ZnS/C/MoS2 Nanocomposite Derived from Metal-Organic Framework for High-Performance Photo-Electrochemical Immunosensing of Carcinoembryonic Antigen.

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 MoS2 nanosheets synthesis and further carbonized to yield light-responsive ZnS/C/MoS2 nanocomposites. Zn-MOF, carbonized-Zn-MOF, and ZnS/C/MoS2 nanocomposites are characterized by Fourier transform infrared spectroscopy, transmission electron microscopy, X-ray diffraction pattern, scanning electron microscopy (SEM), element mapping, Raman spectroscopy, X-ray photoelectron spectroscopy, fluorescence, and nitrogen-adsorption analysis. Carcinoembryonic antigen (CEA) is selected as a model to construct an immunosensing platform to evaluate the photo-electrochemical (PEC) performances of ZnS/C/MoS2 nanocomposites. A sandwich-type PEC immunosensor is fabricated by immobilizing CEA antibody (Ab1 ) onto the ZnS/C/MoS2 /GCE surface, subsequently binding CEA and the alkaline phosphatase-gold nanoparticle labeled CEA antibody (ALP-Au-Ab2 ). The catalytic conversion of vitamin C magnesium phosphate produces ascorbic acid (AA). Upon being illuminated, AA can react with photogenerated holes from ZnS/C/MoS2 nanocomposites to generate a photocurrent for quantitative assay. Under optimized experimental conditions, the PEC immunosensor exhibits excellent analytical characteristics with a linear range from 2.0 pg mL-1 to 10.0 ng mL-1 and a detection limit of 1.30 pg mL-1 (S/N = 3). The outstanding practicability of this PEC immunosensor is demonstrated by accurate assaying of CEA in clinical serum samples.

Label-Free Colorimetric Detection of Mercury (II) Ions Based on Gold Nanocatalysis.

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⁻100 µM, 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.

Molecularly Imprinted Photo-electrochemical Sensor for Human Epididymis Protein 4 Based on Polymerized Ionic Liquid Hydrogel and Gold Nanoparticle/ZnCdHgSe Quantum Dots Composite Film.

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) decreased with increasing HE4 concentration (cHE4), and it was linearly proportional to cHE4 varied from 25 pg mL-1 to 4.0 ng mL-1. The detection limit of the imprinted sensor for determining HE4 was estimated to be 15.4 pg mL-1 (S/N = 3). The imprinted photo-electrochemical sensor was used to determine HE4 in human serum samples accurately.

Facile Preparation of Tannic Acid-Gold Nanoparticles for Catalytic and Selective Detection of Mercury(II) and Iron(II) Ions in the Environmental Water Samples and Commercial Iron Supplement.

Tannic acid (TA), a plant-derived polyphenol rich in hydroxyl groups, serves as both a reducing agent and stabilizer for synthesizing gold nanoparticles (TA-AuNPs). This study presents a groundbreaking method that utilizes TA to fabricate TA-AuNPs and develop two distinct colorimetric detection systems for mercury (Hg2+) and iron (Fe2+) ions. The first detection system leverages the interaction between TA-AuNPs and Hg2+ to enhance the peroxidase-like activity of TA-AuNPs, facilitating the production of hydroxyl radicals upon reaction with hydrogen peroxide, which subsequently oxidizes 3,3',5,5'-tetramethylbenzidine (TMB) into a blue-colored product (ox-TMB). The second system capitalizes on TA-AuNPs to catalyze the Fenton reaction between Fe2+ and hydrogen peroxide in the presence of 2, 6-pyridinedicarboxylic acid, boosting the generation of hydroxyl radicals that oxidize TMB into a blue-colored ox-TMB. Absorbance measurements at 650 nm display a linear relationship with Hg2+ concentrations ranging from 0.40 to 0.60 µM (R2 = 0.99) and Fe2+ concentrations from 0.25 to 2.0 µM (R2 = 0.98). The established detection limits for Hg2+ and Fe2+ are 18 nM and 96 nM, respectively. Applications to real-world samples achieved an excellent spiked recovery, spanning 101.6% to 108.0% for Hg2+ and 90.0% to 112.5% for Fe2+, demonstrating the method's superior simplicity, speed, and cost-effectiveness for environmental monitoring of these ions compared to existing techniques.

