Step-Scheme SnO2/Zn3In2S6 Catalysts for Solar Production of Hydrogen Peroxide From Seawater.

Photocatalytic generation of H2O2, involving both oxygen reduction and water oxidation without sacrificial agents, necessitates maximized light absorption, suitable band structure, and efficient carrier transport. Leveraging the redox capacity this study designs and constructs a step-scheme heterostructured SnO2/Zn3In2S6 catalyst for H2O2 production from seawater under ambient conditions for the first time. This photocatalyst demonstrates a remarkable H2O2 production rate of 43.5 µmol g⁻¹ min⁻¹ without sacrificial agents, which can be increased to 80.7 µmol g⁻¹ min⁻¹ with additional O2 injection. Extensive in situ and ex situ characterizations, supported by theoretical calculations, reveal efficient carrier transport and robust redox ability, enabling complete photosynthesis of H2O2 at the oxidation and reduction sites in the S-scheme SnO2/Zn3In2S6 heterojunction. Furthermore, it is hypothesized that substituting SnO2 with other semiconductors such as TiO2, WO3, and BiVO4 can all form S-scheme and the results confirm the feasibility of such catalyst design. Additionally, it demonstrates the recycling and further utilization of the H2O2 produced. These findings offer new insights into the design of heterostructure catalyst architectures and present new opportunities for H2O2 production from seawater at ambient conditions without sacrificial agents.

A novel molecularly imprinted electrochemical sensor based on quasi-three-dimensional nanomaterials Nb2CTx/AgNWs for specific detection of sulfadiazine.

A novel molecularly imprinted electrochemical sensor (MIECS) was constructed for the specific detection of sulfadiazine (SDZ) in food. Niobium carbide (Nb2CTx) as a typical two-dimensional lamellar nanomaterial has good electrical conductivity and unique structure, which was assembled with one-dimensional silver nanowires (AgNWs) to form quasi-three-dimensional composite nanomaterials (Nb2CTx/AgNWs). As spacer material, AgNWs prevented the aggregation of Nb2CTx and the collapse of Nb2CTx layers. At the same time, a fast electron transport channel was constructed through the synergistic effect between nanomaterials the two. The Nb2CTx/AgNWs realized the enhancement of electrical signals. Molecularly imprinted polymers (MIPs) endowed the sensor with selectivity, achieving the specific detection of sulfadiazine. Under the optimal experimental conditions, the method has a wide linear range (1 × 10-8-1 × 10-4 mol L-1) and a low limit of detection (1.30 × 10-9 mol L-1). The sensor was used to detect sulfadiazine in pork, chicken, and feed samples, and the recovery was 82.61-94.87%. The results were in good agreement with the HPLC results, which proved the accuracy and practicability of the method.

Detection of heterocyclic amine (PhIP) by fluorescently labelled cucurbit[7]uril.

Heterocyclic amines (HCA) are the main mutagenic factors in cooked meat products and are considered to be hazardous chemicals in the field of food safety. In this study, inspired by the "host-guest" interaction mechanism, a new technique for detecting 2-amino-1-methyl-6-phenylimidazo [4,5-b] pyridine (PhIP) was developed, taking advantage of the molecular cavities of cucurbit[7]uril (CB[7]) and the powerful guest recognition properties between CB[7] and PhIP. Based on this recognition mechanism, three steps were included in the detection procedure: firstly, regenerated cellulose (RC) membrane was oxidized by NaIO4 to generate aldehyde groups; secondly, the PhIP molecules to be detected were trapped by the aldehyde groups via amine-aldehyde conjugation chemistry; thirdly, the RC membrane with trapped PhIP was immersed into solutions of dansyl chloride-labelled CB[7] to allow the host-guest interaction to occur, so that PhIP could be quantified by fluorescence of the dansyl chloride dye. The limit of detection, linear range and recovery of this method were about 0.224 µg kg-1, 10-1000 nM and 89.0-96.4%, respectively. So far, most reported techniques for HCA detection are based on HPLC coupled with mass spectroscopy, and the method reported here might be the first quick measurement technique for HCA and may find wide application in food safety detection.

