BiOCl with {010} facets could be a promising material for photodegradation and energy conversion devices such as dye self-photosensitization photocatalytic fuel cells (DSPFCs). However, the {010} facets usually diminish rapidly during the growth process as the result of its high surface energies. In this work, we reported a simple and efficient method to prepare BiOCl with tunable exposed {010} facets. It was found that the solvent used in the synthesis process had important roles in the formation of ultrathin construction and the growth of {010} facets by controlling the [H+]. For decreasing the surface energy and promoting the growth of high-active {010} facets, the thickness of BiOCl and the areas of {001} were reduced in its forming process. We had demonstrated that the enhancement of visible light-harvesting and photosensitization activity of BiOCl was primarily attributed to the decrease of thickness and the growth of {010} facets which could provide large surface areas and more active sites for dye absorption and photoelectron transfer. The BiOCl samples with tunable exposed {010} areas were evaluated as photoanode materials in DSPFCs. As expected, owing to its strong dye absorption capability and high transfer efficiency of charge carriers, the DSPFC with optimal performance was obtained by employing RhB as fuel when BiOCl possessed the larger areas of {010} facets and became a thinner nanosheet structure. Also, the Jsc and Voc of DSPFC were measured to be 0.0058 mA/cm2 and 0.689 V, respectively. Meanwhile, approximately 67% color removal was achieved on BiOCl{010}-Pt cell by treating 40 mL of 5 mg/L RhB under visible light for 240 min, which was much higher than that of P25-Pt (4%).Keywords: BiOCl{010}; DSPFCs; large surface area; low [H+]; visible light;

Visible-light-sensitive Ag/AgCl/SrTiO3 photocatalysts have been successfully assembled through the precipitation reaction between AgNO3 and NaCl at ambient temperature, wherein Ag/AgCl nanoparticles were immobilized on the surface of SrTiO3. The composition, crystallinity, morphologies and optical properties of the as-prepared photocatalysts were sufficiently studied via various characterization techniques. In this paper, rhodamine B (RhB), methyl orange (MO), methylene blue (MB), phenol and bisphenol A (BPA) solutions were photodegraded as target pollutants under visible light irradiation to evaluate the photocatalytic performances of the obtained products. In contrast with the pristine SrTiO3 and Ag/AgCl nanoparticles, the composite photocatalysts presented dramatically boosted visible-light photocatalytic performance in terms of decomposing organic pollutants. It was observed that the Ag/AgCl/SrTiO3 (21.6%) composite possessed the best photocatalytic performance and maintained favorable stability during the consecutive cycling experiment. The improved photocatalytic performance of the catalysts resulted from the surface plasmon resonance effect of Ag/AgCl nanoparticles, as well as exceptional separation efficiency of photogenerated electrons and holes. Meanwhile, a reasonable reaction mechanism on the Ag/AgCl/SrTiO3 (21.6%) composite photocatalysts was brought up upon band energy analysis and a trapping experiment.

•Novel SrTiO3/BiOI heterojunction photocatalysts were fabricated.•A wider application in the degradation of refractory pollutants.•The factors affecting the photocatalytic performance were investigated.•The degradation process of MO and OTTCH was monitor by 3D EEMs.•The in-depth mechanisms insight of charge separation.Novel SrTiO3/BiOI heterostructure photocatalysts were successfully fabricated through a facile chemical bath method with assistant of the ethylene glycol. The photocatalysts were applied to minimize methyl orange (MO), bisphenol A (BPA), antibiotic oxytetracycline hydrochloride (OTTCH) under visible light irradiation. The SrTiO3/BiOI composites exhibited excellent photocatalytic performance towards the different refractory pollutants. Especially, the sample of STB-22.12 possessed the best photocatalytic performance in all the obtained catalysts. Several reaction parameters affecting degradation such as initial concentration, ion species were investigated systematically. Three-dimensional excitation–emission matrix fluorescence spectroscopy (3D EEMs) was used to further investigate the MO and OTTCH molecule degradation process. The photocatalytic mechanism over composite photocatalyst is systematically investigated by active species trapping experiments, ESR technique and Mott–Schottky measurements. Moreover, the energy band alignments of SrTiO3/BiOI heterostructure were confirmed via combining DRS and XPS analysis, which provided strong support for the proposed mechanism. This work could provide a deeper insight for the heterojunction catalyst.SrTiO3/BiOI heterostructure photocatalysts were successfully fabricated through a facile chemical bath method with assistant of the ethylene glycol, which exhibit an efficient charge separation and excellent catalytic ability in removing different refractory pollutants.Download high-res image (70KB)Download full-size image

