Metal Oxide Nanomaterials Research Articles

Photocatalysis vs adsorption by metal oxide nanoparticles

• Metal oxides nanostructures have diverse effect on adsorptive and photocatalytic treatments. • The present review covers a unique technique to boost TiO 2 activity using porous supports. • Z-scheme based oxides to sustain high redox activity by using heterojunction photocatalysts. • Photocatalytic degradation is more eco-friendly than adsorption. Metal oxide (MO) nanomaterials and related nanocomposites have been extensively studied for their potential use in water treatment. Because of their controlled morphologies, texture qualities, variable surface chemistry, distinct crystalline nature, high stability, and tunable band edges, MO nanostructured materials are highly selective towards deleting organic contaminants and heavy metal ions via adsorption and semiconductor photocatalysis. Metal-enhanced photocatalysis has recently received increasing interest, mainly due to the ability of the metal to directly or indirectly degrade pollutants. A diverse selection of MOs, with titanium dioxide (TiO 2 ), zinc oxide (ZnO), iron oxides (IO), and tungsten (W), as well as graphene-MOs nanocomposites with variable structure, crystalline, and morphological properties, offers a powerful platform for the growth of effective catalysts. The current work discusses novel advancements and potential for the removal of adsorptive and photocatalytic degradation of organic compounds (phenolic, pesticide molecules, dyes, and so on) as well as heavy metal ions using semiconductor materials. A photocatalyst based on a MO-scheme heterostructure can manage the appropriate conduction band (CB) and valence band (VB) locations, securing considerable redox aptitude. This review should be of interest to the broad readership dealing with applied and fundamental aspects of water treatments and material sciences. Various strategies including surface modification, plasmonic enhancement, and metal cocatalysts have been introduced to enhance photocatalytic performance. The current article discussed the significantly utilized synthesis strategies and mechanism of heterojunction photocatalysts using a Z-scheme. Furthermore, adsorption sections guarantee that mercury, chromium, cadmium, arsenic, and lead-based ions are successfully removed from polluted water via the adsorption route. Numerous characteristics, such as concentration, coexisting ions, pH, and kind of chemical have converged to comprehend the adsorption procedure. The technological challenges and future approaches are discussed to maximize the photocatalytic and adsorption efficacy and the reusability of MO-based nanomaterials for water security.

Nanomaterials for supercapacitors as energy storage application: Focus on its characteristics and limitations

Demand for energy is steadily increasing due to the ever-increasing population growth, changing lifestyle as well as the depleting natural resources. The result is the increase in the cost of conventional energy devices. Nanotechnology via the application of tailor-made nanomaterials has brought in revolutionary changes in the design and fabrication of various energy storage devices. There have been reports of increased efficiency, decreased cost because of which there has been an enhanced market growth of the energy storage devices. Immense research activities are focused on the fabrication of electrode materials having precise nano-dimensions and morphologies, fabrication of cost-effective storage devices and methods to enhance efficiency. Composite materials based on carbon, metal oxide and polymer-based nanomaterials have been used for fabrication of electrode materials. Nanosized particles in such composites have brought about enhanced material properties as compared to their bulk counterparts, which in turn has contributed to their improved energy storage efficiency. But despite the success attained due to nanotechnological interventions, some of the limiting factors identified that have put a restraint in the demand and market growth of applied nanomaterials for energy capture are related to toxic processes involved during the synthesis of nanomaterials and during the application process.An overview of different nanomaterials used till date for fabrication of electrodes (with special focus on supercapacitors) will be addressed in this study. While the focus is in addressing the advantages of the use of nanomaterials and their composites, the study will also highlight the challenges associated during the fabrication and application in energy devices. It is expected that an update of such literature will benefit those undergoing research on nanotechnology and renewable energy technology.

