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Electron beam induced modifications in electrical properties of Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) films
No full textConducting polymer PEDOT:PSS [Poly(3,4-ethylenedioxythiophene):poly(styrenesulphonate)], owing to its high electrical conductivity, enviornmental stability and low cost, is presently getting most attention for various device applications including thermoelectric, organic light emitting diodes and photovoltaics. We have investigated the irradiation effect of high energy electron beam on the electrical transport properties of PEDOT:PSS films to manifest the scope of this polymer in high radiation field and its suitability for radiation dosimeter applications. PEDOT:PSS films were deposited on flexible polyimide (Kapton) sheets using drop-cast method and irradiated up to 75 kGy dose with 1 MeV electron beam. The electrical conductivity of as deposited polymer film was similar to 3.2 S/cm which consistently falls to similar to 0.76 S/cm on irradiation dose of 75 kGy. Detailed characterization of the samples using x-ray photoelectron spectroscopy, contact angle measurement and solubility test conclusively suggested that the lowering of electrical conductivity in irradiated sample is attributed to the crosslinking of PEDOT chains and dissociation of PSS
Chemistry of extracting high-contrast invisible fingerprints from transparent and colored substrates using a novel phosphorescent label
Get PDFTraditionally 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
Hysteretic Photochromic Switching (HPS) in Doubly Doped GaN(Mg):EuA Summary of Recent Results
Get PDFEuropium is the most-studied and least-well-understood rare earth ion (REI) dopant in GaN. While attempting to increase the efficiency of red GaN light-emitting diodes (LEDs) by implanting Eu+ into p-type GaN templates, the Strathclyde University group, in collaboration with IST Lisbon and Unipress Warsaw, discovered hysteretic photochromic switching (HPS) in the photoluminescence spectrum of doubly doped GaN(Mg):Eu. Our recent work, summarised in this contribution, has used time-, temperature- and light-induced changes in the Eu intra-4f shell emission spectrum to deduce the microscopic nature of the Mg-Eu defects that form in this material. As well as shedding light on the Mg acceptor in GaN, we propose a possible role for these emission centres in quantum information and computing
Highly Efficient, Chemically Stable, and UV/Blue-Light-Excitable Biluminescent Security Ink to Combat Counterfeiting
No full textA strategy has been demonstrated to design a biluminescent security ink using Eu(TTA)(3)Phen (ETP) and fluorescein for protecting the currency and other essential documents, viz., passport, bank check, certificates, etc. against counterfeiting. The biluminescent security ink exhibits strong red and green emission under 367 and 445 nm excitations, respectively. As it is quite challenging to prepare a material that possesses two prominent (green and red) and distinguishable colors upon excitation with two separate light-emitting diode (LED) sources, emitting at different wavelengths, the biluminescent security ink would be hard to counterfeit as compared with the existing luminescent security ink that exhibits single color under UV light exposure. To check its feasibility for security application, the patterns printed out using the biluminescent security ink were kept under a hot and humid atmosphere for 150 days. Also, the ETP and fluorescein fluorophores were exposed to UV light for a prolonged time, which do not show any sign of deterioration in their luminescence intensities. Furthermore, to check their chemical stability, printed patterns were also exposed to chemicals that have potential to wipe out ink, viz., detergent, ethanol, acetone, and sodium hypochlorite (bleach) solution, and it was noticed that it is well stable against these chemicals. Because of the reasons mentioned above and easy availability of 367 and 445 nm LEDs at low cost, authors believe that the application of this biluminescent security ink can trigger the realization of the full potential of this advanced security feature in detecting fake currency
Fabrication and characterization of W-Cu functionally graded material by spark plasma sintering process
No full textIn this study, seven-layered W/Cu functionally graded material (FGM) (100 W, 80W-20Cu, 60W-40Cu, 50W-50Cu, 40W-60Cu, 20W-80Cu, 100Cu, by wt %) were fabricated by a spark plasma sintering process (SPS). The influences of sintering temperature on microstructure, physical and mechanical properties of the sintered bulk FGM were investigated. Results indicated that the graded structure of the composite densified after the SPS process and interfaces of the layers are clearly visible. All of the layers had a very high relative density, thereby indicating their densification and excellent sintering behavior. SEM and EDX study of the bulk sample crosssection reveal that the graded structure can be retained up to sintering temperature of 1050 degrees C. In addition fine microstructure within each layer with good interface bonding was also observed. Sample sintered at 1050 degrees C exhibited excellent mechanical and physical properties (hardness 239 +/- 5 Hv and relative density of 90.5%). The result demonstrates that SPS is a promising and more suitable process for fabrication of W-Cu functionally graded materials
