In this work, multifunctional CuO nanowires (NWs) electrode-based extended-gate (EG) field-effect transistor (FET) has been explored for both pH and glucose sensing applications. The CuO nanowires ...(NWs) electrode-based EGFET gives good pH sensitivity (~48.34 mV/pH), high linearity (99.84%), good stability for pH level in between 2 and 12 for 12 hours with a drift rate of 2.5mV/h, and good reversibility in terms of low hysteresis loss of 2.5mV. The selectivity of this pH sensor towards hydrogen ion is significantly higher as compared to Na + , K + , Zn ++ and Mg ++ ions. In addition to the pH sensing, CuO NWs based electrode-based EGFET has also been explored for glucose-sensing for the first time without taking the help of neither any enzyme nor any organic receptor. The proposed glucose sensor gives a good sensitivity of 3.03 mV/mM with a high range of linearity (1mM-12mM), which covers up the glucose level of human blood ranging from 3.6 mM to 6.6 mM. This novel concept of CuO NWs based EG-FET glucose sensing is believed to be extended for sensing other saccharides such as fructose, sucrose, and mannose.
This paper explores gold nanoparticle (GNP) modified copper oxide nanowires(CuO NWs)based electrode grown on copper foil for non-enzymatic glucose detection in a wide linear ranging up to 31.06 mM, ...and 44.36 mM at 0.5 M NaOH and 1 M NaOH concentrations. The proposed electrode can be used to detect a very low glucose concentration of 0.3 µM with a high linearity range of 44.36mM and sensitivity of 1591.44 µA mM
cm
. The electrode is fabricated by first synthesizing Cu (OH)
NWs on a copper foil by chemical etching method and then heat treatment is performed to convert Cu (OH)
NWs into CuO NWs. The GNPs are deposited on CuO NWs to enhance the effective surface-to-volume ratio of the electrode with improved catalytic activity. The surface morphology has been investigated by XRD, XPS, FE-SEM and HR-TEM analysis. The proposed sensor is expected to detect low-level of glucose in urine, and saliva. At the same time, it can also be used to measure extremely high sugar levels (i.e. hyperglycemia) of ~ 806.5454 mg/dl. The proposed sensor is also capable of detecting glucose after multiple bending of the GNP modified CuO NWs electrode. The proposed device is also used to detect the blood sugar level in human being and it is found that this sensor's result is highly accurate and reliable.
Abstract
Herein, electrochemically assisted dissolution-deposition (EADD) is utilized over a three-electrode assembly to prepare an electrocatalyst for hydrogen evolution reaction (HER). Cyclic ...voltammetry is performed to yield atomistic loading of platinum (Pt) over SnS
2
nanostructures via Pt dissolution from the counter electrode (CE). Astonishingly, the working electrode (WE) swept at 50 mV/s is found to compel Pt CE to experience 1000–3000 mV/s. The effect of different potential scan rates at the WE have provided insight into the change in Pt dissolution and its deposition behaviour over SnS
2
in three electrode assembly. However, uncontrolled overpotentials at CE in a three-electrode assembly made Pt dissolution-deposition behavior complex. Here, for the first time, we have demonstrated bi-potentiodynamic control for dissolution deposition of Pt in four-electrode assembly over Nickel (Ni) foam. The dual cyclic voltammetry is applied to achieve better control and efficiency of the EADD process, engendering it as a pragmatically versatile and scalable synthesis technique.
Plasmon-induced hot-electron generation and its efficient transfer to the conduction band (CB) of neighboring metal oxides is an effective route to solar energy harvesting. However, until now, this ...process has been very inefficient due to the poor charge transfer rate from plasmonic metal nanoparticles (NPs) to the CB of the oxide semiconductor. In this work, an in situ grown synthesis method has been developed to grow plasmonic Ag NPs within a titanium oxide (TiO2) matrix. This synthesis method allows us to deposit Ag NPs surrounded by a TiO2 semiconductor, which results in an efficient charge transfer from the Ag NPs to the CB of TiO2 and has been utilized for highly enhanced electro-photocatalytic H2 generation. Photoelectrochemical measurement of optimized Ag(NPs)-TiO2 thin film photoanodes showed a high photocurrent generation at a density of 42 mA cm–2 in 1 M KOH solution, which is three orders of magnitude higher than that of pure TiO2, and stability for more than 1.5 h. These data indicates that it has excellent potential application for photoelectrochemical (PEC) water splitting. An intense photocurrent generation in the region of plasmonic absorption of Ag NPs with a peak position of 435 nm has been observed; this photocurrent generation reveals direct evidence of a strong contribution of plasmon-induced hot electrons for solar energy conversion.
