2D material-based surface plasmon resonance biosensors for applications in different domains: an insight.

The design of surface plasmon resonance (SPR) sensors has been greatly enhanced in recent years by the advancements in the production and integration of nanostructures, leading to more compact and efficient devices. There have been reports of novel SPR sensors having distinct nanostructures, either as signal amplification tags like gold nanoparticles (AuNPs) or as sensing substrate-like two-dimensional (2D) materials including graphene, transition metal dichalcogenides (TMDCs), MXene, black phosphorus (BP), metal-organic frameworks (MOFs), and antimonene. Such 2D-based SPR biosensors offer advantages over conventional sensors due to significant increases in their sensitivity with a good figure of merit and limit of detection (LOD). Due to their atomically thin structure, improved sensitivity, and sophisticated functionalization capabilities, 2D materials can open up new possibilities in the field of healthcare, particularly in point-of-care diagnostics, environmental and food monitoring, homeland security protection, clinical diagnosis and treatment, and flexible or transient bioelectronics. The present study articulates an in-depth analysis of the most recent developments in 2D material-based SPR sensor technology. Moreover, in-depth research of 2D materials, their integration with optoelectronic technology for a new sensing platform, and the predicted and experimental outcomes of various excitation approaches are highlighted, along with the principles of SPR biosensors. Furthermore, the review projects the potential prospects and future trends of these emerging materials-based SPR biosensors to advance in clinical diagnosis, healthcare biochemical, and biological applications.

Recent advancements of smartphone-based sensing technology for diagnosis, food safety analysis, and environmental monitoring.

The emergence of computationally powerful smartphones, relatively affordable high-resolution camera, drones, and robotic sensors have ushered in a new age of advanced sensible monitoring tools. The present review article investigates the burgeoning smartphone-based sensing paradigms, including surface plasmon resonance (SPR) biosensors, electrochemical biosensors, colorimetric biosensors, and other innovations for modern healthcare. Despite the significant advancements, there are still scarcity of commercially available smart biosensors and hence need to accelerate the rates of technology transfer, application, and user acceptability. The application/necessity of smartphone-based biosensors for Point of Care (POC) testing, such as prognosis, self-diagnosis, monitoring, and treatment selection, have brought remarkable innovations which eventually eliminate sample transportation, sample processing time, and result in rapid findings. Additionally, it articulates recent advances in various smartphone-based multiplexed bio sensors as affordable and portable sensing platforms for point-of-care devices, together with statistics for point-of-care health monitoring and their prospective commercial viability.

A Eu3+doped functional core-shell nanophosphor as fluorescent biosensor for highly selective and sensitive detection of dsDNA.

Lanthanide-doped core-shell nanomaterials have illustrated budding potential as luminescent materials, but their biological applications have still been very limited due to their aqueous solubility and biocompatibility. Here, we report a simple and cost-effective approach to construct a water-stable chitosan-functionalized lanthanoid-based core shell (Ca-Eu:Y2O3@SiO2) nanophosphor. The as-synthesized Ca-Eu:Y2O3@SiO2-chitosan (CEY@SiO2-CH) nanophosphor has been characterized for its structural, morphological, and optical properties, by employing different analytical tools. This sensing platform is suitable for dsDNA probing by tracing the "turn on" fluorescence signal generated by CEY@SiO2-CH nanophosphor with the addition of dsDNA. The ratio of fluorescence intensity enhancement is proportional to the concentration of dsDNA in the range 0.1-90 nM, with the limit of detection at ⁓16.1 pM under optimal experimental conditions. The enhancement in fluorescence response of functionalized core-shell phosphor with dsDNA is due to the antenna effect. Additionally, response of probe has been studied for the real samples displaying percent recovery in between 101 and 105, maximum RSD% upto 5.23 (n = 3). This outcome can be applied to the selective sensing of dsDNA through optical response. These findings establish the CEY@SiO2-CH a simple, portable, and potential candidate as a sensor for rapid and analytical detection of dsDNA.

Magneto-strain effects in 2D ferromagnetic van der Waal material CrGeTe[Formula: see text].

