Bang n Li

Hemin-functionalized MoS2 nanosheets: enhanced peroxidase-like catalytic activity with a steady state in aqueous solution

Hemin-functionalized MoS2 nanosheets (hemin/MoS2-NSs) are first obtained via van der Waals interactions between few-layered MoS2 nanosheets (MoS2-NSs) and hemin molecules. It is demonstrated that a portion of MoS2-NSs undergoes a phase transition from semiconducting to metallic phase under the influence of hemin, which shows the coexistence of semiconducting and metallic phases in the crystal structure of hemin/MoS2-NSs. MoS2-NSs prepared from sonication-induced exfoliation of bulk MoS2 crystals in aqueous surfactant solution exhibit intrinsic peroxidase-like activity for the oxidation of 3,3,5,5-tetramethylbenzidine in the presence of H2O2, which is further improved by the functionalization of hemin. Significantly, MoS2-NSs are presented as a new support of hemin, and when compared to MoS2-NSs, hemin/MoS2-NSs exhibit better dispersity in aqueous solution, which is used in the development of H2O2 sensor based on the enhanced peroxidase-like activity.

Anodic stripping voltammetric measurement of trace cadmium at tin-coated carbon paste electrode

A carbon paste electrode modified with tin was used for the determination of trace cadmium by anodic stripping voltammetry. The electroanalytical performance for the determination of Cd(II) on the tin-coated carbon paste electrode(SnF-CPE) was better than that on the carbon paste electrode. The measuring conditions have been optimized. The measurement of trace cadmium on the SnF-CPE has the best response under the conditions of 0.10molL(-1) acetate buffer solution (pH 3.9), 3.5mgL(-1) Sn(II), deposition potential of -1.40V, and deposition time of 150s. The SnF-CPE revealed highly linear behavior in the concentration range of 2.0-90.0μgL(-1) with the detection limit of 1.13μgL(-1) for Cd(II). The developed sensor has been applied to the determination of Cd(II) in real water samples with satisfactory results.

A potential fluorescent probe: Maillard reaction product from glutathione and ascorbic acid for rapid and label-free dual detection of Hg2+ and biothiols

Maillard reactions and their fluorescent products have drawn much attention in the fields of food and life science, however, the application of fluorescent products separated from the reaction as an indicator for detection of certain substances in sensor field has not been mentioned. In this article, we report on an easy-to-synthesize and water-soluble fluorescent probe separated from the typical Maillard reaction products of glutathione and ascorbic acid, with excellent stability and high quantum yield (18.2%). The further application of the probe has been explored for dual detection of Hg(2+) and biothiols including cysteine, homocysteine, and glutathione, which is based on Hg(2+)-induced fluorescence quenching of the Maillard reaction fluorescent products (MRFPs) and the fluorescence recovery as the introduction of biothiols. This sensing system exhibits a good selectivity and sensitivity, and the linear ranges for Hg(2+), cysteine, homocysteine, and glutathione are 0.05-12, 0.5-10, 0.3-20, and 0.3-20μM, respectively. The detection limits for Hg(2+), cysteine, homocysteine, and glutathione are 22, 47, 96, and 30nM at a signal-to-noise ratio of 3, respectively. Furthermore, the practical applications of this sensor for Hg(2+) and biothiols determination in water samples and human plasma sample have been demonstrated with satisfactory results.

A fluorescence detection of d-penicillamine based on Cu2+-induced fluorescence quenching system of protein-stabilized gold nanoclusters

In this contribution, a luminescent gold nanoclusters which were synthesized by bovine serum albumin as novel fluorescent probes were successfully utilized for the determination of D-penicillamine for the first time. Cupric ion was employed to quench the strong fluorescence of the gold nanoclusters, whereas the addition of D-penicillamine caused obvious restoration of fluorescence intensity of the Cu(2+)-gold nanoclusters system. Under optimum conditions, the increment in fluorescence intensity of Cu(2+)-gold nanoclusters system caused by D-penicillamine was linearly proportional to the concentration of D-penicillamine in the range of 2.0×10(-5)-2.39×10(-4) M. The detection limit for D-penicillamine was 5.4×10(-6) M. With the off-on fluorescence signal at 650 nm approaching the near-infrared region, the present sensor for D-penicillamine detection had high sensitivity and low spectral interference. Furthermore, the novel gold nanoclusters-based fluorescent sensor has been applied to the determination of D-penicillamine in real biological samples with satisfactory results.

