Metal Oxide Nanomaterials Research Articles

Review on Nanomaterial-based Electrochemical Aptasensors for Heavy Metal Detection in Food

Heavy metal ions are highly toxic contaminants in food and environment, which can easily cause foodborne diseases and irreversible damage to human being. There are several limitations in traditional detection methods for heavy metal ions such as time consuming and expensive, so it’s urgent to develop a rapid technology for heavy metal detection in food. Due to their rapid, high sensitivity and specificity, nanomaterial-based electrochemical aptasensors are perspective in real-time detection of heavy metal ions. This paper summarize the characters of metallic nanomaterials (such as gold nanoparticles), metal oxide nanomaterials (such as Fe3O4 nanoparticles), and carbon nanomaterials (such as carbon nanotubes and graphene) and then review the application of electrochemical aptasensors based on nanomaterials in heavy metal detection (mainly lead (II), mercury (II), arsenic (III) and cadmium (II)), in order to provide inspiration for the development of heavy metal detection methods.

Importance and Analytical Perspective of Green Synthetic Strategies of Copper, Zinc, and Titanium Oxide Nanoparticles and their Applications in Pathogens and Environmental Remediation

Background: Nanotechnology is a promising field of science which deals with the production and utilization of material under nanoscale dimensions. The nanoscale regime provides exceptional applications in various fields of science due to its large surface to volume ratio and many valuable properties. Hence, the production and use of nanomaterials are the prominent areas of modern research. Amongst the nanomaterials, metal oxide NPs have gained much attention due to their vast number of applications in different areas, including electrochemical applications, dye degradation, catalysis, and are known to be the exceptional entities in the battle against different pathogens. The metal oxides are viably synthesized through chemical methods that require the use of many noxious chemicals. Henceforth, it is the demand of the modern world to carry out research on the synthesis of metal oxide nanomaterials through eco-friendly, greener, and non-toxic routes. Thus, various green methods are employed to engineer the metal oxide NPs by using different greener, cheaper, and eco-friendly sources, employing the use of plant extracts, bacteria, fungi and other biological bodies. The present review covered the green synthesis of CuO, ZnO, TiO2 NPs and their applicability towards different pathogens and environmental remediation reported from the year 2015 to date. Objective: The exceptional catalytic properties, environmental, and anti-microbial applications of metal oxide, especially CuO, ZnO, TiO2, are the main highlights of this review articles. The most cost-effective and greener routes for the synthesis of CuO, ZnO, TiO2, are discussed in the present review. To date, various green synthetic methods for the preparation of mentioned nanoparticles and their applicability towards different pathogens and degradation of different hazardous dyes with some electrochemical applications has been thoroughly covered in this review. Conclusion: The biosynthesis of metal oxide NPs using greener and eco-friendly approaches have been the attentive area in the last decade. Green synthesis requires chemical-free active components from biological sources, which act as both the reducing and stabilizing agent for the size and shapecontrolled production of NPs. The future vision of bacterial, fungal, and plant-mediated production of NPs includes the postponement of laboratory-based work to a large industrial scale, exposition of different phytochemicals involved in the biosynthesis of NPs using bioinformatics techniques and stemming the real mechanism involved in preventing the growth of pathogenic bacteria, fungi, and algae. The plant-mediated NPs can have diverse applications in the arena of pharmaceutical, food, and cosmetic industries, and thus, became a vital area of modern research.

Enhanced catalytic properties of cobaltosic oxide through constructing MXene-supported nanocomposites for ammonium perchlorate thermal decomposition

