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While most of the reports on NH3 gas sensors are either based on metal oxide composites with other 2D materials, polymers or noble metals or involve multi-step-based synthesis routes, this work is the first report on a pristine ternary metal oxide, 2D NiCo2ZnO4 nanoflake based room-temperature (RT) NH3 gas sensor. The 2D NiCo2ZnO4 nanoflakes were prepared by a one-step hydrothermal method. FESEM and TEM images displayed micro-flower like morphologies, containing vertically aligned interwoven porous 2D nanoflakes, whereas XPS and XRD data confirmed the successful growth of this ternary metal–oxide. This sensor revealed a good response, repeatability, linearity (R2 = 0.9976), a low detection limit of 3.024 ppb, and a response time of 74.84 s with excellent selectivity towards NH3 over six other VOCs. This improved performance of the sensor is ascribed to its large specific surface area (127.647 m2 g−1) resulting from the 2D nanoflake like structure, good electronic conductivity, variable valence states and abundant surface-active oxygen of NiCo2ZnO4. Thus, this highly selective 2D NiCo2ZnO4 based RT NH3 gas sensor can be an attractive solution for the fabrication of next-generation NH3 gas sensors. [ABSTRACT FROM AUTHOR]

We report an ultra-low level of Lead ion (Pb2+) detection technique using solution-processed Bovine Serum Albumin (BSA) conjugated ZnO nanoparticle (BCZ) networks. Drop of the BCZ solution casting was performed in-between photolithography patterned two Au electrodes for sensor device. BCZ formation was confirmed by UV-Visible spectroscopy (UV-Vis spectroscopy) and Transmission Electron Microscopy (TEM) prior to device fabrication. The working principle of the sensor device depends on the variation of conductance with Pb2+ concentration. The limit of detection (LOD) of this fabricated device was determined as 0.1 pM (S/N > 3). [ABSTRACT FROM AUTHOR]

Electrocatalytic hydrogen evolution reaction (HER) is regarded as a sustainable and green way for H2 generation, which faces a great challenge in designing highly active, stable electrocatalysts to replace the state‐of‐art noble metal‐platinum catalysts. 1T MoS2 is highly promising in this regard, but the synthesis and stability of this is a particularly pressing task. Here, a phase engineering strategy has been proposed to achieve a stable, high‐percentage (88%) 1T MoS2/chlorophyll‐a hetero‐nanostructure, through a photo‐induced donation of anti‐bonding electrons from chlorophyll‐a (CHL‐a) highest occupied molecular orbital to 2H MoS2 lowest unoccupied molecular orbital. The resultant catalyst has abundant binding sites provided by the coordination of magnesium atom in the CHL‐a macro‐cycle, featuring higher binding strength and low Gibbs‐free energy. This metal‐free heterostructure exhibits excellent stability via band renormalization of Mo 4d orbital which creates the pseudogap‐like structure by lifting the degeneracy of projected density of state with 4S in 1T MoS2. It shows extremely low overpotential, toward the acidic HER (68 mV at the current density of 10 mA cm−2), very close to the Pt/C catalyst (53 mV). The high electrochemical‐surface‐area and electrochemical turnover frequency support enhanced active sites along with near zero Gibbs free energy. Such a surface‐reconstruction strategy provides a new avenue toward the production of efficient non‐noble‐metal‐catalysts for the HER with the aim of green‐hydrogen production. [ABSTRACT FROM AUTHOR]

Demand for the detection of poisonous arsenic ions in water is increasing due to uncontrolled industrial and human activities. Conventional detection methods are found to be very complex, cumbersome, and non-portable. This paper presents curcumin functionalized zinc oxide field effect transistor for selective detection of arsenic ions in water, with high sensitivity and stability. The operating voltage of the device is optimized to 2.9 V through output characteristics, which ensures low power consumption. The presence of curcumin on ZnO surface imparts high degree of selectivity toward arsenic ions, and ZnO nanorods ensures high surface to volume ratio for adsorption. The device is tested against eight metal ions commonly found in water and is found to be highly selective toward arsenic. The device exhibits a sensitivity of 102 nA/ppb at zero gate voltage, which is further amplified to 366 nA/ppb by applying 2.4 V gate bias. The application of gate bias plays a pivotal role for enhancing the device sensitivity by 266% for 5 ppb arsenic concentration. The sensor shows a response time of 67 s and is found to be highly stable against adverse conditions. The sensor shows high resilience in the degradation of sensing performance for a duration of 40 days. Therefore, curcumin functionalized zinc oxide field effect transistor with proper gate bias shows promising results to be used as a portable, low-cost, and user-friendly arsenic ion detector system in future. [ABSTRACT FROM AUTHOR]