Electrochemical detection of organophosphorus pesticides based on amino acids-conjugated P3TAA-modified electrodes.

In this work, amino acids (AAs) including serine (S), histidine (H) and glutamic acid (E)-conjugated poly(3-thiophene acetate acid) (P3TAA) were synthesized to promote the catalytic hydrolysis and in situ electrochemical detection of organophosphorus pesticides (OPs). The hydrolysis of OPs followed the mechanism of proton transfer relay composed of AAs of S, H, E, called the "catalytic triad", found in biomimetic hydrolases. P3TAA was used as a carrier to attach S, H, E, and these AA sites have the hydrolysis activity of Ops; the polymer P3TAA-AAs behaved like biomimetic enzymes. After the hydrolysis of OPs (e.g., methyl paraoxon, ethyl paraoxon and methyl parathion), p-nitrophenol (PNP) was generated, which can be detected electrochemically. Herein, an electrochemical method using P3TAA-conjugated S, H, E-modified electrodes for the determination of OPs was developed. OPs can be quantified by the electrochemical responses of PNP. This technique was selective toward OPs with the p-nitrophenol group. The detection limit of OPs (methyl paraoxon, methyl parathion and ethyl paraoxon) reached 0.5 µM. This detection technique was successfully applied to the detection of OPs in real samples with high detection accuracy.

Nanocomposites based on quasi-networked Au1.5Pt1Co1 ternary alloy nanoparticles and decorated with poly-L-cysteine film for the electrocatalytic application of hydroquinone sensing.

A mildly one-pot method is developed for the synthesis of quasi-networked Au1.5Pt1Co1 ternary alloy nanoparticles (TANPs) at room temperature through the co-reduction of AuCl4-, PtCl6- and Co2+ with hydrazine hydrate. Characterizations of XRD, XPS, HRTEM, EDS and SAED successfully reveal the crystal structure, composition, valence and morphology of Au1.5Pt1Co1 TANPs, respectively. The glassy carbon electrode (GCE) modified by Au1.5Pt1Co1 TANPs with good dispersion and multi-density surface defects occupies the optimal electrochemical active surface area (ECSA). After the coated poly-L-cysteine (P-L-Cys) film on the Au1.5Pt1Co1/GCE surface, the morphology, element mapping and surface roughness of the P-L-Cys/Au1.5Pt1Co1/GCE are investigated via FESEM and AFM to verify continuous electrode modification processes. The electrochemical behaviors of the composite electrode for hydroquinone (HQ) are evaluated by cyclic voltammetry (CV) with interfacial properties of adsorption and diffusion. Differential pulse voltammetry (DPV) for HQ electrochemical sensing at 0.10 V (vs. SCE) exhibits two linear response ranges from 0.1 to 30 and 30-200 µM, respectively. A low detection limit (S/N = 3) of 0.045 µM is obtained with a sensitivity of 4.247 µA µM-1·cm-2. The resulting P-L-Cys/Au1.5Pt1Co1/GCE also presents ascendant selectivity, repeatability, reproducibility and stability. In addition, the established method is applied to the assessment of the HQ level in real water samples (mineral water, tap water and lake water) with the satisfactory results of spiked recoveries. The sensor may become a promising tool for the trace analysis of the electroactive substance in food or environmental samples.

Carboxyl-functionalized hollow polymer microspheres for detection of trace metal elements in complex food matrixes by ICP-MS assisted with solid-phase extraction.

