Interaction of noble metal nanoparticles (NPs) with fluorophores has been an important research area in the field of material science and biomedical field. In the proximity of a metal nanoparticle, there is a quenching or enhancement in the intrinsic fluorescence of the fluorophore . The conditional quenching of the fluorescence can be used for negative sensing whereas enhancement in the fluorescence can be used to gain greater sensitivity and high signal to noise ratio in the molecular sensing/imaging. The current work deals with the systematic studies to understand the fluorescence quenching for few bio-fluorophores (NADH and FAD) when interacted with different sized silver nano-particles of (10nm, 40nm and 100nm). Home assembled Laser Induced Fluorescence (LIF) set-up was used to study the fluorescence quenching of NADH and FAD for different sized silver nanoparticles.
The present work deals with the evaluation of a high-performance liquid chromatography laser-induced fluorescence (HPLC-LIF) technique developed in our laboratory for early detection of oral cancer from protein profiles of body fluids. The results show that protein profiles of serum samples from a given class of samples, say, normal, premalignant, or malignant, are statistically very close to each other, while profiles of members of any class are significantly different from other classes. The performance of the technique is evaluated by the use of sensitivity and specificity pairs, receiver operating characteristic (ROC) analysis, and Youden's Index. The technique uses protein profile differences in serum samples, registered by the HPLC-LIF technique. The study is carried out using serum samples from volunteers diagnosed as normal or premalignant clinically, and as malignant by histopathology. The specificities and sensitivities of the HPLC-LIF method at an ideal threshold (M-distance = 2) for normal, malignant, and premalignant classes are 100, 69.5, and 61.5%, and 86.5, 87.5, and 87.5% respectively.
A laser induced photoacoustic technique has been employed to measure the thermal effusivity value of natural rubber latex
in the liquid as well as in the solid state. The nano Zinc Oxide particles synthesized via precipitation technique is incorporated to the
natural rubber latex. The influence of molar fractions of nanoparticles on the thermal effusivity value of host polymer is investigated.
Detailed analysis of the results shows that the rubber latex in the solid state exhibits lower value for the thermal effusivity value in
comparison to the liquid state. The molar fraction of the nanoparticle is found to influence the effective thermal effusivity value in a
substantial manner. Results are explained in terms of nanoparticle and phonon assisted thermal energy transport in these samples.
Polymers incorporating photochromic molecules are promising materials for flexible optical switches and
optical data storage devices. A study on reversible photoswitching of azobenzene incorporated polydimethylsiloxane is
carried out using transmittance and UV-VIS absorption measurements. The influence of light intensity on the
photoswitching behavior is also investigated. The transmittance measurements are correlated with the change in the
intensity of the corresponding bands in the UV-VIS absorption spectra. It is shown that the photoswitching occurs
reversibly and that the switching time scale decreases with increase in intensity.
A laser induced thermal lens technique has been employed to evaluate the dynamic thermal parameter, the thermal
diffusivity, of gold nanofluids. Gold nanoparticles were synthesized by citrate reduction of HAuCl4 in water. The UVVIS
optical absorption spectra show an absorption peak around 540 nm owing to surface Plasmon resonance band of the
gold particles. The thermal diffusivity of gold nanoparticles was evaluated by knowing the time constant of transient
thermal lens obtained by fitting the experimental curve to the theoretical model of the mode-matched thermal lens.
Analyses of the results show that the nanofluid exhibits lower thermal diffusivity value in comparison to the host
medium, water. Further investigations also reveal that the concentration of nanoparticles in the fluid have influence on
the measured thermal diffusivity value. Results are interpreted in terms of interfacial thermal resistance around the
nanoparticles as well as on the clustering of nanoparticles.
