Figure - available from: Microchimica Acta
This content is subject to copyright. Terms and conditions apply.
a XPS spectrum showing the different sub-stoichiometric states of Mo in α-MoO3-x nanoflakes. b XPS spectrum showing the oxidation of α-MoO3-x nanoflakes in the presence of Hydrogen peroxide
Source publication
An optical method is described for the quantitation of glucose by using oxygen-deficient α-MoO3-x nanoflakes. It is based on the use of glucose oxidase (GOx) which produces hydrogen peroxide on oxidation of glucose. Hydrogen peroxide then oxidizes the α-MoO3-x nanoflakes, and this results in a visible color change from blue to colorless. The color...
Citations
... Transition-metal dichalcogenides and layered transition metal oxides attracted a lot of attention for biosensing and phototherapy [207,208]. For instance, 2D molybdenum trioxide (MoO3) nanosheets were employed to develop facile determination of some key analytes, such as glucose and hydrogen peroxide [209,210]. It was shown that the change in oxidation state of oxide nanosheets leads to a rapid bare eye detection probe for biological fluids [211]. ...
The development of modern cutting-edge technology relies heavily on the huge success and advancement of nanotechnology, in which nanomaterials and nanostructures provide the indispensable material cornerstone. Owing to their nanoscale dimensions with possible quantum limit, nanomaterials and nanostructures possess a high surface-to-volume ratio, rich surface/interface effects, and distinct physical and chemical properties compared with their bulk counterparts, leading to the remarkably expanded horizons of their applications. Depending on their degree of spatial quantization, low-dimensional nanomaterials are generally categorized into nanoparticles (0D); nanorods, nanowires, and nanobelts (1D); and atomically thin layered materials (2D). This review article provides a comprehensive guide to low-dimensional nanomaterials and nanostructures. It begins with the classification of nanomaterials, followed by an inclusive account of nanofabrication and characterization. Both top-down and bottom-up fabrication approaches are discussed in detail. Next, various significant applications of low-dimensional nanomaterials are discussed, such as photonics, sensors, catalysis, energy storage, diverse coatings, and various bioapplications. This article would serve as a quick and facile guide for scientists and engineers working in the field of nanotechnology and nanomaterials.
... [287]. Various MoO3 morphologies, such as nanobelts [287], nanoflakes [288], films [186], and nanorods [172], are being studied for applications such as energy storage devices, solar cells, memory devices, gas sensors, light detectors, and so on [181,[289][290][291]. Among them, one-dimensional nanorods are being extensively researched for use as gas sensors due to the existence of multiple surface atoms that are easily accessible because of their high ratio of surface to volume. ...
... The absence of 916 cm -1 as well as To get the high-resolution XPS spectra shown here, the sensor surface was etched with argon. High-resolution XPS spectra of the sensor's molybdenum (3d) state (S350/S400) were identified at 232.7 eV/232.5 eV as well as 235.8 eV/235.6 eV, which matched with the 3d5/2 and 3d3/2 levels were in line with earlier literature (Fig: 7.6 a and c) [288,295]. Additionally, two different oxygen peaks were identified in the magnified spectra of O (1s) after the deconvolution for both the sensors S350 and S400 ...
Purpose and method of the study: One of the primary goals of the researchers is to develop sustainable and clean energy to replace traditional fossil fuels, as environmental difficulties are becoming more prevalent owing to the release of hazardous gases from the burning of such fuels. Proper monitoring of the emission of those gases is also critical for which gas sensors with higher sensing response, long term stability, fast response, and recovery times are needed. Hydrogen is considered as the fuel for the near future as a replacement for non-renewable fossil fuels and the cleanest way of its production is by the means of electrocatalytic/photocatalytic water splitting. Molybdenum based one dimensional and two-dimensional nanostructured materials have been proven for their applications in gas sensing as the sensing element and in the clean production of hydrogen by the means of electrochemical water splitting as the catalyst, but the research is still inadequate for meeting the real application. In this work, we attempt the synthesis, characterization, and applications of one-dimensional molybdenum trioxide, two-dimensional molybdenum carbide MXenes, and their composites for their applications in gas sensing and electrochemical hydrogen evolution reaction for a real device with less environmental impact.
