Exploring the weak visible-near-infrared and NO2detection capabilities of PbS/Sb2O5heterostructures with DFT interpretations.

The need for photosensors and gas sensors arises from their pivotal roles in various technological applications, ensuring enhanced efficiency, safety, and functionality in diverse fields. In this paper, interlinked PbS/Sb2O5thin film has been synthesized by a magnetron sputtering method. We control the temperature to form the nanocomposite by using their different nucleation temperature during the sulfonation process. A nanostructured PbS/Sb2O5with cross-linked morphology was synthesized by using this fast and efficient method. This method has also been used to grow a uniform thin film of nanocomposite. The photo-sensing and gas-sensing properties related to the PbS/Sb2O5compared with those of other nanomaterials have also been investigated. The experimental and theoretical calculations reveal that the PbS/Sb2O5exhibits extraordinarily superior photo-sensing and gas-sensing properties in terms of providing a pathway for electron transport to the electrode. The attractive highly sensitive photo and gas sensing properties of PbS/Sb2O5make them applicable for many different kinds of applications. The responsivity and detectivity of PbS/Sb2O5are 0.28 S/mWcm-2and 1.68 × 1011Jones respectively. The sensor response towards NO2gas was found to be 0.98 at 10 ppb with an limit of detection (LOD) of 0.083 ppb. The PbS/Sb2O5exhibits high selectivity towards the NO2gas. Density functional theory (DFT) and time-dependent density functional theory (TD-DFT) were used to analyze the geometries, electronic structure, and electronic absorption spectra of a light sensor fabricated by PbS/Sb2O5. The results are very analogous to the experimental results. Both photosensors and gas sensors are indispensable tools that contribute significantly to the evolution of technology and the improvement of various aspects of modern life.

A simple and fast method for the fabrication of p-typeß-Ga2O3by electrochemical oxidation method with DFT interpretation.

In this work, a simple electrochemical oxidation method has been used to prepare p-typeß-Ga2O3nanoparticles. This method overcomes the problem of doping high energy gap semiconductors to form p-type. The electron holes ofß-Ga2O3were caused by oxygen vacancy (Vo) and showed the shorter lattice constant and preferred orientation in XRD analysis. The peak area of oxygen vacancy also reflects a higher ratio than n-type Ga2O3in x-ray photoelectron spectroscopy (XPS). The adsorption of reducing gas (CO, CH4, and H2) enhanced the resistance of theß-Ga2O3confirming the p-type character of NPs. The DFT calculations showed that oxygen vacancy leads to higher energy of the Fermi level and is near the valence band. The binding energy of Ga2O3and after interaction with gas molecular was also calculated which is analogous to our experimental data.

Comparative DFT dual gas adsorption model of ZnO and Ag/ZnO with experimental applications as gas detection at ppb level.

By experimental and density functional theory calculations, the toxic gases (O3and NO2) sensing capability and mechanism of ZnO NRs and Ag/ZnO NRs have been comparatively studied in this work. Ag NPs arrays were employed for the growth of ZnO NRs. The experimental results show that when ZnO NRs are grown on Ag NPs, the response and adsorption rate towards the gases change significantly. The TDOS plot shows that the HOMO-LUMO gap changes after interaction with different oxidizing gases, and the peak intensity also decreases confirming the electron are transferred from ZnO to NO2and O3. The response to gases decreases and the adsorption reaction rate increases in Ag/ZnO NRs, as calculated by the Eyring-Polanyi equation, which is very similar to our experimental data. We also find that the absorption coefficient is different for O3and NO2. Finally, experimental response and theoretical results were compared and found to be in good agreement.

Analysis of the Sensing Properties of a Highly Stable and Reproducible Ozone Gas Sensor Based on Amorphous In-Ga-Zn-O Thin Film.

In this study, the sensing properties of an amorphous indium gallium zinc oxide (a-IGZO) thin film at ozone concentrations from 500 to 5 ppm were investigated. The a-IGZO thin film showed very good reproducibility and stability over three test cycles. The ozone concentration of 60-70 ppb also showed a good response. The resistance change (ΔR) and sensitivity (S) were linearly dependent on the ozone concentration. The response time (T90-res), recovery time (T90-rec), and time constant (τ) showed first-order exponential decay with increasing ozone concentration. The resistance-time curve shows that the maximum resistance change rate (dRg/dt) is proportional to the ozone concentration during the adsorption. The results also show that it is better to sense rapidly and stably at a low ozone concentration using a high light intensity. The ozone concentration can be derived from the resistance change, sensitivity, response time, time constant (τ), and first derivative function of resistance. However, the time of the first derivative function of resistance is shorter than other parameters. The results show that a-IGZO thin films and the first-order differentiation method are promising candidates for use as ozone sensors for practical applications.

Atomic-Level Insights of Polypyrrole Grafted InGaZnO Structure for ppb-Level Ozone Gas Sensing at Low Operating Temperature.