Low reflecting hierarchically textured silicon by silver assisted chemical etching for potential solar cell application
No full textPresent study reports fabrication of silicon nanowires over micro-textured Si substrates. Silver assisted electroless chemical etching route has been adopted for fabrication of the nanowires. Influence of HF concentration on the formation kinetics has been investigated by using scanning electron microscopy. The hierarchical binary structures have been able to reduce solar weighted reflectance (SWR) to direction. However, with increase in the concentration, etching in both and non- directions such as also occurs on the micro-pyramids of similar dimensions and results in the binary structures with slanted silicon nanowires on 3-dimansional micro-pyramids
Structural, vibrational and electronic properties of CuO nanoparticles synthesized via exploding wire technique
No full textThe study of mixed phase Cu/Cu2O/CuO nanoparticles synthesized by Exploding Wire Technique has been recently reported by us. Aiming to achieve single phase CuO nanoparticles, the mixed phase Cu/Cu2O/CuO nanoparticles were subjected to annealing at different temperature and time durations in oxygen environment. In this article, we discussed two samples; two phase Cu2O/CuO and single phase pure CuO nanoparticles obtained by annealing at 500 degrees C and 900 degrees C for 10 h. Rietveld refinement and Williamson-Hall analyses revealed formation of pure phase of CuO at 900 degrees C with an average crsytallite size of 27.6 nm. Irregular shape of nanoparticles with average size of 8 nm was observed by Transmission Electron Microscopy. Selected Area Electron Diffraction pattern matches with standard interplanar distance of CuO. Fourier Transform Infrared and Micro-Raman (mu R) spectra exhibit broadening of vibrational modes; indicative of pure phase CuO at 900 degrees C. Extensive X-ray Photoelectron Spectroscopy analysis revealed that the percentage contributions of Cu1+ and oxygen vacancy (V-O) decreases whereas; Cu2+ and interstitial oxygen (O-1) enhances on increasing the annealing temperature from 500 degrees C to 900 degrees C and thus, resulting the pure phase formation of CuO nanoparticles. Notably, through our analyses we propose an electronic band structure diagram on the basis of valance band maximum, as obtained by XPS and the band gap energy as estimated via UV-visible spectroscopy for mixed phase of Cu2O/CuO (1.6 +/- 0.02 eV) and pure phase of CuO (1.3 +/- 0.02 eV) nanoparticles
Tuning violet to green emission in luminomagnetic Dy,Er co-doped ZnO nanoparticles
No full textThis paper discusses the synthesis of undoped ZnO, 2 mol% Dy doped ZnO, 2 mol% Er doped ZnO and 1 mol% Dy,Er co-doped ZnO nanoparticles by simple combustion technique and the characterization of their structural, morphological, magnetic and optical properties by X-ray diffraction (XRD), X-Ray Photoelectron Spectroscopy (XPS), Field Emission Scanning Electron Microscope (FESEM), High Resolution Transmission Electron Microscope (HRTEM), Diffuse Reflectance Spectroscope (DRS), Vibrating Sample Magnetometer (VSM) and Photoluminescence(PL). All samples are of hexagonal wurzite type structure which was found from XRD analysis. The effects of annealing on morphology and luminescence emission wavelengths were noticed in FESEM and PL, respectively. As-prepared sample displayed spherical morphology and annealed co-doped sample showed interwoven hexagonal stacking like morphology. VSM revealed the room temperature ferromagnetism in doped samples. The photoluminescence under the UV and IR excitations was observed in experiment. The as prepared samples had violet region emission at the 325 nm excitation. The annealed samples had green region emission under the same excitation. Due to the annealing effect, the enhancement of upconversion luminescence intensity in co-doped sample in green (535 nm) and red (665 nm) regions was observed at the 980 nm excitation
Biospectroscopic analysis of human breast cancer tissue: probing infrared signatures to comprehend biochemical alterations
No full textBreast cancer (BC) is one of the most studied and lead-
ing form of malignancy in human females. Currently,
studies conducted in the
fi
eld of breast cancer focuses on
its early detection using noninvasive or minimally inva-
sive techniques in lieu of traditional excisional biopsy, as
cancer treatment is often simpler and effective, when
diagnosed at an early stage. Mammography is the
fi
rst
step, usually performed in diagnosing breast cancer, but
at times mammogram may not be able to provide a clear
picture. In addition, biopsy is performed to con
fi
rm the
presence or absence of tumor, which is associated with
false-positive results. Consequently, the limitations of
current screening methods have shifted the focal area of
oncological research in applying biospectroscopy tech-
niques for diagnostics (Gajjar et al.,
2014
).