Contributions and Conclusions: In this study, we carried out the gas sensing and hydrogen evolution application of molybdenum-based 1D and 2D nanostructures with the help of a systematic study of the synthesis and characterization strategies involved. To detect the presence of ammonia gas, gas sensors were produced in this work using vacuum thermal evaporation of α-MoO3 nanorods on glass substrates, followed by an annealing technique in
ambient air. The gas sensing assessment of the produced sensors demonstrated that the specimen annealed at 400 oC had exceptional sensitivity towards ammonia gas at room temperature (28 oC). In the process of the testing, it was determined that the sensors remained responding to ammonia levels as low as 1ppm, highly repeatable, and remarkably stable after one year of working, with just a 1% decline in the sensing response. Additionally, a porous silicon/molybdenum trioxide hybrid structure, that was produced via simple thermal evaporation of the MoO3 over an electrochemically produced silicon substrate, proved effective in sensing CO2 gas at a low concentration level (50 ppm) and working temperature (150 oC). We compared the effect of the substrate in the sensing performance, and it was found that at 250 oC, the sensor fabricated on porous silicon demonstrated approximately fourfold the sensitivity (15 % at 150 ppm) of the sensor fabricated on crystalline silicon (3.9 % at 200 oC and 150 ppm) and a much faster response time (8s at 100 ppm). Meanwhile, Mo2CTx MXene was prepared from Mo-In-C non-MAX phase using a solid-state process followed by UV aided phosphoric acid etch and ultrasonic exfoliation for the first time. We developed Mo2CTx MXene sensors that were supported on a different substrate (glass, crystalline, and porous silicon) and used them to detect CO2 at room temperature. The gas sensing experiments were carried out at temperatures ranging from 30 to 250 oC and CO2 concentrations ranging from 50 to 150 ppm. When compared to crystalline silicon sensors, sensors built of porous silicon and glass demonstrate superior room temperature sensing response as well as rapid reaction and recovery time of 30 and 45 s, respectively, when operated at 30 °C and 50 ppm of CO2, which are the fastest recorded values at ambient temperature to the date. Finally, electrochemical hydrogen evolution reaction (HER) application of the produced Mo2CTx MXenes as working electrodes was carried out and the MXene synthesized from the non-MAX phase at 850 oC exhibited the lowest overpotential, with a value of -138 mV at 10 mA/cm2 current density and a Tafel slope of 41 mV/dec.
... Moreover, the PdCl 2 solution could bleach the obtained blue colloidal solution via oxidation of substoichiometric Mo oxide nanosheets, promising accurate colorimetric sensing of oxidizing analytes. Despite this observation, few reports have been published to date on LSPR molybdenum oxide nanosheets as a sensitive and cost-effective colorimetric sensor for hydrogen peroxide [52,53]. Therefore, this nanomaterial should be explored further as its optical properties strongly correlate with the oxidation states in these materials. ...
Plasmon coupling effect occurs in plasmonic nanostructures when interparticle distances are in the order of particle size leading to spectral shifts in the plasmonic band. This effect has been recently highlighted for measurement of fluctuations in the interparticle distance at nanoscale level. In this study, nanostructured thin Au films were deposited on quartz substrates by pulsed laser deposition (PLD) for sensing of hydrogen gas. A blue shift from 730 to 560 nm in LSPR of Au films was observed when substrate temperatures rises from 25 to 600 °C due to variation in morphology of films from a continuous surface composed of tiny agglomerates to granular surface composed of bigger particles with increased interparticle spacing. For plasmon coupling sensing of hydrogen, a thin Pd film was deposited on top of nanostructured Au films. Upon hydrogen exposure, up to12 nm blue shift within few seconds was observed depending on hydrogen concentration. Based on field emission scanning electron microscope (FESEM) images and finite-difference time-domain (FDTD) simulations, this plasmon sensing is explained by hydrogen-induced decoupling due to the formation of surface stresses in Pd, which can affect the LSPR via an increase in interparticle spacing of Au nanoislands.
... Moreover, the PdCl 2 solution could bleach the obtained blue colloidal solution via oxidation of substoichiometric Mo oxide nanosheets, promising accurate colorimetric sensing of oxidizing analytes. Despite this observation, few reports have been published to date on LSPR molybdenum oxide nanosheets as a sensitive and cost-effective colorimetric sensor for hydrogen peroxide [52,53]. Therefore, this nanomaterial should be explored further as its optical properties strongly correlate with the oxidation states in these materials. ...
Hydrogen peroxide sensing is crucial for various medical diagnostics and industrial monitoring. On the other hand, doped metal oxides have recently emerged as cost-effective materials with localized surface plasmon resonance (LSPR) for colorimetric sensing of hydrogen peroxide. In this paper, using a simple anodic oxidation method, plasmonic MoO3-x colloidal nanosheets with deep blue color were fabricated and examined for the colorimetric sensing of hydrogen peroxide. X-ray photoelectron spectroscopy (XPS) revealed the presence of a considerable level of oxygen vacancy in the nanosheets composition. Depending on its concentration, hydrogen peroxide weakens the LSPR and the blue color of colloids with a sigmoidal sensing behavior. The impact of anodizing potential (10, 20, and 30 V) and time on a sensing performance was investigated and a limit of detection (LOD) as low as 0.2–0.9 μM was obtained. Furthermore, it was found that the LSPR undergoes redshift and the optical bandgap increases in a sigmoidal manner with analyte concentration that was explained by the existing theory on plasmonic semiconductors. To make a colorimetric assay, we immobilized MoO3-x nanosheets on felt fibers, which was observed by scanning electron microscope (SEM) images. The assay was examined to detect hydrogen peroxide by the naked eye in the concentration range of 800 μm to 100 mM and was analyzed using digital image analysis. Overall, our study develops a facile approach to produce MoO3-x nanosheets to detect hydrogen peroxide at the human-positive diabetes level (2.8–5.6 mM).