One-Pot Synthesis of Tannic Acid-Au Nanoparticles for the Colorimetric Determination of Hydrogen Peroxide and Glucose.

This study introduces a novel one-pot method employing tannic acid (TA) to synthesize stable gold nanoparticles (TA-AuNPs), which are characterized using transmission electron microscopy, X-ray powder diffraction, and Fourier transform infrared spectroscopy. We apply these TA-AuNPs in a newly developed colorimetric assay for hydrogen peroxide (H2O2) detection that utilizes the oxidation of iodide (I-) on TA-AuNPs, leading to a detectable yellow color change in the solution. The reaction kinetics are captured by the rate equation R = 0.217[KI]0.61[H2O2]0.69. The possible sensing mechanism was proposed through density functional theory calculations. At the optimum conditions, the proposed TA-AuNPs/I- system demonstrated a linear relationship between H2O2 concentration and absorbance intensity (λ = 350 nm) and achieved a limit of detection (LOD) of 7.33 µM. Furthermore, we expand the utility of this approach to glucose detection by integrating glucose oxidase into the system, resulting in a LOD of 10.0 µM. Application of this method to actual urine samples yielded spiked recovery rates ranging from 96.6-102.0% and relative standard deviations between 3.00-8.34%, underscoring its efficacy and potential for real-world bioanalytical challenges.

Green Synthesis of Carbon Quantum Dots and Carbon Quantum Dot-Gold Nanoparticles for Applications in Bacterial Imaging and Catalytic Reduction of Aromatic Nitro Compounds.

This study delves into the green synthesis and multifaceted applications of three types of carbon quantum dots (CQDs), namely, CQDs-1, CQDs-2, and CQDs-3. These CQDs were innovatively produced through a gentle pyrolysis process from distinct plant-based precursors: genipin with glucose for CQDs-1, genipin with extracted gardenia seeds for CQDs-2, and genipin with whole gardenia seeds for CQDs-3. Advanced analytical techniques, including X-ray photoelectron spectroscopy (XPS) and Fourier-transform infrared spectroscopy (FT-IR), were employed to detail the CQDs' structural and surface characteristics, revealing their unique functional groups and surface chemistries. The study further explores the CQDs' bioimaging potential, where confocal fluorescence microscopy evidenced their swift uptake by Escherichia coli bacteria, indicating their suitability for bacterial imaging. These CQDs were also applied in the synthesis of gold nanoparticles (AuNPs), acting as reducing agents and stabilizers. Among these, CQD3-AuNPs were distinguished by their remarkable stability and catalytic efficiency, achieving a 99.7% reduction of 4-nitrophenol to 4-aminophenol in just 10 min and maintaining near-complete reduction efficiency (99.6%) after 60 days. This performance notably surpasses that of AuNPs synthesized using sodium citrate, underscoring the exceptional capabilities of CQD3-AuNPs. These insights pave the way for leveraging CQDs and CQD-stabilized AuNPs in bacterial imaging and catalysis, presenting valuable directions for future scientific inquiry and practical applications.

Combined Electrochemical Deposition and Photo-Reduction to Fabricate SERS-Active Silver Substrates: Characterization and Application for Malachite Green Detection in Aquaculture Water.

This research introduces a novel approach using silver (Ag) nanostructures generated through electrochemical deposition and photo-reduction of Ag on fluorine-doped tin oxide glass substrates (denoted as X-Ag-AgyFTO, where 'X' and 'y' represent the type of light source and number of deposited cycles, respectively) for surface-enhanced Raman spectroscopy (SERS). This study used malachite green (MG) as a Raman probe to evaluate the enhancement factors (EFs) in SERS-active substrates under varied fabrication conditions. For the substrates produced via electrochemical deposition, we determined a Raman EF of 6.15 × 104 for the Ag2FTO substrate. In photo-reduction, the impact of reductant concentration, light source, and light exposure duration were examined on X-Ag nanoparticle formation to achieve superior Raman EFs. Under optimal conditions (9.0 mM sodium citrate, 460 nm blue-LED at 10 W for 90 min), the combination of blue-LED-reduced Ag (B-Ag) and an Ag2FTO substrate (denoted as B-Ag-Ag2FTO) exhibited the best Raman EF of 2.79 × 105. This substrate enabled MG detection within a linear range of 0.1 to 1.0 µM (R2 = 0.98) and a detection limit of 0.02 µM. Additionally, the spiked recoveries in aquaculture water samples were between 90.0% and 110.0%, with relative standard deviations between 3.9% and 6.3%, indicating the substrate's potential for fungicide detection in aquaculture.