The novel Co3O4@MXene nanocomposites (CMNs) were fabricated by a facile, green and highly tunable strategy without using any chemical modifiers. Various characterization results proved that nano-size Co3O4 was loaded on MXene nanosheets and CMNs exhibited a large specific surface area, especially for CMNs-3 (76.9 m2·g−1). The catalytic properties of CMNs for ammonium perchlorate (AP) thermal decomposition were investigated by a series of catalytic experiments. The results showed that the high-temperature decomposition (HTD) temperature and decomposition heat of AP mixed with CMNs-3 (2 wt%) could significantly decrease to 316.3 °C and remarkably increase to 1457.9 J·g−1, respectively. Moreover, the CMNs-3 could significantly reduce the apparent activation energy of AP by 49.1% and increase the value of reaction rate constant of AP by 482.0%. As for the effects of mass content of CMNs-3 on AP decomposition, the HTD temperature could decrease by as high as 128.0 °C with ratios of 10.0 wt% CMNs-3. It could be predicted that CMNs-3 with excellent catalytic performance would be a potential catalyst to promote AP decomposition and the synthesis method of CMNs-3 could provide an idea for the preparation of other metal oxide nanomaterials with high catalytic activity.

NANOMATERIAL SENSORS FOR ENVIRONMENTAL POLLUTANTS

Nowadays, global environment of water, soil, and atmospheric systems has continuously been deteriorating due to the incessant release of toxic chemicals from various constructed sources. The existence of heavy metal ions in the environment poses serious threats to human health and the ecosystem. Therefore, this review focuses on the advent of nanotechnology that has given immense opportunities for developing advanced nanomaterials with unique functionalities. This review reports on the development of sensing techniques based on nanomaterials including metal and metal oxide nanomaterials, quantum dots, carbon nanomaterials and polymer nanocomposites. Nanomaterials well possess excellent electrical, optical, thermal, catalytic properties and strong mechanical strength, which offer great opportunities to construct nanomaterials-based sensors or devices for environmental pollutants. The nanosorbents themselves should be nontoxic, the sorbents present relatively high sorption capacities and selectivity to the low concentration of pollutants. The adsorbed pollutants can be removed from the surface of the nanoadsorbent easily and sorbents infinitely recycled.

MoO3 structures transition from nanoflowers to nanorods and their sensing performances

Morphology transformation and crystal growth strategies of metal oxide semiconductors are still extensively studied in material science recently, because the morphology and crystallinity significantly affect the physicochemical characteristics of metal oxide nanomaterials. However, understanding the morphology changes of α-MoO3 induced by annealing is still a challenge. Herein, the nanostructure transition of α-MoO3 induced by the annealing temperature is carefully investigated via the XRD and SEM methods. It can be found that crystallization is highly dependent on the annealing temperature. Interestingly, the MoO3 nanoflowers can change into nanosheets at 500 °C. Afterward, the nanosheets turned into microrods with the increase in annealing temperature due to the continuous growth of MoO3 crystal. On the other hand, the sensing performances of various MoO3 nanostructures are studied toward ethanol gas. Compared to the MoO3 nanoflowers and microrods, the MoO3 nanosheets-based sensor exhibits superior sensing performance to ethanol, and the maximum response value is 8.06.

Self-assembled MXene-based Schottky-junction upon Transition metal oxide for regulated tumor microenvironment and enhanced CDT/PTT/MRI activated by NIR irradiation

Transition metal oxide nanomaterials (TMOs) have been adopted to produce reactive oxygen species (ROS) and adjust tumor microenvironment (TME) in cancer therapy. However, mono-modal treatment and the incompatibility of biological enzyme both hampered the therapeutic effect. Herein, we developed a multimodal TMO-based nanoplatform that the ultrathin Ti3C2 nanosheets were attached onto the MnFe2O4 nanoparticles self-assembled by applying chitosan as a chemical crosslinker to construct an interfacial Schottky junction, Ti3C2@Chitosan-MnFe2O4 (TC@Ch-MFO), achieving improved ROS generation as well as optimized biocompatibility. This heterojunction can controllably catalyze hydrogen peroxide (H2O2) to generate O2 and deplete the overexpressed glutathione (GSH) levels in hypoxic TME, which realizes the chemodynamic therapy (CDT) by cyclized Fenton reaction under NIR excitation. TC@Ch-MFO also constructs a multimodal treatment nanoplatform by introducing available high-efficiency photothermal agent (PTA), Ti3C2, for phtotheraml therapy (PTT). In addition, it simultaneously integrates the visualization with T1- and T2-weighting magnetic resonance imaging (MRI). The toxicity of TC@Ch-MFO to normal tissue cells is negligible. This platform could provide new insights into the development of multimoded synergistic nanoplatform for biological applications, especially breaking the shackles of MXenes merely used as a photo-thermal agent, adopting it to bioimaging sensor and drug loading.

