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Non-covalently anchored multi-walled carbon nanotubes with hexa-decafluorinated zinc phthalocyanine as ppb level chemiresistive chlorine sensor
No full textA cost effective solution assembly method has been explored for preparing zinc(II) 1,2,3,4,8,9,10,11,15,16,17,18,22,23,24,25-hexa-decafluoro-29H, 31H-phthalocyanine/multi-walled carbon nanotubes (F16ZnPc/MWCNTs-COOH) hybrid. Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy, transmission electron microscopy (TEM) and field emission scanning electron microscopy (FE-SEM) investigations confirm the non-covalent anchoring of F16ZnPc onto MWCNTs-COOH through Pi-Pi stacking interactions. Further, a highly sensitive and selective chemiresistive Cl-2 sensor has been fabricated using F16ZnPc/MWCNTs-COOH hybrid. The response of sensor is found to be 21.28% for 2 ppm of Cl-2 with a response time of 14 s and theoretical detection limit of the sensor is found down to 0.06 ppb. The improved Cl-2 sensing characteristics of hybrid are found to be originated from the synergetic interaction between F16ZnPc and MWCNTs-COOH. The underlying mechanism for improved gas sensing performance of F16ZnPc/MWCNTs-COOH sensor towards Cl-2 has been explained using Raman, X-ray photoelectron spectroscopy (XPS) and electrochemical impedance spectroscopy (EIS) studies
Nanostructured titania based electrochemical impedimetric biosensor for non-invasive cancer detection
No full textIn the present work, the utilisation of bio-functionalised TiO2 nanoparticles has been reported for biosensing application especially in oral cancer detection. The bio-sensing electrode was fabricated on indium tin oxide coated conducting glass electrode using electrophoretic deposition technique. The proposed technique holds tremendous potential to make the approach effectively simple, label-free and most importantly a non-invasive technique. The prepared nanoparticles were characterised using x-ray diffractometer; Fourier transforms infrared spectroscopy, and x-ray photoelectron spectroscopy. In conjunction with this, the morphological studies of immunoelectrode (bovine serum albumin/anti-CYFRA-21-1/(3-aminopropyl) triethoxysilane/TiO2/indium tin oxide) were conducted by field emission scanning electron microscopy. The average roughness of various electrodes were investigated through atomic force microscopy. The biosensing properties of fabricated immunoelectrode were investigated using differential pulse voltammetry and cyclic voltammetry. However, the electrochemical response studies were carried out by using electrochemical impedance spectroscopy technique to measure the concentration of oral cancer biomarker (CYFRA 21-1). Additionally, we have also calculated the sensitivity and stability of fabricated immunoelectrode. It has been observed that the fabricated immunoelectrode shows a high sensitivity of 0.573 Omega mL ng(-1), linear detection range of 0-12 ng mL(-1), lower detection limit of 0.24 ng mL(-1) and having a stability of 5 weeks
Directional growth, physicochemical and quantum chemical investigations on pyridinium 2-carboxylate: 4-nitrophenol (P2C4N) single crystal for nonlinear optical (NLO) applications
No full textAn organic nonlinear optical (NLO) single crystal of pyridinium 2-carboxylate: 4-nitrophenol (P2C4N) was grown by the Sankaranarayanan-Ramasamy (SR) method using the (1 1 -1) plane. A transparent crystal of size 180 mm in length and 10 mm in diameter was grown over a period of 60 days. The lattice parameters and the molecular structure of the grown crystal were confirmed by single crystal XRD and nuclear magnetic resonance (NMR) spectrum analysis, respectively. The crystalline perfection of the SR method-grown crystal was evaluated by HRXRD analysis; from the observed results, it is evident that the crystal quality is quite good. UV-Vis-NIR analysis shows that the SR method-grown crystal has good transparency (90%) in the visible and NIR regions. The band gap of the title crystal was estimated by the Tauc's plot method and was found to be 3 eV. The title material is thermally stable up to 141 degrees C, and it demonstrates positive photoconductive behaviour. Vickers microhardness studies revealed that the grown crystal can be categorized as a soft material. The laser damage threshold of P2C4N was found to be 2.9 GW cm(-2), which shows that the grown crystal possesses excellent resistance to high power radiation. Z-Scan studies proved that the grown crystal possesses self-defocusing effects and negative nonlinearity. The theoretical spectra were calculated using the B3LYP/cc-pVTZ basis set and were compared with the experimental FT-IR and FT-Raman spectra of the title molecule. The full vibrational assignments of the observed spectra have been proposed by normal coordinate analysis (NCA) followed by force-field calculations. Quantum chemical studies, such as optimized geometry, HOMO-LUMO, natural bonding orbital (NBO) analysis, AIM analysis, hyperpolarizability and molecular electrostatic potential (MEP) were performed for the title molecule. The results are discussed in detail