In this work, carboxyl-functionalized hollow polymer microspheres (CHPMs) was successfully fabricated using poly (styrene-itaconic anhydride) particles as the core template and itaconic anhydride and trans-anethole cross-linked with divinylbenzene as the shell. The desirable microspheres and hollow structure of CHPMs were demonstrated by scanning and transmission electron microscopies, respectively. The characterized CHPMs as an adsorbent was packed into a solid phase extraction column to simultaneously detect the V(V), Cr(III), Cu(II), Cd(II), and Pb(II) in digested food samples by inductively coupled plasma-mass spectrometry (ICP-MS). A series of experimental parameters of solid-phase extraction (SPE) were investigated through vast experiments to improve sensitivity of the proposed method in metal ions detection. The detection limits of the method reached 0.8-3.2 ng L-1 for the target elements, and the relative standard deviations (RSDs) ranging from 1.2% to 3.5% were obtained from eleven parallel experiments using a 1.0 µg L-1 sample solution. The stability allowed the material to withstand more than 15 cycling while the recoveries remained above 88%. In food samples, the detection limits were at 0.20-0.80 µg kg-1, and satisfactory recoveries of 85-104% were obtained in spike tests of laver, fish as well as chicken.

Ratiometric determination of Cr(VI) based on a dual-emission fluorescent nanoprobe using carbon quantum dots and a smartphone app.

A simple dual-colour fluorescent nanoprobe has been designed composed of blue and yellow emission carbon quantum dots (CQDs). This system is inexpensive and easy to operate and was successfully employed for on-site measurements based on a smartphone app. The designed nanoprobe exhibited increased selectivity for Cr(VI), leading to a double stable response of the two CQDs. The dual-emission nanoprobe showed blue-violet fluorescence upon UV irradiation, and the fluorescent emission peaks were located at 418 nm and 552 nm. The blue light emission of CQDs was quenched with increasing Cr(VI) concentration due to the inner filter effect, whereas the yellow light emission was enhanced due to the aggregation-induced emission effect. The different responses of the dual emissions to Cr(VI) resulted in a fluorescent colour variation, thus enabling facile macroscopic visualization. With a smartphone, the change in the fluorescence colour could be observed more apparently than that of a single fluorescence nanoprobe, and the response increased linearly so that the nanoprobe could be applied to instantaneous measurements. Furthermore, the dual-emission nanoprobe was successfully employed for analysing food and water samples. Accurate concentrations were obtained by constructing a calibration plot using a fluorescence spectrometer and a smartphone app; the recoveries were 81.6% to 107.7%, and the relative standard deviation was below 3.6%. Therefore, this smartphone-integrated dual-emission detection system is promising as a new portable method for the on-site measurement of Cr(VI) ions. * Y-CQDs: yellow emission carbon quantum dots. B-CQDs: blue emission carbon quantum dots. B/Y-CQDs: a mixture of B-CQDs and Y-CQDs.

Nano-crystalline cellulose-coated magnetic nanoparticles for affinity adsorption of glycoproteins.

A new core-shell structured nanomaterial based on Fe3O4 nanoparticles and 2,3-dialdehyde nanocrystalline cellulose (DAC) coating and its high efficiency in the preconcentration of glycoproteins were described in this work. DAC was obtained after the periodate oxidation of nanocrystalline cellulose to form aldehyde groups; then, Fe3O4 nanoparticles were coated with DAC, which were further attached to 4-aminophenylboronic acid (PBA) to form PBA-functionalized magnetic core-shell structured materials (Fe3O4@DAC-PBA). The oxidation of cellulose and the production of sufficient amounts of aldehyde group sites were essential for the preparation of Fe3O4@DAC-PBA used for the affinity adsorption of glycoproteins because the aldehyde groups on DAC allowed DAC to attach to the Fe3O4 nanoparticles and bind with PBA, which was active in forming a complex with the glyco sites in glycoproteins. Moreover, the preconcentration properties of Fe3O4@DAC-PBA through PBA adsorption can be pH-triggered without the disassembly of the structures; thus, the developed Fe3O4@DAC-PBA can be efficiently prepared to provide a promising affinity material for the affinity adsorption and purification of glycoproteins.

Fluorescent methylammonium lead halide perovskite quantum dots as a sensing material for the detection of polar organochlorine pesticide residues.