This paper describes a label-free 17E DNAzyme-based time-gated fluorescence sensor for Pb2+ detection by unmodified gold nanoparticles (GNPs) and a terbium ternary complex. The fluorophore that used in this paper is a terbium ternary complex. Its signal can be measured in a time-gated manner which could eliminate most of the unspecific fluorescent background. It is well known that unfolded single-stranded DNA (ssDNA) could be adsorbed on GNPs while double-stranded DNA could not. The cleavage of the substrate by the 17E DNAzyme in the presence of Pb2+ causes the release of ssDNA from the 17E-17S duplex to be absorbed onto GNPs, preventing the aggregation of GNPs and then leading to a fluorescence decrease of terbium ternary complex. By means of this method, the authors have successfully detected Pb2+ over a range of 10 nM to 2500 nM with a detection limit of 1.7 nM. The sensor also exhibited good selectivity. The sensor provided a simple, cost-effective, rapid and sensitive measurement tool for Pb2+ detection.

A high-efficiency nanocube-like composite, Ag@AgCl/CaSn(OH)6 (Ag@AgCl/CSH), was successfully synthesized via an ultrasonic-assisted deposition-photoreduction method. The as-synthesized samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), elemental mapping, transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), UV-vis diffuse reflectance spectroscopy (DRS), X-ray photoelectron spectroscopy (XPS), energy dispersive spectroscopy (EDS), BET analysis, photoluminescence emission spectroscopy (PL), and photocurrent (PC) methods. Photodegradation experiments for the decomposition of single dye, multiple dyes, and colorless organic pollutants, such as tetracycline (TC) and bisphenol A propane (BPA), were carried out under visible-light irradiation. Among the as-synthesized samples, the Ag@AgCl(20.5 wt%)/CSH composite exhibited optimal photocatalytic activities. The experimental conditions, including solar light and water source, were also considered to study their effects on photodegradation. The trapping experiment was carried out to clarify the possible mechanism of enhanced photocatalytic performance, which could be attributed to surface plasmon resonance (SPR) effects via the introduction of Ag@AgCl nanoparticles. After five recycling experiments, highly efficient photocatalytic activity was still maintained, demonstrating that the as-synthesized composite possessed excellent reusability and stability. It can be anticipated that the Ag@AgCl/CSH composite will have great potential in real applications such as in the treatment of wastewater.

Recently, visible-light-driven photocatalysts have been widely used in environmental pollutant remediation. In the present study, BiOI/CeO2 p–n junction photocatalysts were successfully fabricated using a facile in situ chemical bath method. The BiOI/CeO2 p–n junction photocatalysts exhibited excellent photoactivity for the decomposition of the refractory pollutant bisphenol A (BPA) and methylene orange (MO) under visible light illumination. The sample with a 1 : 1 mole ratio of BiOI : CeO2 possessed the highest photocatalytic performance out of all of the as-obtained catalysts. Mott–Schottky plots indicated that p–n junctions were successfully constructed between BiOI and CeO2. The optical and electrical properties of the materials demonstrate that the introduction of BiOI can broaden the visible-light absorption region of CeO2, and the transfer rate of the electron–hole pairs dramatically improves through forming a p–n junction. Furthermore, the BPA degradation efficiency exhibited excellent photostability after four consecutive cycles. These features show that the BiOI/CeO2 p–n junction has great application potential for refractory pollutant removal from wastewater.

Highly efficient BiOI/Bi2MoO6 photocatalysts were successfully synthesized by a facile and economical deposition-precipitation method at lower temperature, and characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), energy dispersive X-ray (EDX) and UV–vis diffuse reflectance spectroscopy (DRS). The photocatalytic performance of BiOI/Bi2MoO6 was examined and evaluated by the decomposition of methyl orange (MO) and phenol under visible-light irradiation. The as-prepared BiOI/Bi2MoO6 composites exhibited much superior photocatalytic activities than pure BiOI and Bi2MoO6 in the photodegradation of the target organic pollutants. The synergistic effects were found to lead to an improved photo-generated carrier separation. Additionally, on the basis of trapping experimental results and band structure analysis, a possible photodegradation mechanism was proposed to elucidate the photocatalytic process and the reuse experiments were employed to confirm the durability and stability of the catalysts.

