Silicon nanocrystals are an extensively studied light-emitting material due to their inherent biocompatibility and compatibility with silicon-based technology. Although they might seem to fall behind their rival, namely, direct band gap based semiconductor nanocrystals, when it comes to the emission of light, room for improvement still lies in the exploitation of various surface passivations. In this paper, we report on an original way, taking place at room temperature and ambient pressure, to replace the silicon oxide shell of luminescent Si nanocrystals with capping involving organic residues. The modification of surface passivation is evidenced by both Fourier transform infrared spectroscopy and nuclear magnetic resonance measurements. In addition, single-nanocrystal spectroscopy reveals the occurrence of a systematic fine structure in the emission single spectra, which is connected with an intrinsic property of small nanocrystals since a very similar structure has recently been observed in specially passivated semiconductor CdZnSe nanoparticles. The organic capping also dramatically changes optical properties of Si nanocrystals (resulting ensemble photoluminescence quantum efficiency 20%, does not deteriorate, radiative lifetime 10 ns at 550 nm at room temperature). Optically clear colloidal dispersion of these nanocrystals thus exhibits properties fully comparable with direct band gap semiconductor nanoparticles.

In this report, we describe the submission of Brno University of Technology (BUT) team to the VoxCeleb Speaker Recognition Challenge (VoxSRC) 2019. We also provide a brief analysis of different systems on VoxCeleb-1 test sets. Submitted systems for both Fixed and Open conditions are a fusion of 4 Convolutional Neural Network (CNN) topologies. The first and second networks have ResNet34 topology and use twodimensional CNNs. The last two networks are one-dimensional CNN and are based on the x-vector extraction topology. Some of the networks are fine-tuned using additive margin angular softmax. Kaldi FBanks and Kaldi PLPs were used as features. The difference between Fixed and Open systems lies in the used training data and fusion strategy. The best systems for Fixed and Open conditions achieved 1.42 % and 1.26 % ERR on the challenge evaluation set respectively.

In this work, monomeric 3-([7]helicen-9-yl)thiophene was synthesized and used for the preparation of a polymeric film by electrosynthesis.

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Excitation profiles of SERS (surface-enhanced Raman scattering) and/or SERRS (surface-enhanced resonance Raman scattering) spectral bands of two forms of a Ag-bpy (bpy = 2,2'-bipyridine) surface complex and of [Ru(bpy)3]2+ on Ag nanoparticle (hydrosol) surfaces were determined from the spectra excited in the 458-600 nm region and are reported together with the FT-SERS spectra of the Ag-bpy surface complex and FT Raman spectra of [Ru(bpy)3] Cl2. Seven of the observed 11 fundamentals as well as their first overtones and combination bands are selectively enhanced in SERS of the Ag-bpy surface complex formed in the Ag colloid/HCl/bpy system. The profiles of these bands show a common maximum at approximately 540 nm. The selectively enhanced bands of the Ag-bpy surface complex have nearly the same wavenumbers as those enhanced in the SERRS and resonance Raman spectra of [Ru(bpy)3]2+ upon excitation close to the 453 nm maximum of its MLCT absorption band. Moreover, the intensity patterns of the bpy vibrations of the two species match both in resonance (541 nm excitation for Ag-bpy, 458 nm for [Ru(bpy)3]2+) and in off-resonance (458 and 1064 nm for Ag-bpy, 1064 nm for [Ru(bpy)3]2+). The distinct band shapes of the excitation profiles of the selectively enhanced vibrational modes of the Ag-bpy surface complex, as well as the observation of overtones and combination bands in the SERS spectra upon excitation into this "band", are interpreted in terms of a charge-transfer resonance contribution to the overall SERS enhancement. In view of the near-coincidence of the vibrational modes coupled to the resonant electronic transition of Ag-bpy with those coupled to the MLCT transition of [Ru(bpy)3]2+, the resonant electronic transition is tentatively assigned to a Ag metal to bpy (pi*) CT transition.

The review article is devoted mainly to the description of applications of gold nanoparticles (GNPs) in separation sciences, especially in electromigration and chromatographic techniques. The applications of GNPs in particular separation methods, CE, microchip CE, MEKC, CEC, HPLC and GC, are classified according to the molecular size of the analytes from low-molecular-mass compounds via medium sized substances to biopolymers (proteins and nucleic acids). A very recent and promising utilization of GNPs for sample preparation, preconcentration and preseparation of selected analytes from complex matrices is presented as well. Moreover, in two introductory sections, typical preparation procedures of the GNPs and their modifications are presented and physicochemical and analytical methods employed for characterization of the native and modified GNPs are briefly introduced.

Surface-enhanced resonance Raman scattering (SERRS) spectra of free base 5,10,15,20-tetrakis(4-carboxypheny1)porphyrin (TPPC4) and of its silver complex, Ag(II)TPPC4, have been investigated under conditions of (I) the direct adsorption of the porphyrin on the surface of Ag colloid and (11) the attachment of the porphyrin to the surface of Ag colloid via a nonionic surfactant, Triton X-100 (p-( 1,1,3,3-tetramethylbutyl)phenylply-(oxyethylene)), functioning as a molecular spacer. For both types of porphyrin adsorption, the mechanisms of the SERS-active system formation have been elucidated. In the former case (I), the system is formed by a two-step process involving (1) preaggregation of Ag colloid by adsorption of phosphate introduced to the system by phosphate buffer and (2) elimination of phosphate from the surface by chemisorption of free base TPPC4.Step 2 of the process is effectively accomplished provided that the concentration of free base (f.b.) TPPC4 in the system is higher than 5 X lo-' M. Formation of theAg(II)TPPC4 surface complex by chemisorption of f.b. TPPC4 on the surface of Ag colloid was proven by SERRS and UV-vis absorption spectroscopy. For the synthetically prepared Ag(II)TPPC4, the second step of the SERS-active system formation is absent, and the SERRS spectrum of the metalloporphyrin is not obtained. In contrast to that, high-quality SERRS spectra of both the free base TPPC4 and Ag(1I)TPPCd were obtained by the spectral study of organized Ag colloid/ Triton X-100/porphyrin systems (11) assembled by a different type of the two-step adsorption process: (1) adsorption of Triton X-100 on the surface of Ag colloid by its hydrophilic part and (2) attractive, hydrophobic interaction between the hydrophobic part of adsorbed Triton X-100 and the porphyrin. SERRS spectra of Ag(II)TPPC4 surface complex, of Ag(II)TPPC4 (synthetic), and of free base TPPC4 were interpreted. The observed coincidence of the vibrational frequencies of Ag(I1)TPPCs surface complex with those of its synthetically prepared analogue signifies a mutual structural equivalence of the porphyrin core parts of the two species. The minor differences in relative band intensities originate from the effect of the surface on the orientation of phenyl rings with respect to the porphyrin macrocycle as well as on the electronic structure of the surface complex.

Application of the finite impulse response (FIR) filtration technique for the removal of spectral noise and background broadband deformations from the Raman spectra is tested. Optimal parameters of FIR filters are found and their effectiveness is compared with the Savitzky-Golay (SG) smoothing procedure. The FIR filtration is found to be an effective procedure to treat the whole Raman spectra, but high computing power is needed.