Au-Cu alloy nanostructures have been synthesized in aqueous phase through co-reduction of HAuCl4.3H2O and CuCl2.2H2O by glucose in presence of hexadecylamine at ∼80 °C. By changing the synthesis ...conditions, nanostructures of various shapes such as nanowires, multiply twinned tripod, tetrapod, etc were observed. Systematic variation of the synthesis condition not only leads to change in size and particle morphology but also develops various other crystallographic characters in the nanoparticles. Alloying behavior of Au-Cu has been examined through transmission electron microscope operating in its conventional and analytical modes coupled with high resolution phase contrast microscopy. These results suggested that nanostructures are composed of homogeneous Au-Cu alloy. Preferential attachment along {111} and {100} crystallographic facets of Au-Cu alloy nanoparticles led to the formation of nanowires. Multiply twinned branched shape Au-Cu (width of branch ∼30 nm) nanostructures exhibit localized surface plasmon resonance maxima in the near-infrared region. The branched shape Au-Cu alloy nanostructures display better surface enhanced Raman scattering response in the detection of methylene blue as compared to spherical Au nanoparticles.
A solution-processed in situ grown synthesis method has been developed to grow electronically coupled silver sulfide (Ag2S) nanoparticles (NPs) inside a titanium oxide (TiO2) thin film. Taking the ...advantage of better charge transport between Ag2S and TiO2, this composite thin film has been utilized for electro-photocatalytic H2 generation. This thin film growth requires three successive steps, including sol-gel derived ion-conducting thin film fabrication containing loosely bound light ion (Li+) followed by ion-exchange (with Li+↔Ag+) and subsequent sulfurization process. This entire solution-processed deposition technique is capable to fabricate cost-effective large area Ag2S–TiO2 thin film containing Ag2S NPs ranging ~10–70 nm. Since, Ag2S has a lower band gap and consider as a promising material for photoelectrochemical H2 generation, therefore Ag2S (NPs)-TiO2 thin film is grown on three different substrates, including fluorine-doped tin oxide (FTO), FTO/TiO2 (sol-gel), and FTO/TiO2 (NPs) to fabricate photoanode for this study. A comparative photo-electrocatalytic measurement of these three different Ag2S(NPs)-TiO2 thin film coated photoanodes showed that sample on FTO/TiO2 (NPs) substrate generate highest photocurrent of density ~50 mA cm−2 at 0.5 V vs NHE in 1 M KOH solution which is three orders higher than pure TiO2 and stable for more than 1.5 h, indicating it's excellent potential application for photoelectrochemical water splitting. The photocurrent generation of this Ag2S–TiO2 thin film is significantly higher than earlier reported Ag2S–TiO2 system, which is originated due to the reduced carrier recombination from electronically coupled Ag2S/TiO2 interface state of such in situ grown Ag2S NPs.
•Ag2S nanoparticle has been grown inside TiO2 thin film.•Ion-exchange and sulfurization process of Li4Ti5O12 convert to Ag2S/TiO2 thin film.•Deposition technique is capable for low cost-large area Ag2S/TiO2 thin film.•Efficient photoelectrochemical H2 generation of Ag2S/TiO2 film has been studied.•Stability photoelectrochemical H2 generation has been demonstrated.
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•Sulfonic acid (SO3H) functionalized 2D-MoS2 nanosheet is a novel and promising electrocatalyst for hydrogen generation.•SO3H molecules are intercalate through the 2D-MoS2 ...interlayers, which resulted in interlayer expansion up to 9.4 Å.•Functionalization improves the electrocatalytic activity and stability of the 2D-MoS2.•SO3H-MoS2 improves catalytically-active charge-transfer sites thereby outperforms the pristine 2D-MoS2.•Localized charge concentrations in SO3H-MoS2 lowers the work function to ∼4.82 eV, thus, enhances charge-transfer kinetics.
