The magnetic and electronic properties of the hydrogenated highly conductive zinc oxide (ZnO) microparticles were investigated by electron paramagnetic resonance (EPR) and contactless microwave (MW) conductivity techniques in the wide temperature range. The EPR spectra simulation allowed us to resolve four overlapping EPR signals in ZnO microparticles. The Lorentzian EPR line with isotropic g-factor 1.9623(5) was related to the singly ionized oxygen vacancy. Another Lorentzian line with g|| = 1.9581(5), g⊥ = 1.9562(5) was attributed to the zinc interstitial shallow donor center, while EPR signal with g|| = 1.9567(5), g⊥ = 1.9556(5) and Gaussian lineshape was assigned to the hydrogen interstitial shallow effective-mass-like donor. The EPR signal with g|| = 1.9538(5), g⊥ = 1.9556(5) and Lorentzian lineshape was tentatively attributed to the shallow donor center. The charge transport properties in ZnO microparticles have been investigated by the contactless MW conductivity technique at T = 5–296 K. Two conduction mechanisms, including ionization of electrons from the shallow donors to the conduction band and hopping conduction process, have been distinguished. The hopping conduction process follows Mott’s variable-range hopping T−1/4 law at T = 10–100 K. The evaluated values of the average hopping distance (15.86 Å), and hopping energy (1.822 meV at 40 K) enable us to estimate the donor concentration in the investigated ZnO microparticles as ~ 1018 cm−3.

Methyl, methoxy and alcoxy groups with different number of carbon atoms were chemically grafted onto the surface of fumed silica nanoparticles. After chemical modification the nanopowders were annealed in vacuum at 700 °C. The effect of the amount of carbon atoms in grafted hydrocarbon groups and type of bonding to silica surface (Si-C v.s. Si-O-C) were studied. It was demonstrated that carbon incorporation results in the development of broad band photoluminescence that covers the wholevisible spectral range. Increasing of carbon incorporation resulted in increasing of photoluminescence intensity and red shift of the photoluminescence band maximum.

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We demonstrate a very simple method of carbon incorporation in silica nanopowder using sucrose as a carbon precursor. Dehydration of sucrose adsorbed in fumed silica host resulted in formation highly luminescent SiO2:C nanocomposite. Effects of chemical and thermal dehydration of sucrose molecules as well as carbon content on spectral properties of broad band photoluminescence (PL) and PL relaxation properties were studied. It is shown that carbon incorporation plays a crucial role in formation of light emitting centers but thermal stimulation is not necessary for those centers emitting in near ultraviolet-violet-blue spectral range while formation of green-orange emission centers needs thermally activated reconstruction in the material. Mechanism of white PL in SiO2:C nanocomposites is discussed in terms of carbon related point defects and carbon nanoclsuters.