Methylammonium lead halide perovskite quantum dots (MAPB-QDs) have been widely used for photovoltaic devices due to their special electronic structures. In this work, MAPB-QDs were used for the first time to detect polar organochlorine pesticides (OCPs) based on the phenomenon that the fluorescence spectra of MAPB-QDs were blue-shifted in the presence of polar OCPs. Furthermore, 1H NMR, FTIR, XPS and XRD were performed first to illustrate the sensing mechanism. In the presence of polar OCPs, the MAPB-QDs' capping ligands, oleic acid (OA) and oleylamine (OAm), were replaced with OCPs and then the chlorine element was adequately doped into QDs, resulting in the increase of the MAPB-QDs' bandgap. As result of the insufficient stability of MAPB-QDs in the presence of moisture, MAPB-QDs were mixed with PDMS and used as the colorimetric cards for fast detection of OCPs in real samples.

A molecularly imprinted fluorescence nanosensor based on upconversion metal-organic frameworks for alpha-cypermethrin specific recognition.

A sensitive molecularly imprinted fluorescent nanosensor based on zeolitic imidazolate frameworks-8 (ZIF-8) and upconversion nanoparticles (UCNPs) was developed for the determination of trace alpha-cypermethrin (α-CPM) for the first time. The sensor was synthesized by a layer-by-layer self-assembly strategy. UCNPs with a maximum emission wavelength of 544.5 nm under 980 nm excitation were firstly prepared as the luminous core. Then, ZIF-8 with the large specific surface and porosity was introduced, which not only improved the mass transfer and adsorption capacity of the sensor but also increased the fluorescence intensity of UCNPs as a protective layer. Finally, molecularly imprinted polymers (UCNPs@ZIF-8@MIPs) were fabricated in mixed solutions containing UCNPs@ZIF-8 (support material), α-CPM (template), acrylamide (functional monomer), and divinylbenzene (cross-linker). Under the optimal condition, the fluorescence intensity of UCNPs@ZIF-8@MIP was linearly quenched with increasing concentration of α-CPM in the range 0.10-12 mg L-1 with a detection limit of 0.03 mg L-1 (S/N = 3). The developed UCNPs@ZIF-8@MIP probe was used to detect α-CPM in real samples; the satisfactory results obtained were consistent with those obtained by GC-MS.Graphical abstract.

Fluorometric determination of tyramine by molecularly imprinted upconversion fluorescence test strip.

A fluorometric method based on molecularly imprinted upconversion fluorescence test strip was developed for the determination of tyramine. It exploited the green fluorescence of upconversion nanoparticles (UCNPs) and the specific recognition property of molecularly imprinted polymers (MIPs). UCNPs were attached to filter paper with glue, and MIPs were prepared via in situ polymerization on the surface of UCNPs by using tyramine as template, methacrylic acid as functional monomer, and ethylene glycol dimethacrylate as cross-linker. The green fluorescence of the test strip, with excitation/emission wavelength 980/550 nm, was enhanced by tyramine. The test strip was suitable for the determination of tyramine in the linear range 1.0-100.0 mg L-1, and a relatively low limit of detection (0.2 mg L-1) was achieved. The test strip also worked well for the quantitation of tyramine in spiked red wine and mature vinegar. Recoveries are ranged from 84.9 to 99.9%. The relative standard deviations are below 5.6%. Graphical abstract.

AuNP-peptide probe for caspase-3 detection in living cells by SERS.

Colloidal nanoparticles can be used as surface-enhanced Raman scattering (SERS) substrates because the very close spacing between particles existing in these colloidal systems is beneficial for the generation of extremely strong and highly spatially localized electric field enhancements. Herein, a caspase-3-specified peptide was used as a molecular cross-linker to engineer gold nanoparticle (AuNP) junctions in a controllable manner. The peptide was designed with a sequence of CCALNNPFFDVED (Cys-Cys-Ala-Leu-Asn-Asn-Pro-Phe-Phe-Asp-Val-Glu-Asp) or CCALNNKYDDVED (Cys-Cys-Ala-Leu-Asn-Asn-Lys-Tyr-Asp-Asp-Val-Glu-Asp), where the CALNN (Cys-Ala-Leu-Asn-Asn) fragment helps to stabilize AuNP suspension in aqueous media and the sequence of DVED (Asp-Glu-Val-Asp) can be cleaved by caspase-3. In addition, the PFF (Pro-Phe-Phe) or KYD (Lys-Tyr-Asp) was exposed and interacted via the hydrophobic or alternate negative and positive electro-interaction in the presence of caspase-3, inducing the aggregation of colloidal Au-peptides accompanied with the enhancement of SERS. It can be observed that the SERS-enhanced signals were correlated with the caspase-3 concentrations and the limit of detection can reach 1.5 ng mL-1. Finally, this caspase-3-specified AuNP-peptide probe has been found to be a promising candidate for its application in the analysis of caspase-3 in living cells.

