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SUMMARY:XAFS spectroscopy - a useful tool for determining structure parame
 ters and the electronic state of various nanosystems
DTSTART;VALUE=DATE-TIME:20160707T042000Z
DTEND;VALUE=DATE-TIME:20160707T044000Z
DTSTAMP;VALUE=DATE-TIME:20260722T163700Z
UID:indico-contribution-1196@indico.inp.nsk.su
DESCRIPTION:Speakers: Simon Erenburg (Nikolaev Institute of Inorganic Chem
 istry SB RAS\, Budker Institute of Nuclear Physics SB RAS)\nSome of the EX
 AFS spectra above Ga*K*-and Ge*K*- edges were measured at the VEPP-3 stora
 ge ring (beamline 8) of Siberian Synchrotron and Terahertz Radiation Cente
 r (SSTRC) of the Budker Institute of Nuclear Physics (BINP SB RAS\, Novosi
 birsk\, Russia). Other part of the spectra was measured at the ESRF (Greno
 ble\, France). The high energy resolution fluorescence detected HERFD-XANE
 S and EXAFS experiments have been performed at 12K at the beamline ID26 or
  ID20 equipped by 5-analyzer x-ray emission spectrometer.\n\n**1. Electron
 ic and spatial structure of "calibrated" gold clusters in the cavities of 
 cucurbit[*6\, 7*] uril molecules.**\n\nThe Au*L$_{III}$* X-ray absorption 
 fine structure (XAFS) spectra have been measured for samples containing ca
 librated gold nanoparticles *D* ≤ 1nm nm in cavities of cucurbituril mol
 ecules (CB[*6\, 7*]). It has been found that gold clusters are characteriz
 ed by smaller 0.03 Å interatomic distances and a considerable reduction i
 n the Au-Au coordination numbers (*N* ≤ 8) as compared with bulk gold. N
 o visible shifts of Au*L$_{III}$* absorption edges (±0.02 eV) and differe
 nces in the Au charge state for Au@СВ[*6\, 7*] samples containing small 
 Au clusters were detected in comparison with bulk Au metal. A threefold an
 d more increase in the Debye-Waller factor at 12K was found for the nanopa
 rticles in comparison with bulk metal and correspondingly\, a substantial 
 increase in the structural disorder. It has been found that special chemic
 al (catalytic) and physical (optical) properties of small gold particles a
 re likely to be attributed to this structure changes and the size effect w
 ith the appearance of a band gap between the occupied and unoccupied elect
 ronic states\, rather than changes in the charge state of gold clusters an
 d presence of strongly pronounced vertices and edges in structure of nanop
 articles.\n\n**2. Microstructure of multilayered heterosystems GaNAlN.**\n
 \nA minimal drop (~0.01 Å) in the interatomic Ga–Ga distances *R*(Ga) r
 elative to a thick solid film was obtained from the analysis of GaK EXAFS 
 spectra for multilayered GaN/AlN samples with "thick" (550–850 nm) super
 lattices\, agreeing with the numerous dislocations found in them and the c
 orresponding stress relaxation in the GaN layers. The interatomic Ga–Ga 
 distances *R*(Ga) for samples with fewer layers and "thin" (80–150 nm) s
 uperlattices fell more substantially (by $\\sim{0.03}$ Å)\, corresponding
  to the more substantial deformations and stresses indicated by our earlie
 r results for GaN quantum dots in a AlN host.  The influence of the growth
  conditions and the thickness of the superlattices on mixing in the near b
 oundary layers and the optical properties of the GaN/AlN superlattices wer
 e revealed. It was established that Ga–Al mixing occurs only in the laye
 r nearest to the interface. Anomalously long Ga–Al distances ($\\sim{3.2
 5}$ Å) were observed for samples with thick superlattices. This effect ca
 n be explained by a nonequilibrium transition from GaN growth to AlN growt
 h and the more substantial stresses at the interface of such superlattices
 .\n\n**3. Structural characteristics of K-Bi citrate (De-Nol) and its clus
 ters in aqueous solutions.**\n\nBi*L$_{III}$* EXAFS spectra of an amorphou
 s solid Bi complex with citrate (De-Nol) and its aqueous solutions in a wi
 de concentration range are measured. For the solutions good agreement is r
 evealed between their structural parameters and the averaged interatomic d
 istances and coordination numbers of 12-nuclear Bi clusters. So\, it is fo
 und that droplets of the colloidal solution have a structure close to the 
 solid $Bi_{12}O_{22}$ cluster structure. When the concentrated solution is
  diluted the cluster structure is somewhat modified\, it remaining similar
  to the structure of the $Bi_{12}O_{22}$ cluster and even at a tenfold dil
 ution and the nearest (oxygen) spheres of the Bi environment changing insi
 gnificantly.\n\nThis work was supported by the Russian Foundation for Basi
 c Research (project no. 16-02-00175a)\n\nhttps://indico.inp.nsk.su/event/3
 /contributions/1196/
LOCATION:Budker INP Conference Hall
URL:https://indico.inp.nsk.su/event/3/contributions/1196/
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