We report the effect of neodymium (Nd) doping of TiO₂ thin films produced on quartz, soda lime and silicon substrates by RF co-sputtering of two targets of TiO₂ and metallic Nd. The Nd/Ti ratio was varied in the range of 0.9–100 at.%. A study based on a joint use of Auger electron spectroscopy and X-ray fluorescence analysis allowed us to define the chemical composition of all the deposited films. A piece of direct evidence of the structural changes (phase transformation from anatase to rutile for Nd/Ti atomic ratio up to 43 at.%) and amorphization for an Nd/Ti ratio equal to 100 at.%, a lattice distortion due to Nd incorporation and also the rare-earth ion location site was obtained by X-ray diffraction studies, in correlation with the optical properties analysis. NIR photoluminescence properties of the doped films in the wavelength range of 800–1200 nm were investigated by direct (green, blue-green and blue lines at 514.5, 496 and 476 nm respectively) and indirect excitations of Nd (using the UV line at 355 nm), in the latter case excitation through the titania host. In both cases, an intense NIR photoluminescence was observed at 907 and 1093 nm pertaining to the transitions between the excited ⁴F_3/2 to ⁴I_9/2 and ⁴I_11/2 levels of the Nd³⁺ ions for the lowest ion concentration (Nd/Ti ratio equal to 0.9 at.%) and a correlation between the phase structure of the matrix and Nd concentration and the emission properties was found.

Antibiofilm properties of bulk and nano-sized copper oxide (CuO) were investigated using four species of bacteria viz: Staphylococcus aureus, E. coli, Pseudomonas aeuriginosa (PAO1) and Pseudomonas putida. The effect of both commercial and synthesized nanoparticles on biofilm formation was investigated using different concentrations 0.02, 0.12, 0.24, 0.5, 1.0, 1.2, 1.4 & 1.8 μg / mL). Both bulk (91% reduction) and nano-sized (93% reduction) particles significantly reduced biofilm formation in all the four species of bacteria. Concentration and size/shape of nanoparticles seemed to influence biofilm inhibition. Increase in NP concentration from 0.02 to 1.8 μg/mL resulted in a marginal increase in inhibition. While a similar increase in concentration of bulk particles, resulted in 18% decrease in biofilm inhibition. Differences in biofilm inhibition between bulk and nano-sized particles were marginal at low concentrations (0.02, 0.12 & 0.24 μg/mL), whereas prominent differences were observed from concentration of 0.5 μg/mL onwards for the bulk particles. The decrease in inhibition efficiency of bulk nanoparticles with increase in concentration may be attributed to the differences in size, shape, aggregation and settling behaviour. In general, higher efficiency was observed with S. aureus, E. coli and P. putida biofilms, whereas P. aeuriginosa cells showed more resistance in the presence of CuO nanoparticles. Results of the present study indicated that size and shape of the nanoparticles, seem to have an influence on the effective concentration, required for inhibition of biofilms.