Large-scale efficient mid-wave infrared optoelectronics based on black phosphorus ink.

The mid-wave infrared (MWIR), ranging from 2 to 5 micrometers, is of substantial interest for chemical sensing, imaging, and spectroscopy. Black phosphorus (bP)-based MWIR light emitters and detectors have been shown to outperform the state-of-the-art for commercial devices due to the low Auger recombination coefficient of bP. However, the scalability of these devices remains a challenge. Here, we report a bP ink formula that preserves the exceptional MWIR optoelectronic properties of bP to deposit centimeter-scale, uniform, and pinhole free films with a photoluminescence quantum yield higher than competing III-V and II-VI semiconductors with similar bandgaps at high excitation regime. As a proof of concept, we use bP ink as a "phosphor" on a red commercial light-emitting diode to demonstrate bright MWIR light emission. We also show that these films can be integrated into heterostructure device architectures with electron and hole selective contacts for direct-injected light emission and detection in MWIR.

Single-pixel reconstructive mid-infrared micro-spectrometer.

Miniaturized spectrometers in the mid-infrared (MIR) are critical in developing next-generation portable electronics for advanced sensing and analysis. The bulky gratings or detector/filter arrays in conventional micro-spectrometers set a physical limitation to their miniaturization. In this work, we demonstrate a single-pixel MIR micro-spectrometer that reconstructs the sample transmission spectrum by a spectrally dispersed light source instead of spatially grated light beams. The spectrally tunable MIR light source is realized based on the thermal emissivity engineered via the metal-insulator phase transition of vanadium dioxide (VO2). We validate the performance by showing that the transmission spectrum of a magnesium fluoride (MgF2) sample can be computationally reconstructed from sensor responses at varied light source temperatures. With potentially minimum footprint due to the array-free design, our work opens the possibility where compact MIR spectrometers are integrated into portable electronic systems for versatile applications.

Conductive Ink-Coated Paper-Based Supersandwich DNA Biosensor for Ultrasensitive Detection of Neisseria gonorrhoeae.

Herein, we report results of the studies relating to the development of an impedimetric, magnetic bead-assisted supersandwich DNA hybridization assay for ultrasensitive detection of Neisseria gonorrhoeae, the causative agent of a sexually transmitted infection (STI), gonorrhea. First, a conductive ink was formulated by homogenously dispersing carboxylated multiwalled carbon nanotubes (cMWCNTs) in a stable emulsion of terpineol and an aqueous suspension of carboxymethyl cellulose (CMC). The ink, labeled C5, was coated onto paper substrates to fabricate C5@paper conductive electrodes. Thereafter, a magnetic bead (MB)-assisted supersandwich DNA hybridization assay was optimized against the porA pseudogene of N. gonorrhoeae. For this purpose, a pair of specific 5' aminated capture probes (SCP) and supersandwich detector probes (SDP) was designed, which allowed the enrichment of target gonorrheal DNA sequence from a milieu of substances. The SD probe was designed such that instead of 1:1 binding, it allowed the binding of more than one T strand, leading to a 'ladder-like' DNA supersandwich structure. The MB-assisted supersandwich assay was integrated into the C5@paper electrodes for electrochemical analysis. The C5@paper electrodes were found to be highly conductive by a four-probe conductivity method (maximum conductivity of 10.1 S·cm-1). Further, the biosensing assay displayed a wide linear range of 100 aM-100 nM (109 orders of magnitude) with an excellent sensitivity of 22.6 kΩ·(log[concentration])-1. The clinical applicability of the biosensing assay was assessed by detecting genomic DNA extracted from N. gonorrhoeae in the presence of DNA from different non-gonorrheal bacterial species. In conclusion, this study demonstrates a highly sensitive, cost-effective, and label-free paper-based device for STI diagnostics. The ink formulation prepared for the study was found to be highly thixotropic, which indicates that the paper electrodes can be screen-printed in a reproducible and scalable manner.

Recent developments in wearable & non-wearable point-of-care biosensors for cortisol detection.