A novel ternary composite AgI/Ag/Bi2MoO6 photocatalyst was successfully synthesized by a facile hydrothermal method combined with an ultrasonic-assisted precipitation-photoreduction technique. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV-vis diffuse reflectance spectroscopy (DRS) and photoluminescence emission spectra (PL) analysis were employed to characterize the composition, phase structures, crystallinity, morphologies and optical properties of the obtained catalysts. The experimental results indicated that the AgI/Ag/Bi2MoO6 (15.0%) composite display higher visible light photoactivity for organic pollutants degradation compared with pure Bi2MoO6 and Ag/AgI nanocrystals. On the basis of band structure analysis and active species trapping experimental results, the excellent photocatalytic performance of the AgI/Ag/Bi2MoO6 photocatalysts can be ascribed to the efficient electron transfer and lower recombination of photogenerated electron–hole pairs through the Z-scheme system. And the Ag nanoparticles act as the charge transmission bridge in the process. The physicochemical features and high degradation efficiencies were maintained after five cycling experiment, indicating that the samples exhibited good durability and stability. It is expected that the novel AgI/Ag/Bi2MoO6 hybrid is a promising candidate material for the environmental applications.

BiOIO3/BiOBr composite photocatalysts were successfully fabricated through a hydrothermal and subsequent chemical precipitation method. The as-prepared samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), UV-vis diffuse reflectance spectroscopy (UV-vis DRS), Brunauer–Emmett–Teller (BET) surface area, photoluminescence (PL) and photocurrents to investigate the structures, crystallinity, morphology and optical properties. Compared with pure BiOIO3 and BiOBr, BiOIO3/BiOBr composites exhibited significantly enhanced visible light photocatalytic activity towards the degradation of organic dyes. Specifically, the 1I/6Br composite was found to show the maximum value of the activity and maintained good stability in the recycling process. The enhanced photocatalytic activity could be attributed to the formation of a p–n heterojunction between BiOIO3 and BiOBr, which resulted in the effective separation and transfer of photogenerated electron–hole pairs. Moreover, the active species trapping experiment confirmed that ˙O2− and h+ were the main active species during the photocatalytic process.

Novel α-Fe2O3/BiOBr composites were synthesized by a simple in hydrolysis method for the first time, and were fully characterized by X-ray diffraction patterns (XRD), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM) and UV-vis diffuse reflectance spectra (DRS). The α-Fe2O3/BiOBr composite showed much higher visible-light-driven (VLD) photocatalytic activity than pure α-Fe2O3 and BiOBr for rhodamine B (RhB) degradation. Specifically, the 10Fe/100Bi composite showed the highest photocatalytic activity for the degradation of dyes under visible light irradiation. The stability of the photocatalyst is found to be satisfying, which gives it potential in practical applications. The high photocatalytic activity could be attributed to the enhanced light absorption and the improved separation of photogenerated charge carriers, due to the formation of a p–n heterojunction between α-Fe2O3 and BiOBr.

A novel visible-light-driven photocatalyst Ag/AgCl/CaTiO3 was successfully synthesized via a simple ultrasonic assisted precipitation–photoreduction process. The morphologies, phase structures as well as optical properties of the as-prepared samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), ultraviolet-visible diffuse reflectance spectroscopy (UV-vis DRS), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), Raman spectra and photoluminescence emission spectra (PL). The photocatalytic activity of Ag/AgCl/CaTiO3 was examined by the photodegradation of rhodamine B (RhB) under visible-light irradiation. Experimental results showed that the composites exhibited higher photocatalytic activity than pure CaTiO3 and Ag/AgCl. Among them, the Ag/AgCl-5/CaTiO3 composite exhibited the optimal photocatalytic activity. The enhanced photocatalytic activity of the Ag/AgCl/CaTiO3 photocatalyst was attributed predominantly to the synergetic effect between the Ag/AgCl nanoparticles and the fern-like CaTiO3 nanoparticles, which was superior for the separation of photogenerated electrons and holes. Based on the band structure analysis and trapping experimental results, a possible photocatalytic mechanism for Ag/AgCl/CaTiO3 was put forward.

