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Molybdenum–silver orthophosphate (Mo–Ag3PO4) composites were synthesized through a simple co-precipitation method. Structure and optical characterization by X-ray diffraction, scanning electronic microscopy, transmission electronic microscopy, and UV–Vis diffused reflectance spectroscopy were used to elucidate morphology, structure, and topology of these newly developed materials. The photocatalytic performance of Mo–Ag3PO4 composites toward the degradation of Rhodamine B (RhB) was investigated, and the results proved that the degradation rate of RhB in Mo–Ag3PO4 composites (the mass ratio percentages of Mo2(OCOCH3)4 to AgNO3 were controlled as 1%, S2) was 0.2365 min−1, which was approximated to 103 and 1.2 times higher than that of Ag2O⋅MoO3 and bare Ag3PO4, respectively. In the stability study, Mo–Ag3PO4 composite (S2) exhibited no apparent loss of activity after four catalytic usages (92.4% degradation efficiency) compared with Ag3PO4 (45.5% degradation efficiency), which confirmed its stability. The feasibility of this Mo–Ag3PO4 composite (S2) was validated according to its ability to degrade RhB in environmental water samples, which also demonstrated its high photocatalytic activity. Hole and oxygen radicals are the two main reactive species generated photocatalytically in the mechanism from the light irradiation on Mo–Ag3PO4 composite (S2). The enhanced photocatalytic activity of Mo–Ag3PO4 composite (S2) could be attributed to a low electron–hole recombination rate, and highly efficient charge separation. Thus, a sustainable, low-power (merely 0.38 W/cm2) water treatment option by visible light was demonstrated.

A new conductive metal–organic-framework (MOF) photocatalyst, (WO4)2−-doped bismuth terephthalate (referred to as nNa2WO4BiBDC), was synthesized and characterized by varying the precursor molar ratio (n = 0.1, 0.3, 0.4, and 0.5) of Na2WO4/Bi(NO3)3 in the presence of terephthalic acid through a one-pot solvothermal process. This study found that doping (WO4)2− into BiBDC enhanced the separation of photo-generated carriers, improved the photocatalytic properties of bismuth terephthalate (BiBDC), and enabled the application in Cr(VI) reduction under UV light irradiation with the synergic effect from citric acid acting as a hole scavenger. Among all the precursor ratios of Na2WO4/Bi(NO3)3 used, 0.4Na2WO4BiBDC has the optimum performance, leading to triple gain in reduction efficiency for undoped BiBDC. The synthetic strategy to dope (WO4)2− into a layered MOF as a viable option for modification of MOFs was demonstrated in this study. Finally, the photoreduction of Cr(VI) by (WO4)2-doped bismuth terephthalate enables a new promising wastewater treatment option.

In this study, Chalcopyrite (CuFeS2) was prepared by a hydrothermal and co-precipitation method, being represented as H-CuFeS2 and C-CuFeS2, respectively. The prepared CuFeS2 samples were characterized by scanning electron microscope (SEM), transmission electron microscope (TEM), energy dispersive X-ray spectroscopy mapping (EDS-mapping), powder X-ray diffractometer (XRD), X-ray photoelectron spectrometry (XPS), and Raman microscope. Rhodamine B (RhB, 20 ppm) was used as the target pollutant to evaluate the degradation performance by the prepared CuFeS2 samples. The H-CuFeS2 samples (20 mg) in the presence of Na2S2O8 (4 mM) exhibited excellent degradation efficiency (98.8% within 10 min). Through free radical trapping experiment, the major active species were •SO4− radicals and •OH radicals involved the RhB degradation. Furthermore, •SO4− radicals produced from the prepared samples were evaluated by iodometric titration. In addition, one possible degradation mechanism was proposed. Finally, the prepared H-CuFeS2 samples were used to degrade different dyestuff (rhodamine 6G, methylene blue, and methyl orange) and organic pollutant (bisphenol A) in the different environmental water samples (pond water and seawater) with 10.1% mineral efficiency improvement comparing to traditional Fenton reaction.

Amino group functionalized hydrophobic ionic liquid, 1-ethylamine hydrobromide-3-methylimidazolium hexafluorophosphate (ILPF6) ionic liquid, was employed as the functional monomer to fabricate a carbon-based hole-conductor-free perovskite solar cells with high performances. The photoactive perovskite layer was facilely acquired by one-step spin-coating the precursor solution on a TiO2/FTO electrode surface, and subsequently annealed at an initial annealing at 60 °C for 3 min followed by annealing at 100 °C for 10 min to crystallize. The perovskite precursor solution was prepared by mixing ILPF6 ionic liquid and methylammonium iodide with an equal molar ratio of PbI2. In the optimized conditions, the power conversion efficiency (PCE) was enhanced from 10.08% to 13.01% by doping ILPF6 into the perovskite crystal film. This study demonstrates the multifaceted functions of ILPF6 ionic liquid in improving the efficiency and stability of PSCs. First, ILPF6 can react with PbI2 to form perovskite and can also play a role of the controlling and crosslinking reagent to obtain large grain size and minimize defects. Secondly, ILPF6 can improve the loading amount of perovskite crystals on the TiO2 film. Third, ILPF6 can promote the transport rate of the photogenerated carriers in the perovskite crystal layer. Lastly, ILPF6 ionic liquid with its high hydrophobicity creates a moisture barrier to improve the stability of PSCs effectively. The PSCs were stored under dark in a low relative humidity atmosphere (RH of 20%) at 25 °C without sealing. After 840 h, the PSC can maintain 94% of its initial PCE under the identical intensity illumination. This study demonstrates an excellent strategy to break through the bottleneck of the traditional PSCs and the enhanced effect of ionic liquid for carbon-based PSCs.