INTRODUCTION: Cortisol is one of the most prominent biomarkers used for the detection of psychological stress and related disorders. It plays an important role in many physiological processes including immunomodulation and fat metabolism. Thus, monitoring of cortisol levels can be used to indicate different pathological conditions including stress disorders. There has been a gradual rise in the development of point of care (PoC) biosensors for continuous cortisol monitoring. AREAS COVERED: This review discusses recent breakthroughs toward the development of PoC sensors (wearable and non wearable) for cortisol monitoring. Challenges associated with them have also been summarized. EXPERT OPINION: Electrochemical PoC devices have recently emerged as a powerful tools for continuous monitoring of cortisol that can be utilized for stress management and treatment of related disorders. However, there are many challenges that should be addressed before such devices can be deployed at mass level, such as inter-individual variability, changing the device calibration with the circadian rhythm, interference from other endocrine moieties, etc. [Figure: see text].

Bright Mid-Wave Infrared Resonant-Cavity Light-Emitting Diodes Based on Black Phosphorus.

The mid-wave infrared (MWIR) wavelength range plays a central role in a variety of applications, including optical gas sensing, industrial process control, spectroscopy, and infrared (IR) countermeasures. Among the MWIR light sources, light-emitting diodes (LEDs) have the advantages of simple design, room-temperature operation, and low cost. Owing to the low Auger recombination at high carrier densities and direct bandgap of black phosphorus (bP), it can serve as a high quantum efficiency emitting layer in LEDs. In this work, we demonstrate bP-LEDs exhibiting high external quantum efficiencies and wall-plug efficiencies of up to 4.43 and 1.78%, respectively. This is achieved by integrating the device with an Al2O3/Au optical cavity, which enhances the emission efficiency, and a thin transparent conducing oxide [indium tin oxide (ITO)] layer, which reduces the parasitic resistance, both resulting in order of magnitude improvements to performance.

Actively variable-spectrum optoelectronics with black phosphorus.

Room-temperature optoelectronic devices that operate at short-wavelength and mid-wavelength infrared ranges (one to eight micrometres) can be used for numerous applications1-5. To achieve the range of operating wavelengths needed for a given application, a combination of materials with different bandgaps (for example, superlattices or heterostructures)6,7 or variations in the composition of semiconductor alloys during growth8,9 are used. However, these materials are complex to fabricate, and the operating range is fixed after fabrication. Although wide-range, active and reversible tunability of the operating wavelengths in optoelectronic devices after fabrication is a highly desirable feature, no such platform has been yet developed. Here we demonstrate high-performance room-temperature infrared optoelectronics with actively variable spectra by presenting black phosphorus as an ideal candidate. Enabled by the highly strain-sensitive nature of its bandgap, which varies from 0.22 to 0.53 electronvolts, we show a continuous and reversible tuning of the operating wavelengths in light-emitting diodes and photodetectors composed of black phosphorus. Furthermore, we leverage this platform to demonstrate multiplexed nondispersive infrared gas sensing, whereby multiple gases (for example, carbon dioxide, methane and water vapour) are detected using a single light source. With its active spectral tunability while also retaining high performance, our work bridges a technological gap, presenting a potential way of meeting different requirements for emission and detection spectra in optoelectronic applications.

Point-of-Care PCR Assays for COVID-19 Detection.

Molecular diagnostics has been the front runner in the world's response to the COVID-19 pandemic. Particularly, reverse transcriptase-polymerase chain reaction (RT-PCR) and the quantitative variant (qRT-PCR) have been the gold standard for COVID-19 diagnosis. However, faster antigen tests and other point-of-care (POC) devices have also played a significant role in containing the spread of SARS-CoV-2 by facilitating mass screening and delivering results in less time. Thus, despite the higher sensitivity and specificity of the RT-PCR assays, the impact of POC tests cannot be ignored. As a consequence, there has been an increased interest in the development of miniaturized, high-throughput, and automated PCR systems, many of which can be used at point-of-care. This review summarizes the recent advances in the development of miniaturized PCR systems with an emphasis on COVID-19 detection. The distinct features of digital PCR and electrochemical PCR are detailed along with the challenges. The potential of CRISPR/Cas technology for POC diagnostics is also highlighted. Commercial RT-PCR POC systems approved by various agencies for COVID-19 detection are discussed.

Ultrasensitive biosensing platform based on yttria doped zirconia-reduced graphene oxide nanocomposite for detection of salivary oral cancer biomarker.

