Gradually Fe-doped Co3O4 nanoparticles in 2-propanol and water oxidation catalysis with single laser pulse resolution.

Controlling the surface composition of colloidal nanoparticles is still a challenging yet mandatory prerequisite in catalytic studies to investigate composition-activity trends, active sites, and reaction mechanisms without superposition of particle size- or morphology-effects. Laser post-processing of colloidal nanoparticles has been employed previously to create defects in oxide nanoparticles, while the possibility of laser-based cation doping of colloidal nanoparticles without affecting their size, remains mostly unaccounted for. Consequently, at the example of doping iron into colloidal Co3O4 spinel nanoparticles, we developed a pulse-by-pulse laser cation doping method to provide catalyst series with gradual surface composition but maintained extrinsic properties such as phase, size, and surface area for catalytic studies. Laser pulse number-resolved doping series were prepared at laser intensity chosen to selectively heat the Co3O4-NPs to roughly 1000 K and enable cation diffusion of surface-adsorbed Fe3+ into the Co3O4 lattice while maintaining the spinel phase, particle size, and surface area. The combination of bulk-sensitive X-ray fluorescence (XRF) and surface-sensitive X-ray photoelectron spectroscopy (XPS) was used to confirm a surface enrichment of the Fe-dopant. XRD, Magnetometry, and Mössbauer spectroscopy revealed an increasing interaction between Fe and the antiferromagnetic Co3O4 with an increasing number of pulses, in line with a proposed laser-induced surface doping of colloidal Co3O4 with Fe. Using Fick’s second law the thermal diffusion-related doping depth was estimated to be roughly 2 nm after 4 laser pulses. At the example of gas-phase 2-propanol oxidation and liquid-phase oxygen evolution reaction, the activity of the laser-doped catalysts is in good agreement with previous observations on binary iron-cobalt oxides. The catalytic activity was found to linearly increases with the calculated doping depth in both reactions, while only catalysts processed with at least one laser pulse were catalytically stable, highlighting the presented method in providing comparable, active, and stable gradual catalyst doping series for future catalytic studies.

Фотоуправляемые обратимые изменения электронных и колебательных спектров фотохромного диарилэтена в различных наноструктурированных системах

An analysis of the results of complex experimental and theoretical studies of photoinduced changes in the spectral properties of photochromic diarylethene in various nanostructured systems is presented. The properties of diarylethene were studied in solutions in the presence of colloidal metal and semiconductor nanoparticles, as well as in the form of solid-phase composite nanostructured core-shell systems based on colloidal nanoparticles with a shell of diarylethene molecules (including in a polymer matrix). A photoinduced reversible change in the electronic and vibrational spectra of diarylethene in various studied matrices was found. The results can be used to create optoelectronic photo-switchable elements for ultra-high-capacity memory devices, photo-controlled molecular switches and sensors.

Liquid Surface-Enhanced Raman Spectroscopy (SERS) Sensor-Based Au-Ag Colloidal Nanoparticles for Easy and Rapid Detection of Deltamethrin Pesticide in Brewed Tea

Deltamethrin pesticides can cause inflammation, nephrotoxicity and hepatotoxicity as well as affect the activity of antioxidant enzymes in tissues. As a result of this concern, there is a rising focus on the development of fast and reliable pesticide residue testing to minimise potential risks to humans. The goal of this study is to use Au-Ag colloid nanoparticles as liquid surface-enhanced Raman spectroscopy (SERS) to improve the Raman signal in the detection of deltamethrin pesticide in a brewed tea. The liquid SERS system is fascinating to study due to its ease of use and its unlikeliness to cause several phenomena, such as photo-bleaching, combustion, sublimation and even photo-catalysis, which can interfere with the Raman signal, as shown in the SERS substrate. Our liquid SERS system is simpler than previous liquid SERS systems that have been reported. We performed the detection of pesticide analyte directly on brewed tea, without diluting it with ethanol or centrifuging it. Femtosecond laser-induced photo-reduction was employed to synthesise the liquid SERS of Au, Au-Ag, and Ag colloidal nanoparticles. The SERS was utilised to detect deltamethrin pesticide in brewed tea. The result showed that liquid SERS-based Ag NPs significantly enhance the Raman signal of pesticides compared with liquid SERS-based Au NPs and Au-Ag Nanoalloys. The maximum residue limits (MRLs) in tea in Indonesia are set at 10 ppm. Therefore, this method was also utilised to detect and improve, to 0.01 ppm, the deltamethrin pesticide Limit of Detection (LOD).

Detection of Galactose and Glycerophospholipids by Galactose Biosensors and Advancement Their Proficiency Using Berkelium Colloidal Nanoparticles and Poly(3,4-Ethylenedioxythiophene)-Poly(Styrenesulfonate)-Based Biosensors

In the current paper, galactose-oxidase enzyme is used as stabilization medium due to its more proficiency, ability for more accurate controlling the enzyme reaction, protecting against wasting of enzyme as well as simple and easy use and exchange of enzyme medium after performing some levels of surface modification and developing multi-walled carbon nanotubes (MWCNTs) on Berkelium plate. For better connecting and stabilizing the enzyme on the medium, the prepared medium is washed by high concentration sulfuric acid and nitric acid and a large volume of deionized water and for protecting enzyme from devastating effect of Berkelium and prohibiting them to become inactive, surface is covered with cystamine before stabilization. Regarding the large size of galactose-oxidase enzyme compared to surface of medium, a connective material with amid at one end and pyrine at the other end is used as transfer agent and for stabilizing this connection, the prepared medium is placed into dimethylformamide (DMF) solution for a couple of hours. Activity of stabilized enzyme at 460 (nm) wavelength recorded by spectroscope was depicted against time to evaluate its stability in various times. The prepared medium, which have a large amount of galactose-oxidase enzyme, can be used as electrode in sensors. Furthermore, galactose-oxidase electrochemical sensor is one of the best methods for detecting low amount of galactose and applying Berkelium colloidal nanoparticles as a supplementary material in the structure of biosensor can be effective for advancement its proficiency and optimum proficiency. On the other hand, in the current study, electrode biosensor entitled as modified carbon paste electrode with Berkelium colloidal nanoparticles (Bknano/CPE) is produced by carbon graphite powder, paraffin oil and Berkelium colloidal nanoparticles (24 nm) and it is compared with carbon paste electrode (CP). In semi-permeable membranes, a combination of 1 (ml) of 0.1 (M) phosphate buffer with specified pH and 10 (mg) of galactose-oxidase enzyme is placed around each electrode. In the same potential of 0.7 (V), biosensors are tested with galactose in concentration range of (0-1) (mM) and various amounts of pH (4,6,8) which lead to producing the maximum current and tracing galactose in pH=6 and concentration of 1 (M) as the optimum condition. Currentmetry induced from both biosensors are compared and it is confirmed that using Berkelium colloidal nanoparticles in the structure of (Bknano/CPE) electrode leads to increasing the conductivity and currentmerty of biosensor. In addition, qualitative and quantitative measurement of food components is of great importance due to high cost of traditional methods, in addition to tendency for more accurate and sensitive detecting of these components. galactose and glycerophospholipids are such compounds that they frequently measure. Various methods are used to detect these food elements. However, the necessity for accurate measurement of these two compounds with high sensitivity, especially for food health issue, leads to developing biological methods, especially biosensors. Among them, biosensors based on conductive polymer nanostructures, especially Poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate), have been recently interested due to their unique characteristics. The current paper aims to introduce and investigate the previously performed studies about Poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate)-based biosensors for detecting galactose and glycerophospholipids.