•A “turn-on” and highly sensitive fluorescent method for Hg2+ was developed.•Hybridization chain reactions improved the sensitivity of this method.•Separating report probes from matrix is benefit to decrease the background signal.•Display the advantages of high sensitivity (LOD: 0.36 nM) and good selectivity.•Applied successfully to the determination of Hg2+ in environmental water samples.In this manuscript, the authors molecularly engineered a hybridization chain reactions (HCRs) based probe on magnetic Fe3O4 nanoparticles for the sensitive detection of Hg2+. The sensing system comprised three probes: capture probe H1, report probe H2, and report probe H3. The capture probe was modified on the surface of magnetic Fe3O4 nanoparticles. The report probes were labeled with fluorescein isothiocyanate (FITC). Without Hg2+, the report probes were stable as molecular beacons in solution. In the presence of Hg2+, the T-rich capture probes and report probes will hybridize into double-helical DNA domains with the aid of T–Hg2+–T coordination chemistry. Trigged by this reaction, more molecular beacons open and form a super tandem structure. Herein, the fluorescence signal was magnified by capturing more report probes. Separating the target and captured report probes from reaction solution was benefit to decrease the background signal and interference from other metal ions. The detection limit of this method was about 0.36 nM, which is much lower than the regulations of World Health Organization and U.S. Environmental Protection Agency on Hg2+ in drink water. This proposed sensing strategy also showed favorable selectivity over other common metal ions. In addition, it has good practicability in real water samples.

This paper describes an internal reference fluorescent sensor for pH determination. The fluorescent carrier contained two pH-dependent fluorophores, 2-allyl-6-((2-aminoethyl)amino)-1H-benzo[de]isoquinoline-1,3(2H)-dione (AAEAN) and meso-5,10,15,20-tetra-(4-aminophenyl)porphyrin (TAPP), that were derived from naphthalimide derivatives and porphyrin derivatives respectively. The two fluorophores acted as reference fluorophores for each other. The fluorescent carrier was copolymerized with acrylamide, (2-hydroxyethyl)methacrylate and triethylene glycol dimethacrylate on the silanized glass surface for an internal reference pH sensor. The sensor showed satisfactory selectivity, reproducibility as well as sufficient stability and fast response time. It covered a broad dynamic range of pH value 1.00–9.50. The sensor provided an alternative concept to apply the fluorescence carrier with two fluorophores for the development of internal reference sensors covering a broad range of pH value. The synthesis of one fluorescent carrier, with two properly selected fluorophores paved the way to construct a series of internal reference sensors.

A novel composite Ag/AgCl/BiPO4 photocatalyst was successfully fabricated via a hydrothermal method combined with an ultrasonic-assisted precipitation–photoreduction technique. The phase structures, crystallinity, morphologies and optical properties of the as-prepared samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), UV-vis diffuse reflectance spectroscopy (UV-vis DRS), N2 absorption–desorption isotherms and photoluminescence (PL) spectroscopy. The experimental results showed that the Ag/AgCl species could efficiently improve the separation efficiency of photo-generated electron–hole pairs, and then improve the photodegradation efficiency. The Ag/AgCl/BiPO4 (15.4%) composite shows the highest photocatalytic activity for the degradation of dyes under visible light irradiation. In addition, a possible photocatalytic mechanism for Ag/AgCl/BiPO4 was proposed by a trapping experiment, which can be ascribed to the surface plasmon resonance (SPR) effect of Ag nanoparticles.

In this paper, the authors proposed an optical-fiber sensor based on time-gated fluorescence with high sensitivity for water content determination in organic solvents, and a type of europium ion fluorescent chelate (EIFC) with a long fluorescence lifetime was synthesized and used as the fluorescent indicator. Covalent immobilization was used to solve the problem caused by the leakage of fluorescent dye during the fabrication process of the proposed sensor. The EIFC was photo-copolymerized with 2-hydroxy-2-methyl-1-phenyl-1-propanone, triethylene glycol dimethacrylate, acrylamide, and (2-hydroxyethyl)methacrylate on a silanized glass slide, yielding the optode membrane. With increasing water content in the organic solvents, the time-gated fluorescence intensity of the optode membrane decreased obviously. The time-gated fluorescence intensity of the optode membrane changed as a linear function of the water content. For ethanol and acetonitrile this change was in the range of 0.20–10.0% (v/v), and for 1,4-dioxane it was in the range of 0.20–4.0% (v/v). The limits of detection were 0.031%, 0.016%, and 0.012% for ethanol, acetonitrile, and 1,4-dioxane, respectively. The optical-fiber sensor exhibited satisfactory reproducibility, reversibility, response times, and practicability. The lifetime of the prepared optode membrane was at least one month.

