantitatively, eliminating the error caused by the probe concentration and environment. The intracellular concentration of H2O2 in the ER is calculated to be 0.692 μM under normal conditions and 1.26 μM under the stimulation of phorbol myristate acetate.

A BINOL-based perfluoroalkyl ketone shows a highly enantioselective fluorescence enhancement in the presence of various amino acid-TBA salts and can be used to determine the enantiomeric composition of these compounds. It was found that the amino acid-TBA salts can act as nucleophiles to cleave the perfluoroalkyl group off of the ketones to form the corresponding amides at room temperature in DMSO. This is the first example of an enantioselective fluorescent sensor for the recognition of amino acids by forming amide bonds under very mild conditions. This study has also revealed an unusual concentration effect leading to an “off-on-off” fluorescence response of the sensor toward one enantiomer of the amino acids.

Development of selective fluorescent probes for rapid and ultrasensitive detection of nitroxyl (HNO) is of great importance for biomedical researchers to investigate the detailed functions and mechanisms of HNO in living systems. Herein, based on an internal charge transfer (ICT) mechanism, we developed a novel ratiometric, colorimetric and far-red fluorescent probe (HNO-TCF) for the rapid and ultrasensitive detection of HNO in living cells. HNO-TCF exhibits high HNO-selectivity even in the presence of a high concentration of biological reductants including glutathione (GSH), hydrogen sulfide (H2S) and ascorbate (AA), which might be ascribed to the adoption of the 2-(diphenylphosphino)benzoate recognition moiety. The ICT-based fluorescent probe HNO-TCF displays a large (185 nm) red-shifted absorption spectrum and the color changes from yellow to blue upon addition of HNO. In addition, the results showed that HNO-TCF could quantitatively detect HNO in the range of 0 to 4 μM with a detection limit of 10 nM by ratiometric absorption and fluorescence spectrometry methods. Importantly, HNO-TCF was successfully applied to the fluorescence imaging of HNO levels in living cells, and it is expected to be a useful chemical tool for investigating the detailed functions and mechanisms of HNO in living systems.

The development of techniques for detecting HOCl at the subcellular level is very important to elucidate its cellular functions. Due to its relatively low concentration, it is still a great challenge to specifically track the basal HOCl in normal cells. In this paper, based on the unique chlorination of HOCl by the initiation of chlorinium ions (Cl+) in an acidic medium, we have developed a simple pH-mediated lysosome-targetable fluorescent probe Lyso-HOCl for the specific detection of HOCl over other bioactive molecules at higher concentration (500 μM). Our results show that Lyso-HOCl possesses a detection limit of 8.0 pM, and can quantitatively detect HOCl at the picomolar level. The ultrasensitive and ultrafast response property of probe Lyso-HOCl offers a good opportunity to monitor the basal HOCl and the fluctuation of endogenous HOCl levels in the lysosomes of macrophages (Raw 264.7 cells), and we thus anticipate that this probe would provide a promising tool for further unraveling the biological functions of HOCl in subcellular lysosomes.

Inspired by the zinc protoporphyrin found in red blood cells during heme production, we have developed a novel type of bimetallic Fe, Zn/N/C catalyst with high metal loading (Fe 1.2 wt% and Zn 1.7 wt%), demonstrating high activity and high stability for oxygen reduction processes in acidic electrolytes.

•A well-designed turn on fluorescent nanoprobe has been constructed by integrating polyethyleneimine (PEI) modified-CDs (P-CDs) and hyaluronic acid (HA) conjugated doxorubicin (Dox) through electrostatic self-assembly.•The nanoprobe can effectively distinguish Hela cell (cancer cell) from NIH-3T3 cells (normal cell) based on expression of different amount of CD44 protein on surface of cells.•The MTT assay confirmed that the release of Dox from the turn-on fluorescent nanoprobe can efficiently induce apoptosis in HeLa cells.This paper reports a turn-on theranostic fluorescent nanoprobe P-CDs/HA-Dox obtained by electrostatic assembly of polyethylenimine (PEI)-modified carbon dots (P-CDs) and Hyaluronic acid (HA)-conjugated doxorubicin (Dox) for hyaluronidase (HAase) detection, self-targeted imaging and drug delivery. P-CDs/HA-Dox show weak emission in a physiological environment. By utilizing the high affinity of HA to CD44 receptors overexpressed on many cancer cells, P-CDs/HA-Dox are capable of targeting and penetrating into cancer cells, where they are activated by HAase. As a result, HA-Dox can be digested into small fragments, causing the release of Dox and thereby restoring the fluorescence of P-CDs. The theranostic fluorescent nanoprobe can effectively distinguish cancer cells from normal cells. The as-prepared nanoprobe achieves a sensitive assay of HAase with a detection limit of 0.65 U mL−1. Furthermore, upon Dox release, the Dox could efficiently induce apoptosis in HeLa cells, as confirmed by MTT assay. The design of such a turn-on theranostic fluorescent probe provides a new strategy for self-targeted and image-guided chemotherapy.

Hypochlorite plays a significant role in various physiological and pathological processes; however, its role is still less clear than the role of other reactive oxygen species. Herein, we report an ultrafast responsive (<0.2 s) and highly selective probe B-Ts for hypochlorite with high sensitivity and a detection limit as low as 7.5 nM. The probe was compatible in a wide pH range of 4–13. More importantly, experiments in live cells showed that the probe could penetrate the cell membrane easily and was capable of imaging endogenous and exogenous hypochlorite specifically with a fast response.

Hypochlorite plays a significant role in various physiological and pathological processes; however, its role is still less clear than the role of other reactive oxygen species. Herein, we report an ultrafast responsive (<0.2 s) and highly selective probe B-Ts for hypochlorite with high sensitivity and a detection limit as low as 7.5 nM. The probe was compatible in a wide pH range of 4–13. More importantly, experiments in live cells showed that the probe could penetrate the cell membrane easily and was capable of imaging endogenous and exogenous hypochlorite specifically with a fast response.

