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QUENCHING OF SURFACE PLASMON MODES IN COLLOIDAL SILVER NANOPARTICLES ON OZONIZATION
R. C. BUDHANI,R. K. RAKSHIT,SAYANTANI BHATTACHARYA 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2006 NANO Vol.1 No.3
Oxidation characteristics of colloidal silver nanoparticles produced by pulsed laser ablation in pure and chemically treated water are studied as a function of the degree of ozonization. The bright yellow colloidal solution of silver characterized by a sharp surface plasmon mode at ~400 nm, becomes colorless in the initial stages of O3 flow, and then acquires a brown hue with a broad plasmon peak centered at ~440 to ~450 nm on further ozonization. The solution again becomes colorless in a few days once the O3 flow is stopped. We present a qualitative model for the reaction dynamics and analyze the optical absorption in the framework of an effective medium theory. The aqueous phase laser ablation chemistry described here provides a unique means to produce ionic silver for enhanced antimicrobial effects.
Aberration in the structural paradigm of lens protein α crystallin by UV-C irradiation
R. K. Ghosh,T. Kar,B. Dutta,A. Pathak,R. Rakshit,R. Basak,A. Das,K. Waheeda,P. Basak,M. Bhattacharyya 한국응용생명화학회 2018 Applied Biological Chemistry (Appl Biol Chem) Vol.61 No.3
The conformation of lens protein α crystallin was investigated using different spectroscopic techniques under normal and UV-C-irradiated condition. The structural elucidation of commercially available lens protein α crystallin under the effects of UV-C irradiation has never been reported earlier. To study the effects of irradiation on the lens protein, we used UV–visible spectroscopy, CD spectroscopy, and steady-state and time-resolved fluorescence measurements along with FTIR study, under increasing doses of UV-C irradiation. Using the secondary and tertiary structural changes as parameters for detecting conformational perturbation, we investigated the structural paradigm shift in the lens protein α crystallin. Increasing doses of UV-C radiation resulted in decreasing β sheet content of α crystallin from 30 to 10%. The fluorescence profile confirmed the formation of ROS species in the protein upon extensive exposure to UV-C irradiation. These results inferred UV-C irradiation may induce alteration of secondary structure of the lens protein leading to impaired biological functioning.
Aberration in the structural paradigm of lens protein α crystallin by UV-C irradiation
Ghosh, R.K.,Kar, T.,Dutta, B.,Pathak, A.,Rakshit, R.,Basak, R.,Das, A.,Waheeda, K.,Basak, P.,Bhattacharyya, M. The Korean Society for Applied Biological Chemistr 2018 Applied Biological Chemistry (Appl Biol Chem) Vol.61 No.3
The conformation of lens protein ${\alpha}$ crystallin was investigated using different spectroscopic techniques under normal and UV-C-irradiated condition. The structural elucidation of commercially available lens protein ${\alpha}$ crystallin under the effects of UV-C irradiation has never been reported earlier. To study the effects of irradiation on the lens protein, we used UV-visible spectroscopy, CD spectroscopy, and steady-state and time-resolved fluorescence measurements along with FTIR study, under increasing doses of UV-C irradiation. Using the secondary and tertiary structural changes as parameters for detecting conformational perturbation, we investigated the structural paradigm shift in the lens protein ${\alpha}$ crystallin. Increasing doses of UV-C radiation resulted in decreasing ${\beta}$ sheet content of ${\alpha}$ crystallin from 30 to 10%. The fluorescence profile confirmed the formation of ROS species in the protein upon extensive exposure to UV-C irradiation. These results inferred UV-C irradiation may induce alteration of secondary structure of the lens protein leading to impaired biological functioning.
High yield strength bulk Ti based bimodal ultrafine eutectic composites with enhanced plasticity
Misra, D. K.,Rakshit, R. K.,Singh, M.,Shukla, P. K.,Chaturvedi, K. M.,Sivaiah, B.,Gahtori, B.,Dhar, A.,Sohn, S. W.,Kim, W. T.,Kim, D. H. BUTTERWORTH - HEINEMANN 2014 MATERIALS AND DESIGN Vol.58 No.-
Ti-based bulk metallic glass (BMGs) and their bimodal composites are linked with the pronounced strain hardening after yielding but with much low value of strength. Therefore, developing Ti-based alloys with high yield strength and high plasticity is the current challenge. Here, we report the synthesis of ultra-fine grained bulk (UFG) (Ti0.705Fe0.295) 100 Ga-x(x) (0 <= x <= 2) bimodal eutectic composites with not only high strength and larger plasticity but also with high yield strength which is one of the important mechanical property for structural application. Reasonably high strength, high yield strength, strain to failure ratio, and enhanced plasticity of similar to 7 +/- 0.8% was observed in (Ti70.5Fe29.5)(98)Ga-2 composite which is superior than Ti-based BMGs and bimodal composites. Modification of degree of eutectic structure refinement and volume fraction of constituent phases with the addition of Ga are the crucial factors in enhancing the mechanical properties of Ti-Fi-(Ga) composites. (C) 2014 Elsevier Ltd. All rights reserved.