A holistic approach to fully characterize the physical–chemical properties of N doped TiO2 and evaluate its true impact on photoelectrochemical applications.

Here we present the first example of excitationindependent blue-emitting carbon dots (iC-dots) obtained by pyrolysis of citric acid (CA) without post-treatment chromatographic separation. To confine the growth and shape of carbon nanoparticles, silica gel with immobilized aminopropyl groups (SiO 2 −NH 2 ) was used as a nanoreactor. It was demonstrated that the carbonization of SiO 2 − NH 2 with embedded CA resulted in the formation of unbound wCdots and immobilized iC-dots. Because of their firm attachment to the surface, iC-dots can be easily separated from low-molecular impurities and wC-dots by simply rinsing the nanocomposite with water. From atomic force and transmission electron microscopies iC-dots can be represented as flattened spheroids with 2−4 nm of height and 5 nm in lateral size. The size distribution profile for wC-dots is very wide with about 95% the particles within the 2.5−5.5 nm size range. Increasing the template pore size from 4.9 up to 9.1 nm has no effect on the size of the iC-dots. From Fourier transform infrared analysis and X-ray photoelectron spectroscopy data it was assumed that iC-dots belong to N-doped C-nanoparticles with 9:1 carbon to nitrogen atomic ratio. As-prepared iC-dots demonstrate excitation-independent photoluminescence at 445 nm with quantum yields up to 16.8%, which makes them attractive for bioanalytical application.

No abstract

No abstract

The effect of Furnace Annealing (FA) and Rapid Thermal annealing (RTA) on the structural and optical properties of GaAs1-xBix/GaAs single quantum wells (SQW) grown on (001) and (311)B substrates by molecular beam epitaxy (MBE) was investigated. The structural properties were investigated by high-resolution X-ray diffraction (HR-XRD) and Transmission Electron Microscopy (TEM). The Bi concentration profiles were determined by simulating the HR-XRD 2θ-ω scans using dynamical scattering theory to estimate the Bi content, lattice coherence and quality of the interfaces. The Bi composition was found to be similar for both samples grown on (001) and (311)B GaAs substrates. However, the simulations indicate that the Bi composition is not only limited in the GaAsBi QW layer but extends out of the GaAsBi QW towards the GaAs barrier. Photoluminescence (PL) measurements were performed as a function of temperature and laser power for samples with a nominal Bi composition of 3%. PL spectra showed that (001) and (311)B samples have different peak energies at 1.23 eV and 1.26 eV, respectively, at 10 K. After RTA at 300 o C for 2 mins, the PL intensity of (311)B and (001) samples was enhanced by a factor of ~2.5 and 1.75, respectively. However, for the (001) and (311)B FA samples an enhancement of the PL intensity by a factor of only 1.5 times could be