The bactericidal properties of copper oxide nanoparticles have growing interest due to potential application in the medical area. The present research investigates the influence of sodium dodecyl sulfate (SDS) and poly(vinylpyrrolidone) (PVP) on the production of copper oxide nanoparticles prepared from copper sulfate (CuSO₄) and sodium borohydride (NaBH₄) solutions. Different analytical techniques were used to determine the crystal nature, mean size diameter, and surface morphology of the copper oxide nanoparticles. The X-ray diffraction (XRD) patterns showed formation of nanoparticles of cuprite (Cu₂O) and tenorite (CuO) when PVP and SDS were added at the beginning of the reaction. In fact, when the Cu/PVP ratio was 1.62, Cu₂O nanoparticles were obtained. In addition, nanoparticles of CuO were synthesized when the Cu/PVP ratios were 0.54 and 0.81. On the other hand, a mixture of copper oxides (CuO and Cu₂O) and cuprite (Cu₂O) was obtained when PVP (Cu/PVP = 0.81 and 1.62) and SDS (Cu/SDS = 0.90) were added 30 min after the beginning of the reaction. Transmission electron microscopy (TEM) images show agglomerated nanoparticles with a size distribution ranging from 2 to 60 nm, while individual particles have sizes between 4.1 ± 1.9 and 41.6 ± 12.8 nm. The Kirby–Bauer method for the determination of antibacterial activity shows that small CuO (4.1 ± 1.9 nm) and Cu₂O (8.5 ± 5.3 nm) nanoparticles inhibit the growth of Escherichia coli, Staphylococcus aureusMRSA, S. aureus and Pseudomonas aeruginosa bacteria. The antibacterial test of cotton fabric impregnated with nanoparticles shows positive results. The determination of the optimal ratio of copper oxide nanoparticles per cm² of fabric that are able to exhibit a good antibacterial activity is ongoing.

This research presents the synthesis of nanoparticles of ZnO (Nps-ZnO) obtained by two methods: chemical precipitation (method 1) and combustion in solution (method 2). The effect of each method on the crystallographic properties of Nps-ZnO is studied. The Nps-ZnO obtained present, according to EDS analysis, an atomic Zn: O ratio of 0.95 and 1.36 when two methods were used respectively. The formation of Nps-ZnO with Wurtzite-type hexagonal arrangement is confirmed with XRD analysis. XRD results show there is not a big difference between the lattice parameters and interplanar spacing for the samples obtained by the two synthesis methods. However, the Nps-ZnO obtained by chemical precipitation show higher values of dislocation density (1.780 × 10^− 3) nm^− 2 than those obtained by combustion in solution (0.152 × 10^− 3) nm^− 2. A similar behavior is observed with the micro-strain values (2.137 × 10^− 3-6.388 × 10^− 3) and (1.170 × 10^− 3-1.971 × 10^− 3), respectively. TEM images show nanoparticles with mean diameters between 17.2 ± 10.8 nm and 73.4 ± 6.0 nm when the method of chemical precipitation and combustion in solution were applied, respectively. Larger and semi-square nanoparticles are formed with the combustion in solution method is applied. Size of Nps-ZnO estimated from TEM images analysis, Debye-Scherer’s formula and Rietveld refinement are highly inter-correlated. Finally, the Nps-ZnO presented a narrow bandgap of 3.19 eV and 3.16 eV, a value lower than that of the bulk material (3.7 eV). No drastic change in bandgap is observed for samples synthesized with two different methods.

Copper oxide (Cu ₂ O) is a promising semiconductor for photovoltaic and photocatalytic applications since this material has a high optical absorption coefficient and lower band gap (2.17 eV). Doped lanthanum (La), magnesium (Mg) and manganese (Mn) Cu ₂ O nanoparticles (Cu ₂ O Nps) were prepared by a displacement reaction. The doped and undoped Cu ₂ O Nps were characterized with scanning electron microscopy–energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), transmission electron microscopy (TEM) and ultraviolet–visible spectroscopy. The EDS results confirm the presence of La, Mg and Mn in the Cu ₂ O Nps. The XRD results confirm the formation a single cubic phase of Cu ₂ O with a cuprite structure. TEM images confirm the formation of Nps with mean diameters between 12.0 ± 6.1 and 30.8 ± 11.0 nm. Doped and undoped Nps present a narrow band gap (2.40 eV), blue shifted with respect to bulk Cu ₂ O.

Zinc oxide in nanometric dimensions, thanks to its optical properties, is an oxide of great interest for its potential use as a revealing agent for latent fingerprints. In this article we present the synthesis and characterization of ZnO nanoparticles obtained by two methods and it uses in revealing of latent fingerprints on non-porous surfaces. The nanoparticles synthetized present an atomic Zn:O ratio of 0.99 and 1.15 when precipitation and combustion in solution method were used, respectively. Both samples show a hexagonal arrangement (wurtzite) according to the X-ray diffraction and Raman spectra. Raman results show a shift at 439 cm⁻¹ corresponding to the E₂ (high) mode of the ZnO crystalline hexagonal wurtzite structure. Transmission electron microscopy images show that nanoparticles with smaller average diameters are obtained by chemical precipitation (17.2 ± 10.8 nm) than combustion in solution (73.4 ± 6.0 nm). Samples presented a narrow band gap of 3.69 and 3.59 eV, values higher than that reported for the bulk material (3.37 eV). The photoluminescence spectrum showed a characteristic ultraviolet emission peak around 387 nm and green emissions peaks from ZnO when excitation wavelength of 325 and 488 nm were experiment, respectively. Finally, ZnO nanoparticles were used to reveal latent fingerprints on non-porous surfaces using a 325 nm laser. Fingerprint development is better on black glass surface when using precipitated ZnO. However, Fingerprints are better observed in aluminum foil when ZnO obtained by combustion in solution is applied. The results show that it is possible to use ZnO nanoparticles obtained by both methods as latent fingerprint revealing agents.