Synthesis and modification of salicylic acid (SA) adsorbed titanium dioxide (SA-TiO2) was proposed through a sol–gel reaction following annealing treatment. The prepared SA-TiO2 exhibited visible light absorption because of the formation of an intramolecular ligand to metal charge transfer transition. The photocatalytic activity of SA-TiO2 for the degradation of fast green FCF under visible light irradiation was evaluated. The experimental results suggest that the enhanced photocatalytic activity of SA-TiO2 is attributed to the visible light absorption ability. Moreover, •OH and •O2 − radicals are major active species involved in dye degradation. The practicality of SA-TiO2 was validated through the degradation of various dyestuff in environmental water samples under visible light irradiation.

A facile morphological specific precipitation method by volumetric control of the precursors has been demonstrated to achieve tetrapod-like and dodecahedron-like Ag3PO4 microparticles, which show superior visible-light responsive of photocatalytic activity when comparing to TiO2 (P25). This study also reveals that the tetrapod-like Ag3PO4 microparticles exhibit significantly higher photocatalytic activity (95.6% degradation within 20 min, k: 0.1937 min−1) than the dodecahedrons (78.9% degradation within 30 min, k: 0.0593 min−1) for the degradation of rhodamine B (RhB, 10 ppm) under low-power white light-emitting diode irradiation (300 mW cm−2), which may be attributed to the high reactivity of {110} facets. Moreover, holes and superoxide radicals were the main reactive species involved in RhB degradation.

Facile and template-free two-step synthesis of bismuth oxychloride/graphene oxide (BiOCl/GO) and bismuth oxychloride/reduced graphene oxide (BiOCl/rGO) photocatalysts for degradation of rhodamine B (RhB) under low-power white light–emitting diode (wLED) irradiation (1.6 W/cm2) and sunlight is demonstrated. These photocatalysts were characterized by transmission electron microscopy, scanning electron microscopy, energy-dispersive X-ray spectrometry, X-ray diffraction, and micro-Raman, Fourier-transform infrared, X-ray photoelectron, and UV–Vis diffuse reflectance spectroscopy. Under wLED irradiation, the prepared BiOCl/rGO photocatalysts exhibited excellent photodegradation activity toward RhB through chromophore cleavage mechanism and toward phenol in the presence of RhB with notable dye-sensitized effect. Through scavenging experiments, superoxide radicals were notably involved in RhB degradation. With the highest charge separation efficiency and lowest recombination rate, the photocatalytic activity of BiOCl/rGO reached a maximum rate constant of 0.1899 min−1, 2.0 and 3.0 times higher than those of BiOCl/GO and BiOCl, respectively. In the stability study, only a slight loss (4.5%) in photodegradation was observed after BiOCl/rGO was used in five cycles of photodegradation runs. Compared with commonly used photocatalyst such as TiO2 (P25), BiOCl/rGO demonstrated superior photocatalytic activity and stability under wLED irradiation for various dyestuffs (rhodamine 6 G, methylene blue, and fast green FCF) in different environmental water samples (lake, pond, and sea water).

We demonstrated a sensitive electrochemical method for the determination of nonelectroactive melamine (Mel) using a modified glassy carbon electrode (GCE), with uric acid (UA) as the signal reporter. To increase the anodic response of UA, GCE was coated with Au-Ag nanoparticles and a Nafion thin film (Au-Ag/Nafion/GCE). The sensing mechanism was based on the competitive adsorption behavior of Mel on the Au-Ag/Nafion/GCE, which reduces the electroactive surface area of nanoparticles and thus hinders anodic response of UA. Under optimal conditions and the use of an analytical method of differential pulse voltammetry, this modified electrode detected Mel concentrations ranging from 2.5 to 70 nM, with a detection limit of 1.8 nM. The Au-Ag/Nafion/GCE demonstrated satisfactory reproducibility and stability, with relative standard deviations (RSDs) of 9.3% and 7.1%, respectively. The proposed electrochemical method was then successfully used to determine the Mel content in spiked milk powder and cat food samples, with RSDs of 1.7%-9.3% and recoveries of 92.4%-103.7%.