The idea of strain based manipulation of spins in magnetic two-dimensional (2D) van der Waal (vdW) materials leads to the development of new generation spintronic devices. Magneto-strain arises in these materials due to the thermal fluctuations and magnetic interactions which influences both the lattice dynamics and the electronic bands. Here, we report the mechanism of magneto-strain effects in a vdW material CrGeTe[Formula: see text] across the ferromagnetic (FM) transition. We find an isostructural transition in CrGeTe[Formula: see text] across the FM ordering with first order type lattice modulation. Larger in-plane lattice contraction than out-of-plane give rise to magnetocrystalline anisotropy. The signature of magneto-strain effects in the electronic structure are shift of the bands away from the Fermi level, band broadening and the twinned bands in the FM phase. We find that the in-plane lattice contraction increases the on-site Coulomb correlation ([Formula: see text]) between Cr atoms resulting in the band shift. Out-of-plane lattice contraction enhances the [Formula: see text] hybridization between Cr-Ge and Cr-Te atoms which lead to band broadening and strong spin-orbit coupling (SOC) in FM phase. The interplay between [Formula: see text] and SOC out-of-plane gives rise to the twinned bands associated with the interlayer interactions while the in-plane interactions gives rise to the 2D spin polarized states in the FM phase.

Local magnetic behaviour of highly disordered undoped and Co-doped Bi2Se3 nanoplates: a muon spin relaxation study.

Magnetism induced by defects in nominally non-magnetic solids has attracted intense scientific interest in recent years. The local magnetism in highly disordered undoped and Co-doped topological insulator (TI) Bi2Se3nanoplates has been investigated by muon spin relaxation (µSR). UsingµSR spectroscopy, together with other macroscopic characterizations, we find that these nanoplates are composed of a core with both static fields and dynamically fluctuating moments, and a shell with purely dynamically fluctuating moments. The fluctuations in the core die out at low temperatures, while those in the shell continue till 2 K. When Bi2Se3is doped with Co, the static magnetic component increases, whilst keeping the dual (static-plus-dynamic) nature intact. The findings indicate that highly disordered TI's could constitute a new class of promising magnetic materials that can be engineered by magnetic impurity doping.

Silicon Nitride-BP-Based Surface Plasmon Resonance Highly Sensitive Biosensor for Virus SARS-CoV-2 Detection.

In this study, we propose a surface plasmon resonance (SPR)-based biosensor using silicon nitride (Si3N4), black phosphorous (BP), and thiol-tethered DNA as a ligand for fast detection of the SARS-CoV-2 virus. In the proposed biosensor, we have deposited silver (Ag), Si3N4, and BP on the base of the BK-7 prism and investigated the performance parameters on the probe in different combinations of the mentioned materials. Herein, three (Ag, Si3N4, and BP) different configurations are introduced and compared for the detection of SARS-CoV-2. Furthermore, with the help of the transfer matrix method (TMM), all the three configurations have been analyzed. Notably, the combination of Ag, Si3N4, and BP shows better sensitivity (154°/RIU) when compared with other configurations for the detection of SARS-CoV-2. This work may facilitate a new sensing device to detect SARS-CoV-2, based on the hybrid materials.

Electrochemical Sensing of Roxarsone on Natural Biomass-Derived Two-Dimensional Carbon Material as Promising Electrode Material.

Herein, we report the electrochemical detection of roxarsone (ROX) on a two-dimensional (2D) activated carbon (AC)-modified glassy carbon electrode (GCE). Meso/microporous 2D-AC is synthesized from a natural biomass Desmostachya bipinnata, commonly known as Kusha in India. This environment-friendly material is synthesized by chemical activation using potassium hydroxide (KOH) and used as a sensitive electrochemical platform for the determination of ROX. It is an arsenic-based medicine, also used as a coccidiostat drug. It is widely used in poultry production as a feed additive to increase weight gain and improve feed efficiency. Long-term exposure to arsenic leads to serious health problems in humans and demands an urgent call for sensitive detection of ROX. Therefore, the green synthesis of 2D-AC is introduced as new carbon support for the electrochemical sensing of ROX. It provides a large surface area and efficiently supports enhanced electron transfer. Its electrocatalytic activity is seen in potassium ferri/ferrocyanide by cyclic voltammetry, where the 2D-AC-modified GCE delivered five to six times higher electrochemical performance as compared to the unmodified GCE. Electrochemical impedance spectroscopy is also performed to show that the prepared material has faster electron transfer and permits a diffusion-controlled process. It works well in real samples and also on disposable screen-printed carbon electrodes, thereby showing great potential for its application in clinical diagnosis. Our results exemplify a modest and innovative style for the synthesis of excellent electrode material in the electrochemical sensing platform and thus offer an inexpensive and highly sensitive novel approach for the electrochemical sensing of ROX and other similar drugs.

