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

Abstract

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.

Detonation Nanodiamonds: A Comparison Study by Photoacoustic, Diffuse Reflectance, and Attenuated Total Reflection FTIR spectroscopies

“…Thus, the estimation of the penetration (signal-gathering) depth by ATR, Eq. (1) at 4000 cm -1 gives the value is 240 nm, which is comparable to the characteristic size of ND clusters [44,51,52]. The maximum penetration depth of radiation in ATR measurements for a wavenumber of 400 cm -1 is ca.…”

“…However, some caution in this is in order: such bulk spectra relate to nanodiamonds as materials, which in fact can contain ND clusters as well some accompanying components that may seriously affect IR spectra. For instance, ND analysis of visible spectra of some ND brands with visible transmission/optoacoustic spectroscopy with multistage centrifugation reveals a smallest non-diamond sp 2 fraction [52], which can affect the overall unfractionated sample spectra.…”

Short-wavelength optoacoustic spectroscopy based on water muting

“…Optoacoustic spectroscopy has also been considered for characterizing a range of biologically relevant chromophores in aqueous environments, including haemoglobin, melanin or contrast agents such as gold nanoparticles and organic dyes [19]- [23] and in analytical chemistry and nanomedicine applications [24], [25]. The method detects the emission of sound waves from target molecules following absorption of incident light of transient intensity.…”

Photoacoustic effect applied on model membranes and living cells: direct observation with multiphoton excitation microscopy and long-term viability analysis

“…This kind of cNP did not cause cytotoxicity in human prostate adenocarcinoma cells DU145 at concentrations lower than 200 mg/L 15 , five times higher than the maximum concentration used in the experiments here reported. Additional examples of photoacoustic spectroscopy as applied to molecular imaging are known [20][21][22][23] , see review by Chen et al 23 .With other forms of carbon nanosystems, e.g. graphene or carbon nanotubes, controversy exists about their possible toxicity in biomedical applications [24][25][26] .…”