Observing the Evolution of Metal Oxides in Liquids.

Metal oxides with diverse compositions and structures have garnered considerable interest from researchers in various reactions, which benefits from transmission electron microscopy (TEM) in determining their morphologies, phase, structural and chemical information. Recent breakthroughs have made liquid-phase TEM a promising imaging platform for tracking the dynamic structure, morphology, and composition evolution of metal oxides in solution under work conditions. Herein, this review introduces the recent advances in liquid cells, especially closed liquid cell chips. Subsequently, the recent progress including particle growth, phase transformation, self-assembly, core-shell nanostructure growth, and chemical etching are introduced. With the late technical advances in TEM and liquid cells, liquid-phase TEM is used to characterize many fundamental processes of metal oxides for CO2 reduction and water-splitting reactions. Finally, the outlook and challenges in this research field are discussed. It is believed this compilation inspires and stimulates more efforts in developing and utilizing in situ liquid-phase TEM for metal oxides at the atomic scale for different applications.

Eggshell membrane-templated gold nanoparticles as a flexible SERS substrate for detection of thiabendazole.

The authors describe a three-dimensional (3D) flexible interconnected porous nanocomposite membrane for use in surface-enhanced Raman scattering (SERS). It was obtained via in -situ deposition of gold nanoparticles (AuNPs, ca. 10 nm) on eggshell membranes (ESM). The AuNP/ESM nanocomposites were used as a SERS substrate for detection of the pesticide thiabendazole (TBZ) with prominent Raman bands at 1180, 1280, and 1580 cm-1. The abundant "hot spots" are generated by the closely arranged AuNPs in the 3D geometry of the ESM networks. This makes the SERS substrate highly sensitive because of remarkable signal amplification. The substrates were applied to the rapid detection of TBZ in Oolong tea. The limit of detection for TBZ is 0.1 ppm. Graphical abstract Schematic presentation of a three-dimensional flexible interconnected porous nanocomposite membrane as surface-enhanced Raman scattering (SERS) substrate for detection of thiabendazole (TBZ) in tea.

ZnO/C nanocomposite grafted molecularly imprinted polymers as photoelectrochemical sensing interface for ultrasensitive and selective detection of chloramphenicol.

Nanomaterials-based photoelectrochemical (PEC) detection is becoming a rapidly-developing analytical technique in chemical and biological assays due to its unique advantages of easy miniaturization, high sensitivity, and rapid turnaround time. Herein, a molecularly imprinted polymer-assisted PEC sensor based on ZnO/C nanocomposite was successfully fabricated for the highly sensitive and selective determination of chloramphenicol (CAP). Benefiting from the hydrophilic functional groups (-OH, -COOH) and large surface area of bio-templated ZnO/C nanocomposite, the tight grafting of MIP with excellent recognition ability on substrate is easier and more stable than traditional PEC sensor, thus significantly increasing the performance. Under optimal conditions, the PEC sensor exhibited significant CAP detection performance in the range of 0.01-5000 ng mL-1 with a detection LOD of 5.08 pg mL-1 (S/N = 3) and successfully applied to the detection of CAP in milk sample. Our results show that ZnO/C nanocomposite and MIP can act as an efficient photo-responsible matrix to fabricate PEC sensor, providing important application potentials for pollutants control in food and environment.

Designing waste Bioresource-derived value-added Nanohybrids for efficient photocatalysis water treatment.

Although photocatalysis with ultraviolet-visible (UV-vis) light has made considerable advances, it is limited by the low efficiency of UV-vis energy conversion. To overcome this problem, UV-vis light can be replaced with near-infrared (NIR) light. Herein, we coupled eggshell-derived CaCO3 with a NIR-absorbing CuSe semiconductor and fabricated an insulator-based heterojunction structure. In application case studies of 4-nitrophenol (4-NP) and bacteria, the nanocomposites showed enhanced photocatalysis activity under NIR light induction. A first-principles calculation indicated that photoexcited electrons could transfer from the conduction band of CuSe to the conduction band of CaCO3. The main reactive species generated by the photocatalysis were ·CO3-, and ·OH free radicals. The antibacterial mechanisms of photocatalysis on the cell permeability and DNA layers of the bacterial cells were also revealed. Besides providing novel perspectives and mechanistic understanding of the fabrication of NIR light-driven photocatalysts, this study demonstrates the valorization of eggshell bio-wastes in environmental remediation.

A fish-scale derived multifunctional nanofiber membrane for infected wound healing.

