Calculation of the highly excited SF6 vibrational state distributions and dissociation yields in different gas mixtures

Influence of the buffer gas on the multiphoton absorption and dissociation in different mixtures was investigated. Simple method based on the empirical and theoretical vibrational energy distribution is applied for high fluence regime. Collisional effects of buffer gas (Ar) are introduced to enhance the absorption and relaxation of irradiated molecules (SF6 and C2H4). Functional dependences of mean number of absorbed photons per molecule ( LT n GT (total)) on the Molecular excitation level are presented, enabling us to confirm or predict the level of excitation, number of molecules directly involved in the absorption process and dissociated during the laser pulse.International School and Conference on Optics and Optical Materials, Sep 03-07, 2007, Belgrade, Serbi

Polyacrilic Acid and Chitosan Assisted Solvothermal Synthesis of Up-converting NaYF4: Yb,Er Particles

There is a growing interest for development of a facile and reproducible approach for the synthesis of biocompatible lanthanide doped up-converting nanoparticles (UCNPs) for deep tissue imaging and targeted drug delivery. Synthesis of such particles is usually performed through the decomposition of organometallic compounds, followed either with a ligands exchange or with a biocompatible layer coating. In this work, biocompatible NaYF4:Yb,Er (17 mol% Yb; 3 mol% Er) nanoparticles were synthesized by one-pot hydrothermal processing with an assistance of chitosan (Ch) or polyacrylic acid (PAA). Obtained powders were analyzed by X-ray powder diffraction (XRPD, Bruker D8 Discovery), field emission scanning electron microscopy (FE-SEM, Zeiss, DSM 960), transmission electron microscopy (TEM, JEOL JEM 2010), Fourier transform infrared (FTIR, Thermo Scientific Nicolet 6700) and photoluminescence (PL, Spex Fluorolog with C31034 cooled photomultiplier) spectroscopy. The results showed that although both powders crystallize in the same crystal arrangement (cubic, Fm-3m), particles size, shape and optical properties are dependent on the polymer used

Photothermal response of a double-layered semi-transparent sample

In this work, a double-layered sample is considered. One layer of the sample is assumed to have high optical absorption coefficient (β1>>1, surface absorber) while the other layer’s optical absorption coefficient, β2 is low, which is a common situation in transmission photothermal experiments with optically transparent samples [1-5] (Figure 1). The expressions are derived for surface temperature variations due to the absorption of excitation EM radiation and its conversion into heat within the sample. The study focused on two experimental cases: In the first, the surface absorber is considered to be exposed to the excitation EM beam, while in the second, the other layer is the one to be exposed. The differences in amplitude and phase characteristics, predicted by theory in these two cases, are discussed.V International School and Conference on Photonics and COST actions: MP1204, BM1205 and MP1205 and the Second international workshop "Control of light and matter waves propagation and localization in photonic lattices" : PHOTONICA2015 : book of abstracts; August 24-28, 2015; Belgrad

One-Step Synthesis of Biocompatible NaY0.65Gd0.15F4:Yb,Er Upconverting Nanoparticles for In Vitro Cell Imaging

There is a great technological interest in synthesis of lanthanide doped upconverting nanoparticles (UCNPs) with controlled crystal phase, morphology and intense luminescence properties suitable for biomedical use. A conventional approach for synthesis of such particles comprises decomposition of organometallic compounds in an oxygen-free environment, followed either with a ligand exchange, or biocompatible layer coating. Biocompatible NaY0.65Gd0.15F4:Yb,Er nanoparticles used in this study were synthesized through chitosan assisted one-pot hydrothermal synthesis and were characterized by X-ray powder diffraction (XRPD), Fourier-transform infrared (FTIR) spectroscopy, scanning electron microscopy coupled with energy dispersive X-ray spectroscopy (SEM/EDS) and photoluminescence measurement (PL). Due to the presence of the amino groups at their surface, excellent biocompatibility and notably low cytotoxicity against MRC-5 cells (line of normal human fibroblasts) and A549 cells (human lung cancer cells) were detected using MTT assay. Furthermore, upon 980 nm laser irradiation, particles were successfully used in vitro for labeling of both, MRC-5 and A549 cells

One-Step Synthesis of Biocompatible NaY0.65Gd0.15F4:Yb,Er Upconverting Nanoparticles for In Vitro Cell Imaging

There is a great technological interest in synthesis of lanthanide doped upconverting nanoparticles (UCNPs) with controlled crystal phase, morphology and intense luminescence properties suitable for biomedical use. A conventional approach for synthesis of such particles comprises decomposition of organometallic compounds in an oxygen-free environment, followed either with a ligand exchange, or biocompatible layer coating. Biocompatible NaY0.65Gd0.15F4:Yb,Er nanoparticles used in this study were synthesized through chitosan assisted one-pot hydrothermal synthesis and were characterized by X-ray powder diffraction (XRPD), Fourier-transform infrared (FTIR) spectroscopy, scanning electron microscopy coupled with energy dispersive X-ray spectroscopy (SEM/EDS) and photoluminescence measurement (PL). Due to the presence of the amino groups at their surface, excellent biocompatibility and notably low cytotoxicity against MRC-5 cells (line of normal human fibroblasts) and A549 cells (human lung cancer cells) were detected using MTT assay. Furthermore, upon 980 nm laser irradiation, particles were successfully used in vitro for labeling of both, MRC-5 and A549 cells

Polyacrilic Acid and Chitosan Assisted Solvothermal Synthesis of Up-converting NaYF4: Yb,Er Particles