Facile synthesis of silver phosphate (Ag3PO4) microcrystals was developed for the novel application in the disinfection of pathogens with visible light. Ag3PO4 microcrystals from different synthesis routes were produced and characterised by scanning electron microscopy and UV–visible diffuse reflectance spectroscopy. The antibacterial activity of the Ag3PO4 microcrystals was also evaluated for its effectiveness in eradicating pathogens (Escherichia coli and Staphylococcus aureus) under white-light light-emitting-diode irradiation. The prepared Ag3PO4 microcrystals displayed higher and more stable photocatalytic antibacterial activity (>99% eradication rate within 10 min) comparing to Ag+ ions used only. This can be attributed to the oxidation of the photogenerated hole and the adsorption of Ag+ ions. This study demonstrated the strong photocatalytic activity of the as-prepared Ag3PO4 microcrystals, promising for industrial applications related to the eradication of pathogens from wastewater.

Innovative dual detection methods for mercury(II) ions (Hg(II)) have been developed based on the formation of gold nanostructures (AuNSs) following the addition of mercury-containing solution to a mixture containing an optimized amount of Au(III), H2O2, HCl, and silver nanoparticles (AgNPs). In the absence of Hg(II), the addition of Au(III), H2O2, and HCl to the AgNP solution changes the solution's color from yellow to red, and the absorption peak shifts from 400 to 526nm, indicating the dissolution of AgNPs and the formation of gold nanoparticles (AuNPs). Because of the spontaneous redox reaction of Hg(II) toward AgNPs, the change in the amount of remaining AgNP seed facilitates the generation of irregular AuNSs, resulting in changes in absorption intensity and shifting the peak within the range from 526 to 562nm depending on the concentration of Hg(II). Under optimal conditions, the limit of detection (LOD) for Hg(II) at a signal-to-noise ratio (S/N) of 3 was 0.3μM. We further observed that AgNP-assisted catalytic formation of Au nanomaterials deposited on a surface enhanced Raman scattering active substrate significantly reduced the Raman signal of 4-mercaptobenzoic acid, dependent on the Hg(II) concentration. A linear relationship was observed in the range 0.1nM-100μM with a LOD of 0.05nM (S/N 3.0). As a simple, accurate and precise method, this SERS-based assay has demonstrated its success in determining levels of Hg(II) in real water samples.

A novel electropolymerizable material, 1-[3-(N-pyrrolyl) propyl]-3-butylimidazolium bromide (NPBimBr) ionic liquid, was synthesized and used as a modifier to functionalize graphene oxide nanosheets (GO) for fabricating an electrochemical sensor. X-ray photoelectron spectroscopy, transmission electron microscopy, scanning electron microscopy and electrochemical impedance spectroscopy were used to characterize both GO-NPBimBr and GO-poly(NPBimBr) film electrode. Electrochemical performance in the detection of bisphenol A at the GO-poly(NPBimBr) modified glassy carbon electrode (GCE) was investigated and optimized. Compared with the bare GCE, the oxidation peak current of bisphenol A at the nanocomposite film modified electrode was significantly increased. A good linear relationship between the oxidation peak current and the bisphenol A concentration was found in the range of 2.0 × 10−7 ∼ 1.0 × 10−5 mol L−1, with a detection limit of 1.7 × 10−8 mol L−1. The method was successfully applied to determine bisphenol A content in commercially available plastic drinking cups and the results are consistent with the ones from high performance liquid chromatography.

Effective surface-enhanced Raman scattering (SERS)-active substrates from gold nanoparticle and gold nanohole arrays were successfully fabricated through electron beam lithography with precise computer-aided control of the unit size and intergap distance. Their SERS performance was evaluated using 4-mercaptobenzoic acid (4-MBA). These gold arrays yielded strong SERS signals under 785 nm laser excitation. The enhancement factors for 4-MBA molecules on the prepared gold nanoparticle and nanohole arrays maxed at 1.08 × 107 and 8.61 × 106, respectively. The observed increase in SERS enhancement was attributed to the localized surface plasmon resonance (LSPR) wavelength shifting toward the near-infrared regime when the gold nanohole diameter increased, in agreement with the theoretical prediction in this study. The contribution of LSPR to the Raman enhancement from nanohole arrays deposited on fluorine-doped tin oxide glass was elucidated by comparing SERS and transmission spectra. This simple fabrication procedure, which entails employing electron beam lithography and the controllability of the intergap distance, suggests highly promising uses of nanohole arrays as functional components in sensing and photonic devices.

Various three-dimensional TiO2 hollow structures have attracted strong scientific and technological attention due to their excellent properties. 3D hierarchical TiO2 hollow nanocubes (TiO2-HNBs) are not good candidates for industrial photocatalytic applications due to their large energy gap which is only activated by UV light. Herein, visible-light-responsive carbon doped and coated TiO2-HNBs (C@TiO2-HNBs) with a dominant exposure of {001} facets have been prepared via a template-engaged topotactic transformation process using facile one-step solvothermal treatment and a solution containing ethanol, glucose and TiOF2. The effects of reaction time and glucose/TiOF2 mass ratio on the structure and performance of C@TiO2-HNBs were systematically studied. We found that glucose played an important role in providing H2O during the topological transformation from self-templated TiOF2 cubes into 3D hierarchical TiO2 hollow nanocubes versus dehydration reactions, where its main function was as a carbon source. Coated carbon was deposited predominantly on the surface as sp2 graphitic carbon in extended p conjugated graphite-like environments, and doped carbon mainly replaced Ti atoms in the surface lattice to form a carbonate structure. The results were confirmed using TEM SEM, EDS, XRD, FT-IR, XPS and Raman spectroscopic studies. The C@TiO2-HNBs achieved greatly improved RhB photodegradation activity under visible light irradiation. The catalyst prepared with glucose/TiOF2 at a mass ratio of 0.15 (T24-0.15) showed the highest photodegradation rate of 96% in 40 min, which is 7.0 times higher than those of the TiO2-HNBs and P25. This new synthetic approach proposes a novel way to construct carbon hybridized 3D hierarchical TiO2 hollow nanocubes by combining two modification methods, “element doped” and “surface sensitized”, at the same time.