The rapid development of modern medicine has put forward new requirements for wound infection healing methods in clinical treatment. Despite the great achievements made in the research and development of various types of dressings in recent years, yet there is still a challenge of multifunctional dressings for effective wound treatment. Herein, a multifunctional nanofibrous membrane was prepared by encapsulating NIR-adsorbed CuS (FSC/CuS) nanoparticles, polyvinylpyrrolidone (PVP) and polyvinyl butyral (PVB) with electrospun fish scale collagen. During the evaluation of wound healing, four parameters, including hemostasis time, inflammatory response, cell proliferation, and tissue remodeling, were considered. The results of H&E, Masson and immunohistochemical staining showed that the synergistic effect of composite nanofibers and near-infrared light can inhibit the inflammatory response, promote the proliferation and migration of fibroblasts and keratinocytes, rebuild new tissues, form well-dispersed collagen fibers, etc. It was shown that the FSC/CuS NPs combined with an NIR-driven experimental group exhibited excellent performance in accelerating wound healing in these stages. This kind of nanofibrous scaffold prepared with fish scale and NIR-absorbing agents will have broad application prospects in the healing of infected wounds.

Facile Synthesis of Eggshell Membrane-Templated Au/CeO2 3D Nanocomposite Networks for Nonenzymatic Electrochemical Dopamine Sensor.

Dopamine acts as a neurotransmitter to regulate a variety of physiological functions of the central nervous system. Thus, the fabrication of electrochemical active nanomaterials for sensitive dopamine detection is extremely important for human health. Herein, we constructed a highly efficient dopamine nonenzymatic biosensor using eggshell membrane (ESM) as a 3D network-like carrier-loaded Au and CeO2 nanocomposites. This approach has led to the uniform distribution of CeO2 and Au nanoparticles on the surface of ESM. The structure and properties of the as-prepared ESM templated Au/CeO2 (ESM-AC) nanocomposites were characterized. The electrochemical properties of non-enzymatic oxidation of dopamine by ESM-AC electrode were studied by cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The detection limit of the ESM-AC modified electrode for dopamine is 0.26 µM with a linear range from 0.1 to 10 mM. The ESM-AC-modified electrode performs a higher catalytic activity for dopamine electrocatalytic oxidation than that ESM-templated CeO2 (ESM-C) electrode, which is mainly due to the unique structure of ESM and more active sites provided from Au. Collectively, this biological waste-ESM provides a cheap and unique template for the preparation of 3D network-like nanostructures and expands the application in electrochemical dopamine detection. ESM-AC nanocomposites prepared from biological waste was successfully modified on the surface of glassy carbon electrode and a dopamine-based electrochemical biosensor was constructed.

Rapid pyrolysis of Cu2+-polluted eggshell membrane into a functional Cu2+-Cu+/biochar for ultrasensitive electrochemical detection of nitrite in water.

Bioremediation is one of efficient methods to solve the issues of water or soil contaminated by metal ions. However, the harvested biowaste is often troublesome to handle owing to the second pollution. Herein, the waste eggshell membrane was used to adsorb Cu2+ in wastewater, which was then converted into biochar containing copper ions (Cu2+-Cu+/Biochar) via a rapid pyrolysis. By integrating the collective advantages of eggshell membrane and Cu2+-Cu+, such as superior electrical conductivity, enlarged electrochemically active surface area, unique three-dimensional porous network characteristics, and fast charge transport, the Cu2+-Cu+/Biochar system can be used as a self-supporting sensor for detection of nitrite (NO2-). The sensor demonstrated superior electrochemical sensing abilities accompanied by a broad linear range (1-300 µM), ultralow detection limit (0.63 µM), and high sensitivity (30.0 µA·mM-1·cm-2). In addition, the fabricated electrochemical sensor has excellent stability, good reproducibility, and strong anti-interference performance. More importantly, the sensor has a high recovery rate when it is used to detect nitrite in tap water, mineral water, and sausage, indicating the feasibility of using this sensor in practical applications. This study provides a green and sustainable approach for simultaneous treatment of biomass waste eggshell membrane, remedy of heavy metals, and electrochemical detection of nitrite.

Plant-mediated synthesis of dual-functional Eggshell/Ag nanocomposites towards catalysis and antibacterial applications.