A novel conducting poly(p-aminobenzene sulphonic acid)-based electrochemical sensor for sensitive determination of Sudan I and its application for detection in food stuffs.

In the present work, a new method for the determination of Sudan I has been developed based on a conducting poly(p-aminobenzene sulphonic acid) (poly(p-ABSA)) film modified electrode. The new electrochemical sensor showed strong accumulation ability and excellent electrocatalytic activity for Sudan I. Electrochemical oxidation signal of Sudan I at the poly(p-ABSA) modified glassy carbon electrode (poly(p-ABSA)/GCE) was significantly increased when compared to that at the bare GCE. The experimental conditions such as amount of alcohol, pH of buffer solution, accumulation time, and instrumental parameters for square wave anodic stripping voltammetry were optimised for the determination of Sudan I. Under optimum conditions, the linear regression equation of Sudan I was ip=1.868+0.1213c (ip: μA, c: μgL(-1), R=0.9981) from 1 to 500 μg L(-1) with a detection limit of 0.3 μg L(-1). Finally, this sensor was successfully employed to detect Sudan I in some hot chili and ketchup samples.

A selective and sensitive optical sensor for dissolved ammonia detection via agglomeration of fluorescent Ag nanoclusters and temperature gradient headspace single drop microextraction

In this paper, a simple sensor platform is presented for highly selective and sensitive detection of dissolved ammonia in aqueous solutions without pretreatment based on temperature gradient headspace single drop microextraction (HS-SDME) technique, and fluorescence and UV-vis spectrophotometry are utilized with the Ag nanoclusters (Ag NCs) functioned by citrate and glutathione as the probe. The sensing mechanism is based on the volatility of ammonia gas and the active response of Ag NCs to pH change caused by the introduction of ammonia. High pH can make the Ag NCs agglomerate and lead to the obvious decrease of fluorescence intensity and absorbance of Ag NCs solution. Moreover, the presented method exhibits a remarkably high selectivity toward dissolved ammonia over most of inorganic ions and amino acid, and shows a good linear range of 10-350μM (0.14-4.9mgNL-1) with a low detection limit of 336nM (4.70μgNL-1) at a signal-to-noise ratio of 3. In addition, the practical applications of the sensor have been successfully demonstrated by detecting dissolved ammonia in real samples.

Bio-friendly Maillard reaction fluorescent products from glutathione and ascorbic acid for the rapid and label-free detection of Fe3+ in living cells

Developing probes with good biocompatibility and realizing intracellular detection in living cells are of great significance for biomedicine and life sciences, but remain a challenge presently. In this paper, we describe a rapid and highly selective biosensor for Fe3+ detection in living cells based on the Maillard reaction fluorescent products (MRFPs) of glutathione and ascorbic acid as a probe. Experiments show that the MRFPs are non-cytotoxic and possess excellent biocompatibility. Moreover, the MRFPs show a rapid response and good selectivity towards Fe3+ over other metal ions under physiological pH conditions in vitro. The introduction of Fe3+ can quench the fluorescence of MRFPs, and the fluorescence intensity of system decreases linearly with the increasing concentration of Fe3+ in the range of 0.05-50 μM with the detection limit of 4.6 nM at a signal-to-noise ratio of 3. Moreover, the recognition mechanism has been discussed, which is attributed to the charge transfer from excited-state MRFPs molecules to metal ions. In addition, the MRFPs have been successfully demonstrated to be a good imaging probe for Fe3+ sensing in living cells. This study shows that the biocompatible MRFPs might hold great potential for applications in bioimaging, diagnosis, and therapy of intracellular diseases.