Chemical bath deposition of h-MoO3 on optical fibre as room-temperature ammonia gas sensor

This study successfully developed a semiconductor metal oxide-based ammonia gas sensor that was powered by an Ultraviolet–Visible-near-IR optical light source. However, optical fibre gas sensors using single metal oxide nanomaterial are limited. To address this situation, a h-MoO3 nanorod was grown on a tapered region of optical fibre glass using a simple chemical bath deposition to form a unique sensing element. An additional annealing treatment was then performed to modify the oxidation state of h-MoO3. The property changes of the samples were characterised using different techniques, such as FESEM, TEM, XRD, XPS, TGA and UV–Vis. Overall, the annealing treatment improved the sensitivity performance, response and recovery time of the sensor towards NH3. h-MoO3 that was annealed at 150 °C in air showed stable room temperature absorbance responses of 0.05, 0.18, 0.22, 0.28 and 0.35, a fast response time of 210 s towards 500 ppm of NH3 and strong stability and repeatability. The optical NH3 gas-sensing behaviour was significantly correlated with the non-stoichiometric Mo5+ content. The chemisorbed oxygen species and physiosorbed NH3 altered the refractive index and its absorption coefficient on the nanorod, which manipulated the optical signal and acts as a sensing mechanism. These results verify that a chemical bath deposition growth of the h-MoO3 nanorod exhibits a promising optical sensing characteristic, which paves a path for emerging gas-sensing technology.

Manganese vanadium sulfate-oxide cylindrical core-shell heterostructures by electro-spray deposition on graphite foil for Li+ ion intercalation

Heterostructure based on metal sulfides and oxides nanomaterials can be relevant to the charge storage devices. Here, we show that Mn(CH3COO)2·4H2O and VOSO4·xH2O can react in ethanol/water droplets generated by an electric field assisted spray system, so that MnSx-VSx/MnzV2O5 heterostructures in the shape of nanometric cylindrical particles can be deposited on a graphite foil substrate. The composite material phases were detected by several microscopies and microscopic probes spectroscopies, i.e., micro-Raman and scanning X-ray photoemission microscopy. The nanometric cylindrical particles were relatively homogenously distributed throughout the film covering the graphite foil. Film thickness modulation on surface was calculated between 100 and 300 nm range. We show that the segregation of MnV-O and MnV-S relative abundance in the internal and external volume of the cylindrical nanoparticles respectively, can be exploited during faradaic and non-faradaic processes in charge/discharge.

MnxOy embedded within CNT supporting porous carbon for enhanced lithium storage

Achievement of improved structural stability and conductivity for Mn-based oxides is the crucial premise for them to be high-performance anodes of lithium-ion batteries due to their large volume effect and poor intrinsic conductivity. Herein, the lithium storage performance of the MnxOy nanoparticles containing dominant MnO and slight MnO2 and Mn3O4 has been significantly improved by embedding them into a CNT supporting porous carbon. This composite is therefore denoted as CNT/MnxOy/C. The comparison results of the electrochemical performance of thus CNT/MnxOy/C with CNT/Mn3O4 and pure Mn3O4 nanoparticles demonstrate that the well-designed synergistic effect of high conductive CNT support and flexible spongy porous carbon is responsible for its improved performance, which efficiently enhances not only the structural stability but also the electrochemical kinetics of the CNT/MnxOy/C. As a result, this CNT/MnxOy/C anode shows outstanding performance, obtaining high capacities of 936.5 and 410.5 mAh g-1 at 200 and 1000 mA g-1 after 260 and 800 cycles, respectively. Moreover, this strategy proposed here will be hopefully instructive in constructing other advanced metal oxide nanomaterials toward improved performance of lithium-ion battery anodes.