Optimistic and possible contribution of nanomaterial on biomedical applications: A review

Nanomaterials have many advantages over bulk materials, including enhanced surface-to-volume proportion as well as magnetic traits. It has been a steady rise in research with using nanomaterials in various biomedical fields in the past few decades. Constructing nanomaterials has emerged as a leading research primary concern in order to discover specialized biomedical applications. Since, their advantageous properties including chemical stability, non-toxicity, bio - compatibility, relatively high magnetization, and strong magnetic vulnerability, nanoparticles of iron oxide had already influenced implementations in different biomedical fields. Nanomaterials can be divided up into four nanomaterials such as metallic nanomaterials, bimetallic or alloy nanomaterials, metal oxide nanomaterials, as well as magnetic nanomaterials. Hence, the purpose of this review is to conduct such in discussion on emerging advancements in nanomaterials for biomedical, with such a special emphasis upon those options of nanomaterials including metallic nanomaterials: Au and Ag, bimetallic nanomaterials: Fe–Co and Fe–Pt, and metal oxides: TiO2 and CeO2. Securing this information gap will result in a better comprehension of the contribution of nanomaterial type and subsequent huge-scale applications in aspects of both their potential and challenges.

Ultra-sensitive triethylamine gas sensors based on polyoxometalate-assisted synthesis of ZnWO4/ZnO hetero-structured nanofibers

One-dimensional hetero-structured nanofibers (NFs) have recently received great attention because of their rich architectures and potential applications in the field of gas sensors. Polyoxometalate (POM) is a unique nanosized transition metal-oxygen cluster used as a molecular platform to prepare metal oxide nanomaterials and accompanied by high negative charges that readily combine with various metal oxide precursors to form metal oxide complexes. Herein, with the assistance of POM, ZnWO 4 /ZnO hetero-structured NFs were prepared by combining facile electrospinning with thermal oxidation. Adjusting the molar ratio of POM (H 3 PW 12 O 40 ·xH 2 O, denoted as PW 12 ) and Zn(NO 3 ) 2 ·6H 2 O (denoted as Zn 2+ ) in the precursor solution, a series of ZnWO 4 /ZnO hetero-structured NFs were obtained. Compared with pure ZnO NFs, the optimized ZnWO 4 /ZnO hetero-structured NFs demonstrate more excellent sensing performance. A high relative response of 108.5 was achieved for 50 ppm triethylamine (TEA) and with a low detection limit about 150 ppb. Furthermore, the ZnWO 4 /ZnO hetero-structured NFs exhibited remarkable TEA selectivity and outstanding reproducibility. The enhanced sensing mechanism toward TEA could be attributed to n-n heterojunctions with the obvious barrier-control electron transfer effect at the interface between ZnWO 4 and ZnO. The one-dimensional ZnWO 4 /ZnO hetero-structured nanofibers were prepared with the assistance of polyoxometalate to realize the ultra-sensitive detection of triethylamine. • ZnWO 4 /ZnO hetero-structured nanofibers were prepared by an electrospinning method with the assistance of polyoxometalate. • As-prepared porous nanofibers exhibited an enhanced selectivity to triethylamine with excellent stability/repeatability. • The excellent sensing performance is mainly ascribed to porous structure and synergetic sensing effect of ZnWO 4 and ZnO.

Failure analysis on silicon semiconductor device materials: optical and high-resolution microscopic assessments

Defects of silicon (Si) semiconductor epilayers are crucial to be identified at laboratory environs. The identification of failure and its rectification at laboratory settings is essential for large-scaling manufacturing of narrowed down semiconductor devices. This research documented the inspection, identification and the solution for defects found in the Si semiconductor epilayers, fabricated by a simple and conventional photolithography technique, with the integration of metal oxide nanomaterial, zinc oxide (ZnO). The semiconductor epilayers, Si wafer, Si oxide and ZnO coated SiO2 layer were formed and examined. Optical microscope images [high power microscope (HPM) and 3D profilometer] reveal smooth surface of semiconductor epilayers development through thermal oxidation and photolithography techniques. High power ultraviolet-visible (UV-Vis) justified the accuracy of wet thermal oxidation by examining the thickness of oxide layer on Si wafer at 3837.3 Å. The X-ray diffraction (XRD) analysis of sol-gel synthesized ZnO affirmed the hexagonal crystalline state and its nanoscale size at 54 nm. Field emission scanning electron microscopy (FESEM) has shown the insight of Si epilayer morphology with its elemental composition, which provides details of foreign substances on semiconductor surface. ZnO deposited Si epilayer was prepared through lamella preparation, prior to the cross-sectional field emission transmission electron microscopy (FETEM) analysis of the semiconductor, which revealed the uniformity of fabrication and ZnO distribution at Si epilayer. Failure analysis reported several defects on the Si epilayers in the state of patches and accumulation of impurities. The potential cause of the defects and the respective solutions are discussed as the accuracy and handling must be ensured throughout the fabrication process, to develop a flawless semiconductor for high performance applications.