This work demonstrates the implementation of thioglycolic acid (TGA) functionalized water-soluble NH2–molybdenum disulfide (MoS2) nanosheets as sensitive layers for toxic heavy metal ion sensing in drinking water. The sensor device was tested for several ions commonly found in drinking water, e.g., As (III), Pd (II), Hg (II), and Cd (II). When the sensor was exposed to individual ions, it showed negligible response toward elements such as As (III), Pd (II), and other commonly present metal ions. However, at 25 ppb, some cross sensitivity was observed between Cd (II) and Hg (II) ions. The mathematical analysis was performed to investigate the cross-sensitive behavior, and a model was put forward. It was evident from the higher attachment factor (${N}$) for Cd concerning Hg (II), derived from the model which supported Cd’s higher response when exposed individually (${N}_{\text {Cd}}= 4\times 10^{{16}}$ cm−3/ppb and ${N}_{\text {Hg}}= 1.6\times 10^{{14}}$ cm−3/ppb). Furthermore, the band structure and electron concentration were plotted for individual Cd (II) and Hg (II) ions. Compared to Hg (II), Cd (II) efficiently depleted the amine–MoS2 and TGA junction. To better understand selectivity and response, the device was exposed to Cd (II) and Hg (II) ions simultaneously at different concentrations, which looked into the effect of the two interacting ions. A mathematical model was hence established. It was found that the absorption coefficient (${K}_{\text {Hg}}$) was much higher (63 ppb−1) than Cd (${K}_{\text {Cd}}$) (0.38 ppb−1). The interaction factor (${K}_{\text {Hg-Cd}}$), i.e., the absorption coefficient of Cd in the presence of Hg, was calculated as −0.086 ppb−2, which is lower than ${K}_{\text {Cd-Hg}}{(}-0.013$ ppb−2), which indicated that Hg is more active toward adsorption in competition to the Cd ions. This competitive dominance for Hg (II) adsorption may be attributed to the affinity of thiol groups present in the TGA molecules for Hg (II) over Cd (II) ions. The device was repeatable after testing with five different devices with a standard deviation of 0f 0.5322 and stable up to 50 days with ±3% response variation. Thus, the proposed sensor may be a suitable candidate for low-cost water quality monitors. [ABSTRACT FROM AUTHOR]

In this paper, ultra-low level selective detection of bovine serum albumin (BSA) has been demonstrated, based on chemically derived graphene i.e., reduced graphene oxide (RGO) nanosheets. The working principle of the sensor is based upon change in conductance of the RGO nanosheets with different concentration of BSA. The change in conductance is based on the charge transfer between BSA and functional groups of RGO. The morphological and structural characterizations of RGO nanosheets were carried out by scanning electron microscopy (SEM), transmission electron microscopy (TEM), atomic force microscopy (AFM), Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). Raman spectroscopy is performed to further validate the interaction between RGO sensing layer and BSA molecules. Electrical impedance spectroscopy is performed to observe the impedance variation when BSA interacts with RGO. The sensor device exhibits sensitivity of 10 nA/pM. The lower limit of detection (LOD) of the sensor is found to be 1 pM and response time around 35 s, confirming very high sensitivity for BSA. All electrical (current-voltage) measurements were carried out at 2 V bias for low power operation. The sensor exhibits highest sensitivity at 30 °C and for RGO thickness ~4 nm. The RGO based sensor device is selective towards BSA when compared to proteins like L-Histidine, HSA, BHB and Biotin. Our results suggest that RGO based devices are promising for low-cost, portable and real time detection of BSA at room temperature. [ABSTRACT FROM AUTHOR]

