A film of benzenesulfonamide azo dye has been prepared by spray pyrolysis method onto BK7 glass substrate with average thickness of 2.7μm. This azo dye was derived from sulfamethoxazole and ...chromotropic acid by the Fox method. The optical constants (refractive index, n, extinction coefficient, k, dielectric constant, ɛ, optical, σopt, and electrical, σe, conductivities) were calculated for azo dye film by using spectrophotometer measurements of the absorption, transmittance and reflectance at normal incidence in the spectral range 300–900nm. Third order nonlinear properties has been characterized by calculating the effective thermal nonlinear refractive index, n2, and thermo-optic coefficient, dn/dT, of the azo dye solution using thermal lens technique. Furthermore, the thermal lens effect was utilized to demonstrate all optical switching for the sample solution.
•Preparation of Casein based zinc oxide nanocolloids using the two-step approach.•Thermal diffusivity studies of prepared samples using dual-beam thermal lens techniques.•Tunable behavior of thermal ...diffusivity depending on volume fraction and morphology.
Nanofluids with suitable heat transfer properties were found to be applied in thermal insulators, transport, nanodevices, medicine, etc. Their heat transfer properties are influenced by the particle size, morphology, and concentration of the nanoparticles present in the nanofluids. Nanofluids of different morphologies of zinc oxide such as nanospheres, nanoflowers, and nanorods were synthesized and their thermal properties were evaluated using a dual-beam thermal lens technique. All these nanofluids were found to exhibit tunable thermal diffusivity depending on concentration. The nanofluids with flower-like morphology show maximum deviation in diffusivity due to the layered structure and the increased surface area. As compared to pristine zinc oxide nanofluids, casein-capped zinc oxide nanofluids show excellent thermal insulation properties at 60 μg/ml. The findings suggest that biofunctionalized zinc oxide nanofluid is a promising candidate for a variety of thermal applications.
Thermal and optical properties of fluorescent carbon dots (CDs) prepared from citric acid anhydrous as the precursor and ethylenediamine as the passivation agent by microwave assisted synthesis ...technique is explored in the present study. Optical absorption and emission spectra of carbon dots reveal the presence of surface states with an absorption peak around 350 nm and emission around 450 nm. Fourier Transform Infra-Red (FT-IR) spectra also indicate the presence of surface states. Transmission electron microscopy images of these nano particles indicate an average particle size of 5.8 nm. Dual Beam thermal lens (TL) spectrometry, a highly sensitive photothermal technique, is employed to measure the thermal diffusivity of the carbon dots. Thermal diffusivity is found to decrease from 0.135 m2/sec to 0.0365 m2/sec as the weight percentage of carbon dots are increased from 0.0005 g/15 ml to 0.005/15 ml which can be attributed to the enhanced scattering of thermal waves with particle density in the medium. Studies reveal carbon dots to be promising candidates as thermal insulating materials.
•Synthesized highly fluorescent carbon dots using simple one pot synthesis of microwave irradiation technique with Citric acid anhydrous as the precursor.•First report on thermal diffusivity studies on carbon dots using thermal lens technique.•With the high concentration of carbon dots, diffusivity become very low and it can be used as a thermal insulator.•Enhanced phonon-phonon coupling in the medium is the main reason for the reduction thermal diffusivity.
One of the components of biodiesels is ethyl myristate and the study and measurement of its thermal parameters are of great importance. The dual-beam laser thermal lens spectroscopy is used for ...accurate measurement of thermophysical parameters of ethyl myristate. First, to check the accuracy of our optical setup, thermal lens characteristic time, thermal diffusivity and thermal conductivity of carbon disulfide and benzene were measured at 298 K. There was a reasonable agreement between the measured values and the reference values. Then, the effect of temperature changes on thermal diffusivity and thermal conductivity values of ethyl myristate was studied. The results showed that with increasing temperature from 285 to 358 K, thermal diffusivity decreases from 8.75 to 7.45 × 10−8 m2/s, and thermal conductivity from 0.155 to 0.1432 W/mK. It was also shown that by changing in pump laser energy in the range of 0.06–0.12 joules, both thermal diffusivity and thermal conductivity of ethyl myristate are almost constant.
Chalcogenide glasses are renowned inorganic materials with remarkable applications in the field of optoelectronics. In this work concentration dependent thermal diffusivity of Ge25Se65Sb10 and ...Ge25Se60Sb10Ag5 chalcogenide glass nanocolloids have been analysed using dual beam thermal lens technique. Nanocolloids of five different concentrations from each composition were prepared by dissolving finely powdered bulk glasses in organic solvent ethylenediamine (EDA). Enhancement in thermal diffusivity observed with increase in solute concentration is attributed to increased number of localised defects states, phonon scattering at particle liquid interface and Brownian motion of the particles. Chalcogenide nanocolloids also exhibit improved thermal diffusivity on incorporating silver to the glass matrix by replacing selenium. Results are discussed on the basis of factors such as increased nanoparticle surface area, microconvection, nanoparticle clustering, increased network connectivity and rigidity etc.
•Thermal diffusivity (TD), an important thermo-optic effect characterises heat transfer ability of materials.•Dual beam thermal lens technique has been used to analyse TD in solution processed GeSeSb and GeSeSbAg chalcogenide glasses.•TD increases with solute concentration which further enhances with the addition of more metallic element silver in glass matrix.•Results reveal the possibility of tuning optical band gap, photoluminescence and thermal diffusivity in solution processed chalcogenide glasses.