Effect of endogenous hormones, antisperm antibody and oxidative stress on semen quality of crossbred bulls.

The present study was designed to evaluate the effect of factors like hormones, antisperm antibody (ASA), and oxidative stress and its relation with semen quality in crossbred bulls. Ejaculates from two bulls were categorized into good (n = 12) and poor (n = 12) based on initial progressive motility, that is, ≥70% and ≤50%, respectively. The level of hormones like Testosterone (p < 0.05) and PGE2 (p < 0.01) was significantly higher in good-quality ejaculates compared to poor-quality ejaculates; however, estradiol (p < 0.05), progesterone, oxidative stress, and ASAs were significantly higher (p < 0.01) in poor-quality ejaculates compared to good-quality ejaculates. Therefore, it could be concluded that oxidative stress and hormonal imbalance might have resulted in high number of dead and defective spermatozoa which was ultimately responsible for poor quality semen ejaculates.

Synthesis of high luminescent Eu3+ doped nanoparticle and its application as highly sensitive and selective detection of Fe3+ in real water and human blood serum.

The present work reports a highly efficient Ca doped Eu: Y2O3 i.e Ca0.05Eu0.01Y1.94O3 (CEY.) nanophosphor material synthesized through a facile combustion method, as a simple and selective turn-off fluorescence probe for the quantitative analysis of iron ions (Fe3+). The proposed sensor allows the quantification of iron in the range of 10 µM-90 µM with a limit of detection (LOD) ∼ 63.2 nM under the natural pH range. Moreover, CEY nanophosphor shows an excellent fluorescence phenomenon with a gradual increase in the Fe3+ ion concentration. It has been observed that the corresponding PL intensity gets completely quenched with 500 µM Fe3+ ion concentration. Furthermore, the applicability of the sensor as an efficient probe has been investigated with real water samples, iron tablets, and human blood serum (HBS). The selectivity of the probe has also been analyzed with various metal ions and biomolecules. Thus, in turn, the as-obtained sensing probe illustrates an excellent accuracy, sensitivity, and selectivity, and offers potential application in clinical diagnosis, biological and real water sample studies, with the detection of Fe3+ ion. Furthermore, it does not require any acidic medium for a level-free, and non-enzymic detection of a real sample with almost not affecting the sample quality and henceforth provides more reliable results.

In Situ Fabrication of Activated Carbon from a Bio-Waste Desmostachya bipinnata for the Improved Supercapacitor Performance.

Herein, we demonstrate the fabrication of highly capacitive activated carbon (AC) using a bio-waste Kusha grass (Desmostachya bipinnata), by employing a chemical process followed by activation through KOH. The as-synthesized few-layered activated carbon has been confirmed through X-ray powder diffraction, transmission electron microscopy, and Raman spectroscopy techniques. The chemical environment of the as-prepared sample has been accessed through FTIR and UV-visible spectroscopy. The surface area and porosity of the as-synthesized material have been accessed through the Brunauer-Emmett-Teller method. All the electrochemical measurements have been performed through cyclic voltammetry and galvanometric charging/discharging (GCD) method, but primarily, we focus on GCD due to the accuracy of the technique. Moreover, the as-synthesized AC material shows a maximum specific capacitance as 218 F g-1 in the potential window ranging from - 0.35 to + 0.45 V. Also, the AC exhibits an excellent energy density of ~ 19.3 Wh kg-1 and power density of ~ 277.92 W kg-1, respectively, in the same operating potential window. It has also shown very good capacitance retention capability even after 5000th cycles. The fabricated supercapacitor shows a good energy density and power density, respectively, and good retention in capacitance at remarkably higher charging/discharging rates with excellent cycling stability. Henceforth, bio-waste Kusha grass-derived activated carbon (DP-AC) shows good promise and can be applied in supercapacitor applications due to its outstanding electrochemical properties. Herein, we envision that our results illustrate a simple and innovative approach to synthesize a bio-waste Kusha grass-derived activated carbon (DP-AC) as an emerging supercapacitor electrode material and widen its practical application in electrochemical energy storage fields.