Nafion/Silver Nanoparticles as an Electrochemically Sensitive Interface for the Detection of Ractopamine in Pork Liver.

Many countries have allowed farmers to feed ß-adrenergic receptor agonists, such as ractopamine (Rac), to animals to improve the quality of their meat. However, Rac consumption can cause health problems for humans; thus, detecting Rac in meat before its packaging is essential. Consequently, this study developed a simple and sensitive electrochemical sensor by modifying a glassy carbon electrode (GCE) with Nafion/silver nanoparticles (Nafion/AgNPs). When this electrochemical sensor is used to detect Rac, electrostatic interaction occurs between Nafion and Rac, and the AgNPs oxidize Rac; thus, the accumulation and electrochemical sensing of Rac are achieved. Differential pulse voltammetry indicated that the as-prepared Nafion/AgNP-GCE sensor exhibited suitable electrochemical sensing ability under optimum conditions (6.0 µL of 0.10% Nafion/AgNPs in a Britton-Robertson buffer solution with a pH of 1.8, an accumulation potential of -0.2 V, and a Rac accumulation duration of 300 s). Moreover, this sensor has an extremely low limit of detection and high sensitivity (1.60 × 10-3 ppm and 2.14 µA/ppm, respectively) in the Rac concentration range 7.50 × 10-3-1.00 ppm. The as-prepared sensor also exhibits satisfactory reproducibility and storage stability, with the corresponding relative standard deviations (RSDs) being 4.27% (n = 5) and 1.56% (n = 10), respectively. The proposed electrochemical sensor was successfully used to determine the Rac content in pig liver samples, with spiked recoveries of 95.2-101.8% and RSDs of 0.55-4.83% being achieved.

Green synthesis of gardenia seeds-based carbon dots for bacterial imaging and antioxidant activity in aqueous and oil samples.

In this work, luminescent carbon dots with gardenia seeds as carbon precursors (GCDs) were synthesized using a one-step mild pyrolysis process and were then used as probes for imaging of bacterial (Escherichia coli). The GCDs showed a strong emission at 430 nm when excited at 370 nm. The relative fluorescence quantum yield of GCDs was found to be 1.13% in an aqueous medium. Rapid internalization of the GCDs by bacteria was confirmed by three colors (blue, green, and yellow) images that were obtained using confocal fluorescence microscopy. In addition, GCDs were noted to exhibit potent scavenging activities against DPPH˙, ˙OH, and ˙O2- free radicals. GCDs were also assayed as antioxidants in an oil sample by volumetric determination of the peroxide value. Thus, GCDs exhibited good antioxidant properties both in aqueous and oil media. In addition, a free fatty acid quantification kit in the presence of GCDs showed enhanced fluorescence detection of palmitic acid with a remarkably good limit of detection of 0.08 µM, which is lower than that in the absence of GCDs (0.76 µM). The proposed fluorescence method was then successfully used to determine the concentration of palmitic acid spiked in milk powder samples, with spiked recoveries of 82.6-109.6% and relative standard deviations of 0.9-4.6%.

A high performance dual-mode biosensor based on Nd-MOF nanosheets functionalized with ionic liquid and gold nanoparticles for sensing of ctDNA.

A dual-mode biosensor constructed based on photoelectrochemical (PEC) and electrochemical (EC) property was developed for assaying circulating tumor DNA (ctDNA), which is commonly used for triple-negative breast cancer diagnosis. Ionic liquid functionalized two-dimensional Nd-MOF nanosheets were successfully synthesized through a template-assisted reagent substituting reaction. Nd-MOF nanosheets integrated with gold nanoparticles (AuNPs) were able to improve photocurrent response and supply active sites for assembling sensing elements. To achieve selective detection of ctDNA, thiol-functionalized capture probes (CPs) were immobilized on the Nd-MOF@AuNPs modified glassy carbon electrode surface, thereby generating a "signal-off" photoelectrochemical biosensor for ctDNA under visible light irradiation. After the recognition of ctDNA, ferrocene-labeled signaling probes (Fc-SPs) were introduced into the biosensing interface. After hybridization between ctDNA and Fc-SPs, the oxidation peak current of Fc-SPs generated from square wave voltammetry can be employed as a "signal-on" electrochemical signal for ctDNA quantification. Under the optimized conditions, a linear relationship was obtained to the logarithm of ctDNA concentration in between 1.0 fmol L-1 to 10 nmol L-1 for the PEC model and 1.0 fmol L-1 to 1.0 nmol L-1 for the EC model. The dual-mode biosensor can provide accurate results for ctDNA assays, effectively eliminating the probable occurrence of false-positive or false-negative results in single-model assays. By switching DNA probe sequences, the proposed dual-mode biosensing platform can serve as a strategy for detecting other DNAs and possesses broad applications in bioassay and early disease diagnosis.

