In this study, nanostructured gold was successfully prepared on a bare Au electrode using the electrochemical deposition method. Nanostructured gold provided more exposed active sites to facilitate the ion and electron transfer during the electrocatalytic reaction of organophosphorus pesticide (methyl parathion). The morphological and structural characterization of nanostructured gold was conducted using field-emission scanning electron microscopy (FESEM), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD), which was further carried out to evaluate the electrocatalytic activity towards methyl parathion sensing. The electrochemical performance of nanostructured gold was investigated by electrochemical measurements (cyclic voltammetry (CV) and differential pulse voltammetry (DPV)). The proposed nanostructured gold-modified electrode exhibited prominent electrochemical methyl parathion sensing performance (including two linear concentration ranges from 0.01 to 0.5 ppm (R² = 0.993) and from 0.5 to 4 ppm (R² = 0.996), limit of detection of 5.9 ppb, excellent selectivity and stability), and excellent capability in determination of pesticide residue in real fruit and vegetable samples (bok choy and strawberry). The study demonstrated that the presented approach to fabricate a nanostructured gold-modified electrode could be practically applied to detect pesticide residue in agricultural products via integrating the electrochemical and gas chromatography coupled with mass spectrometry (GC/MS-MS) analysis.

Morphologically tunable copper oxide-based nanomaterials on Cu wire have been synthesized through a one-step alkali-assisted surface oxidation process for non-enzymatic glucose sensing. Subsequently, copper oxide-based nanomaterials on Cu wire as a supporting matrix to deposit manganese oxide for the construction of heterostructured Mn-Cu bimetallic oxide architectures through spontaneous redox reaction in the KMnO₄ solution for supercapacitors. Field emission scanning electron microscopy (FESEM), field emission transmission electron microscopy (FETEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) confirmed that morphological and phase transformation from Cu(OH)₂ to CuO occurred in copper oxide-based nanomaterials on Cu wire with different degrees of growth reaction. In non-enzymatic glucose sensing, morphologically tunable copper oxide-based nanomaterials owned the high tunability of electrocatalytically active sites and intrinsic catalytic activity to meet efficient glucose electrooxidation for obtaining promoted non-enzymatic glucose sensing performances (sensitivity of 2331 μA mM⁻¹ cm⁻² and the limit of detection of 0.02 mM). In the supercapacitor, heterostructured Mn–Cu bimetallic oxide-based nanomaterials delivered abundant redox-active sites and continuous conductive network to optimize the synergistic effect of Mn and Cu redox species for boosting the pseudo-capacitance performance (areal capacitance value of 79.4 mF cm⁻² at 0.2 mA cm⁻² current density and capacitance retention of 74.9% after 1000 cycles). It concluded that morphologically tunable copper oxide-based nanomaterials on Cu wire with/without deposition of manganese oxide could be good candidates for the future design of synergistic multifunctional materials in electrochemical techniques.

Nanocomposites of the binary transition metal sulfide Zn-Co-S/graphene (Zn-Co-S@G) were synthesized through a one-step hydrothermal method. They may be useful in the construction of an electrochemical immunosensor for carbohydrate antigen 19-9 (CA19-9) detection. Zn-Co-S dot-like nanoparticles uniformly covered the surface of graphene to form an interconnected conductive network, ensuring strong interaction between transition metal sulfide and graphene, which can expose numerous electroactive sites leading to the improvement of the amplified electrochemical signal toward a direct reduction of H₂O₂. Thus, the construction of an electrochemical immunosensor using Zn-Co-S@G nanocomposites showed outstanding sensing properties for detecting CA19-9. The constructed electrochemical immunosensor exhibited a good linear relationship in the range of 6.3 U·mL⁻¹–300 U·mL⁻¹, with the limit of detection at 0.82 U·mL⁻¹, which makes it a promising candidate for an electrochemical immunosensor.