Hydrazine (N2H4) is considered as an environmental contaminant and a potential carcinogen, and its large-scale application could pose a great threat to the environment and human health. In the present work, a new colorimetric and fluorescent probe NAA was developed for the sensitive and selective detection of N2H4 in air and aqueous solution. The probe shows a selective response to N2H4 against various interferences (e.g., anions, cations, amines and small biomolecules) and a detection limit as low as 0.716 ppb (22.5 nM) far below the threshold limit value (10 ppb) of EPA. By observing the color and fluorescence changes, the test strip coated with NAA provides an economical and convenient tool for the rapid detection of N2H4 gas. Moreover, the probe was proved to possess low cytotoxicity as well as good membrane permeability and thus shows great potential in N2H4 imaging in living cells.

Monitoring intracellular selenocysteine (Sec) is of significant interest for studying Sec metabolism and disease-relevant changes in Sec homeostasis. Herein, we rationally designed an ICT-based ratiometric probe (Rat-Sec) for selectively discriminating endogenous Sec in a live cell matrix. By utilizing an acrylate moiety, Rat-Sec manifested significantly ratiometric and red-shifted (∼117 nm) fluorescence signals within 1 min, and concomitantly demonstrated apparent color alteration from colorless to faint yellow in the presence of Sec. When applied to quantitatively detect Sec under physiological conditions, Rat-Sec gives a detection limit of 12 nM. Offering great advantages due to its ratiometric nature and high specificity and selectivity, Rat-Sec provides reliable fluorescence quantification and rapid tracking of exogenous and endogenous Sec in living cells.

Monitoring intracellular selenocysteine (Sec) is of significant interest for studying Sec metabolism and disease-relevant changes in Sec homeostasis. Herein, we rationally designed an ICT-based ratiometric probe (Rat-Sec) for selectively discriminating endogenous Sec in a live cell matrix. By utilizing an acrylate moiety, Rat-Sec manifested significantly ratiometric and red-shifted (∼117 nm) fluorescence signals within 1 min, and concomitantly demonstrated apparent color alteration from colorless to faint yellow in the presence of Sec. When applied to quantitatively detect Sec under physiological conditions, Rat-Sec gives a detection limit of 12 nM. Offering great advantages due to its ratiometric nature and high specificity and selectivity, Rat-Sec provides reliable fluorescence quantification and rapid tracking of exogenous and endogenous Sec in living cells.

Changes in intracellular glutathione (GSH) concentration are closely linked with various cellular physiological and pathological mechanisms. In the present work, four long-wavelength Si-pyronine (SiP) fluorescent dyes are readily synthesized via a UV-assisted aromatization reaction, and used for real-time, dynamic and reversible monitoring of GSH changes in vitro and in living cells. Based on the mechanism that Si atom incorporation greatly increases the pyronine affinity towards sulfhydryl (–SH), SiPs can undergo ultrafast and reversible Michael addition with biological thiols, leading to fluctuations in fluorescence intensity due to the interruption and restoration of their π-conjugation. Relying on the unique reactivity of SiPs with GSH under physiological conditions, the fluorescence intensity of SiPs responds to GSH changes with high sensitivity. SiPs also exhibit excellent photophysical properties including deep-red to near-infrared excitation wavelength (>600 nm), a high fluorescence efficiency (0.20–0.41) in aqueous media, suitable water-solubility and membrane permeability. Using SiP-Pr to incubate with HeLa cells, we achieved real-time, dynamic and repeated imaging of fluctuations in intracellular GSH homeostasis under N-ethylmaleimide stimulation.

Cellular self-regulation of reactive oxygen species (ROS) stress via glutathione (GSH) antioxidant repair plays a crucial role in maintaining redox balance, which affects various physiological and pathological pathways. In this work, we developed a simple yet effective strategy for reversible, dynamic, and real-time fluorescence imaging of ROS stress and GSH repair, based on novel Ge-pyronine dyes (GePs). Unlike the current O-pyronine (OP) dye, the fluorescence of GePs can be quenched in GSH reduction and then greatly restored by ROS (e.g., ClO–, ONOO–, and HO•) oxidation because of their unique affinity toward thiols. The “on–off” and “off–on” fluorescence switch can complete in 10 and 20 s, respectively, and exhibit excellent reversibility in vitro and in cells. GePs also show excitation in the long wavelength from the deep-red to near-infrared (NIR) (621–662 nm) region, high fluorescence quantum yield (Φfl = 0.32–0.44) in aqueous media, and excellent cell permeability. Our results demonstrated that GePs can be used for real-time monitoring of the reversible and dynamic interconversion between ROS oxidation and GSH reduction in living cells. GePs might be a useful tool for investigating various redox-related physiological and pathological pathways.Keywords: cellular redox self-regulation; fast-responsive; fluorescence imaging; Ge-pyronines; near-infrared; reversible;

•The probe displays high specificity toward O3.•The probe shows ratiometric fluorescence response to O3.•The probe undergoes a color change for the visual detection of O3.Ozone (O3) is widely used as oxidant in both industrial and household applications. However, long-term exposure to high concentration of O3 harms lung function and irritates the respiratory system. Therefore, accurate detection of ozone is in great need for both environmental and biological studies for human health. This paper describes a highly specific fluorescent probe for ratiometric detection of O3 concentrations with a detection limit of 39 nM and detection range up to 24.2 μM, which makes it feasible for quantitative detection of O3 in air environment and living cells. Besides fluorescent detection, the probe also undergoes a color change from colorless to yellow, which also allows for convenient visual detection of O3.A highly specific and sensitive fluorescent probe was developed for the ratiometric and visual detection of ozone.