HPLC combined with laser induced fluorescence provides a very sensitive method for the separation and identification
of the many proteins present in clinical samples. Protein profiles of clinical samples like Pap smear and tissue samples,
from subjects with cervical cancer and normal volunteers, were recorded using HPLC-LIF. The protein profiles were
analyzed by Principal Component Analysis (PCA). The profiles were characterized by parameters like scores of the
factors, sum of squared residuals, and Mahalanobis Distance, derived from PCA. Parameters of each sample were
compared with those of a standard set and Match/ No Match results were generated. Good discrimination between
normal and malignant samples was achieved with high sensitivity and specificity.
Proteomics based techniques are rapidly emerging as alternative techniques to conventional histo-pathological methods
for detection and diagnosis of cancers. Tumor markers are of considerable importance in the study of various cancers. A
study of various changes in the protein profile associated with breast cancer will facilitate a better understanding of the
various dynamic changes associated with the disease. In our study we have used High Performance Liquid
Chromatography coupled with highly sensitive Laser Induced Fluorescence for recording the protein profiles of breast
tissue homogenates. The protein profiles were recorded from pathologically certified normal as well as malignant breast
tissue samples. The recorded protein profiles were studied by using Principal Component Analysis. Good
discrimination of normal, benign and malignant samples was achieved in this pilot study.
An open-cell configuration of the photoacoustic (PA) technique is employed to determine the thermal and transport properties of intrinsic Si and Si doped with B (p-type) and P (n-type). The experimentally obtained phase of the PA signal under heat transmission configuration is fitted to that of theoretical model by taking thermal and transport properties, namely, thermal diffusivity, diffusion coefficient, and surface recombination velocity, as adjustable parameters. It is seen from the analysis that doping and also the nature of dopant have a strong influence on the thermal and transport properties of semiconductors. The results are interpreted in terms of the carrier-assisted and phonon-assisted heat transfer mechanisms in semiconductors as well as the various scattering processes occurring in the propagation of heat carriers.
In this paper, we report the measurements of thermal diffusivity of nano Ag metal dispersed ceramic alumina matrix sintered at different temperatures using laser induced non-destructive photoacoustic technique. Measurements of thermal diffusivity also have been carried out on specimens with various concentration of nano metal. Analysis of the data is done on the basis of one-dimensional model of Rosencwaig and Gersho. The present measurements on the thermal diffusivity of nano metal dispersed ceramic alumina shows that porosity has a great influence on the heat transport and the thermal diffusivity value. The present analysis also shows that the inclusion of nano metal into ceramic matrix increases its interconnectivity and hence the thermal diffusivity value. The present study on the samples sintered at different temperature shows that the porosity of the ceramics varies considerably with the change in sintering temperature. The results are interpreted in terms of phonon assisted heat transfer mechanism and the exclusion of pores with the increase in sintering temperature.
An open photoacoustic cell under heat transmission configuration has been employed to evaluate the thermal and transport properties of n-type Si doped GaAs epitaxial layer and p-type Be doped GaAs epitaxial layer grown on GaAs substrate by molecular beam epitaxial method. The variation of the characteristics of the photoacoustic signal with chopping frequency clearly indicate the different heat generation mechanisms occurring in the sample under optical excitation at 2.54eV with laser beam. The values of thermal diffusivity, diffusion coefficient, surface recombination velocity and nonradiative recombination time have been evaluated for the sample by fitting the experimentally obtained phase of the photoacoustic signal with the theoretical model. It has been observed that the nature of dopant influences the values of thermal and transport properties of the semiconductor samples.
An open cell photoacoustic configuration has been employed to evaluate the thermal diffusivity of pure InP as well as InP doped with sulphur and iron. Chopped optical radiation at 488 nm from an Ar-ion laser has been used to excite photoacoustic signals which been detected by a sensitive electret microphone. Thermal diffusivity value have been calculated from phase versus chopping frequency plots. Doped sample are found to show a reduced value for thermal diffusivity in comparison with intrinsically pure sample. The results have been interpreted in terms of the mechanisms of heat generation and transmission in semiconductors.
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