Defects rich nanostructured black zinc oxide formed by nanosecond pulsed laser irradiation in liquid

Zinc oxide (ZnO) is a wide bandgap semiconductor for energy applications while the spectral absorption only in UV region limits the use as a visible light absorber. Here, visible light absorbing modified ZnO (black) is prepared by creating surface defects and vacancies using pulsed laser irradiation in liquid. The modified ZnO nanoparticles have spherical morphology and they are free from impurity phases. The optical bandgap of this modified material is narrowed by increased irradiation time with a morphological transformation to mostly nanospheres. XPS analysis confirmed the oxygen vacancies contribution and the valance band study showed a reduction in the band edge. With the results of Raman and photoluminescence spectra, the oxygen defects and vacancies were confirmed. Thin films were fabricated using these materials via doctor blade method and their photocatalytic studies showed enhanced activity in organic dye decay under visible light. Results of this study show a facile method for fabrication of defects rich metal oxide nanomaterials by pulsed laser irradiation in liquid.

Metal oxides nanocomposite membrane for biofouling mitigation in wastewater treatment

These days our one of the major challenges is the treatment of polluted wastewater produced by the growing population and industrial activities. The conventional wastewater treatment methods are costly and need to be more advanced. For this reason, membrane technology has been used as an effective wastewater treatment method for many decades due to its high removal power, selectivity, and permeability properties. Biofouling causes a serious concern related to membrane permeability, shortens membrane life, and selectivity. Polymeric membranes are widely used in wastewater treatment due to their good pore-forming ability, higher flexibility, and relatively low costs but are limited to their hydrophobicity property and more susceptible to fouling. Metal oxides nanomaterials are widely used in the formation of polymer nanocomposite membranes because of their hydrophilicity, larger surface area, pore channels, and high toxicity towards pathogenic micro-organisms. In this review, we have discussed the factors affecting membrane biofouling and their conventional and current treatment methods with their limitations. We have also referred to the use of metal oxide nanomaterials, as an antibacterial agent, for the fabrication of polymer nanocomposite membranes and discuss their antibacterial activity with antibiofouling behavior.

Self-Assembled Co3O4/GO Composites for Excellent Electrochemical Detection of Heavy-Metal Ions

Recently, electrochemical sensors have been applied for the detection of heavy metal ions. The modifier on the electrochemical electrode is the key factor for enhanced performance. Modification by combining metal oxide nanomaterials with good adsorption property and graphene oxide (GO) with good conductivity can construct a useful sensing interface to detect heavy metal ions. Here, the effects of structures and morphologies of Co3O4/GO composite modifiers on the electrochemical detection performance were studied. The results show that Co3O4/GO composite with holey nano-sheets of pure Co3O4 on lamella GO substrate had the best electrochemical performance for their large active sites and enhanced ion and charge transports. The limits of detection of the electrochemical sensors based on developed Co3O4/GO composite to Cd2+ and Pb2+ were calculated as 57 and 29.4 nM, respectively, which are lower than the guideline values recommended by the World Health Organization for drinking water. Furthermore, the designed sensor also showed excellent stability, selectivity, and acceptable reproducibility and reliablity. The results indicate that Co3O4/GO composite with holey layer structures as a promising electrode modifier could be potentially applied in the electrochemical detection of heavy metal ions on-site.