Design and analysis of a metal-oxide-metal (MOM) capacitor in 0.18- $\mu \text{m}$ RF CMOS process, suitable for the ${L}$ -, ${S}$ -, and ${C}$ -band integrated circuits, is presented in this article. In order to maximize the flux density per unit area, Moore fractal geometry is chosen for the capacitor plates. The capacitor uses lateral electric fields, in contrast to commonly used vertical electric fields. To further increase the capacitance density, four metal layers of the CMOS process are used by efficient contact of vias. The design strategy makes it possible to achieve a high value of capacitance and ${Q}$ factor, noted as 1.15 pF and 51.6, respectively, at 2.4 GHz, for a silicon area of 65 $\times \,\,65\,\,\mu \text{m}^{{2}}$. The obtained self-resonance frequency is 13.5 GHz. A variability analysis is done and parasitics are extracted using a high-frequency capacitor circuit model. An active, third-order image reject filter (IRF) is subsequently realized as a circuit application for the designed fractal capacitor. The filter provides a notch at 1.8 GHz with more than 35-dB attenuation and a controlled passband centered at 2.4 GHz. [ABSTRACT FROM AUTHOR]

A 2.4 GHz industrial, scientific, and medical band on-chip antenna (OCA) is integrated into an on-chip broadband balun in $0.18~\mu \text{m}$ CMOS technology on a die of size 4 mm2. Antenna miniaturization is achieved from the capacitive loading of meandered dipole arms. A back-to-back configuration of the balun on a separate die is characterized with in-band insertion and return loss of better than 0.9 dB and 20 dB, respectively. A commercial low-cost package is used to provide a decoupling effect to the OCA when immersed in tissue, enabling it to maintain stable impedance matching as in the air. A detailed explanation of the decoupling mechanism is provided using field plots and equivalent circuit analysis. The OCA is characterized in air and different tissue phantoms with a gain of −23.8 dBi in air and −25.9 dBi inside skin mimicking gel. The maximum simulated uplink specific absorption rate is obtained as 160 $\mu \text{W}$ /kg for an input power of $25~\mu \text{W}$ to the OCA in the transmitting mode. As the antenna has a small footprint and is analytically estimated to be capable of communicating at a high uplink bit rate of 1 Mb/s over a distance of 5.2 m with a 3 dB link margin, it is most suited as a minimally invasive implantable medical device. [ABSTRACT FROM AUTHOR]

The physical operation and performance of a dual gate β-gallium oxide nanomembrane field effect transistor (NM-FET) with asymmetric top and back gate oxide thicknesses are investigated for different modes of operation. A physics-based device simulator calibrated with experimental data is used for this purpose. Normally-OFF operation of the NM-FET is demonstrated by electrically tuning the top gate threshold voltage with the applied back gate bias. In addition, analytical models of threshold voltage for all the different modes of operation are presented and the proposed models are rigorously validated with simulation results and experimental data. The effect of individual device parameters on the threshold voltage of the normally-OFF NM-FET is further investigated using the analytical model. [ABSTRACT FROM AUTHOR]

2H MoS2 nanoflakes were exfoliated and surface-modified by amine (-NH2) groups in a simple three-step water-based approach. The NH2-modified MoS2 sheets were used as humidity sensitive layer for estimating various levels of relative humidity (RH) (10%–90%). The devices demonstrated a maximum response of 720% for 90% RH with ${t}_{{\text {response}}} =1.2$ s and ${t}_{{\text {recovery}}} =3.1$ s, respectively, when operated at 1 V. The device also displayed low hysteresis and good stability with a maximum error in response to ±5% when tested for 50 days. The device demonstrated a good response at lower RHs. To explain this enhancement of response, a novel “pseudo electron injection model” has been put forward. It established that the enhanced response was due to the increased electron transfer from the MoS2–NH2 system (with lone pairs) to the humidity layer resulting in an electron accumulation at the MoS2 layer, and thus lowering the conduction band minima (CBM) of the MoS2 system beneath. This accumulation amplified the device current significantly resulting in sensor performance enhancement. The CBM-lowering and electron population due to this pseudo electron injection were expressed as a function of the thickness of adsorbed humidity and the MoS2–NH2 layers, thereby finally expressing the enhanced response. From the models, extinction coefficients affecting CBM-lowering were calculated as $\alpha = -0.042$ eV and $\beta = -0.49$ eV nm−1 which supported the obtained results. [ABSTRACT FROM AUTHOR]