Near-infrared-emitting persistent luminescent nanoparticles modified with gold nanorods as multifunctional probes for detection of arsenic(III).

Near infrared (NIR)-emitting persistent luminescent nanoparticles (PLNPs) have advantages such as long afterglow, high photostability and deep tissue spectral penetration. A NIR-emitting inner filter effect (IFE) probe for arsenic(III) is described here. It is composed of polyethyleneimine-coated PLNPs and gold nanorods (AuNPs) coated with dithiothreitol. The probe can detect arsenic(III) (= arsenite) selectively even in the presence of interfering substances. The PLNPs and AuNPs were prepared by a hydrothermal method combined with high-temperature calcination and seed-mediated growth mechanism, respectively. The PLNPs show excellent NIR luminescence (with excitation/emission peaks at 254/695 nm) and long afterglow (lifetime >1200 s). The use of polyethyleneimine improves water solubility and provides positive surface charges for the PLNPs. On exposure to arsenite ions, the luminescence of the probe at 695 nm is restored. Under the optimum conditions, the method can detect As(III) in the 0.067 to 13.4 µmol·L-1 concentration range with good linear relationship (R2 = 0.99734), and the detection limit (at S/N = 3) is 55 nmol·L-1. The precision of this method was demonstrated by 11 replicate detections of 2 µmol·L-1 As(III), and the relative standard deviations (RSD) is 2.1%. The practicality was evaluated by the analyses of real water samples and recoveries for the water samples spiked with 2, 5 and 10 µmol·L-1 of As(III) were 89.8%-100.1% with RSDs ranging from 3.0-5.7%. Graphical abstract A near infrared-emitting inner filter effect (IFE) inhibition probe is presented. It is based on the combination of polyethyleneimine (PEI)-coated NIR-emitting persistent luminescent nanoparticles (type Zn1.25Ga1.5Ge0.25O4: Cr3+, ZGGO) (PLNPs-PEI) with dithiothreitol (DTT)-coated gold nanorods (AuNPs) (DTT-AuNPs) to detect arsenite.

In-situ graft-crosslinked gold nanoparticles with high-density surface defects and coated with a polytaurine membrane for the voltammetric determination of dopamine.

Well-dispersed and graft-crosslinked gold nanoparticles (AuNPs) were synthesized by the reduction of tetrachloroaurate with hydrazine at room temperature. The AuNPs possess a high density of surface defects which is due to grafting of n-octanoic acid to polyvinylpyrrolidone. The physical and chemical properties of the resulting AuNPs were characterized by UV-vis, XRD, TEM/HRTEM, SAED, and XPS, respectively. The modified AuNPs were placed on a glassy carbon electrode (GCE) in an electropolymerized taurine layer to obtain a sensitive, selective, stable and rapid electrochemical dopamine sensor. The peak current, typically measured at 0.17 V (vs. SCE), increases linearly in the 1.0 to 120 µM dopamine concentration range, and the limit of detection (at S/N = 3) is 0.16 µM with a sensitivity of 2.94 µA·µM-1·cm-2. The sensor was successfully applied to the determination of dopamine in injections and spiked serum samples. The recoveries from spiked serum samples range from 97.5 to 102.4%, with RSDs ranging between 2.8 and 3.4%. Graphical abstract Schematic representation of a glassy carbon electrode modified with in-situ graft-crosslinked gold nanoparticles combined with an electropolymerized polytaurine membrane. The sensor exhibits excellent features towards dopamine determination.