... For the T400 sample, the peak positions shifted The high resolution XPS spectra reported here was taken after the soft etching of the sensor surface with argon followed by the calibration of the binding energy peak with respect to carbon at 284.6 eV. The doublet peaks observed in the high resolution XPS spectra (Fig: 6a and 6c) of molybdenum (3d) state of the sensor ( T350/ T400) at 232.7 eV/232.5 eV and 235.8 eV/235.6 eV corresponds to the 3d5/2 and 3d3/2 states respectively, which were in good agreement with the previous reports [43,44]. Also, from the deconvoluted high resolution spectra of O (1s) (Fig: 6b and 6d), two characteristics peaks of oxygen were identified for both T350 and T400 sensors. ...
We report the fabrication of ammonia gas sensors operating at room temperature using aligned one-dimensional orthorhombic molybdenum trioxide (α-MoO3) nanorods. α-MoO3 nanorods were fabricated on glass substrates by thermal evaporation under vacuum condition and subsequent annealing at ambient air. The selectivity of fabricated sensors was performed with different test gases viz. ammonia, xylene, acetone, toluene, isopropanol, 2-methoxyethanol, n-butanol, methanol, and ethanol. Highest sensitivity for ammonia gas at room temperature (28°C, 35% relative humidity) for a concentration of 100 ppm, was achieved. The sensors annealed at 400 °C showed response to lower concentrations of ammonia (1 ppm) with high repeatability. The sensing response dropped only less than 1% after one year of stable performance. The change in morphology and the structural modifications of α-MoO3 nanorods with annealing had improved the sensing response.
... As a result, the fully oxidized white colors of MoO 3 -S(1-4) were converted into the partially reduced 2-D MoO 3-x -S(1-4)-C nanoplates with various colors at calcination treatment as shown in optical images in Fig. S2. The optical properties of of 2-D MoO 3-x -S(1-4)-C nanoplates strongly indicate the presence of the the oxygen vacancies due to TMO originating from characteristic outer most d-shell valance electrons [34,35]. ...
... So far, various techniques for H 2 O 2 determination have been explored, such as fluorometry [3,4], cellular imaging [5], electrochemistry [6,7], and the colorimetric method [8,9]. Among these approaches, the colorimetric method has drawn a lot of attention due to its convenient operation, visibility, facile miniaturization, and low cost [10,11]. In this respect, natural enzymes were extensively used for the detection of H 2 O 2 due to its catalysis capability under mild conditions. ...
We report the facile and economic preparation of two-dimensional (2D) and 0D MoSe2 nanostructures based on systematic and non-toxic top-down strategies. We demonstrate the intrinsic peroxidase-like activity of these MoSe2 nanostructures. The catalytic processes begin with facilitated decomposition of H2O2 by using MoSe2 nanostructures as peroxidase mimetics. In turn, a large amount of generated radicals oxidizes 3,3,5,5-tetramethylbenzidine (TMB) to produce a visible color reaction. The enzymatic kinetics of our MoSe2 nanostructures complies with typical Michaelis–Menten theory. Catalytic kinetics study reveals a ping–pong mechanism. Moreover, the primary radical responsible for the oxidation of TMB was identified to be Ȯ2− by active species-trapping experiments. Based on the peroxidase mimicking property, we developed a new colorimetric method for H2O2 detection by using 2D and 0D MoSe2 nanostructures. It is shown that the colorimetric sensing capability of our MoSe2 catalysts is comparable to other 2D materials-based colorimetric platforms. For instance, the linear range of H2O2 detection is between 10 and 250 μM by using 2D functionalized MoSe2 nanosheets as an artificial enzyme. Our work develops a systematic approach to use 2D materials to construct novel enzyme-free mimetic for a visual assay of H2O2, which has promising prospects in medical diagnosis and food security monitoring.
... Besides, it is known that over 80% of biosensor industry research is related to glucose sensors. Therefore, the development of a facile, low-priced, and accurate sensor for H 2 O 2 and glucose continue to receive tremendous research effort [17,18]. ...