•The probe has a large Stokes shift of 75 nm.•The probe allows the determination of HClO/ClO− with a detection limit of 2.88 nM.•The probe could detect HClO/ClO− within 3 s.•The probe displays high specificity toward HClO over other reactive oxygen species.•The probe successfully applied to PMA-stimulated HClO generation in living cells.A naphthalimide-based fluorescent probe NACl with a large Stokes shift has been successfully developed for highly sensitive, selective and ultrafast detection of hypochlorite (ClO−). This probe utilizes an oxidative deoximation reaction to provide high selectivity and optical dynamic range for detection of ClO− in aqueous solution. Compared to similar systems involving reactive oxygen species (ROS), including superoxide, tert-butyl hydroperoxide, hydroxyl radical, alkylperoxyl radical, and H2O2,NACl provides 138-fold fluorescence enhancement. Its outstanding response time of less than 3 s and detection limit of 2.88 nM establish the potential value of NACl for interrogating the pathology and physiology of intracellular endogenous ClO−.A highly sensitive and fast responsive naphthalimide-based fluorescent probe for imaging intracellular hypochlorite with a large Stokes shift was developed.

DNA nanomachines are becoming useful tools for molecular recognition, imaging, and diagnostics and have drawn gradual attention. Unfortunately, the present application of most DNA nanomachines is limited in vitro, so expanding their application in organism has become a primary focus. Hence, a novel DNA nanomachine named t-switch, based on the DNA duplex–triplex transition, is developed for monitoring the intracellular pH gradient. Our strategy is based on the DNA triplex structure containing C+-G-C triplets and pH-dependent Förster resonance energy transfer (FRET). Our results indicate that the t-switch is an efficient reporter of pH from pH 5.3 to 6.0 with a fast response of a few seconds. Also the uptake of the t-switch is speedy. In order to protect the t-switch from enzymatic degradation, PEI is used for modification of our DNA nanomachine. At the same time, the dynamic range could be extended to pH 4.6–7.8. The successful application of this pH-depended DNA nanomachine and motoring spatiotemporal pH changes associated with endocytosis is strong evidence of the possibility of self-assembly DNA nanomachine for imaging, targeted therapies, and controllable drug delivery.

CdS/ZnS core/shell heterostructured nanocrystals (NCs) with six monolayers (MLs) of ZnS shell on a zinc-blende CdS core were synthesized via successive ionic layer adsorption and reaction. By adjusting the growth temperature of the ZnS shell from 220 to 280 °C, the shape of CdS/ZnS NCs can be tuned to tetrapods, tetrahedra, and dots. Shell growth was confirmed to be uniform by X-ray diffraction, transmission electron microscopy, UV–vis absorption, and photoluminescence spectroscopy. Periodic density functional theory calculations were used to further study the growth mechanism of the differently shaped CdS/ZnS core/shell NCs. Our calculations revealed that the binding energy of model CH3CH2NH2 molecules on the (110), (111), and (001) facets of the CdS core can determine which crystallographic facets are favored during the growth of the ZnS shell. The calculations provided insights into the effect of the interaction between the organic ligand and the facets of the CdS core on the shape engineering of CdS/ZnS core/shell NCs.

A facile strategy for designing a glutathione-capped Mn-doped CdS/ZnS/CdS core/shell/shell QD-based fluorescent nanosensor has been developed for rapid, selective, and ultrasensitive detection of Cu2+. In this nanosensor, glutathione provided the binding and recognition sites for Cu2+, accumulating Cu2+ on the QD surface. The energy transfer pathway from the host to the Mn dopant was sensitive to the interferences from non-radiative recombination pathways caused by Cu2+, resulting in photoluminescence quenching. The nanosensor responded to Cu2+ within one minute and exhibited good selectivity to Cu2+ over other metal ions and good linear correlation over the concentration range of 1 nM to 100 nM, with a detection limit as low as 0.74 nM. Moreover, this nanosensor avoids the self-quenching problem and autofluorescence in biosystems due to the substantial Stokes shift and long lifetime, and thus can be used to monitor Cu2+ in living cells.

Accurate and sensitive detection of palladium (Pd) is essential for both environmental and human health applications. This paper describes a triphenylphosphine (PPh3)-assisted highly sensitive fluorescent chemosensor for ratiometric detection of Pd2+ concentrations up to 300 nM with an LOD of 1 nM. During the detection, PPh3 plays a crucial role in improving the sensitivity of this chemosensor. The chemosensor also has suitable water-solubility which allows detection of Pd2+ in solution. Our studies show that it exhibits excellent selectivity toward Pd2+ and undergoes a color change from colorless to yellow to allow visual detection of Pd2+. Besides detection in solution, this chemosensor also shows great potential as an imaging reagent to detect Pd2+ as low as 0.03 ppm in diverse cells.

A fast-response, highly sensitive and selective fluorescent probe with the 2-(diphenylphosphino)benzoate moiety as a recognition receptor for the ratiometric imaging of nitroxyl in living cells was first developed.

Recently, growing attention has been paid to the accurate determination of hydrogen peroxide (H2O2) for elucidating its detailed biological function in physiology and pathology. A fluorescence method with the help of a fluorescent probe is the preferred technique for in situ visualization of biologically important species in vivo, even in single living cells. In the present manuscript, we developed a simple, fast response and highly selective fluorescent probe (1) with a receptor of the boronate moiety for the ratiometric imaging of H2O2 in living cells. Probe 1 could quantifiably detect H2O2 in the range of 18–540 μM by a ratiometric fluorescence spectroscopy method with a detection limit of 4 μM. Importantly, probe 1 exhibited 81 nm red-shifted absorption spectra accompanied by the color changes from colorless to yellow, and 100 nm red-shifted emission spectra upon addition of H2O2. Thus, 1 can serve as a “naked-eye” probe for H2O2. Preliminary bioimaging application and low cytotoxicity investigations further demonstrated that the proposed probe would be of great benefit to biomedical researchers for investigating the detailed biological function of H2O2 in biological systems.