In the present work, the basic optical characterisation and thermal diffusivity studies of silicon nanofluid were carried out by mode-matched dual-beam thermal lens technique. The silicon ...nanoparticles were synthesised in ethanol, water, DMSO, and ethylene glycol by pulsed laser ablation process using Q-switched Nd: YAG nanosecond laser of wavelength of 1064 nm. The concentration dependence of thermal diffusivity was examined for the prepared silicon nanofluids. A decreasing trend for the thermal diffusivity was found with the increasing concentration of silicon in nanofluid in each solvent. These declining traits in heat diffusivity of silicon nanofluid can be explored for thermal trapping applications such as thermal insulators.
Study of laser-matter interaction and the associated photothermal phenomena have led to the development of several non-destructive evaluation techniques for material characterization. Optical ...modulation being the unavoidable part of these techniques, modulators of different kinds was developed of which electromechanical choppers find wide range of applications. The present work explains the role of the duty cycle in the photothermal phenomenon for getting correct results. For this, chopper wheels with duty cycles 10%–90% are designed and fabricated. The low-cost optical chopper constructed is used in the single beam thermal lens setup for elucidating the impact of the duty cycle in the thermal diffusivity measurement, taking coconut oil as an example. The study reveals that for getting correct results it is advisable to keep the duty cycle less than or equal to 50%.
Herein, novel rodlike CdTe@MPA-PDA particles based on polydopamine (PDA) loaded with CdTe quantum dots (QDs) capped with mercaptopropionic acid (CdTe@MPA QDs) with atypical chemical features are ...evaluated as a potential actuator for photothermal therapy and oxidative stress induction. Under mild conditions established for the safe and efficient use of lasers, temperature increases of 10.2 and 7.8 °C, photothermal conversion efficiencies of 37.7 and 26.2%, and specific absorption rates of 99 and 69 W/g were obtained for CdTe@MPA-PDA and traditional PDA particles in water, respectively. The particles were set to interact with the human breast adenocarcinoma cell line MDA-MB-231. A significant cellular uptake with the majority of particles colocalized into the lysosomes was obtained at a concentration of 100 μg/mL after 24 h. Additionally, CdTe@MPA-PDA and CdTe@MPA QDs showed significantly different internalization levels and loading kinetics profiles. For the first time, the thermal lens technique was used to demonstrate the stability of particle-like CdTe@MPA-PDA after heating at pH 7 and their migration within the heating region due to the thermodiffusion effect. However, under acidic pH-type lysosomes, a performance decrease in heating was observed, and the chemical feature of the particles was damaged as well. Besides, the internalized rodlike CdTe@MPA-PDA notably enhanced the induction of oxidative stress compared with PDA alone and CdTe@MPA QDs in MDA-MB-231 cells initiating apoptosis. Combining these effects suggests that after meticulous optimizations of the conditions, the CdTe@MPA-PDA particles could be used as a photothermal agent under mild conditions and short incubation time, allowing cytoplasmatic subcellular localization. On the other hand, the same particles act as cell killers by triggering reactive oxygen species after a longer incubation time and lysosomal subcellular localization due to the pH effect on the chemical morphology features of the CdTe@MPA-PDA particles.
Zinc tellurite based glasses (TZNbTiNd: TeO2 + ZnO + Nb2O5 + TiO2) doped with various Nd3+ concentrations (0.01, 0.05, 0.1, 0.5, 1.0, 1.5 and 2.0mol% Nd2O3) were prepared and characterized through ...absorption, emission and decay rate measurements. Judd-Ofelt intensity parameters were derived from the absorption spectrum and used to calculate the radiative properties for the 4F3/2 → 4IJ/2 (where J = 9, 11 and 13) transitions of Nd3+ ions. Strong near infrared emission at 1.062µm (4F3/2 → 4I11/2) has been obtained for all the glasses upon 808nm diode laser excitation. The decay times from 4F3/2 level is found to be quite single exponential for different concentrations of Nd3+ ions with a shortening of lifetime with increasing concentration. In these measurements, the electronic refractive index variation is associated with the difference in the polarizabilities (Δαp) of the Nd3+ ion in its ground and excited states. The results indicate that in tellurite glasses, Δαp is relatively very high (4 × 10−25cm3) compared to other Nd3+-doped glasses. We also measured the imaginary part of the non-linear refractive index (n2′′) due to absorption saturation. Hence, the spectroscopic results indicate that the investigated glasses are potentially applicable as a 1062nm laser host as well as optical devices.
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Ageing of engine oil is an important issue determining the engine life and performance. The present work attempts to delineate the ageing-induced changes in engine oil through the mode-mismatched ...dual-beam thermal lens (MMDBTL) technique and other conventional spectroscopic techniques. For the analyses, engine oil samples were collected after every 200 km of runtime. As the thermal diffusivity is related to the nonradiative deexcitation upon optical absorption, comprehensive radiative and nonradiative analyses were carried out. The Ultraviolet-Visible, Fourier transform infrared, and Nuclear magnetic resonance spectroscopic analyses point to the structural modification as a result of the breaking of the long-chain hydrocarbons into ketones, aldehydes, esters, and other compounds. This modifies the absorption pattern, which can also be understood from the nonlinear refractive index study using the Z-scan technique. The compositional variations associated with the degradation upon ageing, the length of the hydrocarbon chain, and the formation of newer molecules account for the enhancement of the thermal diffusivity revealed through the MMBDTL techniques. The complementary nature of the radiative and nonradiative emission is understood from the fluorescence study. Thus, the study reveals the possibility of thermal diffusivity measurement as an effective tool for the quality monitoring of engine oil.