This study explores the utilization of the organic conductive molecule Polypyrrole (PPy) for the modification of Indium Gallium Zinc Oxide (IGZO) nanoparticles, aiming to develop highly sensitive ozone sensors. Pyrrole (Py) molecules undergo polymerization, resulting in the formation of extended chains of PPy that graft onto the surface of IGZO nanoparticles. This interaction effectively diminishes oxygen vacancies on the IGZO surface, thereby promoting the crystallization of the IGZO (1114) facets. The resultant structure exhibits promising potential for achieving high-performance wideband semiconductor gas sensors. The IGZO/PPy device forms a Straddling Gap heterojunction, facilitating enhanced electron transfer between IGZO and ozone molecules. Notably, the adsorption and desorption of ozone gas occur efficiently at a low temperature of approximately 25 °C, obviating the need for additional energy typically associated with wide bandgap semiconductor materials. Density Functional Theory (DFT) calculations attribute this efficiency to the enhanced number of active sites for ozone adsorption, facilitated by hydrogen bonds. The substantial conductivity of PPy, combined with its planar ring structure, induces positively charged polarization on the IGZO side upon ozone adsorption. The resultant device exhibits exceptional sensitivity, boasting a 4-fold improvement compared to sensors reliant solely on IGZO. Additionally, the response time is significantly reduced by a factor of 10, underscoring the practical viability and enhanced performance of the IGZO/PPy sensor field.

Revealing a Highly Sensitive Sub-ppb-Level NO2 Gas-Sensing Capability of Novel Architecture 2D/0D MoS2/SnS Heterostructures with DFT Interpretation.

In this work, we use a chemical method to design novel 2D-material/0D-quantum dot (MoS2/SnS) heterostructures. Furthermore, the unique 2D/0D heterostructure enhanced the NO2 gas-sensing capability 3 times and increased the sensing recoverability by more than 90%. Advanced characterization tools such as SEM, TEM, XRD, and AFM confirm the formation of MoS2/SnS heterojunction nanomaterials. Using AFM data, the average thickness of the MoS2 layer was found to be 5 nm. The highest sensor response of 0.33 with good repeatability was observed at 250 ppb of NO2. Sensing characterization reveals the ultra-fast response time, that is, 74 s, at 50 ppb of NO2. The limit of detection for detecting NO2 was also found to be very low, that is, 0.54 ppb, by using MoS2/SnS heterostructures. The theoretical calculations based on density functional theory well corroborated and quantified the intermolecular interaction and gas adsorption on the surface of MoS2/SnS.

Highly sensitive and rapid responding humidity sensors based on silver catalyzed Ag2S-TiO2 quantum dots prepared by SILAR.

We developed a resistive humidity sensor based on a heterojunction of silver sulfide (Ag2S) quantum dots (QDs) and TiO2 because of its specificity to water vapor adsorption and its insensitivity to environmental gases. The QDs were grown on a mesoporous TiO2 layer using the successive ionic layer adsorption and reaction (SILAR) method. The boundary condition between TiO2 and Ag2S provides a tunable energy gap by adjusting the number of SILAR cycles. Besides, the large surface-to-volume ratio of QDs provides a strong water vapor adsorption ability and electron transfer. Nano-silver precipitated during the SILAR process provides free electrons and lowers the Fermi level to between n-type TiO2 and p-type Ag2S. The resistance response increased significantly to 4600 and the reaction equilibrium time decreased greatly to 7 seconds due to the presence of nano-silver. Finally, the Ag2S QDs possess a best sensing range of 13-90%. To sum up, Ag2S QDs are high sensitivity and selectivity humidity sensors.

Improving the SERS signals of biomolecules using a stacked biochip containing Fe2O3/Au nanoparticles and a DC magnetic field.

This study proposes a magnetic biochip that uses surface-enhanced Raman scattering (SERS) for antigen detection. The biochip was a sandwich structure containing alternating layers of gold and magnetic Fe2O3 nanoparticles. Both single (Au/Fe2O3/Au) and multilayer (Au/Fe2O3/Au/Fe2O3/Au) chips containing Fe2O3 nanoparticles were fabricated to detect bovine serum albumin (BSA). The single-layer chip detected the BSA antigen at a signal-to-noise ratio (SNR) of 5.0. Peaks detected between 1000 and 1500 cm-1 corresponded to various carbon chains. With more Fe2O3 layers, bond resonance was enhanced via the Hall effect. The distribution of electromagnetic field enhancement was determined via SERS. The signal from the single-layer chip containing Au nanoparticles was measured in an external magnetic field. Maximum signal strength was recorded in a field strength of 12.5 gauss. We observed peaks due to other carbon-hydrogen molecules in a 62.5-gauss field. The magnetic field could improve the resolution and selectivity of sample observations.

Influence of magnetoplasmonic γ-Fe2O3/Au core/shell nanoparticles on low-field nuclear magnetic resonance.

Magnetoplasmonic nanoparticles, composed of a plasmonic layer and a magnetic core, have been widely shown as promising contrast agents for magnetic resonance imaging (MRI) applications. However, their application in low-field nuclear magnetic resonance (LFNMR) research remains scarce. Here we synthesised γ-Fe2O3/Au core/shell (γ-Fe2O3@Au) nanoparticles and subsequently used them in a homemade, high-Tc, superconducting quantum interference device (SQUID) LFNMR system. Remarkably, we found that both the proton spin-lattice relaxation time (T1) and proton spin-spin relaxation time (T2) were influenced by the presence of γ-Fe2O3@Au nanoparticles. Unlike the spin-spin relaxation rate (1/T2), the spin-lattice relaxation rate (1/T1) was found to be further enhanced upon exposing the γ-Fe2O3@Au nanoparticles to 532 nm light during NMR measurements. We showed that the photothermal effect of the plasmonic gold layer after absorbing light energy was responsible for the observed change in T1. This result reveals a promising method to actively control the contrast of T1 and T2 in low-field (LF) MRI applications.