Highly Bright Self-Assembled Copper Nanoclusters: A Novel Photoluminescent Probe for Sensitive Detection of Histamine.

In this work, highly photoluminescent (PL) self-assembled copper nanoclusters (Cu NCs) capable of rapid, sensitive, and selective detection of histamine were developed. Cu NCs were synthesized in facile conditions by using 2,3,5,6-tetrafluorothiophenol (TFTP) as both the reducing agent and the protecting ligand, which exhibited intense saffron yellow (590 nm) PL via self-assembled induced emission (SAIE), and the absolute quantum yield (QY) of assembly was as high as 43.0%. The size, electronic states, and morphologies of the assembled nanoribbons were characterized, and the geometric structure and spectral properties of the Cu NCs were investigated by theoretical study. Furthermore, the mechanism of the excellent sensing performance of Cu NCs toward histamine was demonstrated by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and energy dispersive X-ray analysis (EDX). With this sensing system, the amount of histamine in fish, shrimp, and red wine were analyzed, and experiment results verified the application of the sensor. Importantly, the luminescent test strips based on Cu NCs were fabricated for colorimetric detection of histamine in foods. This proposed technique may provide an alternative to traditional methods for histamine detection.

A Colorimetric Probe Based on Functionalized Gold Nanorods for Sensitive and Selective Detection of As(III) Ions.

A colorimetric probe for determination of As(III) ions in aqueous solutions on basis of localized surface plasmon resonance (LSPR) was synthesized. The dithiothreitol molecules with two end thiols covalently combined with Au Nanorods (AuNRs) with an aspect ratio of 2.9 by Au-S bond to form dithiothreitol coated Au Nanorods (DTT-AuNRs), acting as colorimetric probe for the determination of As(III) ions. With the adding of As(III) ions, the AuNRs will be aggregated and leading the longitudinal SPR absorption band of DTT-AuNRs decrease due to the As(III) ions can bind with three DTT molecules through an As-S linkage. The potential factors affect the response of DTT-AuNRs to As(III) ions including the concentration of DTT, pH values of DTT-AuNRs, reaction time and NaCl concentration were optimized. Under optimum assay conditions, the DTT-AuNRs colorimetric probe has high sensitivity towards As(III) ions with low detection limit of 38 nM by rules of 3σ/k and excellent linear range of 0.13⁻10.01 µM. The developed colorimetric probe shows high selectivity for As(III) ions sensing and has applied to determine of As(III) in environmental water samples with quantitative spike-recoveries range from 95.2% to 100.4% with low relative standard deviation of less than 4.4% (n = 3).

A Sensitive Electrochemical Immunosensor Based on PAMAM Dendrimer-Encapsulated Au for Detection of Norfloxacin in Animal-Derived Foods.

In this work, a sensitive electrochemical immunosensor has been reported for the determination of norfloxacin in animal-derived foods. The poly (amidoamine) dendrimer encapsulated gold nanoparticles (PAMAM-Au) played dual roles in the proposed sensing platform which not only accelerated the electron transfer process of sensing, but also increased the efficiency of the immobilized antibody. The HRP-labeled antigen, as the signal labels in the immunosensor, was introduced to catalyze the following reaction of the substrate hydroquinone with the aid of H2O2 in the competitive reaction. On the basis of the signal amplification of PAMAM-Au, the signal intensity was linearly related to the concentration of norfloxacin in the range of 1 μg·L−1⁻10 mg·L−1. All the results showed that the proposed strategy with low LOD (0.3837 μg·L−1) and favorable recovery (91.6⁻106.1%) in the practical sample, and it could provide a suitable protocol for norfloxacin detection in animal-derived foods with high sensitivity, good accuracy, and stability.

Design of Cyclic Peptide Based Glucose Receptors and Their Application in Glucose Sensing.