Chemistry of extracting high-contrast invisible fingerprints from transparent and colored substrates using a novel phosphorescent label
No full textTraditionally used fluorescent powders for developing invisible (latent) fingerprints involve complicated operation and show characteristics of auto-fluorescence interference and high toxicity. To overcome these serious drawbacks we report a novel application and facile methodology to extract high contrast fingerprints on non-porous and porous substrates using a chemically inert, visible light excitable, and nanosized SrAl2O4:Eu2+, Dy3+ phosphorescent label in the dark. The chemistry of non-covalent physisorption interaction between the long afterglow phosphor powder and sweat residue in fingerprints has been discussed in detail. Real-time fingerprint development on porous and non-porous substrates has also been performed
Crystal growth and characterization of bulk Sb2Te3 topological insulator
No full textThe Sb2Te3 crystals are grown using the conventional self flux method via solid state reaction route, by melting constituent elements (Sb and Te) at high temperature (850 degrees C), followed by slow cooling (2 degrees C/h). As grown Sb2Te3 crystals are analysed for various physical properties by x-ray diffraction (XRD), Raman Spectroscopy, Scanning Electron Microscopy (SEM) coupled with Energy Dispersive x-ray Spectroscopy (EDAX) and electrical measurements under magnetic field (6 Tesla) down to low temperature (2.5 K). The XRD pattern revealed the growth of synthesized Sb2Te3 sample along (001) plane, whereas the SEM along with EDAX measurements displayed the layered structure with near stoichiometric composition, without foreign contamination. The Raman scattering studies displayed known (A(1g)(1), E-g(2) and A(1g)(2)) vibrational modes for the studied Sb2Te3. The temperature dependent electrical resistivity measurements illustrated the metallic nature of the as grown Sb2Te3 single crystal. Further, the magneto-transport studies represented linear positive magneto-resistance (MR) reaching up to 80% at 2.5 Kunder an applied field of 6 Tesla. The weak anti localization (WAL) related low field (+/- 2 Tesla) magneto-conductance at low temperatures (2.5 K and 20 K) has been analysed and discussed using the Hikami-Larkin-Nagaoka (HLN) model. Summarily, the short letter reports an easy and versatile method for crystal growth of bulk Sb2Te3 topological insulator(TI) and its brief physical property characterization
Evolution of Intrinsic and Magnetic Field-Induced Magnetic Anisotropies in Strongly Phase-Separated Manganite Thin Films
No full textSingle crystalline thin film ( 100 nm) of La0.18Pr0.40Ca0.42MnO3 is grown on (001) oriented LaAlO3 substrates and the evolution of anisotropy associated with the supercooling behaviour of the magnetic liquid is studied as a function of temperature and magnetic field. The angle-dependent magnetization measurements ascertain that the easy magnetic axis lies in the plane of the film while the hard axis is along the plane normal. The ratio of the easy and hard axes magnetizations (M-|| and M-perpendicular to) measured at 10 K, viz., M-||/M-perpendicular to (10 K) = 2.6, confirms the strongly anisotropic nature of the film. The easy axis ferromagnetic (FM) transition temperature (T-C) is smaller than that along the hard axis. The giant hysteresis in FCC-FCW M-T, which manifests the magnetic liquid behaviour of the strongly phase-separated manganites is appreciably narrowed along the hard axis. The strain glass state is also less dominant along the easy axis. The analysis of the M-H data brings out that the easy axis remanence (M-r perpendicular to ) shows a nonlinear temperature dependence, while the one corresponding to the hard axis (M-r parallel to) shows a nearly linear behaviour. The coercivity (H-C) follows a law of the type . The value of exponent b similar to 0.5 for single-domain particles, but in the present case, the best fit to the experimental data yields the exponent b approximate to 0.25 for both H-C parallel to perpendicular to and H-C perpendicular to. The smaller value of the exponent is attributed to the non-canonical nature of the ferromagnetic state and the associated strongly phase-separated nature of the LPCMO thin film
70 years of Elastohydrodynamic Lubrication (EHL): A Review on Experimental Techniques for Film Thickness and Pressure Measurement