This paper presents power and area optimized, high‐speed metal‐oxide‐semiconductor (MOS) current mode logic (MCML)‐based frequency dividers. Each differential pair in the divider is sized separately to minimize the overall power consumption. The divide‐by‐2 frequency divider has been realized in a 180‐nm complementary MOS (CMOS) process technology, and postlayout simulation results show that the proposed frequency divider can work up to an operating frequency of 18.8 GHz in the worst‐case process corner with a maximum power dissipation of 1.715 mW under 1.8‐V supply. It gives a bandwidth of 19.9 GHz which ranges from 1 to 20.9 GHz. The divider occupies a 0.106 × 0.09 mm2 area. The performance corresponds to the figure of merit (FoM) of 43.61 dB. The same optimized latches and two EX‐OR gates are used to design a divide‐by‐5 frequency divider that is also realized in 180‐nm CMOS process technology. The postlayout simulation results show that the proposed divide‐by‐5 frequency divider can faithfully work up to an operating frequency of 12.12 GHz in worst‐case process corner with an excellent power head performance. The maximum power dissipation of the core circuit is 1.39 mW under 1.8‐V supply. It occupies a 0.166 × 0.116 mm2 area. The performance corresponds to the FoM of 26.56 dB which compares favorably with the state of the art. [ABSTRACT FROM AUTHOR]

A flexible room temperature ammonia gas sensor based on reduced graphene oxide (RGO) nanosheets has been fabricated on a transparent sheet using photolithography. The structural, morphological, and chemical properties of RGO sensing layer have been analyzed. The higher binding energy of hydroxyl groups with ammonia is utilized for ammonia adsorption, and the groups are tuned at low temperatures by processing graphene oxide. Charge transfer from ammonia to the hydroxyl groups in the RGO sheets is responsible for high response and selectivity of the sensor toward ammonia. Gas sensing characteristics of the sensor was analyzed at various temperatures and humidity levels. The sensor exhibited a selective response toward ammonia vapors among seven volatile organic compounds. The sensor showed a very high response of 930% toward 400-ppm ammonia at 25 °C and 45% relative humidity (RH) level. A quick response of 31 s and full recovery of the sensor after 500 s were recorded when exposed to 400-ppm ammonia. The operation of the sensor at only 1 V facilitates its usage in low-power applications. The sensor exhibited almost negligible deviation in response in the presence of humidity, making it humidity resistant. The flexibility of the sensor was tested by bending the sensor over the range 0°–120°, where the sensor performance started deteriorating after 90 bending. The sensor showed very high stability when tested for 75 days. Therefore, the RGO-based flexible device shows potential toward future commercial room temperature ammonia gas sensors. [ABSTRACT FROM AUTHOR]

With the development of separation and sorting techniques, highly enriched semiconducting single-walled carbon nanotubes (SWNTs) have become widely accessible, which has led to the rapid growth of high-performance solution-processed SWNT-based thin-film field-effect transistors (TFTs) showing capabilities comparable to the ideal single-SWNT FETs. With such improvements, theoretical studies and detailed analyses of these networks have become necessary. In this work, a model justifying the near-ideal electrical transport in SWNT networks is presented. The field-dependent resistive properties of the networks are calculated using a numerical solver based on the derived individual resistances of SWNTs and the intertube couplings. The model is capable of simulating mixed SWNT networks consisting of both metallic and semiconducting nanotubes of varying chiralities. Our analysis reveals that the high electrical currents in networks could be largely attributed to the suppression of phonon scattering and strong intertube couplings in highly dense SWNT networks (>30–40 SWNTs μm2). Comparisons between the simulated and experimental results indicate good agreement thereby demonstrating the accuracy of the proposed model. [ABSTRACT FROM AUTHOR]