In order to improve the photocatalytic activities of layered MOF bismuth terephthalate, five multiple halide anion doped bismuth terephthalate composites were prepared by doping three or four halide anions each with a molar ratio of X−/Bi3+ (X = F−, Cl−, Br−, I−) at 0.25. The F−, Cl−, Br− codoped and F−, Cl−, Br−, I− codoped bismuth terephthalate composites exhibit 41 and 35 times higher photocatalytic degradation activities for RhB, 7 and 6 times higher for salicylic acid than that of bismuth terephthalate. Excellent photocatalytic activities could be ascribed to the microstructure of multiple halide anion doped composites, large specific BET surface area and effective separation of photogenerated electron–hole pairs. Incorporating multiple negatively charged F−, Cl−, Br−, I− into layered bismuth terephthalate can improve the photocatalytic and electrochemical activities of bismuth terephthalate. The composites presented in this study can be potentially applied in photocatalysis and electrochemical fields as multifunctional materials.

In this study, a microwave-assisted synthesis of fluorescent egg-white-protected gold nanoclusters (ew–AuNCs) for sensing Hg2+ ions and melamine was developed, optimized, and evaluated. By conducting infrared spectrometry and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry, we confirmed that clusters consisting of 22 Au atoms were successfully embedded in egg white. Transmission electron microscopy measurements revealed that the ew–AuNCs were well dispersed with an average diameter of 2.7 ± 0.7 nm. The ew–AuNCs exhibited red fluorescence emission (λem 648 nm) with high quantum yield (2.37%). In the presence of Hg2+ ions, the fluorescence of these ew–AuNCs was quenched because of the Hg2+–Au+ interaction. The relative change in fluorescence intensity at 648 nm was dependent on the concentration of Hg2+ ions. Detection of melamine was based on the diminished fluorescence quenching of ew–AuNCs by Hg2+ when melamine was added along with Hg2+. The limit of detection for Hg2+ ions and melamine was 0.89 nM and 0.46 μM, respectively. Determination of Hg2+ ions in a pond water sample and of melamine in milk and dog food samples was performed, and the recoveries from the developed method were >92.9%, confirming its potential for sensor applications.

A simple high-performance liquid chromatography (HPLC) method for the simultaneous separation of the highly polar and weakly polar components of traditional Chinese medicines was developed via a strategic combination of isocratic and gradient elution methods. Liu-Shen-Wan and Liu-Wei-Di-Huang-Wan were used as representative examples of traditional Chinese medicines. This is the first time that 6 components of varying degrees of polarity in Liu-Shen-Wan had been successfully resolved in a single chromatographic run using an ultraviolet-visible detector with a fixed wavelength of 296 nm. In contrast to conventional gradient separation methods, this novel method offered a viable route for separation of the highly and weakly polar fractions simultaneously, thus greatly reducing the time and cost of analysis. This method therefore provides a more efficient way to determine the polar components present in traditional Chinese medicines. It would find potential application in drug screening, drug authentication, and product quality control.

In this study, a ternary CdS-ZnS-BiPO4 nanocomposite, synthesized by a solvent-assisted heating method, demonstrated the highest visible light-induced photocatalysis towards the degradation of methylene blue (MB) when comparing with BiPO4, CdS-BiPO4, and ZnS-BiPO4. Transmission electron microscopy (TEM), X-ray powder diffraction (XRD), and UV-Vis diffuse reflectance spectroscopy (UV-vis DRS) were used to characterize the prepared nanocomposites. From UV-DRS results, the energy band gap of the prepared BiPO4 structures was 4.51 eV. When CdS nanoparticles were deposited on BiPO4 surface by a solvent-assisted heating method, the prepared nanocomposites exhibited visible light-responsive photocatalytic degradation toward MB (20 ppm). At a molar ratio of Cd to Zn as 1:7, the prepared CdS-ZnS-BiPO4 nanocomposites exhibited the best photocatalytic activity in degrading 95% of MB dyes, out-performing pure BiPO4, CdS-BiPO4, and ZnS-BiPO4 due to its enhanced charge separation efficiency and the lowered carrier recombination from the efficient p-n junction of unprecedented ternary composites. The investigations on mechanism conclude that the major reactive species responsible for MB degradation are holes and oxygen radicals. For practicality, the degradation efficiency for different dyestuff (Fast Green FCF, Rhodamine 6G, Acid Blue 1, methyl orange, and methyl red) degradation in the different water matrix samples (pond water, seawater, and lake water) by the prepared CdS-ZnS-BiPO4 nanocomposites was evaluated.

