Shiv Govind Singh

Contribution of ohmic contact resistance ( R _c ) to series resistance ( R _s ) was studied during the fabrication of GaAs THz Schottky barrier diodes. Ohmic contacts were characterized by cross-section TEM, EDS, backside SIMS and grazing incidence x-ray diffraction techniques, and correlated with electrical measurements. Very low contact resistances and contact resistivities ( ρ _c ) in the range of ⩽0.01 Ω·mm and 10 ⁻⁹ Ω·cm ² , respectively, were achieved, enabling very low series resistance of 2.2 Ω and high cut-off frequencies ( f _T ) of ∼4.5 THz. Ohmic contact formation was also simulated in a TCAD simulator. The experimentally obtained ultralow ρ _c values were input to the TCAD simulator to extract the I – V characteristics and R _s values which were compared with measurements to verify the self-consistency of device performance.

Glaucoma leads to permanent loss of retinal ganglion cells and progressive optic nerve damage, making early diagnosis essential for preventing vision impairment. Identifying reliable, non-invasive molecular biomarkers can significantly improve early intervention and patient outcomes. In this work, an electrochemical biosensor is reported engineered from a vanadium disulfide–multiwalled carbon nanotube (VS₂–MWCNT) nanocomposite for detecting complement component C3, a biomarker associated with glaucoma progression. The VS₂–MWCNT nanofibers were produced by electrospinning a mixture of hydrothermally synthesized VS₂ and multiwalled carbon nanotubes, followed by comprehensive characterization using Scanning Electron Microscopy (SEM), X-ray Photoelectron Spectroscopy (XPS), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). When deposited onto glassy carbon electrodes (GCEs), the hybrid nanofibers displayed improved surface adhesion, electrochemical performance and stability in comparison with pristine VS₂. The resulting C3 biosensor achieved ultralow detection limits of 3.652 fg/mL (CV) and 1.1052 fg/mL (EIS) with a linear detection range for the logarithm of 100 fg/mL to 1 µg/mL C3 concentrations. These findings highlight a robust and highly sensitive sensing platform with strong promise for early-stage glaucoma detection and potential clinical application. Graphical abstract The alternative text for this image may have been generated using AI.

Compact, flush-mounted antennas with controlled beam tilt and wide beamwidth are vital for aerospace radar applications; however, achieving high efficiency and thermal robustness in such configurations remains challenging. This letter presents a compact branch-waveguide leaky-wave antenna (LWA) with an integrated high-temperature radome to address these requirements. Branch and main waveguide dimensions are systematically optimized to control the phase (β) and leakage (α) constants, enabling a targeted 65° beam tilt when flush-mounted on the airframe. With a compact length of 2.7λ, the antenna achieves over 95% radiation efficiency and ∼50° HPBW in both E- and H-planes across a 12% bandwidth. The dual-layer radome, composed of fused silica and ceramic foam, withstands 1200 °C with minimal insertion loss and pattern distortion. Thermal simulations and kinetic heating tests confirm stable VSWR and radiation patterns before and after high-temperature exposure. The proposed LWA thus provides a compact, efficient, and thermally resilient solution for reliable flush-mounted deployment in high-temperature aerospace environments.

Retinopathy of prematurity (ROP) is a dreadful eye condition and is considered as leading cause of blindness in children around the globe. Lack of timely and appropriate treatment for this ocular condition leads to abnormal development of retinal blood vessels and progression to the severe stage ROP, resulting in irreversible blindness. Based on our previous studies that identified matrix metalloproteinases (MMPs) to be potential tear biomarkers, herein we are demonstrating that the increased levels of MMP-9 in tears can help in ROP risk prediction. A biochip integrated with vanadium disulfide nanowires (VS2NWs) and resistance measurement circuitry for quantitative analysis of MMPs was established. The biochip fabrication process was optimized using a hybrid central composite design (CCD)-support vector regression (SVR) method resulted in an enhanced signal amplification of the sensor output (ΔR/R). The 30 preterm tear samples (10 healthy, 10 mild, and 10 severe ROP) were collected across the neonatal care units, and the tear MMPs were analyzed by the VS2NW-based biochip and commercial ELISA kits. The VS2NW biochip showed a similar inclination for the expression of MMP-2 and MMP-9 as seen using the commercial ELISA kits and exhibited an area under the curve (AUC) of 0.9778 on the external test set, with 100% sensitivity and 96.67% specificity. This study proved the reliability of the VS2NW biochip platform to identify ROP tear biomarkers and screen high-risk ROP babies in a quick and noninvasive manner.

