Coated Oxide Nanoparticles Research Articles

Engineering the Multi-Enzymatic Activity of Cerium Oxide Nanoparticle Coatings for the Antioxidant Protection of Implants.

Imbalance of oxidants is a universal contributor to the failure of implanted devices and tissues. A sustained oxidative environment leads to cytotoxicity, prolonged inflammation, and ultimately host rejection of implanted devices/grafts. The incorporation of antioxidant materials can inhibit this redox/inflammatory cycle and enhance implant efficacy. Cerium oxide nanoparticles (CONP) is a highly promising agent that exhibits potent, ubiquitous, and self-renewable antioxidant properties. Integrating CONP as surface coatings provides ease in translating antioxidant properties to various implants/grafts. Herein, we describe the formation of CONP coatings, generated via the sequential deposition of CONP and alginate, and the impact of coating properties, pH, and polymer molecular weight, on their resulting redox profile. Investigation of CONP deposition, layer formation, and coating uniformity/thickness on their resulting oxidant scavenging activity identified key parameters for customizing global antioxidant properties. Results found lower molecular weight alginates and physiological pH shift CONP activity to a higher H2O2 to O2 --scavenging capability. The antioxidant properties measured for these various coatings translated to distinct antioxidant protection to the underlying encapsulated cells. Information gained from this work can be leveraged to tailor coatings towards specific oxidant-scavenging applications and prolong the function of medical devices and cellular implants.

Antiviral Activity of Silver, Copper Oxide and Zinc Oxide Nanoparticle Coatings against SARS-CoV-2.

SARS-CoV-2 is responsible for several million deaths to date globally, and both fomite transmission from surfaces as well as airborne transmission from aerosols may be largely responsible for the spread of the virus. Here, nanoparticle coatings of three antimicrobial materials (Ag, CuO and ZnO) are deposited on both solid flat surfaces as well as porous filter media, and their activity against SARS-CoV-2 viability is compared with a viral plaque assay. These nanocoatings are manufactured by aerosol nanoparticle self-assembly during their flame synthesis. Nanosilver particles as a coating exhibit the strongest antiviral activity of the three studied nanomaterials, while copper oxide exhibits moderate activity, and zinc oxide does not appear to significantly reduce the virus infectivity. Thus, nanosilver and copper oxide show potential as antiviral coatings on solid surfaces and on filter media to minimize transmission and super-spreading events while also providing critical information for the current and any future pandemic mitigation efforts.

Magnetically assembled iron oxide nanoparticle coatings and their integration with pseudo-spin-valve thin films

Magnetically assembled nanoparticle coatings modulate the properties and performances of pseudo-spin-valve thin films through nanoparticle–thin film interactions.

Water Absorption of Hemp Fibre Nonwovens Modified with Metal and Metal Oxide Nanoparticles

In this paper changes of ability of hemp fibre nonwovens to absorb water after deposition of metal and metal oxide nanoparticles were investigated. Moisture content of samples after storage in different climatic conditions was determined using thermogravimetric method. The obtained results were compared with the results of previous research based on investigation of water absorption of metalized woven fabric of bast fibre. Analysis of measurements showed that nonwoven samples with surface treated in plasma attract water slightly better than sample with untreated surface; this was more pronounced in woven fabric samples. In turn, metal coatings reduced water sorption. Unlike woven fabric samples, nonwoven samples attract similar water quantity irrespectively of surface modification. It can be concluded that metallization of hemp fibre nonwovens retain hygroscopic properties of these textile materials. Therefore, moisture content also needs to be controlled in nonwovens with metal and metal oxide nanoparticle coatings.

Low temperature processing of redispersed tin doped indium oxide nanoparticle coatings

The deposition of transparent conducting oxide (TCO) coatings using for example chemical vapor deposition, spray pyrolysis or a conventional sol–gel routine usually needs high temperatures and is therefore only applicable to temperature-stable substrates like glass. The deposition of TCO coatings on temperature-sensitive substrates requires low-temperature deposition processes like redispersed nanoparticle suspensions combined with e.g. the dip-coating technique. To obtain a tin doped indium oxide (ITO) nanoparticle suspension for the coating process, ITO nanopowder is redispersed in a mixture of solvents, cross-linking agents and stabilizers. In this work it is shown that four different stabilizers and mixtures of these stabilizers can be used and how the choice of the stabilizers influences the properties of the coatings concerning the reflectance of the surface, the layer composition, that means the porosity and the surface roughness of the layers, and the electrical conductivity.