Abstract Photoluminescent zero-dimensional (0D) quantum dots (QDs) derived from transition metal dichalcogenides, particularly molybdenum disulfide, are presently in the spotlight for their advantageous characteristics for optoelectronics, imaging, and sensors. Nevertheless, up to now, little work has been done to synthesize and explore photoluminescent 0D WS2 QDs, especially by a bottom-up strategy without using usual toxic organic solvents. In this work, we report a facile bottom-up strategy to synthesize high-quality water-soluble tungsten disulfide (WS2) QDs through hydrothermal reaction by using sodium tungstate dihydrate and l-cysteine as W and S sources. Besides, hybrid carbon quantum dots/WS2 QDs were further prepared based on this method. Physicochemical and structural analysis of QD hybrid indicated that the graphitic carbon quantum dots with diameters about 5 nm were held onto WS2 QDs via electrostatic attraction forces. The resultant QDs show good water solubility and stable photoluminescence (PL). The excitation-dependent PL can be attributed to the polydispersity of the synthesized QDs. We found that the PL was stable under continuous irradiation of UV light but can be quenched in the presence of hydrogen peroxide (H2O2). The obtained WS2-based QDs were thus adopted as an electrodeless luminescent probe for H2O2 and for enzymatic sensing of glucose. The hybrid QDs were shown to have a more sensitive LOD in the case of glucose sensing. The Raman study implied that H2O2 causes the partial oxidation of QDs, which may lead to oxidation-induced quenching. Overall, the presented strategy provides a general guideline for facile and low-cost synthesis of other water-soluble layered material QDs and relevant hybrids in large quantity. These WS2-based high-quality water-soluble QDs should be promising for a wide range of applications in optoelectronics, environmental monitoring, medical imaging, and photocatalysis.
... Most transition metals are mainly in the form of oxides or sulfides. For example, molybdenum (Mo) mainly exists in MoO x and MoS 2 [22]. These compounds usually exhibit peroxidase activity to certain extent [23]. ...
... These compounds usually exhibit peroxidase activity to certain extent [23]. There have been many studies on MoS 2 NSs as a nanozyme for detecting glucose by visualization, however, the sensitivity is not satisifactory and the detection limit is high [22,24]. Additionally, MoS 2 is toxic to organisms and is not environmentally friendly. ...
The nanozymes, alternative for natural enzymes, have become popular in many research fields because they exhibit relatively high activity and stability. Herein, we utilize abundant, renewable ocean green tide (Enteromorpha prolifera, EP) waste as a biotemplate to facilely prepare MoO3 nanorods supported on EP derived carbon (MoO3/C). The as-prepared MoO3/C exhibited excellent peroxidase-like activity with Km of 0.13 mM and Vmax of 0.292 μM s−1 (H2O2 as the substrate), superior to most mimetic peroxidases reported so far. The catalytic mechanism of the as-synthesized MoO3/C is proven to be a Ping-pong BiBi electron transfer mechanism. Further, the MoO3/C was used for non-enzymatic measurement of H2O2 sensitively, with the linear H2O2 concentration range of 1–100 μM and a low limit of detection (LOD) of 0.181 μM (S/N = 3). Based on its excellent catalytic activity and stability, the MoO3/C was coupled with glucose oxidase to apply for the colorimetrically sensing glucose sensitively and selectively, with two linear parts, 0.02–0.5 mM as well as 0.5–6.0 mM glucose and a LOD of 10 μM glucose (S/N = 3). Moreover, the detection of blood glucose in real human serums was realized successfully. Thus, the green tide biomass waste templated strategy opens up an avenue to develop nanozymes for many applications, which is simple, cost-effective and environmentally friendly.
... [24]. Our group has reported two sensors for alkaline phosphatase (ALP) and glucose based on α-MoO 3-x nanoflakes [25,26]. ...
A method is reported for the synthesis of highly luminescent copper/molybdenum bimetallic nanoclusters (Cu/Mo NCs) using cysteine as both a capping and reducing agent. The nanoclusters display bluish-green luminescence (excitation/emission peaks at 370/490 nm) and a relative quantum yield of 26%. The capped Cu/Mo NCs were used as a fluorescent probe for determination of the antineoplastic drug methotrexate (MTX) via an inner filter effect. Fluorescence intensity decreases linearly in the 50 nM to 100 μM MTX concentration range. The limit of detection is 13.7 nM. This approach has been successfully applied to the determination of MTX in spiked human urine with a typical recovery of 99%.
Graphical abstractSchematic of a fluorometric method for the determination of methotrexate (MTX) which exerts a strong inner filter effect on the fluorescence of cysteine-capped copper/molybdenum nanoclusters (CuMo NCs) at the wavelength of excitation (370 nm).
