In this work, laser-induced Thermal Lens Temperature Scanning technique (TL-TS) is applied to evaluate oxidative stability and time of transesterification during biodiesel synthesis. Samples ...collected at different time intervals during the transesterification process of sunflower (SF) and soybean (SB) oils were submitted to fast oxidation through temperature scanning (between 22 and 190°C), and simultaneously measured with the TL-TS technique. Temperature dependence of Thermal Lens effect amplitude showed the occurrence of oxidation, with the onset (Tonset) changing with the transesterification stages from 149 to 169°C for sunflower and from 120 to 142°C for soybean samples. The characteristic evolution of Tonset with reaction duration was estimated to be ∼7min for sunflower and ∼10min for soybean samples. The thermal diffusivity values were shown to be sensitive to rapid changes at transition temperatures, which could be related to molecular ruptures. Additional measurements were performed with DSC, TG and FTIR, to validate the information obtained by the TL-TS technique. In conclusion, the results showed the TL-TS technique as a promising tool for oxidative stability evaluation and determination of both chosen working temperature and minimal time interval for the solution to reach an optimized transesterification stage, thus contributing for reduction of costs, quality control and consequently for certification of biodiesel fuels.
Nanotechnology offers the potential for creating new optical imaging agents with novel properties which has been used in molecular imaging and photothermal therapy. Mesoporous silica materials have ...attained great attention in industry due to its high thermal and chemical stability and non toxic behavior. The performance of mesoporous silica materials depends on composition, morphology and structure of made-up materials. The synthesis of mesoporous silica nanoparticles is highly sensitive because the size, morphology and pore structure changes with small change in procedure. Surface modification of mesoporous enables to incorporate metal nanoparticles in to its pores by co-condensation and post-synthesis method and hence an enhancement in optical and thermal properties of mesoporous silica nanoparticles. In the present work, we have synthesized gold nanoparticles incorporated mesoporous silica by three methods such as non functionalized, co-condensation and post-synthesis modification which is denoted as sample I, sample II and sample III. Thermal parameters such as thermal diffusivity and effusivity of the synthesized samples are measured by thermal lens and photoacoustic techniques respectively. From the values of thermal diffusivity and effusivity, thermal conductivity is estimated and a high value of thermal conductivity is obtained for sample II because of the proper encapsulation of gold nanoparticles in mesoporous silica. The influence of Rhodamine 6G concentrations on the thermal parameters of mesoporous silica is also studied which shows that thermal conductivity decreases with the addition of higher concentration of Rhodamine 6G due to the interface thermal resistance effects. In addition, we have investigated the influence of gold nanoparticle incorporated mesoporous silica on the emission properties of Rhodamine 6G and fluorescein dyes. Irrespective of dye concentration, due to plasmonic field effect and non aggregation of dye molecules, the fluorescence signal is enhanced for both dyes with the addition of gold incorporated mesoporous silica.
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•Thermal characterization of AuNPs decorated MSN alone and with Rhodamine 6G using thermal lens and photoacoustic techniques.•Thermal characterization reveals that it is possible to tune the thermal parameters with these samples.•The functionalisation method influences the incorporation of AuNPs into its pores and thereby influences the thermal parameters.•Optical characterization of AuNPs decorated MSN – dye mixture shows an enhancement in fluorescence.
The thermal diffusivity values of mixtures comprising ethylene glycol and an aqueous dispersion of gold nanoparticles (50/50 volume ratio) is measured using dual-beam thermal-lens technique, as a ...function of concentration of gold nanoparticles, and the results are compared with the corresponding thermal diffusivity values of gold nanofluids alone. The results show that, in addition to the well-known effect of nanoparticle concentration, the host fluid also play a crucial role in determining the effective thermal diffusivity value of the mixture. The UV–Vis spectroscopic studies of nanoparticles, prepared via citrate reduction method, exhibit the surface plasmon resonance band peaking around 520 nm and the transmission electron microscopic studies reveal that the particles are well dispersed and are having an average size of 15 nm. The transmission electron microscopy images of the gold nanoparticles in the mixture clearly indicate the formation of chain-like aggregates due to dipole–dipole interaction. Such a chain-like structure allows easy transport of thermal energy, which results in enhancement of thermal diffusivity values of the mixture as compared to the gold nanofluids alone.
