A low-cost, simple, portable and sensitive paper-based electrochemical sensor was established for the detection of K-562 cell in point-of-care testing. The hybrid material of 3D Au nanoparticles/graphene (3D Au NPs/GN) with high specific surface area and ionic liquid (IL) with widened electrochemical windows improved the good biocompatibility and high conductivity was modified on paper working electrode (PWE) by the classic assembly method and then employed as the sensing surface. IL could not only enhance the electron transfer ability but also provide sensing recognition interface for the conjugation of Con A with cells, with the cell capture efficiency and the sensitivity of biosensor strengthened simultaneously. Concanavalin A (Con A) immobilization matrix was used to capture cells. As proof-of-concept, the paper-based electrochemical sensor for the detection of K-562 cells was developed. With such sandwich-type assay format, K-562 cells as model cells were captured on the surface of Con A/IL/3D AuNPs@GN/PWE. Con A-labeled dendritic PdAg NPs were captured on the surface of K-562 cells. Such dendritic PdAg NPs worked as catalysts promoting the oxidation of thionine (TH) by H 2 O 2 which was released from K-562 cells via the stimulation of phorbol 12-myristate-13-acetate (PMA). Therefore, the current signal response was dependent on the amount of PdAg NPs and the concentration of H 2 O 2 , the latter of which corresponded with the releasing amount from cells. So, the detection method of K-562 cell was also developed. Under optimized experimental conditions, 1.5×10 −14 mol of H 2 O 2 releasing from each cell was calculated. The linear range and the detection limit for K-562 cells were determined to be 1.0×10 3 –5.0×10 6 cells/mL and 200 cells/mL, respectively. Such as-prepared sensor showed excellent analytical performance with good fabrication reproducibility, acceptable precision and satisfied accuracy, providing a novel protocol in point-of-care testing of cells.
The exploration of bimetallic Pd-based catalysts has become a hot-spot for the application of high performance electrocatalysts with long term stability in fuels cell. In this work, alloyed Pd x Ag 1 nanoparticles (NPs) ( x = 8, 11, 14, 17, and 20) are synthesized via a solvothermal synthesis approach. The morphologies and compositions of alloyed PdAg NPs are characterized by transmission electron microscopy , scanning electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. The optimized Pd 14 Ag 1 NPs exhibited excellent current activity in ethanol oxidation reaction (EOR) of 2430 mA mg −1 in an alkaline ethanol solution, 3.3 times higher than commercial Pd/C counterpart (727 mA mg −1 ), closely related to the change of electron structure and surface active sites. In addition, compared with other PdAg NPs and commercial Pd/C catalysts, Pd 14 Ag 1 NPs performs better antitoxicity, lower reaction barrier, and better long-term stability. Experimental results show that higher catalytic temperature, higher pH values, and higher ethanol concentration should favor the oxidation of ethanol.
Metal nanoparticles have been extensively used as co-catalysts in photocatalytic systems in order to pursue improvements in both reaction kinetics and selectivity. In this work, PdAg dual-metallic nanoparticles synthesized by the co-reduction method were decorated on a well-established α-Fe2O3/CdS Z-scheme photoactive material as a co-catalyst to study their performance for promoting the photoreduction of CO2. Herein, α-Fe2O3 and CdS were in situ synthesized on fluorine-doped tin oxide (FTO) glass by hydrothermal and SILAR (successive ionic layer adsorption and reaction) methods, respectively. The direct Z-scheme charge transfer path between Fe2O3 and CdS and the effective electron migration toward the PdAg mainly contributed to the excellent photocatalytic CO2 reduction performance. The controllable work function based on Pd (5.12) and Ag (4.26) constructed an appropriate band alignment with α-Fe2O3/CdS and displayed favorable production for CH4 rather than CO. The optimum ratio of PdAg 1:2 performed a 48% enhancement than pure Pd for photoreduction of CO2. Meanwhile, the enhanced charge separation improved the photoelectrochemical performance and photocurrent generation, and reduced the electrical resistance between components. This work provided insights into the dual-metallic co-catalyst for boosting the activity and selectivity of photocatalytic CO2 reduction.
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