Icosahedral gold nanocrystals (AuNCs) were synthesized by using the ionic liquid (IL) 1-(10-bromodecyl)-3-methyl-imidazolium bromide as a morphology-controlling reagent. The novel IL 1,3-di-(3-mercaptopropyl)-imidazolium bromide was employed as a bifunctional monomer to integrate the AuNCs onto the surface of a glassy carbon electrode (GCE) modified with gold nanoparticles. After interaction with thioglycolic acid (TGA) and activation of the carboxy groups, the antibody against squamous cell carcinoma antigen was immobilized on the modified GCE. Residual active sites were blocked with bovine serum albumin. The new materials and the steps for immunosensor fabrication were fully characterized. The reduction in peak current (using hexacyanoferrate as an electrochemical probe) due to the recognition of SCCA is linearly related to the SCCA concentration in the 0.02 to 10 ng mL−1 concentration range. The detection limit is as low as 12.6 pg mL−1 (at an S/N ratio of 3). The assay was applied to the quantitation of SCCA in human serum samples. The accuracy was validated by comparison with an ELISA method. The two methods displayed excellent consistency.

Dodecahedral gold nanocrystals (AuNCs) were synthesized by using a 1-(10-bromodecyl)-3-methylimidazolium bromide ionic liquid as functional monomer and protectant. AuNCs were self-assembled onto molybdenum disulfite (MoS2) nanosheets to fabricate AuNCs/MoS2 nanocomposite, which was drop-coated onto a glassy carbon electrode surface to generate an interface for transthyretin (TTR) immobilizing. With a similar chemical structure to thyroxine, tetrabromobisphenol A (TBBPA) was specifically recognized by transthyretin and the TTR/AuNCs/MoS2/GCE provides a sensing platform for TBBPA. Its sensing performance towards TBBPA was found significantly improved by the integration of AuNCs onto MoS2 nanosheets. Three conditions for assay development, such as incubation time, incubation temperature, and pH value, were investigated and found the optimum conditions were 200 s, 35 °C, and pH 7.0 respectively. Under these conditions, the ratio [Ri = (i0 − i)/i0] between the photocurrent variation (△i = i0 − i) and the original photocurrent (i0) is linearly related to the logarithm of TBBPA concentration (cTBBPA) from 0.1 nM to 1.0 μM. The linear relationship can be described by the following equation: Ri = 0.09092 log cTBBPA (M) + 0.8976 (R = 0.993). The detection limit is calculated to be 0.045 nM (S/N = 3). The photoelectrochemical immunosensor was used to accurately determine TBBPA concentration in South-Lake spiked water samples.

Monoclinic-phase bismuth vanadate (BiVO 4 ) with a 2.468 eV band gap exhibited enhanced synergic photodegradation activity toward methylene blue (MB) when combined with silver ions (Ag + ) in an aqueous solution under visible light irradiation. The mass ratio of AgNO 3 to BiVO 4 and the calcination temperature were discovered to considerably affect the degradation activity of BiVO 4 /Ag + . Superior photocatalytic performance was obtained when BiVO 4 was mixed with 0.01%(w/v) AgNO 3 solution, and complete degradation of MB was achieved after 25 min visible light irradiation, outperforming BiVO 4 or AgNO 3 solution alone. The enhanced photodegradation was investigated using systematic luminescence measurements, electrochemical impedance spectroscopy, and scavenger addition, after which a photocatalytic mechanism for MB degradation under visible light irradiation was identified that involved oxygen radicals and holes. This study also discovered the two dominating processes involved in enhancing the electron–hole separation efficiency and reducing their recombination rate, namely photoreduction of Ag + and the formation of a BiVO 4 /Ag heterojunction. The synergic effect between BiVO 4 and Ag + was discovered to be unique. BiVO 4 /Ag + was successfully used to degrade two other dyes and disinfect Escherichia Coli . A unique fluorescent technique using BiVO 4 and a R6G solution to detect Ag + ions in water was discovered.

In this study, a magnetic iron oxide nanoparticle-based solid-phase extraction procedure combined with the online concentration and separation of salicylic acid (SA) through micellar electrokinetic chromatography-UV detection (MEKC-UV) was developed. Under optimal experimental conditions, a good linearity in the range of 0.01-100μmolL-1 was obtained with a coefficient of correlation of 0.9999. The detection sensitivity of the proposed method exhibited an approximately 1026-fold improvement compared with a single MEKC method without online concentration, and the detection limit (S/N=3) was 3.80nmolL-1. The repeatability of the method was evaluated using intraday and interday RSDs (11.5% and 17.0%, respectively). The method was used to determine SA concentrations in tobacco leaves (Nicotiana tabacum L. cv. Samsun) from the NN genotype, nn genotype, and Nt-NahG mutant strains, as well as in shampoo and ointment samples. Rapid extraction and separation (

A hexafluorophosphate ionic liquid is used as a functional monomer to prepare a metal-organic framework (Zn-MOF). Zn-MOF is used as a template for MoS