Electrochemical sensing of pioglitazone hydrochloride on N-doped r-GO modified commercial electrodes.

In this paper, we explain the electrochemical sensing of commercially available pioglitazone hydrochloride (PIOZ) tablets on a nitrogen (N) doped r-GO (Nr-GO) modified commercial glassy carbon electrode (GCE) and a commercial screen printed graphite electrode (SPGE). Nr-GO is synthesized by the chemical reduction of graphene oxide (GO) and simultaneous insertion of an N-dopant by hydrazine monohydrate. Pristine GO itself is prepared by chemical exfoliation of bulk graphite. Upon chemical reduction, the exfoliated GO sheets restack together leaving behind the doped N-atom as evidenced by XRD and Raman spectroscopy. The N-atom exists in the pyrrolinic and pyridinic form at the edge of graphitic domains which is confirmed by XPS. The as-synthesized Nr-GO is used for the preparation of electro-active electrodes with the help of the GCE and SPGE. These electrodes have the capability to oxidize PIOZ by a diffusion dominated process as evidenced by the impedance spectroscopic technique. The differential pulse voltammetric responses of different concentrations of PIOZ are assessed over the Nr-GO modified GCE and SPGE, which exhibit better limits of detection (LODs) of 67 nM and 29 nM, respectively, compared to those from earlier reports. These assays exhibit non-interfering capability in the presence of various body interferents at pH = 7.0.

Ethyl 2-amino-4-methyl-thio-phene-3-carboxyl-ate.

The title compound, C8H11NO2S, crystallizes with two mol-ecules, A and B, in the asymmetric unit. Each molecule features an intramolecular N-H⋯O hydrogen bond and the same H atom is also involved in an intermolecular N-H⋯S bond to generate A + B dimers. Further N-H⋯O hydrogen bonds link the dimers into a [010] chain.

Tagetes erecta as an organic precursor: synthesis of highly fluorescent CQDs for the micromolar tracing of ferric ions in human blood serum.

The present article illustrates the green synthesis of novel carbon quantum dots (CQDs) from biomass viz. Tagetes erecta (TE), and subsequently fabrication of a metal ion probe for the sensing of Fe3+ in real samples. TE-derived CQDs (TE-CQDs) have been synthesized by a facile, eco-friendly, bottom-up hydrothermal approach using TE as a carbon source. The successful synthesis and proper phase formation of the envisaged material has been confirmed by various characterization techniques (Raman, XRD, XPS, TEM, and EDS). Notably, the green synthesized TE-CQDs show biocompatibility, good solubility in aqueous media, and non-toxicity. The as-synthesized TE-CQDs show an intense photoluminescence peak at 425 nm and exhibit excitation dependent photoluminescence behavior. The proposed TE-CQD-based probe offers a remarkable fluorescence (FL) quenching for Fe3+ with high selectivity (K q ∼ 10.022 × 1013 M-1 s-1) and a sensitive/rapid response in a linear concentration range 0-90 µM (regression coefficient R 2 ∼ 0.99) for the detection of Fe3+. The limit of detection (LOD) of the probe for Fe3+ has been found as 0.37 µM in the standard solution. It has further been applied for the detection of Fe3+ in real samples (human blood serum) and displays good performance with LOD ∼ 0.36 µM. The proposed TE-CQD-based ion sensing probe has potential prospects to be used effectively in biological studies and clinical diagnosis.

