Caiyan Kang

Catalysis of aptamer-modified AuPd nanoalloy probe and its application to resonance scattering detection of trace UO22+

AuPd nanoalloy and nanopalladium with a diameter of 5 nm were prepared, using sodium citrate as the stabilizing agent and NaBH(4) as the reductant. The nanocatalyst containing palladium on the surface exhibited a strong catalytic effect on the slow NiP particle reaction between NiCl(2) and NaH(2)PO(2), and the NiP particle system showed a resonance scattering (RS) peak at 508 nm. The RS results showed that the Pd atom on AuPd nanoalloy surface is the catalytic center. Combining the aptamer cracking reaction of double-stranded DNA (dsDNA)-UO(2)(2+), AuPd nanoalloy aggregation, and AuPd nanoalloy catalysis, both AuPd nanoalloy RS probe and AuPd nanoalloy catalytic RS assays were developed for the determination of 40-250 pmol L(-1) UO(2)(2+) and 5.0-50 pmol L(-1) UO(2)(2+), respectively.

Selective determination of trace boron based on resonance Rayleigh scattering energy transfer from nanogold aggregate to complex of boric acid–azomethine-H

The nanogold particles were aggregated to stable nanogold aggregates as nanoprobes that exhibited a resonance Rayleigh scattering (RRS) peak at 400 nm in the pH 5.6 NH4Ac–HAc buffer solutions and in the presence of azomethine-H (AMH). Upon addition of boric acid, it reacts with AMH to form AMH–boric acid (AMH–B) complexes. When the complexes (as receptors) are close to the nanogold aggregates (as donors), the RRS-energy transfer (ET) takes place, which results in the RRS signal quenching at 400 nm. The quenching intensity responds linearly with the concentration of boron over 5–500 ng mL−1 B.

A label‐free DNAzyme‐cleaving fluorescence method for the determination of trace Pb2+ based on catalysis of AuPd nanoalloy on the reduction of rhodamine 6G

The substrate chain of double-stranded DNA (dsDNA) could be specifically cleaved by Pb(2+) to release single-stranded DNA (ssDNA) that adsorbs onto the AuPd nanoalloy (AuPdNP) to form a stable AuPdNP-ssDNA complex, but the dsDNA can not protect AuPdNPs in large AuPdNP aggregates (AuPdNPA) under the action of NaCl. AuPdNP-ssDNA and large AuPdNPA could be separated by centrifugation. On increasing the concentration of Pb(2+) , the amount of released ssDNA increased; AuPdNP-ssDNA increased in the centrifugation solution exhibiting a catalytic effect on the slow reaction of rhodamine 6G (Rh6G) and NaH2 PO2 , which led to fluorescence quenching at 552 nm. The decrease in fluorescence intensity (ΔF) was linear to the concentration of Pb(2+) within the range 0.33-8.00 nmol/L, with a detection limit of 0.21 nmol/L. The proposed method was applied to detect Pb(2+) in water samples, with satisfactory results.

Adsorption Kinetics and Thermodynamics of Auramine-O on Sugarcane Leaf-Based Activated Carbon

The removal efficiency, adsorption kinetics, and thermodynamics of Auramine-O (AO) onto sugarcane leaf-based activated carbon prepared by ammonium dihydrogen phosphate were investigated systematically. The optimal AO removal conditions were found to infuse 1.2 g/L sugarcane leaf-based activated carbon in 200 mg/L AO solution which the initial pH (pH0) was 9.0 for 180 minutes. The adsorption kinetics of AO was described well by the pseudo-second-order and intra-particle diffusion model. The intra-particle diffusion was not the exclusive rate controlling step in the adsorption process. The isotherm obeyed the Langmuir isotherm with a high correlation coefficient (R2 > 0.99), and the thermodynamic analysis suggested that ΔG < 0, ΔH > 0, and ΔS > 0, which indicated that the adsorption of AO onto sugarcane leaf-based activated carbon was a spontaneous chemical and endothermic adsorption process. GRAPHICAL ABSTRACT

Properties and thermal analysis study of modified polyvinyl acetate (PVA) adhesive

Abstract Polyvinyl acetate (PVA) adhesive is one of the most common types of adhesives has been used in the wood industry for decades. However, many drawbacks are still associated with this adhesive including low water resistance, poor bond strength, and low viscosity. In this reported study, two additives, sulfanilamide and N,N-dimethylethylenediamine, were used to modify a PVA adhesive to improve its comprehensive practical performance. The prepared adhesive samples were characterized by Fourier transform infrared spectroscopy (FT-IR). Furthermore, the thermal decomposition characteristics of the PVA adhesives were studied using Thermal Gravimetric Analysis (TGA) and Differential Scanning Calorimetry analysis (DSC) combined with the Kissinger method. The experimental results showed that when compared to the pure PVA adhesive, the solid content, viscosity, dry bond strength, and wet bond strength of the modified PVA adhesive (PVA + N,N-dimethylethylenediamine + sulfanilamide) were improved by 34.8, 41.4, 47.0 and 35.2%, respectively. FT-IR analysis indicate that these two additives altered the chemical bond ratio that resulted from the generation of new chemical bonds, which explained the improved performance of the modified PVA adhesive. The pure PVA adhesive possessed two thermal decomposition steps, while the modified PVA adhesive (PVA + N,N-dimethylethylenediamine + sulfanilamide) exhibited only one thermal decomposition step. The thermal decomposition process of the pure PVA adhesive is characterized by a quick thermal decomposition stage and a slow thermal decomposition stage. Since the ΔH > 0, ΔS < 0 and ΔG > 0 in the thermal decomposition process it can be concluded that the decomposition reactions of the PVA adhesive were non-spontaneously endothermic and the entropy decreased during the reaction.