A flexible fluorescent probe for the determination of Fe(III) in aqueous solution was designed and synthesized by conjugating 4-aminoacetophenone into 9-anthraldehyde as a fluorophore. Its sensing behavior toward metal ions was investigated by fluorescence spectroscopy. The fluorescence intensity of the fluorescent probe decreased with the increasing concentration of Fe(III) when it was excited at λex/λem = 402/560 nm in water–ethanol (21.5/3.5, v/v) solutions at pH = 7.20. In addition, the calibration curve was linear in the concentration range of ca. 5 × 10−9 to 1 × 10−7 mol L−1. The prepared dye presented satisfactory sensitivity, and the detection limit could be as low as 3.04 × 10−10 mol L−1. The Fe(III)-selective quenching was insensitive to the presence of Cr(III), Cd(II), Cu(II), Co(II), Ni(II), Mn(II), Ba(II), Pb(II), Ca(II), Fe(II), Zn(II), Mg(II), and Al(III). The proposed method was successfully employed for preliminary application in natural water, domestic sewage, and human serum samples.

•Described a sensing strategy for Hg2+ detection using time-gated mode.•Employing long lifetime fluorescence Mn:CdS/ZnS QDs to reduce the background signals.•Employing Mn:CdS/ZnS QDs and GO as the energy transfer pairs.•Displays the advantages of high sensitivity (LOD: 0.11 nM) and excellent selectivity.•Applied successfully to the determination of Hg2+ in environmental water samples.In this paper, a sensitive time-gated fluorescent sensing strategy for mercury ions (Hg2+) monitoring is developed based on Hg2+-mediated thymine (T)–Hg2+–T structure and the mechanism of fluorescence resonance energy transfer from Mn-doped CdS/ZnS quantum dots to graphene oxide. The authors employ two T-rich single-stranded DNA (ssDNA) as the capture probes for Hg2+, and one of them is modified with Mn-doped CdS/ZnS quantum dots. The addition of Hg2+ makes the two T-rich ssDNA hybrids with each other to form stable T-Hg2+-T coordination chemistry, which makes Mn-doped CdS/ZnS quantum dots far away from the surface of graphene oxide. As a result, the fluorescence signal is increased obviously compared with that without Hg2+. The time-gated fluorescence intensities are linear with the concentrations of Hg2+ in the range from 0.20 to 10 nM with a limit of detection of 0.11 nM. The detection limit is much lower than the U.S. Environmental Protection Agency limit of the concentration of Hg2+ for drinking water. The time-gated fluorescent sensing strategy is specific for Hg2+ even with interference by other metal ions based on the results of selectivity experiments. Importantly, the proposed sensing strategy is applied successfully to the determination of Hg2+ in environmental water samples.

A fluorescent sensor for the determination of Ag+ by time-gated mode is proposed. The method is based on Ag+-induced formation of quantum dot/DNA/gold nanoparticle complexes. Two ssDNA strands (strand A and strand B) are designed which contain C–C mismatched base pairs that can specifically react with Ag+. The water-soluble long-lifetime fluorescence quantum dots (Mn:CdS/ZnS) functionalized with strand A are selected as the fluorophore. The gold nanoparticles (GNPs) which are labeled with strand B, acted as the quencher. When Ag+ is absent in the sample solution, DNA-modified GNPs and Mn:CdS/ZnS were in the freedom state, the fluorescence signal of Mn:CdS/ZnS is obviously strong. When Ag+ are present in the sample solution, a DNA duplex is formed because of the strong binding ability between Ag+ and cytosine bases and formed stable C–Ag+–C structures. As a result, the Mn:CdS/ZnS and the GNPs are brought into close proximity, which caused the fluorescence quenching of the Mn:CdS/ZnS due to the nanometal surface energy transfer (NSET) between the Mn:CdS/ZnS and GNPs. This fluorescent sensor could present a satisfactory specificity and selectivity for Ag+. Meanwhile, the detection limit of Ag+ was estimated to be 7.9 nM.