The ratiometric fluorescence chemodosimeter N-butyl-4-(prop-1-en-1-yloxy)-1,8-naphthalic anhydride (NT-VE) was designed for Hg2+ recognition by oxymercuration at ambient temperature with high selectivity and no interference from other metal cations such as Cu2+, Ag+, Au3+, Fe3+, etc. The NT-VE could be incorporated into sodium dodecyl-benzenesulfonate (SDBS) micelles, which was confirmed by the clear emission enhancement observed in 0.1 mM SDBS. The hydrophobic core of the SDBS enhanced the solubility of NT-VE, enabling the detection of Hg2+ in aqueous solution, and the negatively charged micelle surface increased the local concentration of Hg2+ for amplified sensitivity. This work demonstrated the excellent performance of the NT-VE chemodosimeter for ratiometric detection of Hg2+ in aqueous solution. The NT-VE/SDBS system could detect Hg2+ over a linear range of 0.05–10 μM and a detection limit of 9 ppb (45 nM) in water.

The development of probes for specific bisulfite (HSO3−) detection is of great importance, due to its toxicity in the environment and important biological functions in living systems. In the present study, we developed a highly selective colorimetric and far-red fluorescent probe (1) for the determination of HSO3− in aqueous solution and living cells. The excellent properties of our proposed probe can be listed as follows. Firstly, probe 1 showed excellent selectivity for HSO3− over various other species including Cys, GSH, S2−, SO32−, and ROS, which might be ascribed to the introduction of a receptor of the electron-poor CC double bond for HSO3−. Secondly, our proposed probe possesses the higher molar absorption coefficient, and it can serve as a sensitive “naked-eye” probe for HSO3−. So, probe 1 would provide a convenient and promising method for the visual detection of HSO3− and the toxic gaseous SO2 in the environment. Thirdly, probe 1 has a long-wavelength emission spectrum at 643 nm, and thus it possesses many superiorities over short-wavelength ones in bioimaging. Finally, probe 1 exhibited excellent cell permeability and low cytotoxicity for the successful detection of HSO3− in living RAW 264.7 macrophage cells, implying that this probe would be of great benefit to biological researchers for investigating the detailed biological and pharmacological functions of HSO3− in biological systems.

Fluorescence properties of C60 nanoparticles produced by sonication in pyridine have been systematically investigated. The fluorescence emission of C60 is dependent on the particle size. A red shift of emission maximum from 424 to 468 nm originates from the average size increase caused by strong interaction among C60 molecules in nanoparticles. In addition, it is also confirmed that the emergence of broad fluorescence emission band in the 550–570 nm region is ascribed to C60 nanoparticles aggregation.Graphical abstractThe average size of C60 nanoparticles determines the position of fluorescence emission. A red shift of emission maximum from 424 to 468 nm occurs with the increase of the average size from tens of nanometers to hundreds of nanometers, clearly demonstrating the potential application of fluorescence spectroscopy in monitoring nanoparticles and aggregation of C60 in suspension.Highlights► The relationship between C60 NPS size and fluorescence emission was investigated. ► A red shift of emission maximum occurs with the increase of average size of C60 NPS. ► Aggregation of C60 NPS causes an emergence of yellow–green fluorescence emission.

Based on the nucleophilic aromatic substitution reaction mechanism, a new highly selective probe for cysteine (Cys), N-butyl-4-bromo-3-nitro-1,8-naphthalimide (1), was designed and synthesized. The probe displayed a remarkable (58 nm) red-shift in the absorption spectra and the color changes from colorless to yellow upon reaction with Cys. The probe could detect Cys quantitatively in the range of 0–0.9 mM by both normal and ratiometric absorption spectrometry methods. Moreover, 1 could also serve as a “naked-eye” probe for Cys with a minimum detectable concentration of approximately 50 μM.Highlights► We have reported a highly selective colorimetric cysteine probe. ► The probe was based on the nucleophilic aromatic substitution reaction mechanism. ► It could be used for the ratiometric quantification of cysteine. ► It’s working range covering the physiological level of cysteine in normal organisms. ► It also could be used as a “naked-eye” probe for the detection of cysteine.

A highly selective, visible-light-excited and OFF–ON fluorescent chemodosimeter 1 employed conjugate addition/cyclization sequence mechanism, was designed and synthesized to discriminatively detect cysteine (Cys) and homocysteine (Hcy). The addition of Cys and Hcy resulted in the color of the solution of 1 changing from colorless to green under the simulation of physiological condition, and 1 could serve as a “naked-eye” indicator. Our chemodosimeter can detect Cys and Hcy quantitatively by fluorescence spectrometry method with a detection limit of 0.5 μM (for Cys) and 0.8 μM (for Hcy). To the best of our knowledge, 1 is the first visual and visible-light-excited fluorescent indicator for discriminative and simultaneous detection of Cys and Hcy. Furthermore, the mechanism of the reaction between 1 and Cys was confirmed using ESI-MS and fluorescence spectra.Graphical abstractHighlights► A probe was developed to discriminatively and simultaneously detect Cys and Hcy. ► Cys and Hcy resulted in the color of 1 changing from colorless to green. ► The addition of Cys or Hcy leads to the remarkable fluorescence enhancement.

An aptamer–molecular beacon (MB) multiple fluorescent probe for adenosine triphosphate (ATP) assay is proposed in this article. The ATP aptamer was used as a molecular recognition part, and an oligonucleotide (short strand, SS) partially complementary with the aptamer and an MB was used as the other part. In the presence of ATP, the aptamer bound with it, accompanied by the hybridization of MB and SS and the fluorescence recovering. Wherever there is only very weak fluorescence can be measured in the absence of ATP. Based on the relationship of recovering fluorescence and the concentration of ATP, a method for quantifying ATP has been developed. The fluorescence intensity was proportional to the concentration of ATP in the range of 10 to 500 nM with a detection limit of 0.1 nM. Moreover, this method was able to detect ATP with high selectivity in the presence of guanosine triphosphate (GTP), cytidine triphosphate (CTP), and uridine triphosphate (UTP). This method is proved to be simple with high sensitivity, selectivity, and specificity.