There is a growing interest for development of a facile and reproducible approach for the synthesis of biocompatible lanthanide doped up-converting nanoparticles (UCNPs) for deep tissue imaging and targeted drug delivery. Synthesis of such particles is usually performed through the decomposition of organometallic compounds, followed either with a ligands exchange or with a biocompatible layer coating. In this work, biocompatible NaYF4:Yb,Er (17 mol% Yb; 3 mol% Er) nanoparticles were synthesized by one-pot hydrothermal processing with an assistance of chitosan (Ch) or polyacrylic acid (PAA). Obtained powders were analyzed by X-ray powder diffraction (XRPD, Bruker D8 Discovery), field emission scanning electron microscopy (FE-SEM, Zeiss, DSM 960), transmission electron microscopy (TEM, JEOL JEM 2010), Fourier transform infrared (FTIR, Thermo Scientific Nicolet 6700) and photoluminescence (PL, Spex Fluorolog with C31034 cooled photomultiplier) spectroscopy. The results showed that although both powders crystallize in the same crystal arrangement (cubic, Fm-3m), particles size, shape and optical properties are dependent on the polymer used

Polyacrilic Acid and Chitosan Assisted Solvothermal Synthesis of Up-converting NaYF4: Yb,Er Particles

There is a growing interest for development of a facile and reproducible approach for the synthesis of biocompatible lanthanide doped up-converting nanoparticles (UCNPs) for deep tissue imaging and targeted drug delivery. Synthesis of such particles is usually performed through the decomposition of organometallic compounds, followed either with a ligands exchange or with a biocompatible layer coating. In this work, biocompatible NaYF4:Yb,Er (17 mol% Yb; 3 mol% Er) nanoparticles were synthesized by one-pot hydrothermal processing with an assistance of chitosan (Ch) or polyacrylic acid (PAA). Obtained powders were analyzed by X-ray powder diffraction (XRPD, Bruker D8 Discovery), field emission scanning electron microscopy (FE-SEM, Zeiss, DSM 960), transmission electron microscopy (TEM, JEOL JEM 2010), Fourier transform infrared (FTIR, Thermo Scientific Nicolet 6700) and photoluminescence (PL, Spex Fluorolog with C31034 cooled photomultiplier) spectroscopy. The results showed that although both powders crystallize in the same crystal arrangement (cubic, Fm-3m), particles size, shape and optical properties are dependent on the polymer used

Limitations of the generalized coupled two-level model during the multiphoton absorption in different gas mixtures

Generalized coupled two-level model is applied in different gas mixtures and investigated for high fluence regime. Functional dependences of mean number of absorbed photons per molecule LT n GT (total) on buffer-gas pressure (P-buff) are presented, used to confirm or predict some possible physical and chemical processes, like enhanced absorption and/or dissociation. Limitations of proposed models are analyzed depending on both gas pressure and laser fluence. Results are compared with other previously obtained by the same experimental technique, but for different absorbing molecule.International School and Conference on Optics and Optical Materials, Sep 03-07, 2007, Belgrade, Serbi

Orange-Reddish Light Emitting Phosphor GdVO 4 :Sm 3+ Prepared by Solution Combustion Synthesis

The gadolinium vanadate doped with samarium (GdVO 4 :Sm 3+ ) nanopowder was prepared by the solution combustion synthesis (SCS) method. After synthesis, in order to achieve the full crystallinity, the material was annealed in air atmosphere at 900°C. Phase identification in the postannealed powder samples was performed by X-ray diffraction, and morphology was investigated by high-resolution scanning electron microscopy (SEM). Photoluminescence characterization of the emission spectrum and time-resolved analysis have been performed using the tunable laser optical parametric oscillator excitation and the streak camera. Several strong emission bands in the Sm 3+ emission spectrum were observed, located at 567 nm ( 4 G 5/2 – 6 H 5/2 ), 604 nm ( 4 G 5/2 – 6 H 7/2 ), and 646 (654) nm ( 4 G 5/2 – 6 H 9/2 ), respectively. The weak emission bands at 533 nm ( 4 F 3/2 – 6 H 5/2 ) and 706 nm ( 4 G 5/2 – 6 H 11/2 ) and a weak broad luminescence emission band of VO 4 3− were also observed by the detection system. We analyzed the possibility of using the host luminescence for two-color temperature sensing. The proposed method is improved by introducing the temporal dependence in the line intensity ratio measurements

Quantum efficiency of up-converting SrGd2O4:Yb,Er nanoparticles

Up-conversion properties of SrGd2O4 nanoparticles co-doped with different Yb3+ and constant Er3+ ions were successfully prepared via sol- gel assisted combustion. Rietveld refinement and scanning/transmission electron microscopy with corresponding energydispersive X-ray spectroscopy revealed that obtained powders are composed of agglomerated nanoparticles with orthorhombic (Pnma) structure that have a uniform distribution of all constituting elements. Photoluminescence measurements implied intensification of the upconversion (UC) emission in the visible part of spectrum with the increase of Yb3+ content, which is followed by a significant change in the green to red ratio. Two-photon UC processes are established as a result of Er3+ f-f electronic transitions: green emission at 523 and 551 nm (2H11/2, 4S3/2 → 4I15/2) as well as a red emission at 661 nm (4F9/2 → 4I15/2). The highest value of absolute quantum efficiency (0.055%) is determined for SrGd2O4 nanoparticles doped with 0.5 at% of Er3+ and co-doped with 5 at% of Yb3+ (λexc=976 nm, power density 200W/cm2)