Selective detection of tricyclazole by optical technique using thiomalic acid-modified Au and Ag nanoparticle mixtures.

This study proposes the use of thiomalic acid-modified Au and Ag nanoparticle mixtures (TMA-Au/AgNP mixes) for the selective detection of tricyclazole. Upon the addition of tricyclazole, the color of TMA-Au/AgNP mixes solution changes from orange-red to lavender (red-shift). According to the density-functional theory calculations, tricyclazole-induced aggregation of TMA-Au/AgNP mixes through electron donor-acceptor interactions was proved. The sensitivity and selectivity of the proposed method are affected by the amount of TMA, volume ratio of TMA-AuNPs to TMA-AgNPs, pH value, and buffer concentration. The ratio of absorbance (A654/A520) of TMA-Au/AgNP mixes solution is proportional to the concentration of tricyclazole over the range 0.1-0.5 ppm with a linear correlation (R2 = 0.948). Moreover, the limit of detection was estimated at 0.028 ppm. The practicality of TMA-Au/AgNP mixes was validated for the determination of tricyclazole concentration in real samples (spiked recovery was 97.5%-105.2%), demonstrating its advantages of simplicity, selectivity, and sensitivity.

Dendritic Forest-Like Ag Nanostructures Prepared Using Fluoride-Assisted Galvanic Replacement Reaction for SERS Applications.

Dendritic forest-like Ag nanostructures were deposited on a silicon wafer through fluoride-assisted galvanic replacement reaction (FAGRR) in aqueous AgNO3 and buffered oxide etchant. The prepared nanostructures were characterized using scanning electron microscopy, energy-dispersive X-ray spectroscopy, inductively coupled plasma-optical emission spectroscopy, a surface profiler (alpha step), and X-ray diffraction. Additionally, the dendritic forest-like Ag nanostructures were characterized using surface-enhanced Raman scattering (SERS) when a 4-mercaptobenzoic acid (4-MBA) monolayer was adsorbed on the Ag surface. The Ag nanostructures exhibited intense SERS signal from 4-MBA because of their rough surface, and this intense signal led to an intense local electromagnetic field upon electromagnetic excitation. The enhancement factor for 4-MBA molecules adsorbed on the Ag nanostructures was calculated to be 9.18 × 108. Furthermore, common Raman reporters such as rhodamine 6G, 4-aminothiolphenol, 5,5'-dithiobis-2-nitrobenzoic acid, and carboxyfluorescein (FAM) were characterized on these dendritic forest-like Ag nanostructures, leading to the development of an ultrasensitive SERS-based DNA sensor with a limit of detection of 33.5 nM of 15-mer oligonucleotide.

Detection of melamine based on the suppressed anodic response of uric acid by a Au-Ag nanoparticles modified glassy carbon electrode.

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%.

Microwave-Assisted Synthesis of Chalcopyrite/Silver Phosphate Composites with Enhanced Degradation of Rhodamine B under Photo-Fenton Process.