We report on the synthesis of shape-controlled ZnS nanocrystals (NCs) through a facile and green phosphine-free one-pot method. Rod-, dot-shaped, and quasi-cubic ZnS NCs were prepared using oleylamine as coordinating solvent, zinc stearate as Zn precursor and sulfur powder, thiourea, and dodecanethiol as S precursors, respectively. Transmission electron microscopy (TEM) studies showed that S source played an important role in synthetic process. When thiourea and dodecanethiol took place of sulfur powder, no nanorods but dot-shaped and quasi-cubic ZnS NCs were formed. Moreover, the obtained different morphologies of ZnS NCs exhibit good optical properties and hold promise for future applications in nanodevices, biomarkers, and so on.Graphical abstractHighlights► We described a phosphine-free recipe for synthesizing ZnS NCs. ► ZnS NCs have three different morphologies. ► This wide variation of shapes is helpful in other shape-controlled synthesis. ► ZnS NCs exhibit good optical properties. ► ZnS NCs hold promise for future applications in nanodevices.

Ni/Au and Ni/Ag hybrid magnetic nanoparticles have been prepared via a facile solution growth method, in which 1-hexadecylamine is used and can function as both reducing agent and stabilizer during the synthetic process. By reduction of Au3+ or Ag+ in the reaction system, the reduced Au or Ag nanoparticles can adhere on the surface of Ni nanoparticles to form uniform hybrid structures after Ni nanoparticles were formed. From the surface-enhanced Raman scattering (SERS) spectrum of rhodamine 6G that obtained on the Ni/Au, Ni/Ag nanoparticles modified substrates; it is believed that the as-synthesized Ni/Au and Ni/Ag hybrid magnetic nanoparticles have great potential for high sensitive optical detection application.Graphical abstractNearly monodispersed Ni/Au and Ni/Ag nanoparticles were prepared by a facile organic solution growth method. The as-synthesized hybrid magnetic Ni/Au and Ni/Ag nanoparticles exhibited good SERS activity.Highlights► Uniform Ni/Au and Ni/Ag hybrid magnetic nanoparticles were synthesized. ► 1-Hexadecylamine was used as reducing agent and stabilizer in the synthetic process. ► The Ni core can induce the reduction of Au3+, Ag+ on its surface. ► The as-synthesized hybrid magnetic nanoparticles could be used as SERS substrates. ► The magnetism of as-synthesized samples plays an important role in SERS detection.

A highly selective ratiometric fluorescent chemodosimeter derived from 4-hydroxynaphthalimide was designed and synthesized to image palladium species in living cells by virtue of a palladium-catalyzed depropargylation reaction, and it could monitor three typical palladium species (0, + 2 and + 4) without additional reagents.

A simple but highly selective colorimetric and ratiometric fluorescent chemodosimeter was designed and synthesized to detect fluoride ions (F−) in aqueous solution and living cells by virtue of the strong affinity of F− toward silicon.

Water-soluble CdSe quantum dots (QDs) were synthesized using mercaptosuccinic acid (MSA) as a stabilizer. The growth process and characterization of CdSe quantum dots were determined by transmission electron microscopy (TEM), X-ray diffraction (XRD), photoluminescence (PL) spectroscopy, Ultraviolet–visible (UV–vis) spectroscopy, and Fourier transform infrared (FT-IR) spectroscopy. Results demonstrated the MSA-capped CdSe QDs were highly crystalline and possessed good optical properties. Further, the resulting products could be used as fluorescent probes to detect Cu2+ ions in physiological buffer solution. The response was linearly proportional to the concentration of Cu2+ ion in the range 2×10−8– 3.5×10−7 mol L−1 with a detection limit of 3.4 nmol L−1.Research highlights► Synthesis of mercaptosuccinic acid (MSA) capped CdSe QDs with narrow emission spectra and its application in fluorescent probe design. ► The luminescence of CdSe QDs was found to respond sensitively to Cu2+. ► Based on the specific response of CdSe QDs toward Cu2+, a novel fluorescent probe for the determination of Cu2+ was developed.

Oleic acid (OA)-capped CdS nanoparticles (NPs) have been successfully synthesized via the direct reaction of Cd(CH2COO)2·2H2O with S powder in OA solvent at 230 °C under nitrogen flow, which was a kind of clean and air-stable solvent. The morphologies and structures of the as-synthesized CdS NPs are examined by transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), X-ray diffractometer (XRD), and Fourier transform infrared (FTIR) spectroscopy, and the typical Ostwald ripening growth mechanism is concluded. Moreover, the collected ultraviolet–visible (UV–vis) absorption spectroscopy and photoluminescence (PL) spectroscopy demonstrate good optical properties of CdS NPs.Highlights► One-pot method, which is suitable for large-scale preparation was developed to prepare CdS NPs. ► Oleic acid is first used as the single coordinating solvent and stabilizer to synthesize CdS NPs. ► UV–vis and PL spectroscopies demonstrate good optical properties of our CdS NPs.

Different alkylamine-capped Au nanoparticles (NPs) and nanowires (NWs) have been successfully prepared through a facile one-pot solution growth method. Alkylamines serve as reducing agents and stabilizers in the synthetic process. As the chain length of alkylamines has an effect on the diffusion rate of monomers, the sizes of NPs and the diameters of NWs can be adjusted by adding different alkylamines in the synthetic process. Surface-enhanced Raman scattering (SERS) spectra of rhodamine 6G (Rh 6G) are obtained on the Au NPs and NWs modified substrates, indicating that the as-synthesized Au nanostructures have great potential for high sensitive optical detection application.Graphical abstractThe sizes of Au nanoparticles and the diameters of Au nanowires can be controlled by using different alkylamines as reducing agents and stabilizers in the synthetic process.Highlights► Au nanoparticles were synthesized by using alkylamines as reducing agents and stabilizers. ► Au nanowires were synthesized by reducing HAuCl4·4H2O in a micellar structure formed by alkylamines and oleic acid. ► The sizes of Au nanoparticles and nanowires could be adjusted by changing the chain length of alkylamines in the synthetic process. ► The synthetic strategy was simple and the as-synthesized Au nanoparticles and nanowires could be used as substrates for SERS detection.

