A novel strategy for the fabrication of a photoelectrochemical system, involving a duo-dye sensitized Au NPs composite, that displays a specific response to mercury.
Since residual chiral pollutants in the environment and toxic or ineffective chiral components in drugs can threat human health, there is an urgent need for methods to separation and analyze chiral molecules. Molecular imprinting technology (MIT) is a biomimetic technique for specific recognition of analytes with high potential for application in the field of chiral separation and analysis. However, since MIT has some disadvantages when used for chiral recognition, such as poor rigidity of imprinted materials, a single type of recognition site, and poor stereoselectivity, reducing the interference of conformationally and structurally similar substances to increase the efficiency of chiral recognition is difficult. Therefore, improving the rigidity of imprinted materials, increasing the types of imprinted cavity recognition sites, and constructing an imprinted microenvironment for highly selective chiral recognition are necessary for the accurate identification of chiral substances. In this article, the principle of chiral imprinting recognition is introduced, and various strategies that improve the selectivity of chiral imprinting, using derivative functional monomers, supramolecular compounds, chiral assembly materials, and biomolecules, are reviewed in the past 10 years.
In this work, a new method named laser-heating-wax-printing (LHWP) is described to fabricate paper devices for developing sensitive, affordable, user-friendly paper-based enzyme-linked immunosorbent assays (P-ELISAs) that initially use common pen-type pH meters for portable, quantitative readout. The LHWP enables a rapid patterning of wax in paper via one step of heating the wax layer coated on the paper surface using a mini-type CO2 laser machine. Wax-patterned paper microzones created in this way are utilized to conduct the pen-type pH meter-based P-ELISAs with enzyme-loaded SiO2 microbeads for highly efficient signal amplification of each antibody-antigen binding event. The results show that this new P-ELISA system is quantitatively sensitive to the concentrations of a model protein analyte in buffer samples ranging from 12.5 to 200 pg mL-1, with a limit of detection of ca. 7.5 pg mL-1 (3σ). Moreover, the satisfactory recovery results of assaying several human serum samples validate its feasibility for practical applications.
CdS thin films were deposited on indium-tin-oxide (ITO) coated glass substrates by a chemical bath deposition method.Then the CdS/ITO slides were immersed in the solution containing 1.6 mM CuCl 2 and 1.4 mM cetyltrimethylamonium chloride at 37 o C for 3 h to growth Cu 2 S nanoparticles on the CdS/ITO slides.The scanning electron microscopy (SEM) and X-ray diffraction analysis demonstrated the presence of Cu 2 S on the surface of CdS/ITO slides.The electrochemical behavior of the Cu 2 S-CdS/ITO slide was studied using voltammetric scanning method.The Cu 2 S-CdS/ITO slides exhibited an enhanced photocatalytic efficiency towards the degradation of methylene blue dye under irradiation with a Xenon lamp.
A facile method to fabricate Au-CdS (or ZnS, PbS) nanocomposites is reported.The method is based on spontaneous growth of Au onto the metal sulfide nanoparticles.Unlike typical synthesis of Ausemiconductor nanocomposites, this method does not require additional steps of introducing other reducing agents.Direct redox reactions occurs between Au(III) ions and metal sulfide nanoparticles.We have probed the Au-semiconductor nanocomposites by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD).A possible mechanism was proposed for spontaneous growth of Au nanoparticles.It was found that H 2 O 2 appeared to inhibit the Au growth onto the metal sulfide surface.We accordingly developed an enzyme-linked sandwich electrochemical immunosensor for the detection of human immunoglobulin G (IgG).In the electrochemical immunosensor, we use the glucose oxidase labeled antibody to generate H 2 O 2 that inhibits the Au growth on CdS films, thereby decreasing the cathodic current at 0.9 V.This immunosensor can detect IgG as low as 1.5 ng/mL.
Cu2−xS (x = 1, 0.2, 0.03) nanocrystals were synthesized with three different chemical methods: sonoelectrochemical, hydrothermal, and solventless thermolysis methods in order to compare their common optical and structural properties. The compositions of the Cu2−xS nanocrystals were varied from CuS (covellite) to Cu1.97S (djurleite) through adjusting the reduction potential in the sonoelectrochemical method, adjusting the pH value in the hydrothermal method and by choosing different precursor pretreatments in the solventless thermolysis approach, respectively. The crystallinity and morphology of the products were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM), which shows that most of them might be of pure stoichiometries but some of them are mixtures. The obtained XRDs were studied in comparison to the XRD patterns of previously reported Cu2−xS. We found consistently that under ambient conditions the copper deficient Cu1.97S (djurleite) is more stable than Cu2S (chalcocite). Corroborated by recent computational studies by Lambrecht et al. and experimental work by Alivisatos et al. This may be the reason behind the traditionally known instability of the bulk Cu2S/CdS interface. Both Cu2S and the copper-deficient Cu1.97S have very similar but distinguishable electronic and crystal structure. The optical properties of these Cu2−xS NCs were characterized by UV−vis spectroscopy and NIR. All presented Cu2−xS NCs show a blue shift in the band gap absorption compared to bulk Cu2−xS. Moreover the spectra of these Cu2−xS NCs indicate direct band gap character based on their oscillator strengths, different from previously reported experimental results. The NIR spectra of these Cu2−xS NCs show a carrier concentration dependent plasmonic absorption.
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