The performances of FinFET, gate-all-around (GAA) nanowire/nanosheet, and U-shaped FETs (UFETs) are studied targeting the 3-nm node (N3) and beyond CMOS dimensions. To accommodate a contacted gate pitch (CGP) of 32 nm and below, the gate length is scaled down to 14 nm and beyond. While going from 5-nm node (N5) to 3-nm node (N3) dimensions, the GAA-lateral nanosheet (LNS) shows 8% reduction in the effective drain current (Ieff) due to an enormous rise in short channel effects, such as subthreshold slope (SS) and drain-induced barrier lowering (DIBL). On the other hand, 5-nm diameter-based lateral nanowire shows an 80% rise in total current driving capability (Ieff). Therefore, to enable future devices, we explored electrostatics and effective drive current (Ieff) in FinFET, GAA-FET, and UFET architectures at a scaled dimension. The performances of both Si- and SiGe-based transistors are compared using an advanced device simulator, TCAD Sentaurus. [ABSTRACT FROM AUTHOR]

Functionalized gold nanoparticles decorated reduced graphene oxide (RGO) sheets were used as an electrical sensing platform for highly selective and sensitive Hg2+ detection. RGO sheets were synthesized by reduction of graphene oxide (GO) produced by well-known Hummer’s method. RGO sheets were further decorated with thioglycolic acid (TGA) functionalized gold nanoparticles (GNPs) by simple chemical approach. Field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD) and Ultraviolet-visible (UV-Vis) absorbance analysis were done to confirm the presence of gold nanoparticles being attached to the RGO sheets. Transmission electron microscopy (TEM) was performed to analyze the shape and size distribution of gold nanoparticles on RGO sheets. TGA functionalization of GNPs was confirmed by Fourier transform infrared (FTIR) spectroscopic analysis. The RGO sheets as fabricated were observed to impart n-type nature to the sensing characteristics which was supported by Hall measurements. The sensor performance towards Hg2+ was investigated electrically in presence of other competitive contaminants. The sensor was found to be highly selective towards Hg2+ in presence of Pb2+, Cd2+ and As5+. The interaction of Hg2+ with the sensing layer was also studied using UV-Vis spectrophotometer. Our work suggests that RGO-GNP-TGA (RGT) hybrid structures are promising for low-cost, portable and real-time room temperature heavy metal ion detectors. [ABSTRACT FROM AUTHOR]

A paradigm shift in conventional insulin delivery techniques is required to provide diabetic patients with painless, precise, safe and accurate insulin delivery solutions. Large size insulin molecules can be pushed through human skin layers by a micropump through hollow microneedles which provide a painless interphase to human skin. Ionic polymer metal composite membranes offer great advantages in micropump actuation due to their large deflections at relatively low actuation voltages. This makes them suitable to be implemented in insulin delivery devices. This article presents a novel integrated design of an insulin delivery device (IDD) consisting of a hollow microneedle array, drug reservoir and Nafion membrane actuation based micropump. To test the feasibility of the gold coated Nafion 115 membrane, it is utilized in the conventional circular as well as modified geometry having greater degree of freedom of movement by introducing cuts in membrane in a micropump structure and then implemented in the proposed IDD structure. The IDD achieves a DI water flowrate of $47.2~\mu $ L/min and Insulin flowrate of $44.8~\mu $ L/min for membrane with modified geometry which is higher as compared to the conventional membrane design. The device can achieve tunable insulin flowrate in the range of 20–45 $\mu $ L/min by varying the frequency (0.1-0.5Hz) and voltage (3-6V) paving way for its commercialization for painless insulin delivery. [2019-0109] [ABSTRACT FROM AUTHOR]

In this study, a multiphase fractional phase‐locked loop (PLL) is presented with methods to reduce spurs. General causes of spurs are non‐idealities of the phase‐frequency detector (PFD) and charge pump (CP) and phase errors between the adjacent phases from the oscillator. In the architecture, the non‐idealities of the PFD and CP are compensated and a phase correction circuit is added after the oscillator phase generator to reduce the phase errors, and hence minimise the spurs. Spurs may still be persistent after these modifications due to process variations and device mismatch. The effect is visible in the perturbations of the loop filter control voltage. The residual spurs are minimised by further filtering the control voltage using a moving average filter and then applying it to the oscillator. The PLL is designed in 180 nm technology and outputs a 400 MHz carrier. The highest fractional spur is decreased from −36 to −66 dBc through phase correction and control voltage filtering. [ABSTRACT FROM AUTHOR]