Large Scale Synthesis of Binary Composite Nanowires in the Mn2O3-SnO2 System with Improved Charge Storage Capabilities

Large scale production of electrochemical materials in non-conventional morphologies such as nanowires has been a challenging issue. Besides, functional materials for a given application do not often offer all properties required for ideal performance; therefore, a composite is the most sought remedy. In this paper, we report large scale production of a composite nanowire, viz. Mn2O3-SnO2, and their constituent binary nanowires by a large scale electrospinning pilot plant consisting of 100 needles. Electrochemical characterization of thus produced composite nanowires showed nearly threefold increase in the discharge capacity compared to their single component counterparts: Mn2O3-SnO2 ∼53 mA h g−1 (specific capacitance, CS ∼384 F g−1); Mn2O3 ∼18 mA h g−1 (CS ∼164 F g−1); and SnO2 ∼14 mA h g−1 (CS ∼128 F g−1) at 1 A g−1 in 6 M KOH. The EIS studies showed that the characteristic resistances and time of the composite electrode are appreciably lower than their constituents. Owing to the scalability of the synthesis processes and promising capacitive properties achieved would lead the composite material as a competitive low-cost and high-performance supercapacitor electrode

Optoelectronic Characterization and Properties of Single-walled Carbon Nanotubes in a Liquid Dispersion Form

Carbon nanotubes (CNTs) are very promising nanodevices due to their extraordinary electrical, thermal, and optical properties. However, as-grown single-walled CNTs (SWCNTs) contain a mixture of semiconducting and metallic species with great features versatility and variation. Solution-based processing of this nanomaterial is vital for further implementation in applicable platforms. In this paper, important optoelectronic intrinsic properties of SWCNTs in dispersions are studied applying a semi-empirical approach of optical characterization and Tauc/Davis-Mott relation and Max-Planck equations. SWCNTs are found to have a direct bandgap of 2.20 eV, an indirect bandgap of 0.27 eV, an optical conductivity of about 107 S cm-1, and exhibited a metamaterial behavior ascribed to the high negative permittivity. In addition, the optimum parameters for the dispersion of SWCNTs, and the separation of the semiconducting species using simple mechanical methods of ultrasonication and density gradient ultracentrifugation, respectively, without using surfactants are also presented

Study on dielectric properties of gel polymer electrolyte based on PVA-K2CO3 composites

The advance of gel polymer electrolyte (GPEs) based on conducting salt-polymer has been a subject of concern recently due to their significant applications. This work presents a study of dielectric properties of GPE based on polyvinyl alcohol (PVA) and potassium carbonate (K2CO3) (PVA-K2CO3) electrolyte for electrochemical applications. The electrolyte material was synthesized by mixing a conducting salt (K2CO3) with PVA in different proportions (from 10 - 50 wt. %) in order to study the effect of the salt on the dielectric properties of the electrolyte. The synthesized GPE was characterized using X-ray powder diffraction (XRD) to study electrolyte's crystal phase. Both complex permittivity and complex modulus formalism (dielectric behaviour) of the electrolyte were analysed through electrochemical impedance spectroscopy (EIS). The characterization result shows that the peak intensity of the PVA is significantly reduced with the increase of K2CO3 wt.%. which could be attributed to the decrease of PVA crystallinity which can enlarge the amorphous region of the polymer due to the strong plasticizing effect of the salt. High values of complex permittivity (dielectric constant and dielectric loss) were observed at low frequencies, which increased with increasing temperature, indicating an increase in conductivity. From the real part of electric modulus, the material is featured to be highly capacitive. Based on the asymmetrical peak shape of the imaginary part of electric modulus, the non-Debye type relaxation is predicted. Straight-line graphs were observed from the frequency dependency of loss tangent (tan 6), showing no single relaxation process is present

Detection of kidney complications relevant concentrations of ammonia gas using plasmonic biosensors : A review