No full textElastic deformation of surfaces and piezo-viscous effect of lubricant make EHL a very complex lubrication regime. Elastohydrodynamic Lubrication becomes much more complex when conditions like rough surfaces, non-newtonian behavior of lubricant and temperature dependent flow are considered. The present paper takes the task of reviewing experimental methods applied till date for measuring film thickness and pressure. The paper has been divided into many sections and sub-sections to deal with these techniques in a lucid manner. Experimental methods have been categorized into Electrical, Optical and Acoustic methods. The difference of 8-10% between theoretical and experimental results are witnessed using Electrical methods. Whereas, this difference is less than 1% using Optical methods. Among all optical methods, Relative Optical Interference Intensity Technique is the most effective technique with an ability to measure the film thickness as small as 1 nm or less. The last section of the paper deals with the scope of improvement in measurement techniques in future to understand EHL in more detail
Design of MWCNT bucky paper reinforced PANI-DBSA-DVB composites with superior electrical and mechanical properties
No full textHigh-strength conducting polymer composites are in high demand in modern aerospace and automobile industries. Therefore, a thermosetting conducting polymer system, polyaniline (PANI) doped with dodecylbenzenesulfonic acid (DBSA) interconnected with divinylbenzene (DVB), has been used to design high-loading multiwalled carbon nanotube (MWCNT)-reinforced composites. Herein, MWCNTs were used on a macroscale in the form of bucky paper (BP) and as secondary reinforcement in the matrix system. The mechanical and electrical properties of the resultant BP reinforced PANI-DBSA-DVB (PDD) composites were investigated. The maximum flexural strength and storage modulus were 45.8 MPa and 18.5 GPa, obtained in 16ply MWCNT BP composite with 0.05 wt% dispersed MWCNT (16ply0.05), representing overall improvements of approximate to 48.2% and approximate to 55.4%, respectively, compared with the neat PDD matrix system. The maximum in-plane and through-plane electrical conductivities of the 16ply0.05 composite were 39.5 and 1.4 S cm(-1), which were three and two orders of magnitude higher, respectively, compared with those of neat PDD matrix. This high electrical conductivity resulted in a maximum electromagnetic power loss of -37.5 dBm for the 16Ply0.05 composite, which represented an overall improvement of approximate to 231% over the neat PDD system. Furthermore, the effect of secondary phase of MWCNTs was investigated using FT-IR, UV-Vis, and DSC analyses
Seasonal and annual trends of carbonaceous species of PM10 over a megacity Delhi, India during 2010-2017
No full textPM10 samples were collected to characterize the seasonal and annual trends of carbonaceous content inPM(10) at an urban site of megacity Delhi, India from January 2010 to December 2017. Organic carbon (OC) and elemental carbon (EC) concentrations were quantified by thermal-optical transmission (TOT) method of PM10 samples collected at Delhi. The average concentrations of PM10, OC, EC and TCA (total carbonaceous aerosol) were 222 +/- 87 (range: 48.2-583.8gm(-3)), 25.6 +/- 14.0 (range: 4.2-82.5gm(-3)), 8.7 +/- 5.8 (range: 0.8-35.6gm(-3)) and 54.7 +/- 30.6gm(-3) (range: 8.4-175.2gm(-3)), respectively during entire sampling period. The average secondary organic carbon (SOC) concentration ranged from 2.5-9.1 gm(-3) in PM10, accounting from 14 to 28% of total OC mass concentration of PM10. Significant seasonal variations were recorded in concentrations of PM10, OC, EC and TCA with maxima during winter and minima during monsoon seasons. In the present study, the positive linear trend between OC and EC were recorded during winter (R-2=0.53), summer (R-2=0.59) and monsoon (R-2=0.78) seasons. This behaviour suggests the contribution of similar sources and common atmospheric processes in both the fractions. OC/EC weightratio suggested that vehicular emissions, fossil fuel combustion and biomass burning could be the major sources of carbonaceous aerosols of PM10 at the megacity Delhi, India. Trajectory analysis indicates that the air mass approches to the sampling site is mainly from Indo Gangetic plain (IGP) region (Uttar Pradesh, Haryana and Punjab etc.), Thar desert, Afghanistan, Pakistan and surrounding areas
Sintering dependent Ca2+ solubility in barium titanate synthesized by sol-gel auto combustion method
No full textWe report the preparation of ferroelectric Ba0.7Ca0.3TiO3 (BCT) ceramics by sol-gel auto combustion technique and its specific functional properties. The structural, dielectric and ferroelectric properties of BCT are strongly depending on the sintering temperature which also improves the phase purity and crystalline quality of the system. The formation of single-phase BCT is realized by sintering at 1450 degrees C for 4h. suggesting the solubility limit of Ca2+ cation. Grain size and relative density are increased as the sintering temperature increased. The Rietveld refinement technique is employed for the detailed crystal structural analysis. The temperature and frequency dependent dielectric properties are investigated; the measured dielectric constant is epsilon(r)=2680at the transition temperature T-c=120 degrees C for the single phase ferroelectric BCT. Sintering and electrical poling improved the shape of the hysteresis curve and reduced the leakage current. Electrical conduction mechanism is also discussed