A naphthalene derivate containing piazselenole (NDP) has been developed as an example of colorimetric and ratiometric fluorescent probes for glutathione (GSH) at physiologically relevant concentration. Upon addition of GSH, the probe displayed a ratiometric fluorescent response with an enhancement of the ratios of emission intensities at 436 and 615 nm, accompanied with the solution color change from jacinth to colorlessness. The detection range is 0–80 mM with the detection limit of 0.178 mM. Moreover, the probe showed good selectivity and satisfying results in the determination of GSH. As the linear response range covers the concentration range of biological samples, the probe may have the potential to determine GSH directly in biological samples in the future.

1-Hexadecylamine (HDA)-capped Au and Ag nanoparticles (NPs) have been successfully prepared by a one-pot solution growth method. The HDA is used as both reducing agent and stabilizer in the synthetic process is favorable for investigating the capping mechanism of Au and Ag NPs’ surface. The growth process and characterization of Au and Ag NPs are determined by Ultraviolet–visible (UV–vis) spectroscopy, transmission electron microscopy (TEM), and X-ray diffraction (XRD). Experimental results demonstrate that the HDA-capped Au and Ag NPs are highly crystalline and have good optical properties. Furthermore, surface-enhanced Raman scattering (SERS) spectra of 2-thionaphthol are obtained on the Au and Ag NPs modified glass surface, respectively, indicating that the as-synthesized noble metal NPs have potentially high sensitive optical detection application.

We have developed a photoresponsive DNA-cross-linked hydrogel that can be photoregulated by two wavelengths with a reversible sol−gel conversion. This photoinduced conversion can be further untilized for precisely controllable encapsulation and release of multiple loads. Specifically, photosensitive azobenzene moieties are incorporated into DNA strands as cross-linkers, such that their hybridization to complementary DNAs (cDNAs) responds differently to different wavelengths of light. On the basis of the rheology variation of hydrogels, it is possible to utilize this material for storing and releasing molecules and nanoparticles. To prove the concept, three different materials―fluorescein, horseradish peroxidase, and gold nanoparticles―were encapsulated inside the gel at 450 nm and then released by photons at 350 nm. Further experiments were carried out to deliver the chemotherapy drug doxorubicin in a similar manner in vitro. Our results show a net release rate of 65% within 10 min, and the released drug maintained its therapeutic effect. This hydrogel system provides a promising platform for drug delivery in targeted therapy and in biotechnological applications.

CdS nanorods and CdSe nanocrystals were prepared via the one-pot synthesis approach in oleylamine (OLA) system. The OLA used in this process as both the solvent and stabilizer is favorable for probing capping mechanism and simplifying experimental steps. The growth process and characterization of cadmium chalcogenide nanocrystals were determined by X-ray diffraction (XRD), transmission electron microscopy (TEM), Ultraviolet–visible (UV–vis) spectroscopy and photoluminescence (PL) spectroscopy. Results demonstrated OLA-capped CdS nanorods and CdSe nanocrystals were highly crystalline and had good optical properties.

A disulfide linked naphthalimide dimer probe was designed for mercury ion (Hg2+) recognition in this work. The recognition was based on the strong affinity of mercury for sulfur. The experimental results revealed that the probe exhibited high selectivity and sensitivity toward Hg2+ in comparison to other metal ions via a turn-on and reversible response to Hg2+ in neutral buffer solution. More importantly, the probe demonstrated a linear response for Hg2+ over a concentration range from 0 to 150 μM with a detection limit of 0.38 μM, which is just the limit of the safe concentration for humans. Upon addition of 150 μM Hg2+, the enhancement of fluorescence reached a maximum (∼7-fold). The performances of the probe indicated that it could meet the selectivity requirements for biomedical and environmental application and also was sensitive enough to detect Hg2+ in environmental and biological samples.

A near-infrared light-responsive drug delivery platform based on Au–Ag nanorods (Au–Ag NRs) coated with DNA cross-linked polymeric shells was constructed. DNA complementarity has been applied to develop a polyacrylamide-based sol–gel transition system to encapsulate anticancer drugs into the gel scaffold. The Au–Ag NR-based nanogels can also be readily functionalized with targeting moieties, such as aptamers, for specific recognition of tumor cells. When exposed to NIR irradiation, the photothermal effect of the Au–Ag NRs leads to a rapid rise in the temperature of the surrounding gel, resulting in the fast release of the encapsulated payload with high controllability. In vitro study confirmed that aptamer-functionalized nanogels can be used as drug carriers for targeted drug delivery with remote control capability by NIR light with high spatial/temporal resolution.Keywords: DNA cross-linked; light-responsive; nanogels; nanorods; near-infrared; targeted drug delivery

A naphthalimide-based colorimetric fluorescent probe containing a disulfide group was designed and synthesized, which could detect the physiological level of GSH quantitatively by a ratiometric fluorescence method and was successfully applied to the imaging of thiols in living HeLa cells.

Pt counter electrodes (CEs) with different platinum loading have been prepared using chemical reduced method on flexible indium-doped tin oxide coated polyethylene naphthalate (ITO-PEN) for dye-sensitized solar cells (DSSCs). H2PtCl6·6H2O terpineol solutions were screen printed on the transparent ITO-PEN substrates. After drying, H2PtCl6 was reduced by treating it in NaBH4 solution followed by the hydrothermal treatment at 100 °C. The obtained Pt CEs with different Pt-loading (2.4–7.7 μg/cm2) were characterized by SEM, XPS, electrochemical impedance and transmission spectrum measurement. The Pt CEs show high catalytic activity, low charge transfer resistance (0.26–1.38 Ω cm2) and good light transmittance (about 70% at 400–800 nm). The light-to-electricity conversion efficiency of the flexible DSSC fabricated with the prepared Pt CE and the TiO2 photoanode prepared on Ti substrate by screen printing technique attains 5.41% under the simulated AM 1.5 sunlight, which is almost same as that based on the thermal decomposited Pt CE on FTO-glass. Compared with other methods to prepare Pt CEs, chemical reduced method is simple and suitable for flexible polymer substrates and the large scale preparation of DSSCs.