Evaluation of antibacterial behavior of in situ grown CuO-GO nanocomposites

The growth of harmful microorganisms is a severe threat to human life. Nowadays, it is necessary to prepare antimicrobials materials with high biocompatibility properties. Hence, the use of nanomaterials and their nanocomposites has been proposed as a suitable way to obtain safe and potent antibacterial materials. Recently, several studies have been conducted on the antibacterial properties of metal oxide and graphene oxide (GO) nanomaterials individually. This study investigated the synergistic effect of GO and copper oxide (CuO) as a nanocomposite. CuO-GO nanocomposite containing 5%, 15%, 25%, 50%, and 75% of GO were synthesized to study antibacterial properties. X-ray diffraction (XRD) results showed that CuO and GO synthesized were free of impurities and unwanted phases. Fourier Transform Infrared Spectroscopy (FTIR) spectrum of the prepared sample has revealed the presence of vibrational modes related to Cu-O, alkoxy group (O-H), epoxy group (C-O-C), and carboxyl group (C-O). In Raman spectroscopy, the CuO nanostructure has a redshift, and in the CuO-GO nanocomposite, D band and G band have blueshift and redshift by increasing the amount of GO, respectively. The results of UV-Vis spectra showed that synthesized CuO and GO have a higher band gap (4.54 eV and 3.03 eV, respectively) than previous studies. Also, the highest amount of band gap of nanocomposites is related to the 50%wt GO nanocomposite (3.40 eV). Field emission scanning electron microscope (FESEM) images showed that CuO nanosheets bonded with GO plates and decorated the GO plates. Antibacterial activity of synthesized nanocomposite investigated using Escherichia coli (E.coli) bacteria. The antibacterial test results showed that CuO nanoparticles have inadequate antibacterial activity (15%), while by composting with GO, the antibacterial activity against E. coli significantly increased (for 50% GO about 76%). However, the antibacterial activity reduced to 68% for the nanocomposite sample with 75% GO concentration; thus, 50% GO nanocomposite is the optimal concentration.

Self-Assembled 2D Networks of Metal Oxide Nanomaterials Enabling Sub-ppm Level Breathalyzers.

For extremely sensitive acetone sensors, here, we introduced an alcohol-assisted surfactant-free Langmuir-Blodgett process to rapidly assemble a single-layered two-dimensional (2D) network as a suitable percolation strategy of metal oxide semiconductor nanomaterials. The single-layered 2D network formation mechanism was investigated using zinc oxide (ZnO) nanobeads (NBs). Furthermore, the correlation between the response of the gas sensor and the average percolation number of the ZnO NBs, controlled by multi-stacking the 2D network, was investigated. It was inferred that a reduction in the number of percolations led to maximization of the response. Additionally, the versatility of the optimal percolation strategy was experimentally verified by confirming similar results to that achieved with ZnO NBs when utilizing different sizes, shapes, and compositions of metal oxides. Finally, the practical effectiveness of our extremely sensitive strategy was solidified by illustrating the response enhancement in a commercial exhalation diagnostic system that measures the amount of acetone in only 1 mL of exhalation.

Sunlight-induced photocatalytic degradation of organic pollutants by biosynthesized hetrometallic oxides nanoparticles.

Dyes and phenols are extensively used chemicals in petrochemicals, pharmaceuticals, textile, and paints industries. Due to high persistence, bioaccumulation, and toxicity, their removal from the environment is highly imperative by advanced techniques. Single metal oxide nanomaterials are generally associated with limitations of large bandgap (> 3eV) and charge recombination. Therefore, heterometallic oxides (HMOs) as CuFe2O4, CuMn2O4, and MnZn2O4 have been synthesized via green route by employing leaf extract of Azadirachta indica. XRD revealed the crystalline nature of HMOs nanospheres with particle size less than 100 nm. Subsequently, HMOs nanocatalysts were used as photocatalyst for removal of 3-amino phenols (3-AP) and eriochrome black T (EBT) from water under sunlight. Reaction parameters namely pollutant concentration (50-130 mgL-1), catalyst dose (20-100 mg), and pH (3-11) were optimized in order to get best results. Substantial degradation (80-95%) of pollutants (50 mgL-1) by HMOs (80 mg) was achieved at neutral pH under sunlight exposure. Highest removal by CuFe2O4 might be due to its high surface area (35.7 m2g-1), low band gap (2.4 eV), larger particle stability (Zeta potential: -22.0 mV), and lower photoluminescence intensity. Sharp declines in curves were visually confirmed by color change and indicated for first-order kinetics of degradation with initial Langmuir adsorption. Spectrophotometric analysis revealed that half-life (t1/2) of 3-AP (0.9-1.7 h) and EBT (0.6-0.8 h) were significantly reduced. Faster degradation of EBT than 3-AP was because of less electronegative N-atom at the diazo group. Scavenger analysis indicated the presence of active radicals in photo-catalytic degradation of 3-AP and EBT. All HMOs have shown high reusability (n=8) which ensures their stability, sustainability, and efficiency. Overall, green synthesized HMOs nanoparticles with prominent surface characteristics offer a viable alternative photocatalyst for industrial applications.