Metal-organic framework nanocrystal (Zn-MOF) was synthesized by using 3,3'-{(propane-1,3-diyl)bis[1-(4-carboxybenzyl)-1H-imidazol-3-ium]} hexafluorophosphate ionic liquid as the functional monomer and Zn2+ as the central metal ion under hydrothermal conditions. Spatially confined gold nanoparticles (Au-NP) were prepared by in-situ reduction of chloroauric acid in the nanopores of Zn-MOF using acetic acid as the reducing agent to fabricate Au-NP@Zn-MOF nanocomposites. Au-NPs@Zn-MOF was further functionalized with 1H-imidazolium-1,3-bis(2-aminoethyl)bromide ionic liquid (IBABr) to prepare IBABr-Au@Zn-MOF nanocomposites. All abovementioned nanomaterials were thoroughly characterized by TEM, SEM, XPS, FTIR, and nitrogen-adsorption surface area analysis. IBABr-Au@Zn-MOFnanocomposites were then deposited onto a glassy carbon electrode and used as the photoactive element to fabricate a label-free photoelectrochemical (PEC) immunosensor by immobilizing anti-squamous cell carcinoma antigen (anti-SCCA). The PEC sensing principle is based on the photocurrent decline due to the blocking effect of SCCA on the electron and mass transfer after binding SCCA to anti-SCCA. The photocurrent variation related to the specific recognition of SCCA shows a linear relationship to the logarithm of SCCA concentration in the range of 5.0 pg mL−1 to 15.0 ng mL−1. The detection limit is as low as 2.34 pg mL−1. Such a signal-off PEC immunosensor is highly selective, sensitive, stable, and reproducible towards SCCA detection. Its performance is comparable to enzyme-linked immunosorbent assay from the studies on clinical samples. This immunosensor is promising for the label-free determining SCCA in clinical human serum samples.

Gold nanorods (AuNRs) integrated with ZnCdHgSe near-infrared quantum dots (AuNRs-ZnCdHgSe QDs) were successfully synthesized and characterized by transmission electron microscope, X-ray photoelectron spectroscopy, and X-ray diffraction. A glassy carbon electrode was decorated with the aforementioned AuNRs-ZnCdHgSe QDs nanocomposite, which provides a biocompatible interface for the subsequent immobilization of prostate specific antibody (anti-PSA). After being successively treated with glutaraldehyde vapor and bovine serum albumin solution, a photoelectrochemical immunosensing platform based on anti-PSA/AuNRs-ZnCdHgSe QDs/GCE was established. The photocurrent response of ZnCdHgSe QDs was tremendously improved by AuNRs due to the effect of resonance energy transfer which can be deduced from the dependence of the enhanced efficiency on the AuNRs with different length-to-diameter ratios and spectral absorption characteristics. A maximum photocurrent was obtained when the absorption spectrum of AuNRs matched well with the emission spectrum of ZnCdHgSe QDs. A photoelectrochemical immunosensor for prostate specific antigen (PSA) was achieved by monitoring the photocurrent variation. The photocurrent variation before and after being interacted with PSA solution exhibits a good linear relationship with the logarithm of its concentration (log c PSA ) in the range from 1.0 pg mL −1 to 50.0 ng mL −1 . The detection limit of this photoelectrochemical immunosensor is able to reach 0.1 pg mL −1 (S/N = 3). Determining PSA in clinical human serum was also demonstrated by using the developed anti-PSA(BSA)/AuNRs-ZnCdHgSe QDs/GCE electrode. The results were comparable with those obtained from an enzyme-linked immunosorbent assay method.

Anthropogenic mercury (Hg) presents serious risks to the surroundings and public health due to its toxicity and bioaccumulation. In this study, a new assay was developed to combat mercury-related issues, and it is based on surface-enhanced Raman scattering (SERS) on an active paper substrate for rapid Hg(II) determination. The sensing principle is based on the hindering effect of Hg(II) on the catalytic growth of SERS-active gold nanoparticles (AuNPs) on a hydrophobically patterned paper substrate. 4-mercaptobenzonic acid (4-MBA) was chosen as an effective Raman reporter molecule, and its Raman signal was enhanced by surface plasmonic 2-[4-(2-hydroxyethel) piperazine-1-yl]ethanesulfonic acid-stabilized gold nanostars (HEPES-AuNSs) on a piece of paper with a hydrophobic surface. After adding a Hg(II) analyte solution to this SERS substrate, an amalgam formed at the solid–liquid interface of the HEPES-AuNSs. The formation of the AuHg amalgam resulted in the dissolution of the branches of the HEPES-AuNSs. In the presence of a growth solution (mixture of Au(III), HCl, and H2O2), the remaining HEPES-AuNSs and the AuHg amalgams acted as seeds to form small AuNPs, resulting in a weak SERS signal of 4-MBA (Raman shift at 1590 cm−1). Solution concentration, temperature, and treatment time were optimized to realize a significant decrease in the Raman intensity of 4-MBA when the paper sensor was exposed to Hg(II). The Raman intensity decreased with the increasing concentration of Hg(II) ions in the range of 0.1 nM–1.0 μM (R2 = 0.98), with a limit of detection (S/N = 3.0) of 0.03 nM. For practicality, the proposed paper substrate was examined by estimating Hg(II) concentrations in environmental water samples (i.e., seawater and pond water) and the certified standard of SRM 1641d through standard addition and a recovery study. The promising selectivity, sensitivity, and reproducibility of the proposed paper sensor constitute substantial progress toward the portable detecting mercury in real water samples, which can facilitate crucial surrounding monitoring.