A pyridylvinylene derivative containing piazselenole displayed high selectivity toward glutathione in the presence of other biorelevant analytes. The compound exhibited a 19 nm red-shift in absorption spectra and ∼3-fold fluorescence intensity enhancement; in addition, it was possible to detect micromolar amounts of glutathione quantitatively using both red-shift absorbance and enhanced fluorescence. The mechanism of the reaction between the modified pyridylvinylene derivative and glutathione was confirmed using ESI-MS and absorption/fluorescence spectra.

We report a simple one-pot route to fabricate PbSe hollow single-crystalline nanoboxes with the presence of trioctylphosphine as the structure-directing agent and stabilizer. Various controlling parameters were examined, such as trioctylphosphine amounts, reaction temperature, reaction time, and lead(II) precursors. On the basis of the experimental results, the gas bubbles assisted Ostwald ripening process was proposed to explain the formation of hollow PbSe nanoboxes. The morphology and composition of the products were characterized by X-ray diffraction, field-emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, and transmission electron microscopy.

A highly selective ratiometric fluorescent probe, which contains an aminonaphthalimide fluorophore and a self-immolative spacer for 1,4-dithiothreitol (DTT) detection was designed and synthesized. The probe displays a 66 nm red-shift of fluorescence emission and the color changes from colorless to jade-green upon reaction with DTT. These properties are mechanistically ascribed to the strong reducing capability of DTT.

A novel low temperature method was used to prepare the mesoporous carbon (MC) counter electrode (CE) on indium-doped tin oxide coated polyethylene naphthalate (ITO-PEN) for flexible dye-sensitized solar cells (DSSCs). The obtained flexible MC CEs with carbon loading of 280 μg cm−2 were characterized by SEM, XRD and electrochemical impedance. The light-to-electricity conversion efficiency of the DSSC fabricated with the prepared flexible MC CE was 86% of that of DSSC based on the decomposited Pt CE.

The hybrid CdS–Au2S–Au dendritic nanocrystals were synthesized in toluene solution at 70 °C. UV–vis and photoluminescence (PL) spectra recorded the optical properties of hybrid nanostructures, which showed an obvious blue shift relative to the absorption peak of CdS dendritic nanocrystals. The initial CdS dendritic nanocrystals exhibited band gap and trap state emission, both of which were quenched by Au parts. Analysis of the hybrid nanostructures by XRD shows the presence of appreciable amounts of Au2S, indicating that the chemical process involving cation exchanges between Au+ ions and Cd2+ ions was found.

We report experimental results on the reaction temperature dependence of luminescence properties in size-controlled CdSe nanocrystals. Such reaction temperature dependent property is also sizedependent. The diameter of the CdSe nanocrystals is tuned from 4–11.0 nm by varying the reaction temperatures. The growth process and characterization of CdSe nanocrystals are determined by photoluminescence (PL) spectroscopy, ultraviolet-visible (UV-Vis) spectroscopy, X-ray photoelectron spectrometry (XPS), X-ray powder diffraction (XRD), transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM). The influence of reaction conditions on the growth of CdSe nanocrystals demonstrates that low reaction temperature is favourable for the formation of high quality CdSe nanocrystals.

Thiorhodamine-based chemodosimeter A, a disulfide linked dimer, was designed for Hg2+ recognition by virtue of the strong affinity of mercury for sulfur. Spectroscopic results reveal that chemodosimeter A exhibits real-time responses, and high sensitivity and selectivity for Hg2+ in comparison to other cations. These properties are mechanistically ascribed to the transfer from rhodamine spirolactam to the thiazoline-derived open-ring rhodamineviaHg2+ induced desulfurization. The in vitro recognition of Hg2+ in living cells pretreated with A was examined, showing that the concentration of Hg2+ that could be imaged reaches the safety limit for human beings.

Triocytlphosphine (TOP)-capped CdSe nanoparticles (NPs) have been successfully prepared by the one-pot solution growth method at 240 °C under argon atmosphere. In particular, The TOP used in this process as the single coordinating solvent is favorable for probing capping mechanism of CdSe NPs surface. The growth process and characterization of CdSe NPs were determined by photoluminescence (PL) spectroscopy, X-ray diffraction (XRD), Transmission electron microscopy (TEM), Ultraviolet-visible (UV-Vis) spectroscopy and Fourier transform infrared spectroscopy (FTIR). Results demonstrated the TOP-capped CdSe NPs to be well dispersed and uniform in shape and the diameter of the particle was confined within 8 nm. PL measurement showed the near band-edge luminescence of the final product.

High quality CdS nanorods are synthesized reproducibly with cadmium acetate and sulfur as precursors in trioctylphosphine solution. The morphology, crystalline form and phase composition of CdS nanorods are characterized by transmission electron microscopy (TEM), high-resolution TEM and X-ray diffraction (XRD). CdS nanorods obtained are uniform with an aspect ratio of about 5:1 and in a wurtzite structure. The influence of reaction conditions on the growth of CdS nanorods demonstrates that low precursor concentration and high reaction temperature (260 °C) are favorable for the formation of uniform CdS nanorods with 85.3% of product yield.

A highly selective ratiometric fluorescent probe, which contains an aminonaphthalimide fluorophore and a self-immolative spacer for 1,4-dithiothreitol (DTT) detection was designed and synthesized. The probe displays a 66 nm red-shift of fluorescence emission and the color changes from colorless to jade-green upon reaction with DTT. These properties are mechanistically ascribed to the strong reducing capability of DTT.