The fabrication of an MoS2 QD-AuNP modified screen-printed electrode for the improved electrochemical detection of cefixime.

Herein, we report a voltammetric method for the nanomolar detection of cefixime, a third-generation antibiotic. The determination of cefixime is validated on a glassy carbon electrode (GCE) as well as on a screen-printed carbon electrode (SPCE). In the present study, we have reported a facile "one step simple hydrothermal synthesis" of MoS2 quantum dots and with the oxidation of aurochloric acid for the further formation of an MoS2 QD-AuNP composite. The as-synthesized nanocomposite was characterized via UV-Vis spectroscopy, FTIR spectroscopy, XRD, TEM and EDX techniques, and further applied in the modification of working electrodes, showing excellent electroactivity. The sensing of cefixime was done via cyclic and differential pulse voltammetry techniques. The presence of the only anodic peak in the voltammogram reveals the irreversible oxidation of cefixime in the potential range of about 1.3 ± 0.1 V vs. Ag/AgCl. The study was also performed at different scan rates, which indicate a diffusion-controlled mechanism. The proposed cefixime sensor showed a linear response in the concentration range of 0.33-90.82 µM (at S/N = 3) with a limit of detection (LOD) of 3.9-4.5 nm. The electrochemical sensitivity is calculated as 8.63 µA µM-1 cm-2 and 7.07 µA µM-1 cm-2 in buffer and pharmaceutical formulation (commercially available cefixime tablet), respectively. The effects of several interferents were also investigated. The proposed sensor is effectively used for estimating cefixime in phosphate buffer and the commercially available cefixime tablets with no cross-reactivity or matrix effects and shows a promising prospect for real applications.

Phase stability and the effect of lattice distortions on electronic properties and half-metallic ferromagnetism of Co2FeAl Heusler alloy: an ab initio study.

Density functional theory calculations within the generalized gradient approximation are employed to study the ground state of Co2FeAl. Various magnetic configurations are considered to find out its most stable phase. The ferromagnetic ground state of the Co2FeAl is energetically observed with an optimized lattice constant of 5.70 Å. After that, the system was subjected under uniform and non-uniform strains, to see their effects on spin polarization (P) and half-metallicity. The effect of spin-orbit coupling is considered in the present study. Half-metallicity (and 100% P) is retained only under uniform strains started from 0 to +4%, and dropped rapidly from 90% to 16% for the negative strains started from -1% to -6%. We find that the present system is much sensitive under tetragonal distortions as half-metallicity (and 100% P) is preserved only for the cubic case. The main reason for the loss of half-metallicity is due to the shift of the bands with respect to the Fermi level (E F). We also discuss the influence of these results on spintronics devices.

Chitosan based new nanocomposites for corrosion protection of mild steel in aggressive chloride media.

Chitosan is one of the important natural bio-polymers. Besides its good green value, it is rarely used to protect metals in aggressive media in direct form due to rapid degradation of its molecules in acid. Hence, it is necessary to use some means to increase protection efficiency of chitosan. In present work, cobalt and tin sulfide nanoparticles are used to synthesize chitosan-cobalt and chitosan-SnS2 nanocomposites, and used for corrosion protection of mild steel (MS) in 1 M HCl at room temperature. The prepared composites are investigated by UV-visible spectroscopy, FTIR spectroscopy, HRSEM, HRTEM and EDAX techniques, which have shown successful formation of nanocomposites. Corrosion behavior of the composites have been examined by Tafel polarization curves (TPC), single sine electrochemical impedance spectroscopy (SSEIS) and surface analyzing techniques. The results have declared that chitosan-cobalt nanocomposite is more effective in corrosion inhibition of mild steel than chitosan-SnS2 nanocomposite. Alone chitosan provide only 77% inhibition to mild steel, while it increases for chitosan­cobalt (>95%) and chitosan-SnS2 (>80%) composites. Isotherm study suggests that adsorption of chitosan/composites over MS is main reason of inhibition and can be best defined with Frumkin isotherm. Adsorption of chitosan and chitosan-nanocomposites over MS is also evident by SEM and AFM.