Kidney-related health problems cause millions of deaths around the world annually. Fortunately, most kidney problems are curable if detected at the earliest stage. Continuous monitoring of ammonia from exhaled breath is considered as a replacement for the conventional blood-based monitoring of chronic kidney disease (CKD) and kidney failure owing to its cost effectiveness, non-invasiveness, excellent sensitivity, and capabilities for real-time measurement. The detection of ammonia for renal failure requires a biosensor with a detection limit of 1000 ppb (1 ppm). Among biosensors, plasmonic biosensors have attracted considerable research interest due to their potential for ultra-sensitivity, single particle/molecular level detection capability, multiplexing capability, photostability, real-time measurement, label-free measurement, room temperature operation, naked-eye readability, ease of miniaturization via simple sensor chip fabrication, and instrumentation, among other features. In this review, plasmonic sensors for the detection of ammonia gas relevant to kidney problems (LOD ≤ 1 ppm) are reviewed. In addition, the utilized strategies and surface functionalization for the plasmonic sensor are highlighted. Moreover, the main limitations of the reported sensors are stated for the benefit of future researchers. Finally, the challenges and prospects of plasmonic-based ammonia gas biosensors for potential application in the monitoring and screening of renal (kidney) failure, as well as the endpoint of the dialysis session, are stated

Magnetoresistance and magneto-plasmonic sensors for the detection of cancer biomarkers : A bibliometric analysis and recent advances

The conventional approaches to diagnosing cancer are expensive, often involve exposure to radiation, and struggle to identify early-stage lung cancer. As a result, the five-year survival rate is significantly reduced. Fortunately, promising alternatives using magnetoresistance (MR) and magneto-plasmonic sensors have emerged for swiftly, accurately, and inexpensively detecting cancer in its initial phases. These sensor technologies offer numerous advantages over their counterparts, such as minimal background noise, immunity to environmental influences, compatibility with nanofabrication methods, ability to detect multiple substances simultaneously, straightforward integration, high specificity, distinctive identifying capabilities, real-time monitoring, stability, label-free detection, and remarkable sensitivity for detecting individual molecules. Nevertheless, since the use of these techniques for cancer biomarker detection is relatively new, it is essential to conduct a bibliometric analysis and review recent literature to offer guidance to both early-career and established researchers in this domain. Consequently, this study performs a scientometric evaluation of the literature related to cancer biomarker detection using MR and magneto-plasmonic methods. The objective is to pinpoint current preferred techniques and challenges by examining statistics such as publication numbers, authors, countries, journals, and research interests. Furthermore, the paper also presents the latest advancements in MR and magneto-plasmonic sensors for cancer biomarker detection, with a focus on the last decade. In addition, an overview of the ongoing research in the field of MR and magneto-plasmonic sensors for detecting cancer biomarkers is highlighted. Finally, a summary on the level of current research including the significant accomplishments, challenges, and outlooks of MR and magneto-plasmonic sensors for the detection of cancer biomarkers are highlighted

Dependence of the optical constant parameters of p-toluene sulfonic acid-doped polyaniline and its composites on dispersion solvents

The optical constants of Para-Toluene sulfonic acid-doped polyaniline (PANI), PANIchitosan composites, PANI-reduced graphene-oxide composites and a ternary composite comprising of PANI, chitosan and reduced graphene-oxide dispersed in diluted p-toluene sulfonic acid (PTSA) solution and N-Methyl-2-Pyrrolidone (NMP) solvent have been evaluated and compared. The optical constant values were extracted from the absorbance spectra of thin layers of the respective samples. The potential utilization of the materials as the active sensing materials of surface plasmon resonance biosensors has also been assessed in terms of the estimated value of the penetration depth through a dielectric medium. The results show a reasonable dependence of the optical constant parameters on the solvent type. Higher real part refractive index (n) and real part complex dielectric permittivity (ε’) values were observed for the samples prepared using PTSA solution, while higher optical conductivity values were observed for the NMP-based samples due to their relatively higher imaginary part refractive index (k) and imaginary part complex dielectric permittivity (ε″) values. In addition, NMP-based samples show improvement in terms of the penetration depth through a dielectric medium by around 9.5, 1.6, 4.4 and 2.9 times compared to PTSA-based samples for the PANI, PANI-chitosan, PANI-RGO and the ternary composites, respectively. Based on these, it is concluded that preparation of these materials using different dispersion solvents could produce materials of different optical properties. Thus, the variation of the dispersion solvent will allow the flexible utilization of the PANI and the composites for diverse applications