Fractal flow model for cluster interfacial nanolayer of magnetized metallic oxides nanomaterials

In this paper, we investigate the novel properties of the cluster interfacial nanolayer theory for a thermal conductivity-based model. Under the influence of magnetohydrodynamics, the interaction of nanomaterials aggregation of metallic oxide nanomaterials with base fluid is explored. This paper discusses a specific form of new low permeability Reynolds number connected with an injection/suction factor related to an absorbent channel. A numerical simulation of higher-order nonlinear differential equations reveals the momentum flow and energy fields predicted by single-phase nanofluid simulations. Shear stress and Nusselt numbers were used to determine the effect of nanoparticle radius and diameter. Insertion of the metallic nanoparticles volume fraction level from 1% to 8% enhances the thermal performance at lower and upper porous walls respectively. Injection/suction and MHD have to decrease and increase behavior respectively in the presence of spherical nanoparticles. Interfacial nanolayer formation has a substantial impact on thermal conductivity performance. Comparing calculated findings to published literature validates their correctness. Graphs are generated to analyze the impact of flow parameters on velocity and temperature profiles. In tabular and graphical style, the effects of all physical factors are explored on the skin friction coefficient and the local Nusselt number.

Tin Oxide Based Hybrid Nanostructures for Efficient Gas Sensing.

Tin oxide as a semiconductor metal oxide has revealed great potential in the field of gas sensing due to its porous structure and reduced size. Especially for tin oxide and its composites, inherent properties such as high surface areas and their unique semiconducting properties with tunable band gaps make them compelling for sensing applications. In combination with the general benefits of metal oxide nanomaterials, the incorporation of metal oxides into metal oxide nanoparticles is a new approach that has dramatically improved the sensing performance of these materials due to the synergistic effects. This review aims to comprehend the sensing mechanisms and the synergistic effects of tin oxide and its composites in achieving high selectivity, high sensitivity and rapid response speed which will be addressed with a full summary. The review further vehemently highlights the advances in tin oxide and its composites in the gas sensing field. Further, the structural components, structural features and surface chemistry involved in the gas sensing are also explained. In addition, this review discusses the SnO2 metal oxide and its composites and unravels the complications in achieving high selectivity, high sensitivity and rapid response speed. The review begins with the gas sensing mechanisms, which are followed by the synthesis methods. Further key results and discussions of previous studies on tin metal oxide and its composites are also discussed. Moreover, achievements in recent research on tin oxide and its composites for sensor applications are then comprehensively compiled. Finally, the challenges and scope for future developments are discussed.

Antitumor Activity of the Zinc Oxide Nanoparticles Coated with Low-Molecular-Weight Heparin and Doxorubicin Complex In Vitro and In Vivo.