AgX/MgBi2O6 composites (X = Cl, Br, and I), prepared from the hydrothermal procedure combined with a co-precipitation method, display unique visible light responsive photocatalytic activity. The catalytic performance of the AgX/MgBi2O6 composites were evaluated through the photodegradation of methylene blue (MB, 15 ppm) under white-light light-emitting diode irradiation (2.5 W, power density: 0.38 Wcm−2). Among the AgX/MgBi2O6 composites, the AgI/MgBi2O6 composite, with molar ratio of AgI to MgBi2O6 as 3:1, exhibited the highest photocatalytic performance within 20 min (degradation efficiency: 99.5 %) while MgBi2O6, AgCl/MgBi2O6, and AgBr/MgBi2O6 composites achieved degradation efficiency of 14.9 %, 24.9 % and 56.1 % respectively. The main reason of superior photocatalytic activity in AgI/MgBi2O6 composite attributes to the pn junction between AgI nanoparticles and MgBi2O6 effectively enhancing the charge separation efficiency and reducing the recombination rate of electron–hole pairs. This study revealed that hydroxyl and oxygen radicals are the major species involved in the degradation of MB from the photoactivated AgI/MgBi2O6 composite. To develop a practical application of this new material, the samples of AgI/MgBi2O6 composite have demonstrated excellent photocatalytic performance in degradation of various dyestuffs (92.3 %–99.5 % degradation within 10 min) under visible light irradiation and 99.8 % MB degradation under sunlight irradiation within 6 min.

In this paper, we report the synthesis and application of enzyme-like DNA-copper oxide/platinum nanoparticles for the separate quantification of inorganic and organomercury species in various real samples. We synthesized a series of poly(thymine) (T60)–copper oxide/metal nanocomposites (T60–CuxO/M NCs; M = Au, Ag or Pt) that exhibited enzyme-like activities [oxidase (OX), peroxidase (POX), and catalase (CAT)]. The enzyme-like activities are tunable due to the incorporation of various metals into the NCs. Among a series of synthesized CuxO/M NCs, T60–copper oxide-platinum nanocomposites (T60–CuxO/Pt NCs) exhibited the highest OX-like activity via the O2-mediated oxidation of substrates, such as Amplex Red (AR), 2,2′-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS), o-phenylenediamine (OPD), and 3,3′,5,5′-tetramethylbenzidine (TMB), to form fluorescent or colored products. Interestingly, inorganic mercury ions (Hg2+) and organomercury species, such as methylmercury (MeHg+), ethylmercury (EtHg+), and phenylmercury (PhHg+), significantly inhibited the OX-like activity of T60–CuxO/Pt NCs. For the selective detection of mercury species, we used ABTS in the T60–CuxO/Pt NCs system, and the ABTS/T60–CuxO/Pt NCs-based assay allowed for the detection of mercury ions at nanomolar concentrations based on the decrease in the catalytic activity caused by the mercury ions. To separately quantify the inorganic and organomercury species in a sample, we employed selenium nanoparticles (Se NPs) as a masking agent, as they preferentially bind with inorganic mercury species. The ABTS/T60–CuxO/Pt NCs-based assay with the masking agent of Se NPs further provided specificity for the detection of organomercury species in environmental water samples (tap water, river water, and seawater) and fish muscle samples (dogfish muscle DORM-II).

Herein, a label-free colorimetric nanosensor for Hg(II) is developed utilizing the hindering effect of Hg(II) on the kinetic aspect of gold nanoparticle (AuNPs) growth on the surface of gold nanostars (AuNSs). H-AuNS probes are synthesized and modified by 2-[4-(2-hydroxyethel) piperazine-1-yl] ethanesulfonic acid (HEPES). After the formulation of the reagents and testing conditions are optimized, HEPES-capped AuNSs (H-AuNSs) demonstrates good selectivity and sensitivity towards Hg(II) determination. A H-AuNS probe, in the presence of HCl/Au(III)/H2O2, is capable of detecting a Hg(II) concentration range of 1.0 nM&ndash, 100 &micro, M, with a detection limit of 0.7 nM, at a signal-to-noise ratio of 3.0, and a visual detection limit of 10 nM with naked eyes. For practicality, the H-AuNS probe is evaluated by measuring Hg(II) in the environmental water matrices (lake water and seawater) by a standard addition and recovery study. The detection limits for environmental samples are found to be higher than the lab samples, but they are still within the maximum allowable Hg concentration in drinking water (10 nM) set by the US Environmental Protection Agency (EPA). To create a unique nanosensor, the competitive interaction between Hg(II) and Pt(IV) toward the H-AuNSs probe is developed into a logic gate, improving the specificity in the detection of Hg(II) ions in water samples.

