Roopa Venkataraj

Cochin University of Science and Technology | CUSAT · International School of Photonics

We demonstrate an enhanced WGM lasing in silica micro capillary with a liquid core made of Rhodamine B dye and silver nanoparticles (AgNP) combination. It is found that the lasing spectra can be tuned in wavelength as well as enhanced or quenched in intensity. Highly modulated sharp lasing spectra with FWHM 0.152 nm were obtained for an optimum con...

We report the photocatalytic and antimicrobial properties of zinc oxide nanostructures synthesized using a low-temperature, facile method with the assistance of milk protein, casein. The nanoflower structure with hexagonal-shaped petals was identified in casein assisted zinc oxide, whereas the flower embryo was obtained without casein. The influenc...

In this report, we demonstrate a novel method to achieve random lasing in the diffusion regime. One of the missing features of a conventional random laser is directionality. Here, a novel cylindrical microstructure cavity made of silica polymer combination has been used to overcome this barrier. The proposed structure makes use of a doped PMMA as a...

Lasing modes of a RhB dye doped hollow polymer fiber filled with AgNPs is studied. • Technique was found to be an extremely simple method of optical feedback for lasing. • Dual threshold mechanism observed for silver nanoparticle solution filled fiber. • Enhanced photo-stability observed for this case, even at high pump powers. • The Q factor achie...

The present work describes lasing output of Rh6G filled RhB doped hollow polymer fiber. The laser system's attributes include its high flexibility, lower threshold and enhanced WGM emission owing to plasmonic enhancement provided by silver nanoparticles. A broad wavelength range lasing output is possible by the use of multiple dyes.

The present work describes C540a dye coated hollow glass capillary used with Rh6g to sensitively and selectively detect fluoride over a broad range from 0 to 7×10-4 M. The output Rh6g and C540a fluorescence emission from the capillary system can respectively be used to detect lower and higher fluoride concentrations.

The present work describes an energy-transfer-based fluoride sensor using the highly photo-stable Coumarin 540a (C540a)–Rhodamine 6g (Rh6g) dye pair. Rh6g exhibits a decrease in fluorescence emission, whereas C540a shows no change in response to fluoride. The increase in fluoride concentration decreases the energy transfer efficiency between the C5...

The present work describes the enhanced photochemical degradation of natural dye Curcumin in acetonitrile–water mixture in the presence of fluoride upon irradiation with light. The strong basicity of fluoride modifies the solvent environment around Curcumin molecule leading to alkaline mediated degradation of Curcumin which is further accelerated b...

The present work describes the degradation of natural dye Curcumin in organic-aqueous media upon irradiation by a multi-wavelength source of light like mercury lamp. The presence of anions in the solution leads to degradation of Curcumin and this degradation is especially enhanced in the case of fluoride ion. The degradation of Curcumin is investig...

Present work reports the preparation of natural dye Curcumin doped silica xerogel and its application towards fluoride ion sensing in aqueous media. Curcumin doped silica xerogel film was observed to possess a clear absorbance peak of 441 nm. The sensitive response of the xerogel film immobilized on a microscopic slide was registered by changes in...

The present work reports a simple fluorescence based tapered fiber optic probe for fluoride ion having a detection range of 2.08 × 10-6 - 2.005×10-4 M. The performance of the tapered probe is evaluated with respect to probes that consist of combinations of bare un-cladded multimode optical fibers. The effect of fluorescence quenching of a natural d...

Fluorescence based fiber optic sensor for fluoride in acetonitrile is implemented using Curcumin dye as the sensing reagent.Curcumin complexes with fluoride ion leading to considerable decrease in fluorescence intensity with increase in fluoride ion concentration

The paper describes the construction and response of evanescent wave straight and U shaped optical fiber sensors for broad range detection of fluoride concentration using Curcumin. The response of the sensor heads at two different wavelengths of excitation were studied and the response exhibited was found to almost linear response at higher concent...