We report the sulfonic acid (SO3H) functionalized two-dimensional (2D) molybdenum disulfide (MoS2) nanosheet with significantly enhanced physical and electrochemical properties as an efficient electrocatalyst for hydrogen evolution reaction (HER). The functionalized 2D-nanosheet shows enhanced electrocatalytic performance than the pristine one. We obtained overpotential as low as ∼82 mV (ƞ10) along with a very low Tafel slope ∼57 mV dec-1 and excellent stability (12 h) in functionalized MoS2. We also found that, with increasing the % of functional group, -SO3Hmolecules were intercalated through the MoS2layers resulting in the increase in interlayer spacing from 6.1 Å to 9.4 Å. The intercalated 2D-MoS2nanosheets with expanded interlayer distance further enhance the surface area, charge-transfer sites, and surface adsorption–desorption by lowering the ΔGH (i.e., the energy barrier of hydrogen adsorption/desorption), thereby accelerating the Volmer step of hydrogen evolution. Finally, density functional theory (DFT) calculations show significant changes in the electronic structure of the functionalized 2D-MoS2with a considerable shift in the total density of states (DOS) as compared to its pristine counterpart. The DFT calculations reveal that hybridizations occur between the SO3Handpanddstates of the S and Mo, which propel the valence band maximum towards higher energies, thus, leading to the narrowing of the bandgap of MoS2. Such changes in electronic properties further reduce work function and facilitate redox-mediated charge-transfer, thereby, enhancing the electrocatalytic activity for HER.
Abstract The synthesis of ordered gold‐copper (Au 3 Cu) alloy nanocrystals (≈10 nm) is reported and used in the semiconductor (2H) to metallic (1T) phase transformation of an atomically thin ...large‐area 2D‐MoS 2 grown via CVD technique. The ordered Au 3 Cu nanocrystals are dispersed over 2D‐MoS 2 , and the phase transformation is confirmed via Raman spectroscopy followed by X‐ray photoelectron spectroscopy (XPS), while the surface properties of the Au 3 Cu/2D‐MoS 2 is determined by the XPS valence band analysis and ultra‐violet photoemission spectroscopy (UPS). By comparing overpotential and Tafel slopes for Hydrogen Evolution Reaction (HER), a decrease is observed in overpotential by 83.2 mV and Tafel slope by ≈58.25 mV per decade for Au 3 Cu/MoS 2 on light irradiation. This electrocatalytic enhancement of Au 3 Cu/MoS 2 refers to the transformation of semiconducting 2D‐MoS 2 to metallic phase under light illumination, thereby altering the surface electronic structures, improving carrier concentrations, lowering the valence band edge, and lowering the free energy of H * adsorption/desorption. Density functional theory (DFT) calculations, along with other surface characterizations, further illustrate that the ordered nanocrystal‐induced phase transformation in 2D‐MoS 2 leads to a more durable metallic characteristic, thus, enhancing the surface electrical conductivity, reducing surface potential and Gibbs free energy, and improving the kinetics of photoelectrocatalytic performance of the hybrid structure.
The optical and electrical properties of Au/ZnO quantum dots (QDs)-based Schottky photodiode are analyzed in this paper. The thin film of ZnO QDs was deposited over the n-Si (111) substrate using the ...low-cost solution processing technique. The Schottky contact gold (Au) electrodes are deposited using thermal evaporation over the ZnO QDs thin films. The responsivity and contrast ratio of the photodiode are found to be 41.17 A/W and 2.289 × 10 4 , respectively, at -5 V applied bias. Furthermore, the spectral response of the photodiode has been analyzed for the spectrum of 250-900 nm. The photodiode shows the full width at half maxima of 90 nm with a central wavelength of 365 nm, which indicates the color selective nature of the photodiode. In further analysis, it is observed that the rectification ratio, ideality factor, and barrier height of this device are 2.21 × 10 3 , 2.57, and 0.80 eV, respectively. The obtained electrical and optical parameters are the best-reported values for the ZnO-based UV detectors. The transient response of the Schottky photodiode is found to be 73.1 ms (rise time) and 17.85 ms (falltime) under the illumination of UV LED for a square pulse of an ON-OFF period of 1 s.
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