The effect of Pd on electrical properties of Sn02 in CH4 detection

The effect of Pd on electrical properties of Tin (IV) oxide (SnO2) as an element for CH4 detection is investigated for samples prepared from a mixture of powders of (100-x)Sn02.xPd (0 =< x wt % =< 15) which were pressed into pellets and sintered at various temperatures ranging from 600°C to 1100°C. In order to achieve the objectives of the study, a Gas Sensor Characterization System (GSCS) was built. The main component of the GSCS is an airtight gas sensor test chamber with a volume of about 405 cm3. The conductance of a sample is monitored in this chamber at various operating temperatures, flow rate of carrier gas (synthetic air) and applied voltages when the sample was exposed to small concentrations (in ppm) of CH4 in air. The GSCS is interfaced, via an ADC card, with a computer for data acquisition, storage and analysis. Results show that SnO2 without Pd cannot detect CH4 in air up to an operating temperature of 400°C. However, the modification of Sn02 by the addition of Pd significantly enhances its sensitivity to CH4 with the highest sensitivity occurring at around 400°C. The general trend is a sharp increase in sensitivity of SnO2 up to about 3wt% Pd and thereafter a gentle decrease up to 15 wt% Pd. Fifty percent (50 %) response time of about 20 seconds and recovery time of 7.27 minutes were calculated for samples with 3 wt% Pd sintered at 900°C. The relationship between sensitivity and the concentration of CH4 in air at the operating temperature of 400°C can be approximated by the logarithmic function. Results on the effect of sintering temperature show that the sensitivity of Sn02 with Pd as additive is higher for samples sintered at lower temperatures. The flow rate of the carrier gas was found to significantly affect the sensitivity of samples sintered at lower temperatures. The response and recovery times generally decreased with increasing flow rate of the camer gas. This effect is attributed to increase in the oxygen partial pressure of the carrier gas in the test chamber with increasing flow rate. On the other hand, it was observed that the sensitivity depends on the applied voltage especially for samples sintered at lower temperatures. Measurements on ethane (C2H6) and hydrogen sulfide WS) in air were carried out in order to test the selectivity of some samples to other gases. It was found that sensitivity to C2H6 is higher than sensitivity to CH4 but in the same operating temperature range with a selectivity of about 1.69 at 400°C. H2S was detectable in air with the highest sensitivity at 100°C and decreased to a minimum at 200°C. SEM micrographs of the samples indicate that the Sn02 crystallites are of sub-micron sizes. The Pd concentration in Sn02 determined by AAS was shown to increase with increasing nominal composition of Pd added to Sn02. It was possible to detect Pd in samples with 15 wt% Pd using EDAX but not for samples with nominal composition of =< 10 wt% Pd

Hysteresis behaviour of sensitivity in Ch4 detection in air using Sno2 with Pd as sensitizing additive

The sensitivity of SnO2 with Pd as an additive showed a hysteresis behaviour when measurement was carried out as the operating temperature is increasing compared to measurement with decreasing temperature. The sensitivities of the samples that were calculated at the various operating temperatures from 200°C to 430°C were found to be higher when measuring with decreasing temperature. This observed hysteresis in sensitivity is discussed in terms of the type of oxygen species adsorbed on the SnO2 surface