Recent advances in hierarchical anode designs of TiO 2 ‐B nanostructures for lithium‐ion batteries

The state-of-the-art development progress of the fabrication, design, modification, and applications of TiO2-B-based hierarchical nanostructures with a well-controlled size and morphology in lithium-ion battery (LIB) applications has been summarized and discussed. Based on studying on lithiation/delithiation on mechanisms of a typical metal oxide nanomaterials, along with doping with foreign atoms (metal or non-metal), using electronically conductive additives (graphene/graphene derivatives), as well as designing and using hierarchical anode-material nanostructures (hybrids/composites) containing two or more constituents in LIB applications, these strategies have provided many great opportunities to take maximum advantage of both the high capacity and rate capacity while avoiding significant capacity loss after charge/discharge cycling. In this review, the advances in TiO2-B-based anode structures at the nanoscale for LIBs have been discussed in two major sections, including (a) hierarchical heterostructures based on TiO2-B and metal, non-metal, transition metal oxides (TMOs), and transition metal dichalcogenides (TMDs); and (b) hybrid designs/nanocomposites between TiO2-B and graphene/graphene derivatives. The in-depth understanding of structure-property relationships as well as detailed suggestions on the mechanism, reason, and origin of the excellent enhancement in electrochemical performance in the above strategies, has been presented and highlighted.

Precipitation at Room Temperature as a Fast and Versatile Method for Calcium Phosphate/TiO2 Nanocomposites Synthesis.

The constantly growing need for advanced bone regeneration materials has motivated the development of calcium phosphates (CaPs) composites with a different metal or metal-oxide nanomaterials and their economical and environmentally friendly production. Here, two procedures for the synthesis of CaPs composites with TiO2 nanoplates (TiNPl) and nanowires (TiNWs) were tested, with the immersion of TiO2 nanomaterials (TiNMs) in corrected simulated body fluid (c-SBF) and precipitation of CaP in the presence of TiNMs. The materials obtained were analyzed by powder X-ray diffraction, spectroscopic and microscopic techniques, Brunauer–Emmett–Teller surface area analysis, thermogravimetric analysis, dynamic and electrophoretic light scattering, and their hemocompatibility and ability to induce reactive oxygen species were evaluated. After 28 days of immersion in c-SBF, no significant CaP coating was formed on TiNMs. However, the composites with calcium-deficient apatite (CaDHA) were obtained after one hour in the spontaneous precipitation system. In the absence of TiNMs, CaDHA was also formed, indicating that control of the CaP phase formed can be accomplished by fine-tuning conditions in the precipitation system. Although the morphology and size of crystalline domains of CaDHA obtained on the different nanomaterials differed, no significant difference was detected in their local structure. Composites showed low reactive oxygen species (ROS) production and did not induce hemolysis. The results obtained indicate that precipitation is a suitable and fast method for the preparation of CaPs/TiNMs nanocomposites which shows great potential for biomedical applications.

What We Currently Know about Carbon‐Supported Metal and Metal Oxide Nanomaterials in Electrochemical CO2 Reduction

AbstractElectrochemical reduction of CO2 is considered important in enhancing the circular‐economy design; it can suppress harmful greenhouse‐gas emissions while, combined with intermittent renewable energy sources, it can employ the surplus energy for production of important chemicals and fuels. In the process, electrocatalysts play an important role as the mediators of the highly active and selective conversion of CO2. Transition and post transition metals and their oxides are an important electrocatalyst group. For practical reasons, these metals need to be applied as nanoparticles supported on highly conducting materials enabling fabrication of 3D electrodes. In this minireview, we focus on gathering our current knowledge on the effects which transition and post transition metal and metal oxide nanoparticles supported on different carbons may have on electrochemical reduction of CO2. We focus on literature of studies conducted in aqueous conditions, under as similar conditions as possible, to ensure comparability. This approach enables us to highlight possible support effects and issues that complicate making conclusions on support effects.

Imaging Constructs: The Rise of Iron Oxide Nanoparticles.