Various metal oxide nanomaterials have been widely used as carriers to prepare pH-sensitive nanomedicines to respond to the acidic tumor microenvironment promoting antitumor efficiency. Herein, we used zinc oxide nanoparticles (ZnO NPs) as metal oxide nanomaterial coated with low-molecular-weight heparin (LMHP) and doxorubicin (DOX) complex (LMHP-DOX) to prepare ZnO-LD NPs for controllable pH-triggered DOX release on the targeted site. Our results indicated that the released DOX from ZnO-LD NPs was pH-sensitive. The oxygen produced by ZnO-LD NPs in H2O2 solution was observed in in vitro experiment. The ZnO-LD NPs entered into both PC-3M and 4T1 tumor cells via clathrin-mediated endocytosis and micropinocytosis pathway. The intracellular reactive oxygen species (ROS) generated by ZnO-LD NPs could significantly increase the caspase 3/7 level, leading to tumor cell apoptosis. The in vitro and in vivo antitumor activity was confirmed in PC-3M and 4T1 cell lines or tumor-bearing mice models. The in vivo and in vitro tumor images via second-order nonlinearity of ZnO-LD NPs indicated that ZnO-LD NPs could penetrate deep into the tumor tissues. Therefore, the ZnO-LD NPs developed in our study could provide an efficient approach for the preparation of pH-sensitive nano delivery systems suitable for tumor therapy and imaging.

Plasma-Assisted Anion Exchange Reactions in Thermally Grown Copper Oxide Nanowires

Copper oxide nanowires represent a popular topic in recent research due to their potential use in gas sensors, batteries, supercapacitors etc. One of their advantages is facile synthesis, as they can be synthesized merely by heating metallic copper in the air. Moreover, their parameters, such as length and diameter, can be easily tailored by adjusting the conditions at which they are synthesized. Once obtained, nanowires can be further processed to enhance their properties. Common processing includes a partial or complete transformation of grown nanowires to another phase via cation or anion exchange. There are many existing methods for achieving such transformations, which are mostly solution-based. On the other hand, great unused potential lies in methods that exploit plasmas to achieve phase transformations in nanomaterials.Even though there are a lot of reports on the synthesis of CuO nanowires, there are still a lot of knowledge gaps when it comes to their production and ion exchange reactions. In both cases, the challenges are associated with fundamental science behind processes during nanowire growth and phase transformations, as mechanisms behind NW growth and ion exchange reactions are not completely understood. In our present research, we tackle challenges connected to the thermal growth of CuO nanowires as well as the fundamental science behind phase transformations in them. In order to study mechanisms of nanowire growth, we performed thermal oxidation of copper to obtain nanowires at different times and temperatures. With detailed microstructural analysis of nanowires and oxide layers on which they grow as well as utilization of theoretical simulations, we obtained valuable information about growth of one dimensional metal oxide nanomaterials. Furthermore, mechanisms of anion exchange reactions were studied in the copper oxide – copper sulfide system. To achieve the oxide to sulfide transformations, copper oxide nanowires were subjected to plasma treatment with sulfur-containing gasses, which allowed us to study anion exchange in non-equilibrium plasma environments.

Nanomaterials for Forensic Applications: A Review

This review paper highlights the utilization of forensic science in latent fingerprint detection by the use of distinct nanomaterials and their advantages as for the nature of unique fingerprint pictures. As of now, conventional creating strategies, for example, powder dusting, cyanoacrylate fuming, Silver Nitrate Method and Ninhydrin Method .The benefits in addition to significant after effects of studies led on latent fingerprint detection with metal oxide doped rare earth nanomaterials, ZrO2:Dy3+ (3mol %) can be employed in forensic science towards latent fingerprint development and C- dot doped metal oxide nanomaterials are basically talked about.

Metal and Metal Oxide Nanomaterials for Fighting Planktonic Bacteria and Biofilms: A Review Emphasizing on Mechanistic Aspects.

The misuse and mismanagement of antibiotics have made the treatment of bacterial infections a challenge. This challenge is magnified when bacteria form biofilms, which can increase bacterial resistance up to 1000 times. It is desirable to develop anti-infective materials with antibacterial activity and no resistance to drugs. With the rapid development of nanotechnology, anti-infective strategies based on metal and metal oxide nanomaterials have been widely used in antibacterial and antibiofilm treatments. Here, this review expounds on the state-of-the-art applications of metal and metal oxide nanomaterials in bacterial infective diseases. A specific attention is given to the antibacterial mechanisms of metal and metal oxide nanomaterials, including disrupting cell membranes, damaging proteins, and nucleic acid. Moreover, a practical antibiofilm mechanism employing these metal and metal oxide nanomaterials is also introduced based on the composition of biofilm, including extracellular polymeric substance, quorum sensing, and bacteria. Finally, current challenges and future perspectives of metal and metal oxide nanomaterials in the anti-infective field are presented to facilitate their development and use.