Herein, we report results of the studies relating to the fabrication of yttria-doped zirconia-reduced graphene oxide nanocomposite (nYZR) based biosensing platform for detection of salivary CYFRA-21-1 biomarker. The nYZR nanocomposite was hydrothermally synthesized and amine-functionalized using 3-aminopropyl triethoxysilane (APTES). This functionalized nanocomposite (APTES/nYZR) was electrophoretically deposited (45 V; 3 min) onto pre-hydrolyzed indium tin oxide (ITO) coated glass substrate (APTES/nYZR/ITO) followed by biofunctionalization via covalent immobilization of the anti-CYFRA-21-1 antibodies (anti-CYFRA-21-1/APTES/nYZR/ITO). The synthesized nanomaterial and the fabricated electrodes were characterized to investigate crystal structure, morphology and electrochemical properties via X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, cyclic voltammetry, differential pulse voltammetry and electrochemical impedance spectroscopy. The fabricated biosensing electrode (BSA/anti-CYFRA-21-1/APTES/nYZR/ITO) has an operating shelf life of 56 days and can be used to detect salivary CYFRA-21-1 biomarker concentration as low as 7.2 pg mL-1 with wide linear detection range of 0.01-50 ng mL-1. This work opens new opportunities to explore the electrochemical behavior of nanostructured yttria stabilized zirconia (YSZ) and its composites at room temperature and its utility in developing biosensors and other electrochemical devices.

Trace-Level, Multi-Gas Detection for Food Quality Assessment Based on Decorated Silicon Transistor Arrays.

Multiplexed gas detection at room temperature is critical for practical applications, such as for tracking the complex chemical environments associated with food decomposition and spoilage. An integrated array of multiple silicon-based, chemical-sensitive field effect transistors (CSFETs) is presented to realize selective, sensitive, and simultaneous measurement of gases typically associated with food spoilage. CSFETs decorated with sensing materials based on ruthenium, silver, and silicon oxide are used to obtain stable room-temperature responses to ammonia (NH3 ), hydrogen sulfide (H2 S), and humidity, respectively. For example, one multi-CSFET sensor signal changes from its baseline by 13.34 in response to 1 ppm of NH3 , 724.45 under 1 ppm H2 S, and 23.46 under 80% relative humidity, with sensitive detection down to 10 ppb of NH3 and H2 S. To demonstrate this sensor for practical applications, the CSFET sensor array is combined with a custom-printed circuit board into a compact, fully integrated, and portable system to conduct real-time monitoring of gases generated by decomposing food. By using existing silicon-based manufacturing methodologies, this room-temperature gas sensing array can be fabricated reproducibly and at low cost, making it an attractive platform for ambient gas measurement needed in food safety applications.

Shape-controlled single-crystal growth of InP at low temperatures down to 220 °C.

III-V compound semiconductors are widely used for electronic and optoelectronic applications. However, interfacing III-Vs with other materials has been fundamentally limited by the high growth temperatures and lattice-match requirements of traditional deposition processes. Recently, we developed the templated liquid-phase (TLP) crystal growth method for enabling direct growth of shape-controlled single-crystal III-Vs on amorphous substrates. Although in theory, the lowest temperature for TLP growth is that of the melting point of the group III metal (e.g., 156.6 °C for indium), previous experiments required a minimum growth temperature of 500 °C, thus being incompatible with many application-specific substrates. Here, we demonstrate low-temperature TLP (LT-TLP) growth of single-crystalline InP patterns at substrate temperatures down to 220 °C by first activating the precursor, thus enabling the direct growth of InP even on low thermal budget substrates such as plastics and indium-tin-oxide (ITO)-coated glass. Importantly, the material exhibits high electron mobilities and good optoelectronic properties as demonstrated by the fabrication of high-performance transistors and light-emitting devices. Furthermore, this work may enable integration of III-Vs with silicon complementary metal-oxide-semiconductor (CMOS) processing for monolithic 3D integrated circuits and/or back-end electronics.

Batch and continuous studies on the removal of heavy metals from aqueous solution using biosynthesised melanin-coated PVDF membranes.