•Highly efficient Ag/AgCl/ZnWO4 photocatalyst was synthesized for the first time.•The catalyst showed great enhanced visible-light-driven photocatalytic activity.•A surface plasmon resonance mechanism was proposed.An efficient visible-light-driven Ag/AgCl/ZnWO4 photocatalyst was synthesized by a facile ultrasonic-assisted precipitation-photoreduction method. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray (EDX) and UV–vis diffuse reflectance spectroscopy (DRS) were employed to characterize the composition, morphology, structure, and optical property of the obtained catalysts. The results indicated that the as-prepared photocatalyst, formed by Ag/AgCl nanoparticles dispersed on the surface of ZnWO4 nanorods, demonstrated remarkable absorbance in the visible light region. The Ag/AgCl/ZnWO4 composite displays much superior visible light photocatalytic activity for methyl orange (MO) and methylene blue (MB) degradation compared with pure ZnWO4 and Ag/AgCl nanocrystals, as well as the conventional visible-light photocatalyst N-doped TiO2. On the basis of the active species trapping experimental results and band structure analysis, a photocatalytic mechanism is proposed. The predominantly enhanced performance can be ascribed to the surface plasmon resonance of Ag nanoparticles and the high separation efficiency of photogenerated electron–hole pairs. In addition, the sample of Ag/AgCl/ZnWO4 also exhibits good stability and durability due to it depicts high photocatalytic activity even after five cycles.

•A sensitive label-free method was designed for the direct detection of glucose.•p-phenylenediamine was used to improve the sensitivity.•This method has advantages of both high sensitivity and simple procedure.•The sensor can be applied directly to determine glucose in human serum.By introducing p-phenylenediamine (PPD) to the hybrid system of Mn-doped CdS/ZnS quantum dots (QDs) and glucose oxidase (GOD), a sensitive label-free method was proposed for direct detection of glucose. With glucose and PPD as substrates, 2,5-diamino-N,N′-di-(4-aminophenyl)-2,5-cyclohexadiene-1,4-diimine (DDACD) that intensively quenches the fluorescence of QDs can be produced by the catalysis of GOD. A detection limit as low as 3.2 μM was obtained with the high-efficient fluorescence quencher. Two linear ranges, from 5.0 μM to 1000 μM and from 1.0 mM to 10.0 mM, were identified between time-gated fluorescence intensity and the concentration of glucose. It is shown that the newly proposed methods have high selectivity for glucose over other saccharides and coexisting biological species in serum. The method can be used directly to determine glucose in normal adult human serum without any complicated sample pretreatments. The recovery rate and repeatability of the method were also shown to be satisfactory.

An ultrasensitive “turn-on” fluorescent sensor was presented for determination of Hg2+. This method is mainly based on Hg2+-induced conformational change of a thymine-rich single-stranded DNA. The water-soluble long-lifetime fluorescence quantum dot (Mn:CdS/ZnS) acted as the fluorophore, which was labeled on a 33-mer thymine-rich single-stranded DNA (strand A). The gold nanoparticles (GNPs) functionalized 10-mer single-stranded DNA (strand B) is selected as the quencher to quench the fluorescence of Mn:CdS/ZnS. Without Hg2+ in the sample solution, strands A and B could form hybrid structures, resulting in the fluorescence of Mn:CdS/ZnS being decreased sharply. When Hg2+ is present in the sample solution, Hg2+-mediated base pairs induced the folding of strand A into a hairpin structure, leading to the release of GNPs-tagged strand B from the hybrid structures. The fluorescence signal is then increased obviously compared with that without Hg2+. The sensor exhibits two linear response ranges between fluorescence intensity and Hg2+ concentration. Meanwhile, a detection limit of 0.18 nM is estimated based on 3α/slope. Selectivity experiments reveal that the fluorescent sensor is specific for Hg2+ even with interference by high concentrations of other metal ions. This sensor is successfully applied to determination of Hg2+ in tap water and lake water samples. This sensor offers additional advantage to efficiently reduce background noise using long-lifetime fluorescence quantum dots by a time-gated mode. With excellent sensitivity and selectivity, this sensor is potentially suitable for monitoring of Hg2+ in environmental applications.