Modification of calcination temperature of NiO/C nanocomposite electrode materials for supercapacitor application

Synthesizing metal oxide nanomaterials for energy storage applications and optimizing their electrochemical performance is critical for developing next generation energy solutions. In this study, nickel hydroxide nanomaterials were synthesized via precipitation and microwave methods and utilized as pseudo-capacitor electrodes. The precipitation method employing starch as a capping agent yielded nickel hydroxide exhibiting a maximum specific capacitance of 333 Fg-1. The nickel hydroxide can be converted to nickel oxide/carbon (NiO/C) by calcination at higher temperatures. Electrochemical supercapacitor performance of NiO/C synthesized at different calcination temperatures (400, 500, 600 °C) was optimized. NiO/C calcined at 500 °C exhibits a maximum specific capacitance value of 450 Fg-1 at a scan rate of 5 mV.s-1. To determine the structural properties XRD technique was used. The identification of functional groups in synthesized nanomaterials was investigated by the FTIR technique. FESEM was employed to examine the morphological analysis of synthesized nanomaterials. Elemental composition in synthesized materials was examined by using the EDS. The electrochemical potential was studied by using CV, GCD, and EIS techniques.

Ultrasensitive detection of Hg(II) by small-sized Mn3O4 loaded on g-C3N4 nanosheets: Heterojunction facilitates electron transfer and Mn(II)/Mn(III)/Mn(IV) cycle

Transition metal oxides are widely used in electrochemical detection because of the promotion of redox of heavy metal ions (HMIs) by valence change behavior. However, it is challenging to favorably promote the valence change to achieve the improvement of detection sensitivity. Herein, a Mn3O4/g-C3N4 composite (named as MO-CN) with small-sized of Mn3O4 and high proportion of Mn(II) and Mn(III) was prepared, which reveals an excellent performance on detecting mercury ion (Hg(II)). It is discovered that Mn3O4 becomes small in size and well disperses on g-C3N4, which solves the adverse effect of agglomeration and also lead to a good conductivity. And g-C3N4 can provide more adsorption sites to enhance the adsorption on Hg(II). Heterojunction is proved to form in MO-CN and thus accelerates electrons to flow from g-C3N4 to Mn3O4. This results in transforming Mn(IV) to Mn(II) and Mn(III) in Mn3O4, thereby promoting the cycle of Mn(II)/Mn(III)/Mn(IV) and furthermore facilitating the redox of Hg(II). Simultaneously, the obtained sensitivity (473.43 μA μM−1 cm−2) and limit of detection (LOD, 0.003 μM) are as expected. The nanocomposites and heterojunction based on transition metal oxide and 2D nanomaterials is promising to boost the detection of HMIs.

Detection of major VOCs in exhaled breath under ppb level using porous ZnO nanobelts

AbstractAtomic defects can enhance catalytic efficiency by providing coordinatively unsaturated sites in the crystal structure of metal oxides. It allows facile chemical reactions because the sites can react with other molecules with relatively lower energy. Therefore, atomic defect engineering can be a cost‐effective strategy to replace novel metal catalysts for the development of ultrasensitive gas sensors. Herein, we fabricated porous ZnO nanobelts with atomic step structures for acetone, ethanol, and isoprene gas sensing under the parts‐per‐billion (ppb) level. Numerous atomic step structures could be formed by removing H and F atoms during the conversion process of ZnOHF at 500°C. The synthesis method of metal oxide nanomaterial by conversion from metal hydroxide fluoride will provide the atomic defects and it will be useful to prepare ultrasensitive sensing material. Furthermore, the gas selectivity of the porous ZnO nanobelt was investigated based on the appearance energy associated with the separation of the methyl group.