Manipulation of the characteristics of laser dyes using metal nanoparticles is one of the rapidly growing areas in nanotechnology due to their promising applications in diverse fields, ranging from ...biomedical imaging to green energy. The energy transfer behavior of a silver nanoparticle (Ag NP) with a dye molecule, Rhodamine 6G (Rh 6G), is interrogated using static photoluminescence as well as a laser based dual beam thermal lens technique. Spherical Ag NPs of various concentrations are prepared using chemical reduction method and is mixed with a fixed concentration of Rh 6G. It is observed that the intrinsic fluorescence of Rh 6G (1×10−6M) is quenched in proximity of the Ag NPs and the quenching efficiency increases with an increase in Ag NP concentration (2.5×10−4▒–▒10×10−4M). The dye–NP distance is evaluated by varying the concentrations of Ag NPs and it is found to decrease with an increase in the NP concentration in the mixture from 92 to 69Å (1Å=10−10m). The distance dependent energy transfer efficiency showed that dye–NP mixture follows R−4 dependence, where R is the dye–NP distance.
► Fluorescence quenching of Rhodamine 6G by Ag nanoparticles is investigated. ► Energy transfer between metal and nanoparticle is studied using the dual beam thermal lens technique. ► Distance dependence energy transfer mechanism is investigated and found that it follows R−4 relation.
The thermal diffusivity of nanofluids containing silver nanorods in cetyltrimethyl ammonium bromide micelle has been investigated by measuring the time constant of transient thermal lens. The ...important observation is that the nanofluids exhibits improved thermal diffusivity in comparison to the base fluid. Also, it is found that, the effective thermal diffusivity of nanofluids with rod-shaped nanoparticles is greater than that of nanofluid with spherical nanoparticles. This is explained on the basis of the empirical shape factor by Hamilton Crosser model. Several factors such as chemical environment, formation of nanolayer around the particle surface, nanolayer thickness and interfacial resistance are also considered to explain the results. These results are discussed in connection with the possibility of using rod-shaped silver nanoparticles to enhance the thermal diffusivity of heat transfer fluids.
► Thermal diffusivity of nano-fluids composed of rod-shaped silver nanoparticles is investigated. ► Rod-shaped nanoparticles improve the heat diffusion in the base fluid more efficiently than the spherical nanoparticles. ► Various factors like shape of the nanoparticles, chemical environment etc. are considered to explain the results.
In the present paper, we optimize the chemical synthesis of guest/host poly(styrene sulphonate) (PSS) doped with neodymium ions (Nd3+) using chemometric and univariate procedure for volume variables ...of acid form of PSS and neodymium chloride (NdCl3) confirmed by FTIR experiment. In optimization procedure, the exchange counter-ions H+ by Nd3+ increases, substantially, the luminescence quantum yield, up to 75%, to 4F3/2→4I11/2 transition of Nd3+. Results show the possibility of using the present material as an efficient optical emission material, in the near infrared range, by adding polymer mechanical properties.
•Luminescence quantum efficiency•Poly(styrene sulphonate) (PSS) doped with neodymium (Nd3+).•Chemometric and univariate procedure•Nd3+ transition 4F3/2→4I11/2 - η~75%
The present work divulges the potential of thermal lens technique for analyzing the absolute porosity of a material in nanofluid using the recently proposed Sankar–Loeb model. The ceria nanoparticles ...synthesized by co-precipitation technique are subjected to morphological and structural characterizations. The study reveals that particle size and thermal diffusivity increase with annealing temperature. The nanocavities formed during the agglomeration of nanoparticles result in closed pores which give rise to absolute porosity that is probed by the thermal wave propagation (or thermal diffusivity) study. The enhancement in the particle size enhances the closed pore volume in the sample resulting in increased absolute porosity. Thus, the TL technique makes the analysis of closed pores possible through the absolute porosity study, which is not possible with the conventional BET (Brunauer–Emmett–Teller) technique.
The absorption and luminescence spectra for the poly(
p-phenylene vinylene)/sol–gel silica with different thermal treatments were measured. A considerable increase in the luminescence was observed ...for the polymer introduced into SiO
2 matrix with thermal treatment at 120 °C. The thermal diffusivity of these samples was measured using the thermal lens technique, and the obtained value 3.3
×
10
−5 cm
2/s (sample treated at 37 °C) is practically independent of the thermal treatment (37–150 °C).
In this paper we report the application of dual beam thermal lens technique to study the effect of gold nanoparticle size on the fluorescence quenching of rhodamine 6G. Gold nanoparticles are ...synthesized using citrate reduction of gold chloride trihydrate in water. The analysis of the results showed that the quenching efficiency increases with increase in size of gold nanoparticle.
The CH overtone spectrum of biphenyl dissolved in carbon tetrachloride is recorded using laser-induced thermal lens and conventional absorption techniques. A local mode analysis shows that the CH ...mechanical frequency in biphenyl is larger than that in benzene. This behaviour is explained as being due to the cumulative effect of resonance structures in which the two phenyl rings are conjugated.
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