The authors herein described a time-gated fluorescence resonance energy transfer (TGFRET) sensing strategy employing water-soluble long lifetime fluorescence quantum dots and gold nanoparticles to detect trace Hg2+ ions in aqueous solution. The water-soluble long lifetime fluorescence quantum dots and gold nanoparticles were functionalized by two complementary ssDNA, except for four deliberately designed T–T mismatches. The quantum dot acted as the energy-transfer donor, and the gold nanoparticle acted as the energy-transfer acceptor. When Hg2+ ions were present in the aqueous solution, DNA hybridization will occur because of the formation of T–Hg2+–T complexes. As a result, the quantum dots and gold nanoparticles are brought into close proximity, which made the energy transfer occur from quantum dots to gold nanoparticles, leading to the fluorescence intensity of quantum dots to decrease obviously. The decrement fluorescence intensity is proportional to the concentration of Hg2+ ions. Under the optimum conditions, the sensing system exhibits the same liner range from 1 × 10–9 to 1 × 10–8 M for Hg2+ ions, with the detection limits of 0.49 nM in buffer and 0.87 nM in tap water samples. This sensor was also used to detect Hg2+ ions from samples of tap water, river water, and lake water spiked with Hg2+ ions, and the results showed good agreement with the found values determined by an atomic fluorescence spectrometer. In comparison to some reported colorimetric and fluorescent sensors, the proposed method displays the advantage of higher sensitivity. The TGFRET sensor also exhibits excellent selectivity and can provide promising potential for Hg2+ ion detection.

Gold nanoparticles (GNPs) can effectively differentiate the unfolded and folded aptamer, and quench the fluorescence of terbium ternary complexes (Tb-complexes), thus the authors herein report a sensitive strategy for protein detection, using label-free aptamer, Tb-complexes and GNPs. In the presence of thrombin, the aptamer is inclined to form G-quartet, and the folded aptamer cannot adsorb on the surface of GNPs, inducing the GNPs aggregation in the presence of 0.5 mol L−1 salt. After centrifugation at low speed to remove the aggregated GNPs, the quenching capability of the supernatant for Tb-complexes is decreased. The fluorescence intensity of Tb-complexes increases as the concentration of thrombin increases. Due to the highly specific recognition ability of the aptamer for thrombin and the strong quenching property of GNPs for Tb-complexes, the proposed protocol has good selectivity and high sensitivity for thrombin. Under the optimum conditions, a linear range from 1.0 × 10−9 M to 1.0 × 10−8 M is obtained with a detection limit of 0.14 nM, which is much lower than those commonly obtained for colorimetric sensors and some fluorescent sensors. The signal of Tb-complexes can be measured by time-resolved manner which made most of the unspecific fluorescent background signals be eliminated. The proposed sensor has been successfully applied in complicated biological samples for thrombin detection, and it can provide a promising potential for label-free aptamer-based protein detection.

In the present paper, the K2S2O8–Fe2+ system without pH adjustment was used as a cathodic reactant in a two-chamber microbial fuel cell (MFC) for the first time. The performance of the MFC with K2S2O8–Fe2+ system was discussed and compared with that of K2S2O8 and H2O2–Fe2+ system, respectively. These results demonstrated that the introduced ferrous ion could improve the power generation significantly. The initial K2S2O8/Fe2+ molar ratios and the pH, which can affect the performance of MFC, were discussed later. The results revealed that K2S2O8–Fe2+ system achieved the best performance at K2S2O8/Fe2+ molar ratios of 2:1 and the K2S2O8-Fe2+ system was stable with varying pH value. This study demonstrated that the K2S2O8–Fe2+ system can be used as an effective cathodic reactant due to its excellent performance.Highlights► The authors proposed a novel cathodic reagent of K2S2O8–Fe2+ system in a two-chamber MFC. ► The power generation of the MFC with K2S2O8–Fe2+ was higher than that with K2S2O8. ► The K2S2O8–Fe2+ system performed better than H2O2–Fe2+ system in MFC. ► The voltage output of MFC using K2S2O8–Fe2+ system was just slightly influenced by pH.

A two-probe tandem nucleic acid hybridization assay for detection of Staphylococcus aureus is presented. It is based on a europium(III) complex as a marker that has a long fluorescence lifetime, high quantum yield and can be easily conjugated to an oligonucleotide signaling probe. The amino-modified capture probe was associated with the signaling probe to form a two-probe tandem DNA pattern that is complementary to the target DNA. The method was optimized in terms of hybridization temperature, hybridization time and washing time. This resulted in good specificity and sensitivity when detecting such bacteria in food samples.

In this paper, CeO2 microplates were synthesized by a sol-gel auto-combustion method. AgI nanoparticles (NPs) were then deposited onto the surface of CeO2 via a facile deposition–precipitation method. The as-prepared AgI/CeO2 samples were characterized by various analytical techniques. The composites exhibited superior photocatalytic activities for the organic dyes (RhB) and the refractory pollutant (tetracycline (TC), a typical antibiotic) degradation under visible light irradiation. The CA-19.03 sample exhibited the highest photocatalytic activity. The enhanced photocatalytic performance could be ascribed to the improved separation of photogenerated charge carriers due to well-matched band structure.