A recent advancement on the applications of nanomaterials in electrochemical sensors and biosensors

Industrialization and globalization, both on an international and local scale, have caused large quantities of toxic chemicals to be released into the environment. Thus, developing an environmental pollutant sensor platform that is sensitive, reliable, and cost-effective is extremely important. In current years, considerable progress has been made in the expansion of electrochemical sensors and biosensors to monitor the environment using nanomaterials. A large number of emerging biomarkers are currently in existence in the biological fluids, clinical, pharmaceutical and bionanomaterial-based electrochemical biosensor platforms have drawn much attention. Electrochemical systems have been used to detect biomarkers rapidly, sensitively, and selectively using biomaterials such as biopolymers, nucleic acids, proteins etc. In this current review, several recent trends have been identified in the growth of electrochemical sensor platforms using nanotechnology such as carbon nanomaterials, metal oxide nanomaterials, metal nanoparticles, biomaterials and polymers. The integration strategies, applications, specific properties and future projections of nanostructured materials for emerging progressive sensor platforms are also observed. The objective of this review is to provide a comprehensive overview of nanoparticles in the field of electrochemical sensors and biosensors.

Spectroscopic Insights into the Near-Infrared Polaronic Transitions in Surface-Passivated Substoichiometric MoO3–x Nanodots

Oxygen vacancies are the key factor that significantly influences physical and/or chemical properties of substoichiometric transitional metal oxide nanomaterials. In this study, we evaluate substoichiometric MoO3–x nanodots protected by penicillamine. In the synthesis, a carboxylic thiol reduction protocol is followed by a hydrothermal treatment, which makes the purification and isolation procedures facile. The obtained MoO3–x nanodots are well redispersed in both water and N,N-dimethylformamide, allowing us to examine the influence of the dispersion solvent on their optical properties. The nanodots exhibit three absorption peaks in the near-infrared (NIR) region, and their positions do not depend on the dispersion solvent, suggesting that the NIR absorption is originated not from the plasmonic resonances but from polaronic transitions caused by the oxygen vacancies. However, the spectral linewidth and intensity for the two lower-energy peaks strongly depend on the solvent, whereas those for the highest-energy peak do not. Magnetic circular dichroism measurements additionally reveal that the highest-energy peak arises from two interacting polaronic transitions that are close in energy, giving a derivative-like response based on the Faraday B term. Since the X-ray photoelectron spectroscopy survey shows that the main defect centers are different between the surface and inside of the nanodots, we propose a new mechanism to account for the NIR transitions from a viewpoint of bulk and surface polarons.

Al doped Sr and Cd metal oxide nanomaterials for resistive response of humidity sensing

In this present work, Al–Sr and Al–Cd nano-materials (NMs) were fabricated trough co-precipitation route. The synthesized NMs were subjected to various advanced techniques such as XRD, XPS, SEM, DRS and BET. XRD patterns showed prominent peaks for Al, Sr and Cd elements within the synthesized samples. SEM images depicted nano size agglomerated particles for Al–Sr and tubular layered structure for Al–Cd-NMs with the average particle size in the range from (40–45) nm. The elemental content within the fabricated samples was investigated in detail via XPS technique. Surface area adsorption (SAA) parameters obtained from BET analysis were ∼122.32 m2/g, 162.41 m2/g (surface area), 0.1231 cm3/g, 0.4312 cm3/g (pore volume) and 0.8996, 0.9982 nm (pore size) for Al–Sr and Al–Cd-NMs. Energy band gaps ∼2.58 (for Al–Sr) and 2.53eV (for Al–Cd) were obtained through DRS. Furthermore, the fabricated samples were tested for humidity sensing ability. The NMs were indicated with decreased resistance as (987–344) MΩ and (924–290) MΩ for Al–Sr and Al–Cd respectively. Response/recovery time ∼60s/44s for (Al–Sr) and ∼29s/45s for (Al–Cd) was calculated. Both the samples were found highly stable for a longer period of 105 days (with the time gap of 20 days) with the variation in resistance less than 2%. Stable microstructure, quick response-recovery behaviour and low hysteresis categorize these two NMs well suited for resistive response of humidity sensing at industrial level.

