Application of Photothermal and Photoacoustic Spectroscopy for the Monitoring of Aqueous Dispersions of Carbon Nanomaterials

Photothermal  and  optoacoustic  spectroscopy  in their  state-of-the-art  techniques—multiwavelength, scanning  and  transient—are  used  for  complex investigation  and analysis  (chemical  analysis  and the  estimation  of  physicochemical  properties and size)  of  novel  carbon  materials—fullerenes  and nanodiamonds—and  their aqueous  dispersions  as promising biomedical nanosystems. The estimation of the cluster size and the possibilities to determine subnanogram  amounts  of  both nanodiamonds  and fullerenes  by  these  techniques  are  shown.  The comparison  of fullerene  solutions  in  various solvents,  toluene, N-methylpyrrolydone and  water, is made.  The  advantages  of  the  photothermal  and optoacoustic  techniques  over conventional spectroscopies  and  the  current  limitation  are discussed. The necessity to develop robust  models for  transient  and  imaging  photothermal  techniques is outlined

Absorption spectra of nanodiamond aqueous dispersions by optical absorption and optoacoustic spectroscopies

The multispectral modality and technique for optically dense samples of optoacoustic spectroscopy were applied to measure spectra and high absorbances of concentrated aqueous dispersions of undoped nanodiamonds. The data from optoacoustic and optical transmission measurements and DSC data of the mean particle size by the Gibbs–Kelvin equation are compared to estimate the difference in composition of various nanodiamond trademarks. Optoacoustic spectra confirm the contribution of surface dimer chains into the absorption of nanodiamonds in the long wavelength range. Optoacoustic and conventional absorption spectra of aqueous solutions of nanodiamond fractions after centrifugation (15300g) and ultracentrifugation (130000g) revealed a separation of a highly absorbing non-diamond sp2 phase. The two-step separation by ultracentrifugation followed by extra centrifugation made it possible to isolate a highly absorbing and soluble nanodiamond phase with the particle size of 3.6 nm, showing a change in spectra compared to the starting nanodiamond material. Keywords: Optoacoustic spectroscopy, Multispectral optoacoustic spectroscopy, Optically dense samples, Nanodiamonds, Nanodiamond aqueous dispersions, Nanodiamond fractionatio

Tests of fundamental symmetries and interactions - using nuclei and lasers

State of the art laser technology and modern spectroscopic methods allow to address issues of fundamental symmetries and fundamental interactions in atoms with high precision experiments. In particular the discrete symmetries Parity (P), Charge Conjugation (C), Time Reversal (T) as well as their combinations CP and CPT are in the center of interest at present. Actual projects are concerned with Parity Violation in atoms, Time Reversal Violation in beta-decays and searches for permanent Electric Dipole Moments (EDMs), and tests of CPT conservation in particle-antiparticle properties, in particular antiprotonic atoms