Engineering one-dimensional trough-like Au-Ag2S nano-hybrids for plasmon-enhanced photoelectrodetection of human α-thrombin

Interface-confined precise processing of Ag nanowire into AgPd-nanoparticle-sealed AgAu nanotroughs for boosting ethanol electrooxidation

The functions of nanomaterials are closely linked with their fine structures and compositions. Precisely processing nanoparticles into morphology- and composition-varied nanostructures can a cutting-edge technology for producing complex nanostructures. Herein, we develop an interface-confined precise processing strategy towards toluene/water-interfacial Ag nanowires. Interfacial Ag nanowires are transformed into AgPd-nanoparticle-sealed AgAu nanotroughs with abundant AgPd/AgAu hetero-junctions (i.e., AgPdAu hetero-junction nanostructures). By adjusting the reaction conditions, composition-varied AgPdAu hetero-junction nanostructures can be obtained. The formation of AgPdAu hetero-junction nanostructures can be attributed to interface-confined precise etching towards Ag nanowires separately from the two subphases of the water and the toluene. Composition-optimized Ag13Pd67Au20 hetero-junction nanostructure shows satisfactory catalytic performance towards ethanol electrooxidation: ∼4 and 2 times in electrochemical-activity-surface-area-normalized activities; ∼6 and 5 times in mass-normalized activities higher than commercial Pd/C and Pt/C, respectively. The outstanding catalytic capability of Ag13Pd67Au20 may be attributed to optimized composition, porous nanostructures as well as abundant AgPd/AgAu hetero-junctions. This work demonstrates the feasibility of precisely processing interfacial nanoparticles, opening the way for creating morphology-well-defined composition-varied complex nanostructures.

PEC thrombin aptasensor based on Ag-Ag2S decorated hematite photoanode with signal-down effect of precipitation catalyzed by G-quadruplexes/hemin

A photoelectrochemical (PEC) aptasensor for thrombin detection was rationally designed based on the photoanode of one-dimensional hematite nanorods (α-Fe₂O₃ NRs) with several steps of modifications. Uniform α-Fe₂O₃ NRs were grown vertically on the surface of fluorine-doped tin oxide (FTO) conductive glass through a one-step hydrothermal method; then Ag was grown on the surface of α-Fe₂O₃ NRs through a photoreduction method followed by a partial in-situ transformation into Ag₂S, conferring an improvement on the initial photocurrent. Two main critical factors, namely, the steric hindrance of thrombin, benzoquinone (BQ) precipitation oxidized by H₂O₂ under the catalysis of G-quadruplexes/hemin, contributed to the sensitive signal-down response toward the target. Photocurrent signals related with thrombin concentration was established for thrombin analysis due to the non-conductive complex as well as their competitive consumption of electron donors and irradiation light. The excellent initial photocurrent was combined with the signal-down amplification in the design of the biosensor, conferring a limit of detection (LOD) as low as 40.2 fM and a wide linear range from 0.0001 nM to 50 nM for the detection of thrombin. The proposed biosensor was also assessed in terms of selectivity, stability, and applicability in human serum analyses, which provided an appealing maneuver for the specific analysis of thrombin in trace amount.

Recent Progresses in Development of Biosensors for Thrombin Detection

Thrombin is a serine protease with an essential role in homeostasis and blood coagulation. During vascular injuries, thrombin is generated from prothrombin, a plasma protein, to polymerize fibrinogen molecules into fibrin filaments. Moreover, thrombin is a potent stimulant for platelet activation, which causes blood clots to prevent bleeding. The rapid and sensitive detection of thrombin is important in biological analysis and clinical diagnosis. Hence, various biosensors for thrombin measurement have been developed. Biosensors are devices that produce a quantifiable signal from biological interactions in proportion to the concentration of a target analyte. An aptasensor is a biosensor in which a DNA or RNA aptamer has been used as a biological recognition element and can identify target molecules with a high degree of sensitivity and affinity. Designed biosensors could provide effective methods for the highly selective and specific detection of thrombin. This review has attempted to provide an update of the various biosensors proposed in the literature, which have been designed for thrombin detection. According to their various transducers, the constructions and compositions, the performance, benefits, and restrictions of each are summarized and compared.

Investigation of photoelectric behaviors of silver sulfide particles in different surroundings

Silver sulfide (Ag2S) is a traditional semiconductor material, however, the photoelectric properties of Ag2S particles under different environments are still lacking. In this paper, we reported the preparation of Ag2S particles and their photoelectric properties under different environments. Results showed that the photoelectric performance of Ag2S particles was closely related to the environment. It was found that a copper phthalocyanine coating could improve the light response, the mixture of alcohols and air could increase the photoconductivity, and the mixture of carbon disulfide and air could decrease the photoconductivity. The mechanism of the effect of various experimental conditions on photoelectric properties was also discussed.

Photoelectrochemical thrombin biosensor based on perylene-3,4,9,10-tetracarboxylic acid and Au co-functionalized ZnO nanorods with signal-off quenching effect of Ag@Ag2S

In this work, a thrombin photoelectrochemical aptasensor was reported based on a photoanode of perylene-3,4,9,10-tetracarboxylic acid (PTCA), Au nanoparticle co-functionalized ZnO nanorods (ZnO NRs) and the "signal-off" amplification effect of Ag@Ag2S. The photocurrent response of the ZnO NRs was improved greatly due to the excellent visible-light photoelectric performance of PTCA and the surface plasmon resonance (SPR) effect of Au nanoparticles. Due to the specific recognition between thrombin and aptamers, the non-conductive complex with a steric hindrance structure blocked the diffusion path of the electron donating ascorbic acid (AA) and then the "signal-off" Ag@Ag2S quencher was captured. The quencher blocked the irradiation light toward the ZnO NRs/PTCA/Au electrode and competitively consumed the electron donor AA that could have been involved in the oxidation reaction with photogenerated holes of PTCA, resulting in the further decrease of the photocurrent. Based on the evident photocurrent response of the photoanode and the superior quenching strategies, the detection limit of thrombin is as low as 33 fM with a wide linear detection range from 0.0001 nM to 50 nM. The prepared biosensor also exhibited good specificity, reproducibility and stability, suggesting potential application in thrombin specific detection.