Over the last decade, an important challenge in nanomedicine imaging has been the work to design multifunctional agents that can be detected by single and/or multimodal techniques. Among the broad spectrum of nanoscale materials being investigated for imaging use, iron oxide nanoparticles have gained significant attention due to their intrinsic magnetic properties, low toxicity, large magnetic moments, superparamagnetic behaviour and large surface area—the latter being a particular advantage in its conjunction with specific moieties, dye molecules, and imaging probes. Tracers-based nanoparticles are promising candidates, since they combine synergistic advantages for non-invasive, highly sensitive, high-resolution, and quantitative imaging on different modalities. This study represents an overview of current advancements in magnetic materials with clinical potential that will hopefully provide an effective system for diagnosis in the near future. Further exploration is still needed to reveal their potential as promising candidates from simple functionalization of metal oxide nanomaterials up to medical imaging.

Suspended 1D Metal Oxide Nanowire Junction Networks for Use As Highly Sensitive Gas Sensors

Introduction Over the last few decades, research has been conducted to build sensitive, reliable and high-performance gas monitoring systems that meet the demands of industrial sites. In particular, 1D metal oxide (MOx) nanomaterials have been actively studied as a gas sensing material because of its excellent sensing performance, low cost, and suitability for a micro/nano device [1]. Besides, the MOx 1D nanostructures are relatively easy to synthesize, easy to control morphology and have various options including surface functionalization to make even further enhancement of the sensing performance [2]. In particular, when the MOx 1D nanostructures linked together and form a junction structure, an additional current path is generated through the formed junction and this forms additional potential barriers. Thus, an additional gas sensing mechanism can be utilized to further improve sensing performance as shown in Figure 1 [3]. In general, however, the fabrication process of MOx nanostructure networks including dense junctions requires complex and precise techniques. In addition, the nanostructure networks are positioned on the substrates. Therefore, gas access to the junctions and mass transfer to the sensing sites are limited. In this study, we report a novel gas sensor architecture including a suspended carbon mesh integrated with ZnO nanowires networks. The nanowires are grown on single carbon wires of the mesh and meet at the void regions of mesh structures. Thus, dese nanowire junctions can be formed in a suspended form (Figure 2). Owing to the suspended architecture, gas access to the sensing sites is effective and the sensing signal is free from the effect of the substrate [4]. The suspended carbon nanomesh was fabricated using the carbon-MEMS process consisting of simple photolithography and pyrolysis processes. The ZnO nanowire networks were precisely patterned at the suspended mesh using the hydrothermal method. The length of the nanowires was adjusted for good junction formation and the advantage of the suspended junctions was evaluated. Method Suspended carbon nanomesh was fabricated by photolithography and pyrolysis (Vacuum, 700°C) processes. Via two successive exposure steps in photolithography, suspended polymer mesh was defined without complex lithography techniques. After the pyrolysis process, microscale polymer mesh was converted into nano-sized carbon mesh because of the large volume reduction (up to 90%) in pyrolysis. After a thin ZnO seed layer was selectively coated on the suspended carbon mesh, ZnO nanowires were grown on the patterend seed layer by a hydrothermal process (Zn(NO3)2 25mM, HMTA 25mM ). The pristine ZnO nanostructures were annealed using RTA (N2 atmosphere, 300°C) for better adhesion and connection. Results and Conclusions Figure 2 shows the SEM images of the fabricated suspended carbon nanomesh (width ~140μm, thickness ~400nm, line spacing ~6μm) and ZnO nanowire networks (diameter ~100 nm, length ~3.5 μm). ZnO nanowires were well grown to form uniform and dense junctions. To characterize the effect of the nanowire junctions, NO2 gas sensing responses were compared between a nanomesh-based gas sensor and a single suspended carbon wire-based sensor. As shown in Figure 3. the suspend mesh-based sensor exhibited higher response and wider linear range due to the effect of junctions. This novel sensor architecture can be widely utilized because all the fabrication processes of the presented sensor were carried out at a wafer-level making it cost-effective and various MOx nanowires can be simple integrated with a bunch of junctions.