Co-axial electrospun hollow MgO nanofibers for efficient removal of fluoride ions from water

Porous and hollow metal oxide nanomaterials receive more attraction towards adsorption of various contaminates from water due to extremely high surface area. Co-axial electrospinning is an advance method to easily fabricate long length hollow nanotubes/nanofibers. Herein, hollow MgO nanofibers were synthesized using co-axial electrospinning method followed by post annealing. The co-axial electrospinning was performed by maintaining applied voltage (15 kV), needle tip to collector distance (12 cm) and flow rate of core and shell solutions (0.3 and 0.5 mL/h respectively). The formation, morphologies, bonding and surface area of the prepared nanofibers was analysed by XRD, FESEM, TEM and BET analytical techniques. The inner pore diameter of hollow MgO nanofibers was 32 nm. The surface area was found to be 527 m2/g which is much higher as compared to solid MgO nanofibers. The prepared hollow MgO nanofibers were used for the adsorption of fluoride ions from water. The effect of dose, contact time, pH and concentration were analysed. The fluoride adsorption process follows Pseudo-second-order kinetic and Langmuir isotherm models. The maximum adsorption capacity of hollow MgO was found to be 294 mg/g which is almost three-time greater than that of solid MgO nanofibers (92 mg/g). All the co-existing ions have showed negligible effect on fluoride adsorption except CO32- and PO43- ions. The adsorption energy of fluoride adsorbed MgO was calculated. The adsorption energy is found to be − 6.9004 eV. The negative value of adsorption energy indicates the feasibility of adsorption process.

Nanomaterials-based electrochemical sensors for the detection of natural antioxidants in food and biological samples: research progress.

Antioxidants are healthy substances that are beneficial to the human body and exist mainly in natural and synthetic forms. Among many kinds of antioxidants, the natural antioxidants have great applications in many fields such as food chemistry, medical care, and clinical application. In recent years, many efforts have been made for the determination of natural antioxidants. Nano-electrochemical sensors combining electrochemistry and nanotechnology have been widely used in the determination of natural antioxidants due to their unique advantages. Therefore, a large number of nanomaterials such as metal oxide, carbon materials, and conducting polymer have attracted much attention in the field of electrochemical sensors due to their good catalytic effect and stable performance. This review mainly introduces the construction of electrochemical sensors based on different nanomaterials, such as metallic nanomaterials, metal oxide nanomaterials, carbon nanomaterials, metal-organic frameworks, polymer nanomaterials, and other nanocomposites, and their application to the detection of natural antioxidants, including ascorbic acid, phenolic acids, flavonoid, tryptophan, citric acid, and other natural antioxidants. In the end, the limitations of the existing nano-sensing technology, the latest development trend, and the application prospect for various natural antioxidant substances are summarized and analyzed. We expect that this review will be helpful to researchers engaged in electrochemical sensors.

A Precise BSA Protein Template Developed the C, N, S Co-Doped Fe3O4 Nanolayers as Anodes for Efficient Lithium-Ion Batteries

Protein has abundant and exquisite multidimensional structures and numerous functional groups that can bind metal ions. Taking protein as a template can effectively promote the synthesis of metal oxide nanomaterials and form multidimensional network structures, which has great prospects in preparing high-performance lithium-ion battery (LIB) anode. However, these templates only act as carbon skeletons to support electrode materials. The biodiversity of proteins in precise regulation is not fully realized, limiting the application potential of protein templates. In this work, we selected biomineralized protein BSA as the template for the electrode materials synthesis, successfully regulated the nanocrystal and microstructure, and obtained a high-quality anode material with nanonetwork and ultrathin nanolayer structure. The nanocrystals of synthesized anode materials showed good uniformity and monodispersity, achieved the heteroatom doping, such as N and S elements, and in situ carbon coating. The carbon nanolayer structure formed by BSA protein improved the capacitance and stability of electrode materials, revealing a good application value for the LIB anode. This research can give us a further understanding and expand the idea of protein templates in the preparation of high-performance energy storage nanomaterials.