Heavy metals like mercury, chromium, lead and copper present in groundwater at lower concentrations cause severe health issues and can even be fatal when consumed. The biopigment/biopolymer melanin can be reaped from different sources like bacterium, fungus, and human hair. It has excellent heavy metal ion scavenging property and can be exploited for non-biological applications, substantially including water purification. In this work, melanin nanoparticles were derived from the marine bacterium Pseudomonas stutzeri and were coated onto hydrophobic polyvinylidene fluoride (PVDF) membrane as a support, for batch and continuous removal of heavy metal studies. Batch studies on the effect of pH, temperature and adsorbate dose and continuous adsorption studies on the effect of flow rate, adsorbate and adsorbent mass loadings were carried out by using biosynthesised melanin-coated PVDF membranes for the removal of Hg(II), Cr(VI), Pb(II) and Cu(II). Scanning electron microscope (SEM) images revealed the surface morphology, Fourier-transform infrared spectroscopy (FTIR) and energy-dispersive X-ray spectroscopy (EDS) deciphered the chemical characteristics of melanin-coated PVDF membranes before and after adsorption. Contact angle measurement confirmed the improvement in hydrophilicity of PVDF membrane upon coating with melanin. The maximum removal percentages of heavy metals achieved by melanin-coated PVDF membranes under batch mode operation were 87.6%, 88.45%, 91.8% and 95.8% for mercury, chromium, lead and copper, respectively optimised at 318 K and pH of 3 for chromium and 5 for other metals. However, the continuous mode of operation with a flow rate of 0.5 mL/min having 1 mg/L of heavy metal solution concentration exposed to 50 mg of melanin loading with a working volume of 200 mL showed better removal efficiencies compared with batch mode. The dynamic studies using Thomas and Yoon-Nelson models described the transient stage of the breakthrough curve and the model constants were calculated for column design and scale-up.

Cell-based biosensors: Recent trends, challenges and future perspectives.

Existing at the interface of biology and electronics, living cells have been in use as biorecognition elements (bioreceptors) in biosensors since the early 1970s. They are an interesting choice of bioreceptors as they allow flexibility in determining the sensing strategy, are cheaper than purified enzymes and antibodies and make the fabrication relatively simple and cost-effective. And with advances in the field of synthetic biology, microfluidics and lithography, many exciting developments have been made in the design of cell-based biosensors in the last about five years. 3D cell culture systems integrated with electrodes are now providing new insights into disease pathogenesis and physiology, while cardiomyocyte-integrated microelectrode array (MEA) technology is set to be standardized for the assessment of drug-induced cardiac toxicity. From cell microarrays for high-throughput applications to plasmonic devices for anti-microbial susceptibility testing and advent of microbial fuel cell biosensors, cell-based biosensors have evolved from being mere tools for detection of specific analytes to multi-parametric devices for real time monitoring and assessment. However, despite these advancements, challenges such as regeneration and storage life, heterogeneity in cell populations, high interference and high costs due to accessory instrumentation need to be addressed before the full potential of cell-based biosensors can be realized at a larger scale. This review summarizes results of the studies that have been conducted in the last five years toward the fabrication of cell-based biosensors for different applications with a comprehensive discussion on the challenges, future trends, and potential inputs needed for improving them.

Protein quality control machinery in intracellular protozoan parasites: hopes and challenges for therapeutic targeting.

Intracellular protozoan parasites have evolved an efficient protein quality control (PQC) network comprising protein folding and degradation machineries that protect the parasite's proteome from environmental perturbations and threats posed by host immune surveillance. Interestingly, the components of PQC machinery in parasites have acquired sequence insertions which may provide additional interaction interfaces and diversify the repertoire of their biological roles. However, the auxiliary functions of PQC machinery remain poorly explored in parasite. A comprehensive understanding of this critical machinery may help to identify robust biological targets for new drugs against acute or latent and drug-resistant infections. Here, we review the dynamic roles of PQC machinery in creating a safe haven for parasite survival in hostile environments, serving as a metabolic sensor to trigger transformation into phenotypically distinct stages, acting as a lynchpin for trafficking of parasite cargo across host membrane for immune evasion and serving as an evolutionary capacitor to buffer mutations and drug-induced proteotoxicity. Versatile roles of PQC machinery open avenues for exploration of new drug targets for anti-parasitic intervention and design of strategies for identification of potential biomarkers for point-of-care diagnosis.

Elimination of Response to Relative Humidity Changes in Chemical-Sensitive Field-Effect Transistors.

Detecting accurate concentrations of gas in environments with dynamically changing relative humidity conditions has been a challenge in gas sensing technology. We report a method to eliminate effects of humidity response in chemical-sensitive field-effect transistors using microheaters. Using a hydrogen gas sensor with Pt/FOTS active material as a test case, we demonstrate that a sensor response of 3844% to a relative humidity change of 50 to 90% at 25 °C can be reduced to a negligible response of 11.6% by utilizing microheaters. We also show the advantage of this technique in maintaining the same sensitivity in changing ambient temperatures and its application to the nitrogen dioxide gas sensors.

Highly Sensitive Bulk Silicon Chemical Sensors with Sub-5 nm Thin Charge Inversion Layers.