Novel plasmonic photocatalyst of Ag/AgCl-CdWO4 was successfully synthesized via an in situ loading and photoreduction process. The as-obtained Ag/AgCl-CdWO4 samples were characterized by various analytical techniques. The Ag/AgCl-CdWO4 nanocomposites present a remarkable visible-light photocatalytic activity. The optimal Ag/AgCl-CdWO4 can completely degrade RhB, MB and MO within 30 min. Moreover, 95% of phenol can also be degraded within 90 min. The enhanced photocatalytic activity was mainly attributed to two factors: the strong SPR of Ag NPs would improve the visible-light absorbance effectively. Simultaneously, the photo-generated electron–hole pairs can transfer and separate among the Ag/AgCl-CdWO4 hybrid effectively.

A fluorescent sensor for the determination of Ag+ by time-gated mode is proposed. The method is based on Ag+-induced formation of quantum dot/DNA/gold nanoparticle complexes. Two ssDNA strands (strand A and strand B) are designed which contain C–C mismatched base pairs that can specifically react with Ag+. The water-soluble long-lifetime fluorescence quantum dots (Mn:CdS/ZnS) functionalized with strand A are selected as the fluorophore. The gold nanoparticles (GNPs) which are labeled with strand B, acted as the quencher. When Ag+ is absent in the sample solution, DNA-modified GNPs and Mn:CdS/ZnS were in the freedom state, the fluorescence signal of Mn:CdS/ZnS is obviously strong. When Ag+ are present in the sample solution, a DNA duplex is formed because of the strong binding ability between Ag+ and cytosine bases and formed stable C–Ag+–C structures. As a result, the Mn:CdS/ZnS and the GNPs are brought into close proximity, which caused the fluorescence quenching of the Mn:CdS/ZnS due to the nanometal surface energy transfer (NSET) between the Mn:CdS/ZnS and GNPs. This fluorescent sensor could present a satisfactory specificity and selectivity for Ag+. Meanwhile, the detection limit of Ag+ was estimated to be 7.9 nM.

Visible-light-sensitive Ag/AgCl/SrTiO3 photocatalysts have been successfully assembled through the precipitation reaction between AgNO3 and NaCl at ambient temperature, wherein Ag/AgCl nanoparticles were immobilized on the surface of SrTiO3. The composition, crystallinity, morphologies and optical properties of the as-prepared photocatalysts were sufficiently studied via various characterization techniques. In this paper, rhodamine B (RhB), methyl orange (MO), methylene blue (MB), phenol and bisphenol A (BPA) solutions were photodegraded as target pollutants under visible light irradiation to evaluate the photocatalytic performances of the obtained products. In contrast with the pristine SrTiO3 and Ag/AgCl nanoparticles, the composite photocatalysts presented dramatically boosted visible-light photocatalytic performance in terms of decomposing organic pollutants. It was observed that the Ag/AgCl/SrTiO3 (21.6%) composite possessed the best photocatalytic performance and maintained favorable stability during the consecutive cycling experiment. The improved photocatalytic performance of the catalysts resulted from the surface plasmon resonance effect of Ag/AgCl nanoparticles, as well as exceptional separation efficiency of photogenerated electrons and holes. Meanwhile, a reasonable reaction mechanism on the Ag/AgCl/SrTiO3 (21.6%) composite photocatalysts was brought up upon band energy analysis and a trapping experiment.

Recently, visible-light-driven photocatalysts have been widely used in environmental pollutant remediation. In the present study, BiOI/CeO2 p–n junction photocatalysts were successfully fabricated using a facile in situ chemical bath method. The BiOI/CeO2 p–n junction photocatalysts exhibited excellent photoactivity for the decomposition of the refractory pollutant bisphenol A (BPA) and methylene orange (MO) under visible light illumination. The sample with a 1:1 mole ratio of BiOI:CeO2 possessed the highest photocatalytic performance out of all of the as-obtained catalysts. Mott–Schottky plots indicated that p–n junctions were successfully constructed between BiOI and CeO2. The optical and electrical properties of the materials demonstrate that the introduction of BiOI can broaden the visible-light absorption region of CeO2, and the transfer rate of the electron–hole pairs dramatically improves through forming a p–n junction. Furthermore, the BPA degradation efficiency exhibited excellent photostability after four consecutive cycles. These features show that the BiOI/CeO2 p–n junction has great application potential for refractory pollutant removal from wastewater.