Glucose assay is of great scientific significance in clinical diagnostics and bioprocess monitoring, and to design a new glucose receptor is necessary for the development of more sensitive, selective, and robust glucose detection techniques. Herein, a series of cyclic peptide (CP) glucose receptors were designed to mimic the binding sites of glucose binding protein (GBP), and CPs' sequence contained amino acid sites Asp, Asn, His, Asp, and Arg, which constituted the first layer interactions of GBP. The properties of these CPs used as a glucose receptor or substitute for the GBP were studied by using a quartz crystal microbalance (QCM) technique. It was found that CPs can form a self-assembled monolayer at the Au quartz electrode surface, and the monolayer's properties were characterized by using cyclic voltammetry, electrochemical impedance spectroscopy, and atomic force microscopy. The CPs' binding affinity to saccharide (i.e., galactose, fructose, lactose, sucrose, and maltose) was investigated, and the CPs' sensitivity and selectivity toward glucose were found to be dependent upon the configuration,i.e., the amino acids sequence of the CPs. The cyclic unit with a cyclo[-CNDNHCRDNDC-] sequence gave the highest selectivity and sensitivity for glucose sensing. This work suggests that a synthetic peptide bearing a particular functional sequence could be applied for developing a new generation of glucose receptors and would find huge application in biological, life science, and clinical diagnostics fields.

Capillary electrochromatography immunoassay for alpha-fetoprotein based on poly(guanidinium ionic liquid) monolithic material.

Alpha-fetoprotein (AFP) is widely used as a tumor marker for the serum diagnosis of primary hepatoma. Sensitive detection of AFP level plays an important role in the early diagnosis of disease and highly reliable prediction. In this study, a novel non-competitive immunoassay (IA) based on poly(guanidinium ionic liquid) monolithic material was developed for detecting ultra trace levels of AFP in capillary electrochromatography (CEC) mode. The AFP was mixed with an excess amount of fluorescently labeled antibody. After incubation, the immunocomplex was separated from the free labeled antibody and detected by CEC coupled with laser-induced fluorescence detector. Under the optimized conditions, the developed CEC-IA performed a low detection limit of 0.05 µg L-1 (S/N = 3) and a wide linearity ranging from 0.1 to 1000 µg L-1 for AFP, which can be largely attributed to the high separation and enrichment efficiency of poly(guanidinium ionic liquid) monolithic material for the targets. The application of this method was demonstrated by determining AFP in human serum.

Synthesis of highly fluorescent gold nanoclusters and their use in sensitive analysis of metal ions.

As a promising fluorescent material, gold nanoclusters (Au NCs) have been used for biosensing and imaging. In metal ion sensing, the fluorescence of Au NCs is usually quenched in the presence of ions, but the reaction mechanism has not been clarified. In this work, mercaptan acids (3-mercaptopropanoic acid (3-MPA), 6-mercaptohexanoic acid (6-MHA), 11-mercaptoundecanoic acid (11-MUA) and 16-mercaptohexadecanoic acid (16-MHA)) were used as reductants and ligands to synthesize fluorescent Au NCs. The Au NCs had a core containing 18 atoms capped by 18 (3-MPA) or 10 (6-MHA, 11-MUA, 16-MHA) ligand molecules. The Au NCs prepared in this work had higher fluorescence quantum yields than those reported previously and the fluorescence showed a red-shift when varying the chain length of the mercaptan acids. It was found that in presence of ions (Mo(vi), Hg(ii)), the fluorescence of the Au NCs is dependent upon the ligands. The Au NCs with 3-MPA and 6-MHA ligands were sensitive to Mo(vi) and Hg(ii), while the Au NCs capped with 11-MUA and 16-MHA ligands were not sensitive to the ions. Various characterization techniques, including transmission electron microscopy, matrix-assisted laser-desorption ionization time of flight mass spectrometry, X-ray photoelectron spectroscopy, UV-Vis absorption spectroscopy and thermogravimetric analysis, were used to investigate the components and electronic structure of the clusters, as well as the emission and excitation properties before and after the reaction with metal ions. The structure of the Au NCs after the reaction with Mo(vi) and Hg(ii) was also studied. It was found that Mo(vi) and Hg(ii) both reacted with the gold atoms at the core site, but the reaction mechanisms were different.