Evaluating the Electrochemical Capacitance of Surface-Charged Nanoparticle Oxide Coatings

While transition metal oxides have been thoroughly investigated as coatings for electrochemical capacitors due to their pseudocapacitance, little work has been done investigating other oxide coatings. There exists a whole class of nanoporous oxides typically synthesized by sol-gel chemistry techniques that have very high differential capacitance. This high differential capacitance has been attributed to the surface potential of these materials and the close approach of counterions near the surface of these oxides. This study focuses on investigating the electrochemical capacitance of non-transition metal oxide nanoparticle coatings when deposited on supporting electrodes. Here, we show that, by adding coatings of SiO(2), AlOOH, TiO(2), and ZrO(2) nanoparticles to graphite support electrodes, we can increase the electrochemical capacitance. We also show that the measured electrochemical capacitance of these oxide-coated electrodes directly relates to the electrophoretic mobility of these materials with the lowest values in capacitance occurring at or near the respective isoelectric pH (pH(IEP)) of each oxide.

Advanced Treatment Process for Brackish Water Desalination

We aim to develop an energy-efficient, low-cost desalination technology for creating new, affordable water sources from brackish waters. Since Qatar has extremely limited rechargeable water sources, technologies facilitating safe use of impaired and unconventional water sources are needed. Capacitive deionization (CDI) technology can meet the unique, logistical and economic needs for inland desalination. CDI technology, unlike reverse osmosis and nanofiltration, operates under ambient pressure and can be sustained with renewable energy sources. In this process, ions move to the electrode surface and build up an electrical double layer (EDL) when an external potential is applied. Metal oxide nano-particle coatings are widely used in super-capacitors to increase the capacitance. We are employing fourth-generation CDI technology (i.e., alumina, silica nano-particle coated porous carbon) for brackish water treatment. The presence of oxides together with the functional groups on the carbon surface enhances the ion removal process. Sorption capacity of up to 0.05 mM/g electrode has been achieved for monovalent ions with high reversibility and no obvious loss of capacity in long-term operation. During regeneration, up to 50% of the charge can be harvested. Preliminary results indicate that higher sorption capacity exists for divalent cations compared to monovalent ions. Comprehensive tests are underway for various electrolytes (1:2, 2:1, 2:2) and brackish water samples to cover a wide gradient in salt concentration and ionic composition. This project will lead to the development of low-cost inland desalination systems and can be expected to boost Qatar's scientific profile in global and regional water industry.

Synthesis and optical properties of organic semiconductor: zirconia nanocomposites

Oxide nanoparticles were used as carrier for organic semiconductor materials. Stable suspensions of ZrO2 nanoparticles coated with anthracene, pentacene, or para-hexaphenyl were obtained by microwave plasma synthesis of ZrO2 cores, subsequent in situ coating with organic compounds, and in situ dispersion in ethylene glycol. Powders of coated oxide nanoparticles were synthesized for comparison. The successful coating and a small uniform size distribution of the ZrO2 cores were confirmed by comprehensive characterization including photoluminescence, absorption spectroscopy, electron microscopy, electron energy loss spectroscopy, mass spectrometry, and X-ray diffraction. Powder compacts of anthracene-coated ZrO2 particles showed good air stability and a significant blue shift accompanied by an attenuation of the emission lines at higher vibronic orders in comparison to samples of pure anthracene as received. For para-hexaphenyl-coated nanoparticles, the same photoluminescence characteristics are observed as for pure para-hexaphenyl. In the case of pentacene-coated nanoparticles indication for degradation is found.

J-aggregation of cyanine dyes by self-assembly

The importance of highly ordered surfaces, containing adsorptive surface states, is discussed for J-aggregation by self-assembly. Such nucleating surfaces are nanometer-sized edges and corners of cubic AgBr microcrystals, or surface iodide-clusters located along edges and corners of AgBr:I microcrystals. Of particular interest are dendrimers, monoatomic steps on terraced silver halide microcrystals and fullerene derivatives as nucleating surfaces. Molecular organisation into J-aggregates by self-assembly was realized using aprotic, apolar solvents for fullerenes, and polar solvents for dendrimers and monoatomic surface steps. By using dendrimers as nucleating agents in mesopores of metal oxide nanoparticle coatings, size-controlled and stable J-aggregates with high optical densities and strong fluorescence were obtained reproducibly. Such films may be useful for sensors, opto-electronics, lighting and photovoltaics.