Although fast-paced ongoing industrial growth, on the one hand, enhances the lifestyle of the population, on the other hand, it affects human health and the environment as a result of the discharge of pollutants. To address this, designing a novel and effective photocatalyst is necessary to mitigate increasing environmental pollutants. In the present work, we aim to synthesize a single-phase high-entropy zirconate pyrochlore oxide (Ce_0.2Pr_0.2Zn_0.2Nd_0.2Tb_0.2)₂Zr₂O₇ using a modified Pechini method. The physicochemical properties of the prepared nanoparticles were investigated using X-ray diffraction, UV-visible spectroscopy, field emission scanning electron microscopy, and X-ray photoelectron spectroscopy. The photocatalytic properties were examined using cationic dye (methylene blue), anionic dye (Congo red), and Cr(VI). Photocatalytic degradation experiments demonstrate exceptional efficiency in the removal of persistent organic pollutants. The photocatalytic results indicate that the prepared high-entropy (Ce_0.2Pr_0.2Zn_0.2Nd_0.2Tb_0.2)₂Zr₂O₇ zirconate pyrochlore oxide could effectively degrade dyes and reduce Cr(VI). Radical trapping experiments indicate that the degradation of dyes was driven by the hydroxyl radicals, superoxide radicals, and holes. Furthermore, the position of the valence band and conduction band promoted efficient photocatalytic reaction kinetics. The prepared photocatalyst remains structurally stable and can be reused three times without losing activity.

Tuberculosis (TB) is a significant public health issue, and the existing diagnostic tests have shortcomings that cause delays in initiating treatment. In this study, we designed a Gene-pimB-based biosensor for the determination of TB and tested it using an electrochemical technique. The Gene-pimB has been reported to be upregulated in mannose-capped lipoarabinomannan (manLAM) in multidrug-resistant TB (MDR-TB). Due to its link with drug resistance, Gene-pimB holds promise as a biomarker for identifying MDR-TB strains. In this work, the biosensor is fabricated using graphite-zinc oxide nanofibers (GPH-ZnO NFs), which are generated using electrospinning and deposited on glassy carbon electrodes. The GPH–ZnO functionalized electrode were further functionalized with MSA/EDC/NHS protocol to provide efficient immobilization which enable the effective binding of pimB-sequences to the nanofibers on the electrodes. In addition, the Gene-pimB hybridization on biosensors immobilized with Gene-pimB probe sequences was quantified using cyclic voltammetry (CV), differential pulse voltammetry (DPV), and electrochemical impedance spectroscopy (EIS) techniques. The experimental tests revealed that the limit of detection (LoD) for CV is 0.1482 pM ml⁻¹, for DPV it is 0.196 pM ml⁻¹, and for EIS it is 0.302 pM ml⁻¹. Our findings suggest that Gene-pimB may prove to be a useful technique in the creation of novel tests for TB prognosis. The efficacy of the developed biosensor was confirmed by a hybridization sensing assay including targeted short oligonucleotide sequences (probe) and Gene-pimB (target) isolated from the urine sample. To assess its potential for clinical detection, urine samples were artificially spiked with the gene to simulate conditions encountered in clinical diagnostics. This approach allows for evaluating the feasibility of detecting Gene-pimB in a non-invasive manner, which could aid in the early identification of drug-resistant TB cases and improve diagnostic strategies for effective disease management.

Prolonged exposure to elevated levels of cadmium ions in water can lead to serious health problems, and efficient detection of these ions is vital for preventing severe consequences. This letter presents an electrochemical detection technique realized via surface modification of working electrodes with metal sulfide and aptamer adaptation, offering a versatile platform for developing a robust, portable, and cost-effective sensor for environmental monitoring and in situ detections. A novel, compact, and miniaturized design of $\mu$-dimensional working electrode along with on-chip counter and reference electrode (RE) fabricated on a silicon wafer has been used as the transducer to subdue the lack of portability of conventional carbon electrode. The electrodeposition technique is employed in this work to obtain superior control, better adhesion, and uniformity in electrode modification, leading to efficient sensor design. Molybdenum disulfide (MoS₂) material is electrodeposited on the working electrode using chronoamperometric technique and functionalized with cross-linkers to bind to amine-terminated aptamers. Cd (II) specific aptamers immobilized on a $\mu$-electrode sensor surface via a covalent surface modifier on electrodeposited MoS₂ exhibit high specificity and a detection limit as low as 1.3 ng/L. The Si wafer-based integrated electrodes with $\mu$-scale dimensions, combined with the electrodeposition technique, are a promising alternative to glassy carbon electrodes with compact design, and harbor the possibility of multiplexing for detecting different heavy metal ions in water.

In this work, a vertical contact–separation mode triboelectric nanogenerator (TENG) engineered with a hierarchically porous silk fibroin scaffold and copper film as the triboelectric pair is presented. The silk scaffold was fabricated via a freeze-drying process and integrated onto a flexible polyethylene terephthalate substrate. The porous architecture significantly increased the effective surface area and interfacial contact, leading to enhanced charge generation compared to conventional thin-film counterparts. Electrical performance was optimized by varying the scaffold thickness. The optimized device, incorporating a 1.5-mm porous scaffold, achieved a peak-to-peak output voltage of 420 V and a power of 17 mW, sufficient to illuminate 12 serially connected micro-LEDs. The proposed TENG is cost effective, mechanically adaptive, and biocompatible. Electrical and mechanical durability tests indicate its suitability as a robust and scalable energy harvesting platform for self-sustaining wearable and biointegrated technologies.