Infrared (IR) and Raman spectroscopy are versatile
vibrational spectroscopy methods that have been used to
discriminate normal and cancer tissue and/or cell of dif-
ferent kinds, including endometrial cancer, cervical can-
cer, lung cancer, precancerous lesion, and brain tumors
(Gajjar et al.,
2013
). Coupled with some algorithms
(Gajjar et al.,
2013
), these spectroscopic outcomes can
deliver an objective, high throughput and low-cost solu-
tion to breast cancer diagnosis. Infrared spectroscopy
(IR) has expanded its application in the
fi
eld of human
biology, since it was revealed that biological molecules
present in a living tissue possess vibrational features that
can be studied to derive their molecular information.
Thus, the biochemical modi
fi
cation in a normal
tissue/cell can be analyzed and compared to its malignant
state (Gajjar et al.,
2014
). Further, several reports have
highlighted its advancement in both near- and mid-
infrared regions, making it an ef
fi
cient and convenient
method for clinical purposes. From last few years, FTIR
spectrophotometer has been exploited to study the
molecular and structural characteristics of proteins, car-
bohydrates, lipids, and nucleic acids. Initially, Chirgadze
and Nevskaya in 1976 studied the infrared spectral fea-
tures of amide I and amide II (Chirgadze & Nevskaya,
1976
). Further, in an investigation, Liquier and his col-
leagues (Liquier, Taboury, Taillandier, & Brahms,
1977
)
demonstrated that FTIR spectroscopy could be utilized to
identify the different conformations of DNA (Liquier
et al.,
1977
). In the year 2000, using infrared spectro-
scopic vibrations, Bouchard and his co-researchers,
revealed the structure of insulin and described the forma-
tion of amyloid
fi
brils via insulin, which involves sub-
stantial unfolding of the native protein (Bouchard,
Zurdo, Nettleton, Dobson, & Robinson,
2000
). Since
then, many more complex studies have been conducted
on proteins and nucleic acids (DNA/RNA) structures,
their conformations and interactions with small ligands.
The biochemical changes in a cell/tissue generally lead
to nuclear, cytoplasmic and morphological variations and
hence, FTIR spectroscopy could detect these alterations
during the developmental stages of cancer before mor-
phological and cytological changes are evident under
light microscope. Many studies have shown that spectro-
scopic techniques (with different sampling modes) can
differentiate the biochemistry of normal and neoplastic
cells. It has been employed to investigate the carcinoma
of the breast, esophagus, colon, stomach, and prostate
signi
fi
cant
AFe(2)O(4)/(Pb0.80Sr0.20)TiO3 (A = Mn, Ni and Co): a New Room-Temperature Magnetoelectric Multiferroic Bi-layered Composite Films
No full textThe room temperature and magnetic field-dependent dielectric, impedance and magnetoelectric (ME) coupling effect of polycrystalline AFe(2)O(4)/(Pb0.80Sr0.20)TiO3 (A = Mn, Ni and Co) bi-layered composite films have been investigated. The structural and microstructural analyses using the X-ray diffraction (XRD), atomic force microscopy (AFM) and scanning electron microscopy (SEM) reveal the presence of homogenous growth of both tetragonal and spinel phases without any extra phase and diffusion in the AFO/PST20 bi-layered composite films. Our results show that all composite films exhibit ferroelectric as well as considerable magnetic, indicating magnetoelectric coupling effect. Our results show that the dielectric and impedance properties of AFO/PST20 bi-layered composite films can be manipulated by the magnetic field at room temperature, also indicating the existence of magnetoelectric coupling. The impedance (Z (') and Z (aEuro3)) Nyquist plots show distinct electrical responses with the magnetic field. The maximum magnetoelectric coefficient (alpha) is found to be alpha (ME) 239 and 195 mV/cm/Oe for the MFO/PST20 and CFO/PST20 bi-layered composite films, respectively. The above results show that the AFO/PST20 bi-layered composite films are room-temperature multiferroic material that can be potentially used in magnetoelectric devices