There is an increasing demand for mass-producible, low-power gas sensors in a wide variety of industrial and consumer applications. Here, we report chemical-sensitive field-effect-transistors (CS-FETs) based on bulk silicon wafers, wherein an electrostatically confined sub-5 nm thin charge inversion layer is modulated by chemical exposure to achieve a high-sensitivity gas-sensing platform. Using hydrogen sensing as a "litmus" test, we demonstrate large sensor responses (>1000%) to 0.5% H2 gas, with fast response (<60 s) and recovery times (<120 s) at room temperature and low power (<50 µW). On the basis of these performance metrics as well as standardized benchmarking, we show that bulk silicon CS-FETs offer similar or better sensing performance compared to emerging nanostructures semiconductors while providing a highly scalable and manufacturable platform.

Silicone vs temporalis fascia interposition in TMJ ankylosis: A comparison.

OBJECTIVE: Temporomandibular joint ankylosis (TMJa) is a distressing condition, but can be surgically managed by gap or interpositional arthroplasty, with an aim to restore joint function and prevent re-ankylosis. The aim of this paper is to compare two interposition materials used in management of TMJ ankylosis. METHODS: 15 patients with TMJa were randomly allocated to two groups: group A (n = 6), interposition material used was medical-grade silicon elastomer, and group B (n = 9) where the interposition material used was temporalis fascia. Patients were followed up at regular intervals of 1 and 2 weeks, 1 month, 3 months, and 6 months and were assessed on following parameters: pain by VAS Scale, maximal mouth opening (MMO), implant rejection, and recurrence. RESULTS: The results showed a loss of 4.6% and 7.9% in maximal interincisal mouth opening at 3rd and 6th months in Group A while Group B had a mean loss of 9% and 10% at 3rd and 6th months respectively without any significant difference. None of our cases showed recurrence or implant rejection. CONCLUSION: We conclude that silicone is comparable to temporalis fascia in terms of stability, surgical ease, and adaptability. It not only restores the function of mandible and ensures good maximum interincisal opening but also maintains the vertical ramal height. Also, it requires less operating time and is easy to handle but is not economical. It might be an effective way to restore function and prevent re-ankylosis.

Lead Exposure in Different Organs of Mammals and Prevention by Curcumin-Nanocurcumin: a Review.

Chronic lead exposure is related to many health diseases in mammals. Exposure to lead forms reactive oxygen species reducing body antioxidant enzymes inflicting injury to numerous macromolecules or cell necrosis. Recent studies have revealed oxidative stress as the vital mechanism for lead toxicity. Lead is found to be toxic to several organ systems such as hematopoietic, skeletal, renal, cardiac, hepatic, and reproductive systems and extremely toxic to the central nervous system (CNS). Curcumin, an active ingredient of the dietary spice, and nanocurcumin, a nanoform of curcumin, are found to decrease toxicity due to lead in various organ systems in mouse models. Higher bioavailability, chelating property, and retention time of nanocurcumin over bulk curcumin may pave the way to expand the utility of nanocurcumin to remove lead toxicity from various organ systems within humans.

Selective blocking of primary amines in branched polyethylenimine with biocompatible ligand alleviates cytotoxicity and augments gene delivery efficacy in mammalian cells.

Recently, polyethylenimines (PEIs) have emerged as efficient vectors for nucleic acids delivery. However, inherent cytotoxicity has limited their in vivo applications. To address this concern as well as to incorporate hydrophobic domains for improving interactions with the lipid bilayers in the cell membranes, we have tethered varying amounts of amphiphilic pyridoxyl moieties onto bPEI to generate a small series of pyridoxyl-PEI (PyP) polymers. Spectroscopic characterization confirms the formation of PyP polymers, which subsequently form stable complexes with pDNA in nanometric range with positive surface charge. The projected modification not only accounts for a decrease in the density of 1° amines but also allows formation of relatively loose complexes with pDNA (cf. bPEI). Alleviation of the cytotoxicity, efficient interaction with cell membranes and easy disassembly of the pDNA complexes have led to the remarkable enhancement in the transfection efficiency of PyP/pDNA complexes in mammalian cells with one of the formulations, PyP-3/pDNA complex, showing transfection in ∼68% cells compared to ∼16% cells by Lipofectamine/pDNA complex. Further, the efficacy of PyP-3 vector has been established by delivering GFP-specific siRNA resulting in ∼88% suppression of the target gene expression. These results demonstrate the efficacy of the projected carriers that can be used in future gene therapy applications.