Synthesis of Antibacterial Copper Oxide Nanoparticles by Pulsed Laser Ablation in Liquids: Potential Application against Foodborne Pathogens.

Spherical copper oxide nanoparticles (CuO/Cu2O NPs) were synthesized by pulsed laser ablation in liquids (PLAL). The copper target was totally submerged in deionized (DI) water and irradiated by an infrared laser beam at 1064 nm for 30 min. The NPs were then characterized by dynamic light scattering (DLS) and atomic emission spectroscopy (AES) to determine their size distribution and concentration, respectively. The phases of copper oxide were identified by Raman spectroscopy. Then, the antibacterial activity of CuO/Cu2O NPs against foodborne pathogens, such as Salmonella enterica subsp. enterica serotype Typhimurium DT7, Escherichia coli O157:H7, Shigella sonnei ATCC 9290, Yersinia enterocolitica ATCC 27729, Vibrio parahaemolyticus ATCC 49398, Bacillus cereus ATCC 11778, and Listeria monocytogenes EGD, was tested. At a 3 ppm concentration, the CuO/Cu2O NPs exhibited an outstanding antimicrobial effect by killing most bacteria after 5 h incubation at 25 °C. Field emission scanning electron microscope (FESEM) confirmed that the CuO/Cu2O NPs destructed the bacterial cell wall.

Synthesis of "Naked" TeO2 Nanoparticles for Biomedical Applications.

Chalcogenide nanoparticles have become a very active field of research for their optoelectronic and biological properties. This article shows the production of tellurium dioxide nanoparticles (TeO2 NPs) by pulsed laser ablation in liquids. The produced nanoparticles were spherical with a diameter of around 70 nm. The energy band gap of those nanoparticles was determined to be around 5.2 eV. Moreover, TeO2 NPs displayed a dose-dependent antibacterial effect against antibiotic-resistant bacteria such as multidrug-resistant Escherichia coli (MDR E. coli) and methicillin-resistant Staphylococcus aureus (MR S. aureus). The "naked" nature of the nanoparticle surface helped to eradicate the antibiotic-resistant bacteria at a very low concentration, with IC50 values of ∼4.3 ± 0.9 and 3.7 ± 0.2 ppm for MDR E. coli and MR S. aureus, respectively, after just 8 h of culture. Further, the IC50 values of the naked TeO2 NPs against melanoma (skin cancer) and healthy fibroblasts were 1.6 ± 0.7 and 5.5 ± 0.2 ppm, respectively, for up to 72 h. Finally, to understand these optimal antibacterial and anticancer properties of the TeO2 NPs, the reactive oxygen species generated by the nanoparticles were measured. In summary, the present in vitro results demonstrate much promise for the presently prepared TeO2 NPs and they should be studied for a wide range of safe antibacterial and anticancer applications.

Electric-Field-Induced Phase Change in Copper Oxide Nanostructures.

Transition-metal oxides such as cupric and cuprous oxides are strongly correlated materials made of earth-abundant chemical elements displaying energy band gaps of around 1.2 and 2.1 eV. The ability to design nanostructures of cupric and cuprous oxide semiconductors with in situ phase change and morphological transition will benefit several applications including photovoltaic energy conversion and photoelectrochemical water splitting. Here, we have developed a physicochemical route to synthesize copper oxide nanostructures, enabling the phase change of cupric oxide into cuprous oxide using an electric field of 105 V/m in deionized water via a new synthetic design protocol called electric-field-assisted pulsed laser ablation in liquids (EFA-PLAL). The morphology of the nanostructures can also be tuned from a sphere of ∼20 nm to an elongated leaf of ∼3 µm by controlling the intensity of the applied electric field. Futuristically, the materials chemistry occurring during the EFA-PLAL synthesis protocol developed here can be leveraged to design various strongly correlated nanomaterials and heterostructures of other 3d transition-metal oxides.

Synthesis of naked vanadium pentoxide nanoparticles.

Vanadium pentoxide is the most important vanadium compound by being the precursor to most vanadium alloys. It also plays an essential role in the production of sulfuric acid as well as in metal-ion batteries and supercapacitors. In this paper, pulsed laser ablation in liquids is used to synthesize "naked" vanadium pentoxide nanostructures. The resulting particles take up "nearly-spherical" and "flower-like" morphologies, composed of α-V2O5 and ß-V2O5 crystalline phases. Even "naked", the nanostructures are stable in time with a zeta potential of -51 ± 7 mV. In order to maximize the production of vanadium pentoxide nanostructure, the optimal repetition rate was determined to be @ ∼6600 Hz when irradiating a pure vanadium target in DI-water. This corresponds to a cavitation bubble lifetime of around ∼0.15 ms. At that repetition rate, the production reached ∼10 ppm per minute of irradiation. Finally, from the characterization of the α-V2O5 and ß-V2O5 nanostructures, the surface energy of each phase has been carefully determined at 0.308 and 1.483 J cm-2, respectively. Consequently, the ß-phase was found to display a surface energy very close to platinum. The exciton Bohr radius has been determined at 3.5 ± 0.7 nm and 2.0 ± 0.6 nm for α-V2O5 and ß-V2O5 phases, respectively.

Naked Selenium Nanoparticles for Antibacterial and Anticancer Treatments.

Currently, antibiotic resistance and cancer are two of the most important public health problems killing more than ∼1.5 million people annually, showing that antibiotics and current chemotherapeutics are not as effective as they were in the past. Nanotechnology is presented here as a potential solution. However, current protocols for the traditional physicochemical synthesis of nanomaterials are not free of environmental and social drawbacks, often involving the use of toxic catalysts. This article shows the production of pure naked selenium nanoparticles (SeNPs) by a novel green process called pulsed laser ablation in liquids (PLAL). After the first set of irradiations, another set was performed to reduce the size below 100 nm, which resulted in a colloidal solution of spherical SeNPs with two main populations having sizes around ∼80 and ∼10 nm. The particles after the second set of irradiations also showed higher colloidal stability. SeNPs showed a dose-dependent antibacterial effect toward both standard and antibiotic-resistant phenotypes of Gram-negative and Gram-positive bacteria at a range of concentrations between 0.05 and 25 ppm. Besides, the SeNPs showed a low cytotoxic effect when cultured with human dermal fibroblasts cells at a range of concentrations up to 1 ppm while showing an anticancer effect toward human melanoma and glioblastoma cells at the same concentration range. This article therefore introduces the possibility of using totally naked SeNPs synthesized by a new PLAL protocol as a novel and efficient nanoparticle fabrication process for biomedical applications.