A new composite by coupling chalcopyrite (CuFeS2) with silver phosphate (Ag3PO4) (CuFeS2/Ag3PO4) was proposed by using a cyclic microwave heating method. The prepared composites were characterized by scanning and transmission electron microscopy and X-ray diffraction, Fourier-transform infrared, UV-Vis diffuse reflectance spectroscopy, and X-ray photoelectron spectroscopy. Under optimum conditions and 2.5 W irradiation (wavelength length > 420 nm, power density = 0.38 Wcm-2), 96% of rhodamine B (RhB) was degraded by CuFeS2/Ag3PO4 within a 1 min photo-Fenton reaction, better than the performance of Ag3PO4 (25% degradation within 10 min), CuFeS2 (87.7% degradation within 1 min), and mechanically mixed CuFeS2/Ag3PO4 catalyst. RhB degradation mainly depended on the amount of hydroxyl radicals generated from the Fenton reaction. The degradation mechanism of CuFeS2/Ag3PO4 from the photo-Fenton reaction was deduced using a free radical trapping experiment, the chemical reaction of coumarin, and photocurrent and luminescence response. The incorporation of CuFeS2 in Ag3PO4 enhanced the charge separation of Ag3PO4 and reduced Ag3PO4 photocorrosion as the photogenerated electrons on Ag3PO4 were transferred to regenerate Cu2+/Fe3+ ions produced from the Fenton reaction to Cu+/Fe2+ ions, thus simultaneously maintaining the CuFeS2 intact. This demonstrates the synergistic effect on material stability. However, hydroxyl radicals were produced by both the photogenerated holes of Ag3PO4 and the Fenton reaction of CuFeS2 as another synergistic effect in catalysis. Notably, the degradation performance and the reusability of CuFeS2/Ag3PO4 were promoted. The practical applications of this new material were demonstrated from the effective performance of CuFeS2/Ag3PO4 composites in degrading various dyestuffs (90-98.9% degradation within 10 min) and dyes in environmental water samples (tap water, river water, pond water, seawater, treated wastewater) through enhanced the Fenton reaction under sunlight irradiation.

Ionic liquid and spatially confined gold nanoparticles enhanced photoelectrochemical response of zinc-metal organic frameworks and immunosensing squamous cell carcinoma antigen.

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.

DNA engineered copper oxide-based nanocomposites with multiple enzyme-like activities for specific detection of mercury species in environmental and biological samples.

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).

Facile Synthesis and Characterization of Ag3PO4 Microparticles for Degradation of Organic Dyestuffs under White-Light Light-Emitting-Diode Irradiation.

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 Facile One-Pot Synthesis of Biomimetic Photocatalyst Zn(II)-Porphyrin-Sensitized 3D TiO2 Hollow Nanoboxes and Synergistically Enhanced Visible-Light Degradation.

A serials of biomimetic photocatalyst zinc(II) meso-tetra(4-carboxyphenyl)porphyrinato (ZnTCP)-sensitized 3D hierarchical TiO2 hollow nanoboxes (TiO2-HNBs) assembled by six ordered nanosheets with dominant {001} facets exposure (ZnTCP@TiO2-HNBs) have been successfully synthesized by a facile one-pot solvothermal method via a topological transformation process with TiOF2 as template. Infrared spectra (IR), UV-vis spectroscopy, and X-ray photoelectron spectroscopy (XPS) confirmed that ZnTCP played a decisive role in constructing 3D hollow nanoboxes through the formation of ester bond combined to TiO2-HNBs, which also provided a transferring photo excited electrons bridge to sensitize TiO2-HNBs for enhancing visible-light response. Due to the superior sensitization and biomimetic activity of ZnTCP, the photodegradation rate of rhodamine B (RhB) of as-prepared ZnTCP@TiO2-HNBs with ZnTCP/TiOF2 mass ratio of 2% (T-2p) improves 3.6 times compared to that of TiO2-HNBs with a degradation yield of 99% for 2 h under simulated sunlight irradiation (> 420 nm). The enhanced photodegradation ability was attributed to synergistic visible photocatalytic mechanism of biomimetic catalyst, which can not only produce hydroxyl radical (•OH) and superoxide radical (•O2-) coming from the excitation process of ZnTCP sensitized TiO2-HNBs, but also generate singlet oxygen (1O2) that was only provided by biomimetic enzyme porphyrins. Furthermore, the photocatalyst showed good recycling stability and dispersibility after five rounds, ascribed to ZnTCP strong chemical bonding to the support TiO2-HNBs. By means of electrochemical cyclic voltammetry analysis, the effect of central zinc ions and parent porphyrin rings on the redox property of biomimetic catalyst was studied.

Determination of mercury (II) ions based on silver-nanoparticles-assisted growth of gold nanostructures: UV-Vis and surface enhanced Raman scattering approaches.

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.

One-step topological preparation of carbon doped and coated TiO2 hollow nanocubes for synergistically enhanced visible photodegradation activity.

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.