This study demonstrated facile synthesis of silver phosphate (Ag3PO4) photocatalysts for the degradation of organic contaminants. Ag3PO4 microparticles from different concentrations of precursor, AgNO3, were produced and characterized by scanning electron microscopy, powder X-ray diffraction, and UV–visible diffuse reflectance spectroscopy. Degradation rates of methylene blue (MB) and phenol were measured in the presence of microparticles under low-power white-light light-emitting-diode (LED) irradiation and the reaction rate followed pseudo-first-order kinetics. The prepared Ag3PO4 microparticles displayed considerably high photocatalytic activity (>99.8% degradation within 10 min). This can be attributed to the microparticles’ large surface area, the low recombination rate of electron–hole pairs and the higher charge separation efficiency. The practicality of the Ag3PO4 microparticles was validated by the degradation of MB, methyl red, acid blue 1 and rhodamine B under sunlight in environmental water samples, demonstrating the benefit of the high photocatalytic activity from Ag3PO4 microparticles.

A novel ionic liquid, 3-{[{4-[((carbamoyl)amino)ethyl methacrylate]butyl} ((carbamoyl)amino)ethyl methacrylate]propyl}-1-ethenyl-1H-imidazol-3-ium bromide (CCPEimBr) functionalized with vinyl, amino, and methacrylate groups, was synthesized and characterized with 1H NMR, FTIR, and HPLC-MS techniques. CCPEimBr was adopted as the functional monomer to prepare a molecularly imprinted polymerized ionic liquid hydrogel film on a glassy carbon electrode surface for human epididymis protein 4 (HE4) sensing. Gold nanoparticles (AuNPs) and ZnCdHgSe QDs were incorporated into the imprinted film as photo-electric active materials. The photocurrent response was measured to investigate the sensing performance of the imprinted sensors toward HE4. The imprinted photo-electrochemical sensor shows excellent selectivity, sensitivity, stability, and accuracy for HE4 determination. Experimental conditions including incubation time and pH value for determining HE4 were optimized in this study. The photocurrent variation (ΔI) ...

Squamous cell carcinoma antigen (SCCA) is a good specific antigen for cancer diagnosis specifically for squamous cell carcinomas. In this study, 3-amine-N-[3-(N-pyrrole)propyl]imidazole bromide (APPIBr) ionic liquid was successfully synthesized and characterized by 1 H NMR, HPLC-MS and FTIR. APPIBr ionic liquid is a unique functional material with a pyrrole moiety which can be polymerized by using electrochemical technique and an amine group for immobilizing biomolecules; thus, it is ideal for the fabrication of biosensors. Using chloroauric acid as precursor and N-dodecyl imidazole as functional monomer, gold nanoroots (AuNRs) were fabricated and characterized with TEM, SEM and XRD. An immunosensor was built on a glassy carbon electrode (GCE), through the steps of forming the poly(APPIBr)/AuNRs/GCE interface by electrodeposition of APPIBr, anti-SCCA immobilization, and several optimization steps to achieve a sensitive, accurate, precise, and selective anti-SCCA/poly(APPIBr)/AuNRs/GCE for the electrochemical immunosensing SCCA. It was found that poly(APPIBr)/AuNRs nanointerface can improve the sensing performance of the immunosensor. Under the optimized experimental conditions, there existed two linear regimes relating the peak current variation to the concentration of squamous cell carcinoma antigen in the range of 0.001–0.1 ng mL −1 and 0.1–5.0 ng mL −1 . The detection limit was calculated to be 0.3 pg mL −1 . The developed sensor was demonstrated its capability in quantitative analysis of squamous cell carcinoma antigen in human serum with recoveries of 97.3%, 102.4% and 107.4%.

Ultrathin-layered carbon intercalated MoS2 hollow nanospheres (C/MoS2) were prepared with a hydrothermal method combined with high-temperature annealing using cetyltrimethylammonium bromide (CTAB) as the morphological control agent and ammonium molybdate as the molybdenum source. The ultrathin-layered C/MoS2, possessing a direct band-gap of ˜1.8 eV, can promote the visible light absorption and the charge-hole separation ideal for photoelectrochemical (PEC) sensing. Then, the gold nanoparticles (AuNPs) were integrated onto the C/MoS2 surface by in-situ reduction of chloroauric acid without adding any reductant to produce AuNPs/C/MoS2 nanocomposites. Subsequently, AuNPs/C/MoS2 nanocomposites and SCCA antibody (anti-SCCA) were sequentially modified on a glassy carbon electrode (GCE) surface to prepare a PEC immunosensing platform which was denoted as anti-SCCA(BSA)/AuNPs/C/MoS2/GCE. Under optimized conditions, the PEC immunosensor shows a broad linear range from 0.005 ng mL−1 to 8 ng mL−1 and a low detection limit of 1.8 pg mL−1 for determining SCCA. For the assay of SCCA in clinical serum samples, the results obtained from the PEC immunosensor are comparable to the generally accepted ELISA method from a commercial immunoassay kit.