K. Upendra Kumar

Nd3+ doped LaF3 nanoparticles as self-monitored photo-thermal agents

In this work, we demonstrate how LaF3 nanoparticles activated with large concentrations (up to 25%) of Nd3+ ions can simultaneously operate as biologically compatible efficient nanoheaters and fluorescent nanothermometers under single beam (808 nm) infrared laser excitation. Nd3+:LaF3 nanoparticles emerge as unique multifunctional agents that could constitute the first step towards the future development of advanced platforms capable of simultaneous deep tissue fluorescence bio-imaging and controlled photo-thermal therapies.

Dy3+-doped zinc fluorophosphate glasses for white luminescence applications

Dysprosium (Dy(3+)) ions doped zinc fluorophosphate (PKAZLFDy: P2O5-K2O-Al2O3-ZnF2-LiF-Dy2O3) glasses have been prepared and investigated their spectroscopic properties using absorption, emission and decay measurements. Judd-Ofelt analysis has been carried out to obtain the intensity parameters and in turn predicted radiative properties for the (4)F9/2 level of 1.0 mol% of Dy2O3 doped glass. Visible luminescence spectra have been obtained due to (4)F9/2→(6)HJ (J=11/2, 13/2, 15/2) transitions of Dy(3+) ions under 385 nm excitation. The yellow-to-blue luminescence intensity ratios and chromaticity coordinates of Dy(3+) ions in these glasses have been analyzed as a function of Dy(3+) ion concentration. The decay profiles for the (4)F9/2 level exhibit perfectly single exponential at lower concentrations (up to 1.0 mol%) and turn into non-exponential for higher concentrations (>1.0 mol%) due to energy transfer between donor (excited state Dy(3+) ion) and acceptor (ground state Dy(3+) ion). The results reveal that these glasses emit bright white light which is suitable for the development of W-LEDs.

Neodymium-doped nanoparticles for infrared fluorescence bioimaging: The role of the host

The spectroscopic properties of different infrared-emitting neodymium-doped nanoparticles (LaF3:Nd3+, SrF2:Nd3+, NaGdF4: Nd3+, NaYF4: Nd3+, KYF4: Nd3+, GdVO4: Nd3+, and Nd:YAG) have been systematically analyzed. A comparison of the spectral shapes of both emission and absorption spectra is presented, from which the relevant role played by the host matrix is evidenced. The lack of a “universal” optimum system for infrared bioimaging is discussed, as the specific bioimaging application and the experimental setup for infrared imaging determine the neodymium-doped nanoparticle to be preferentially used in each case.

Temperature and amino acid-assisted size- and morphology-controlled photochemical synthesis of silver decahedral nanoparticles

Stable silver decahedron nanoparticles were produced under the blue light irradiation (light-emitting diodes) of a modified precursor solution that has been previously reported. To improve the formation of the nano-decahedrons under blue light, we proposed the use of amino acids with electrically charged side chains (L-arginine, L-lysine and L-histidine). Our results show that L-arginine and L-lysine are best suited to improve the yield of the decahedrons. We also followed the kinetics of the photochemical synthesis under different irradiance conditions of 80, 50 and 15 mW/cm2. The maximum irradiance, 80 mW/cm2, resulted in a synthesis that was twice as fast as those associated with lower irradiances, and the corresponding decahedron yield was higher. The optimal temperature of the precursor solution for the improvement of the photochemical synthesis of silver decahedrons with Triton X-100 as a surfactant was also determined.