Selective photoresponse of plasmonic silver nanoparticle decorated Bi2Se3 nanosheets.

The plasmon-enhanced photoresponse properties of a Ag nanoparticle decorated Bi2Se3 nanosheet (AGBS)/p-Si heterojunction device have been studied. The Ag nanoparticles, Bi2Se3 nanosheets, and AGBS nanocomposite are synthesized chemically. Microscopic investigations, ultimately of the AGBS nanocomposite, reveal that the Bi2Se3 nanosheets of thickness ∼20 nm and lateral dimension ∼1 µm are decorated with Ag nanoparticles of sizes 20-40 nm in the nanocomposite. The x-ray diffraction pattern of AGBS shows that apart from being in a metallic state, the Ag in the AGBS is also in the form of compounds with Bi, Se, and additionally O. This observation is further complemented by the x-ray photoelectron spectrum, which shows the presence of Ag0 and Ag+ states of Ag in AGBS. The UV-visible absorption spectra show the plasmonic peak of the Ag nanoparticles occurs at 420 nm; the peak is shifted to ∼500 nm in AGBS due to the modified dielectric environment of the nanoparticles. The AGBS/p-Si heterojunction shows excellent photoresponse properties, with a responsivity of 0.28 A/W, a fairly high detectivity of 4 × 1010 Jones, and an EQE of 71% under 10 V reverse bias at a 500 nm wavelength. The plasmon enhanced photoresponse at the selective wavelength makes this material attractive for high performance optoelectronic devices.

Assessing a thermal spike model of swift heavy ion-matter interactions via Pd1-xNix/Si interface mixing.

The thermal spike model (TSM), a widely accepted mechanism of swift heavy ion (SHI)-matter interactions, provides explanation for various SHI induced effects, including mixing across interfaces. We assess the validity of the model via tuning the electron-phonon coupling strength (G) by taking a series Pd1-xNix of a completely solid soluble binary, and then observing Pd1-xNix/Si interface mixing induced by a combination of 100 MeV Au ion irradiation and 4 keV Ar ion sputtering. If the TSM truly describes the SHI-matter interaction mechanism, any non-linearity in x-variation of G must also result in a similar non-linearity in the x-dependence of mixing. Experimentally, the extent of mixing has been parametrized by the irradiation induced change Δσ2 in variances of Pd and Ni depth profiles derived from XPS. Computationally, G determined using density functional theory has been used to solve the equations appropriate to the TSM, and then an equivalent quantity L2, proportional to Δσ2, has been calculated. Both Δσ2(x) and L2(x) show non-linearities, albeit in slightly dissimilar ways, leading to a conjecture that the present work at least does not invalidate the TSM.

Voltammetric determination of the antimalarial drug chloroquine using a glassy carbon electrode modified with reduced graphene oxide on WS2 quantum dots.

A voltammetric method is described for the determination of chloroquine (CQ) and validated simultaneously by two techniques and in three different conditions. The WS2 quantum dots (WS2 QDs) were synthesized by a hydrothermal method and then placed on reduced graphene oxide (rGO) sheets. The resulting composite material was then deposited on a glassy carbon electrode (GCE) where it showed excellent electroactivity. The modified GCE responds to chloroquine at a typical potential maximum of 1.2 V (vs. AgCl/Ag). Techniques including cyclic voltammetry and differential pulse voltammetry were tested. Features of merit include (a) a wide linear response (in the 0.5 µM to 82 µM CQ concentration range), (b) an electrochemical sensitivity of 0.143-0.90 µA·µM-1·cm-2), and a 40-120 nM limit of detection (at S/N = 3). The sensor has excellent selectivity even in the presence of potentially interfering biological compounds. Responses were tested in phosphate buffer, human serum and pharmaceutical formulations, and no cross reactivity or matrix effects were found. In all the three cases, quite satisfactory recoveries were obtained. Graphical abstract Schematic representation of the mechanism for electro-oxidation of chloroquine on a glassy carbon electrode modified with an rGO@WS2 quantum dot composite. The sensor displays enhanced electrocatalytic activity towards chloroquine. The method was validated in biological samples and pharmaceutical formulations.