The development of techniques for detecting HOCl at the subcellular level is very important to elucidate its cellular functions. Due to its relatively low concentration, it is still a great challenge to specifically track the basal HOCl in normal cells. In this paper, based on the unique chlorination of HOCl by the initiation of chlorinium ions (Cl+) in an acidic medium, we have developed a simple pH-mediated lysosome-targetable fluorescent probe Lyso-HOCl for the specific detection of HOCl over other bioactive molecules at higher concentration (500 μM). Our results show that Lyso-HOCl possesses a detection limit of 8.0 pM, and can quantitatively detect HOCl at the picomolar level. The ultrasensitive and ultrafast response property of probe Lyso-HOCl offers a good opportunity to monitor the basal HOCl and the fluctuation of endogenous HOCl levels in the lysosomes of macrophages (Raw 264.7 cells), and we thus anticipate that this probe would provide a promising tool for further unraveling the biological functions of HOCl in subcellular lysosomes.

Development of selective fluorescent probes for rapid and ultrasensitive detection of nitroxyl (HNO) is of great importance for biomedical researchers to investigate the detailed functions and mechanisms of HNO in living systems. Herein, based on an internal charge transfer (ICT) mechanism, we developed a novel ratiometric, colorimetric and far-red fluorescent probe (HNO-TCF) for the rapid and ultrasensitive detection of HNO in living cells. HNO-TCF exhibits high HNO-selectivity even in the presence of a high concentration of biological reductants including glutathione (GSH), hydrogen sulfide (H2S) and ascorbate (AA), which might be ascribed to the adoption of the 2-(diphenylphosphino)benzoate recognition moiety. The ICT-based fluorescent probe HNO-TCF displays a large (185 nm) red-shifted absorption spectrum and the color changes from yellow to blue upon addition of HNO. In addition, the results showed that HNO-TCF could quantitatively detect HNO in the range of 0 to 4 μM with a detection limit of 10 nM by ratiometric absorption and fluorescence spectrometry methods. Importantly, HNO-TCF was successfully applied to the fluorescence imaging of HNO levels in living cells, and it is expected to be a useful chemical tool for investigating the detailed functions and mechanisms of HNO in living systems.

A naphthalimide-based colorimetric fluorescent probe containing a disulfide group was designed and synthesized, which could detect the physiological level of GSH quantitatively by a ratiometric fluorescence method and was successfully applied to the imaging of thiols in living HeLa cells.

Thiorhodamine-based chemodosimeter A, a disulfide linked dimer, was designed for Hg2+ recognition by virtue of the strong affinity of mercury for sulfur. Spectroscopic results reveal that chemodosimeter A exhibits real-time responses, and high sensitivity and selectivity for Hg2+ in comparison to other cations. These properties are mechanistically ascribed to the transfer from rhodamine spirolactam to the thiazoline-derived open-ring rhodamineviaHg2+ induced desulfurization. The in vitro recognition of Hg2+ in living cells pretreated with A was examined, showing that the concentration of Hg2+ that could be imaged reaches the safety limit for human beings.

A simple but highly selective colorimetric and ratiometric fluorescent chemodosimeter was designed and synthesized to detect fluoride ions (F−) in aqueous solution and living cells by virtue of the strong affinity of F− toward silicon.

A highly selective ratiometric fluorescent chemodosimeter derived from 4-hydroxynaphthalimide was designed and synthesized to image palladium species in living cells by virtue of a palladium-catalyzed depropargylation reaction, and it could monitor three typical palladium species (0, + 2 and + 4) without additional reagents.

A fast-response, highly sensitive and selective fluorescent probe with the 2-(diphenylphosphino)benzoate moiety as a recognition receptor for the ratiometric imaging of nitroxyl in living cells was first developed.

Changes in intracellular glutathione (GSH) concentration are closely linked with various cellular physiological and pathological mechanisms. In the present work, four long-wavelength Si-pyronine (SiP) fluorescent dyes are readily synthesized via a UV-assisted aromatization reaction, and used for real-time, dynamic and reversible monitoring of GSH changes in vitro and in living cells. Based on the mechanism that Si atom incorporation greatly increases the pyronine affinity towards sulfhydryl (–SH), SiPs can undergo ultrafast and reversible Michael addition with biological thiols, leading to fluctuations in fluorescence intensity due to the interruption and restoration of their π-conjugation. Relying on the unique reactivity of SiPs with GSH under physiological conditions, the fluorescence intensity of SiPs responds to GSH changes with high sensitivity. SiPs also exhibit excellent photophysical properties including deep-red to near-infrared excitation wavelength (>600 nm), a high fluorescence efficiency (0.20–0.41) in aqueous media, suitable water-solubility and membrane permeability. Using SiP-Pr to incubate with HeLa cells, we achieved real-time, dynamic and repeated imaging of fluctuations in intracellular GSH homeostasis under N-ethylmaleimide stimulation.

Hypochlorite plays a significant role in various physiological and pathological processes; however, its role is still less clear than the role of other reactive oxygen species. Herein, we report an ultrafast responsive (<0.2 s) and highly selective probe B-Ts for hypochlorite with high sensitivity and a detection limit as low as 7.5 nM. The probe was compatible in a wide pH range of 4–13. More importantly, experiments in live cells showed that the probe could penetrate the cell membrane easily and was capable of imaging endogenous and exogenous hypochlorite specifically with a fast response.

Hypochlorite plays a significant role in various physiological and pathological processes; however, its role is still less clear than the role of other reactive oxygen species. Herein, we report an ultrafast responsive (<0.2 s) and highly selective probe B-Ts for hypochlorite with high sensitivity and a detection limit as low as 7.5 nM. The probe was compatible in a wide pH range of 4–13. More importantly, experiments in live cells showed that the probe could penetrate the cell membrane easily and was capable of imaging endogenous and exogenous hypochlorite specifically with a fast response.