The scarcity of fuels, high pollution levels, climate change, and other major environmental issues are critical challenges that modern societies are facing, mostly originating from fossil fuels-based economies. These challenges can be addressed by developing green, eco-friendly, inexpensive energy sources and energy storage devices. Electrochemical energy storage materials possess high capacitance and superior power density. To engineer highly efficient next-generation electrochemical energy storage devices, the mechanisms of electrochemical reactions and redox behavior must be probed in operational environments. They can be studied by investigating atomic and electronic structures using in situ x-ray absorption spectroscopy (XAS) analysis. Such a technique has attracted substantial research and development interest in the field of energy science for over a decade. The mechanisms of charge/discharge, carrier transport, and ion intercalation/deintercalation can be elucidated. Supercapacitors generally store energy by two specific mechanisms—pseudocapacitance and electrochemical double-layer capacitance. In situ XAS is a powerful tool for probing and understanding these mechanisms. In this Review, both soft and hard x rays are used for the in situ XAS analysis of various representative electrochemical energy storage systems. This Review also showcases some of the highly efficient energy and power density candidates. Furthermore, the importance of synchrotron-based x-ray spectroscopy characterization techniques is enlightened. The impact of the electronic structure, local atomic structure, and electronically active elements/sites of the typical electrochemical energy storage candidates in operational conditions is elucidated. Regarding electrochemical energy storage mechanisms in their respective working environments, the unknown valence states and reversible/irreversible nature of elements, local hybridization, delocalized d-electrons spin states, participation of coordination shells, disorder, and faradaic/non-faradaic behavior are thoroughly discussed. Finally, the future direction of in situ XAS analysis combined with spatial chemical mapping from operando scanning transmission x-ray microscopy and other emerging characterization techniques is presented and discussed.

Silver dendritic nanoforests (Ag-DNFs) on silicon (Ag-DNFs/Si) were synthesized through the fluoride-assisted Galvanic replacement reaction (FAGRR) method. The synthesized Ag-DNFs/Si were characterized by scanning electron microscopy, energy-dispersive X-ray spectrometry, inductively coupled plasma mass spectrometry (ICP-MS), reflection absorbance spectrometry, surface-enhanced Raman scattering spectrometry, and X-ray diffractometry. The Ag⁺ concentration in ICP-MS measurements indicated 1.033 mg/cm² of deposited Ag synthesized for 200 min on Si substrate. The optical absorbance spectra indicated the induced surface plasmon resonance of Ag DNFs increased with the thickness of the Ag DNFs layer. Surface-enhanced Raman scattering measurement and a light-to-heat energy conversion test presented the superior plasmonic response of Ag-DNFs/Si for advanced applications. The Ag-DNFs/Si substrate exhibited high antibacterial activity against Escherichia coli and Staphylococcus aureus. The large surface area of the dense crystal Ag DNFs layer resulted in high antibacterial efficiency. The plasmonic response in the metal–crystal Ag DNFs under external light illumination can supply energy to enhance bacterial inhibition. High-efficiency plasmonic heating by the dense Ag DNFs can lead to localized bacterial inhibition. Thus, the Ag-DNFs/Si substrate has excellent potential for antibacterial applications.

The effects of Au cores in Ag shells in enhancing surface-enhanced Raman scattering (SERS) were evaluated with samples of various Au/Ag ratios. High-density Ag shell/Au core dendritic nanoforests (Au@Ag-DNFs) on silicon (Au@Ag-DNFs/Si) were synthesized using the fluoride-assisted Galvanic replacement reaction method. The synthesized Au@Ag-DNFs/Si samples were characterized using scanning electron microscopy, energy-dispersive X-ray spectroscopy, reflection spectroscopy, X-ray diffraction, and Raman spectroscopy. The ultraviolet-visible extinction spectrum exhibited increased extinction induced by the addition of Ag when creating the metal DNFs layer. The pure Ag DNFs exhibited high optical extinction of visible light, but low SERS response compared with Au@Ag DNFs. The Au core (with high refractive index real part) in Au@Ag DNFs maintained a long-leaf structure that focused the illumination light, resulting in the apparent SERS enhancement of the Ag coverage.