Influence of polyvinylpyrrolidone on properties of flexible electrically conducting indium tin oxide nanoparticle coatings

The influence of the organic film agent polyvinylpyrrolidone (PVP) on the electrical conductivity of indium tin oxide (ITO) nanoparticle coatings on polyethyleneterephthalate films was investigated. The ITO/PVP nanocomposite coatings show a decrease of the specific resistance with increasing PVP content up to 40 vol.%, whereas for higher PVP contents the specific resistance increases. The lowest specific resistance of 6 Ω cm is almost 20 times lower than that of a pure ITO nanoparticle coating. Annealing at 200 °C leads to a further decrease of the specific resistance for all volume fractions of PVP. Specific resistances of 0.5 Ω cm could be achieved for PVP contents of 33–40 vol.%. In addition, the PVP has a strong influence on the electrical conductivity of ITO/PVP coatings under bending which was investigated using a specially constructed device for the application of various bending loads. The ITO/PVP nanocomposite films show a significant lower increase of the sheet resistance under oscillatory bending compared to pure ITO nanoparticle coatings. However, the transmission in the visible range of ITO/PVP nanocomposites decreases with increasing PVP content up to 40 vol.%.

Fluorescence from Coated Oxide Nanoparticles

ABSTRACTIn many cases, coated nanoparticles behave like isolated ones. Using the microwave plasma process, it is possible to produce oxide nanoparticles with ceramic or polymer coating. Coating the particles has the additional advantage that by proper selection of the coating it is possible to suspend the particles in distilled water without using any colloid stabilizer. From quantum dots made of sulfides or selenides, it is well known from literature that fluorescence depends strongly on the coating of the kernels. In the case of CdSe, the kernels are coated with CdS. Within this study, similar phenomena are found with coated oxide nanoparticles having sizes of ca. 6 nm exhibiting a very narrow particle size distribution. The coating consists of a second ceramic phase or a polymer one, each one influencing fluorescence differently. Obviously, the type of coating is a tool to modify fluorescence. This behavior is demonstrated on kernels made of Al2O3, ZrO2, HfO2, ZnO etc. PMMA, PTFE, or Al2O3were used as coating material. In most cases, the fluorescence spectra showed broad bands. In some cases, such as ZnO, additionally, a sharp emission line in the UV appears. It is interesting to note that coatings made of fluorine containing polymer materials did not lead to fluorescence intensities comparable with PMMA coatings. The observed spectra are equivalent whether the powder is in aqueous suspensions or dry on a quartz glass carrier. The experimental results in this study indicate that the combination of non-fluorescent oxide core with a non-fluorescent polymer coating may lead to a nanocomposite with strong fluorescence. This is a phenomenon not described in literature until now.

Superparamagnetic Ferrites Realization and Physical Obstacles

ABSTRACTIn superparamagnetic materials, the change of the direction of the magnetization is not associated with the movement of Bloch walls, but with thermal fluctuation of the magnetization vector. Therefore, the resonance frequency of the Bloch walls is no longer limiting the maximum frequency for applications. The limit found in superparamagnetic materials is given by the frequency of electron spin resonance. This behavior was verified for spinelle type ferrites made of ceramic or polymer coated oxide nanoparticles produced by the microwave plasma process. By selecting the composition of the spinelle type ferrites the energy of magnetic anisotropy controlling the susceptibility and the maximum frequency for applications can be adjusted. Superparamagnetic materials have their frequency limit beyond 2 GHz. Coating of the particles reduces dipole – dipole interaction destroying superparamagnetism. Even when the susceptibility is in the order of magnitude of today's commercial ferrites, the saturation magnetization is found to be smaller than the theoretically expected value. This phenomenon is partly clarified by soft X-ray magnetic circular dichroism (SXMCD) measurements, showing a significant orbital magnetic moment anti arallel to the direction of the spin moment. Additionally, it was found that the amount of Fe2+ ions is possibly larger than expected by thermodynamic data of bulk materials.