Advances in nanotechnology provide plenty of exciting solutions to environmental issues affecting air, soil as well as water. To solve the water pollution problem caused by organics and microorganisms, development of a simple, environment-friendly, and cheap method for the synthesis of nanomaterials is of paramount importance. Herein, we prepared a novel nanocomposite (named Eggshell/Ag) using waste eggshell as a support and Cacumen platycladi extract as reducing and stabilizing agents in aqueous solutions at room temperature. Biogenic-stabilized Ag nanoparticles (Ag NPs) with an average diameter of 60 nm were well-dispersed on the surface of eggshells, exhibiting dual-functional properties of organics catalytic degradation and bacterial growth inhibition. Through five repeated assays, it was established that the reduction efficiency of the nanocomposite for 4-nitrophenol (4-NP) was high. The reduction could be completed rapidly at room temperature. Moreover, significant inhibition zones were observed for Staphylococcus aureus (S. aureus) agar plates and Escherichia coli (E. coli). Meanwhile, the minimum inhibition concentrations (MIC) were determined to be 0.08 and 0.04 mg mL-1, respectively, while the minimum bactericidal concentration (MBC) was measured as 0.64 mg mL-1. The biogenic Eggshell/Ag nanocomposites are promising candidates for a series of applications in the fields of biomedicine, environment as well as energy.

MXene-Ti3C2/CuS nanocomposites: Enhanced peroxidase-like activity and sensitive colorimetric cholesterol detection.

Nanomaterials with enzyme-like activity have attracted much attention recently. Herein, we report the synthesis of a new type of 2D MXene-Ti3C2/CuS nanocomposites with peroxidase-like activity using a simple hydrothermal approach. Significantly, compared with the individual MXene-Ti3C2 nanosheets or CuS nanoparticles, the MXene-Ti3C2/CuS nanocomposites show a synergistically enhanced peroxidase-like activity and can be used as an efficient mimetic peroxidase to catalyze the reaction of 3,3,5,5-tetramethylbenzidine (TMB) in the presence of hydrogen peroxide (H2O2), causing a blue color change. Kinetic studies reveal that the MXene-Ti3C2/CuS nanocomposites have a higher catalytic activity to TMB than their single components, and the catalytic reaction follows the ping-pong mechanism. The MXene-Ti3C2/CuS nanocomposites are used for the colorimetric determination of cholesterol with a linear range of 10-100 µM and a limit of detection (LOD) of 1.9 µM. Our results show that the MXene-Ti3C2/CuS nanocomposites based colorimetric cholesterol biosensor is cost-effective, sensitive, and selective, which has potential application in H2O2 and cholesterol detection and clinic medicine diagnostics.

Supercritical Fluid-Assisted Fabrication of Manganese (III) Oxide Hollow Nanozymes Mediated by Polymer Nanoreactors for Efficient Glucose Sensing Characteristics.

Despite their inherent efficacy in significantly accelerating the rate of chemical reactions in biological processes, the applicability of natural enzymes is often hindered because of their intrinsic limitations such as high sensitivity, poor operational stability, and relatively high cost for purification as well as preparation. Thus, the fabrication of catalytically active nanomaterials as artificial enzymes (nanozymes) has become a newly burgeoning area of research in bionic chemistry, aiming in designing functional nanomaterials that mimic various inherent properties of natural enzymes. To address these issues, we present the supercritical fluid (SCF)-assisted fabrication of discrete, monodisperse, and uniform-sized manganese (III) oxide (Mn2O3)-based hollow containers as high-efficiency nanozymes for glucose sensing characteristics. Initially, the core-shell nanoreactors based on polyvinylpyrrolidone (PVP)-encapsulated manganese (III) acetylacetonate (Mn(acac)3) as precursors are fabricated using the SCF technology and subsequent calcination resulted in the Mn2O3 hollow nanoparticles (MHNs). This eco-friendly approach has resulted in the PVP-coated Mn(acac)3 nanoreactors with an average diameter of 220 nm and subsequent calcined hollow products are about one-fifth to that of the precursor. Such MHNs conveniently catalyzed 3,3',5,5'-tetramethylbenzidine (TMB) in the presence of hydrogen peroxide (H2O2) as a prominent peroxidase mimic, resulting in the oxidation products (TMB*+) at a specific absorption (UV-vis) maxima of 652 nm. Following typical Michaelis-Menten theory, this approach is further utilized to develop visual nonenzymatic sensing of glucose in a linear range of 0.1-1 mM at a detection limit of 2.31 µM. Collectively, this reliable as well as a cost-effective system with high precision potentially allows rapid detection of analytes, providing a convenient way for its utilization in diverse fields.