Chemically made, atomically precise phosphine-stabilized clusters Au9(PPh3)8(NO3)3 were deposited on titania and silica from solutions at various concentrations and the samples heated under vacuum to remove the ligands. Metastable induced electron spectroscopy was used to determine the density of states at the surface, and X-ray photoelectron spectroscopy for analysing the composition of the surface. It was found for the Au9 cluster deposited on titania that the ligands react with the titania substrate. Based on analysis using the singular value decomposition algorithm, the series of MIE spectra can be described as a linear combination of 3 base spectra that are assigned to the spectra of the substrate, the phosphine ligands on the substrate, and the Au clusters anchored to titania after removal of the ligands. On silica, the Au clusters show significant agglomeration after heat treatment and no interaction of the ligands with the substrate can be identified.

Chemically synthesized atomically precise gold clusters stabilized by triphenylphosphine ligands [Au9(PPh3)8]­(NO3)3] were deposited onto the surface of titania fabricated via atomic layer deposition. The titania surface was pretreated by heating and sputtering. After deposition of the clusters onto pretreated titania, the samples were heated at 200 °C for 20 min under ultrahigh vacuum and subsequently investigated using metastable-induced electron spectroscopy to study the electronic structure of the outermost layer of the sample and X-ray photoelectron spectroscopy to determine the chemical composition of the surface of the sample. The former study revealed that two reference spectra are needed to explain the electronic structure of the sample. One reference spectrum is related to the titania substrate, while the second spectrum is related to the presence of the Au cluster cores and the ligands removed from the cluster cores. The latter study found that the Au 4f peak is shifted to lower binding energy and the P 2p peak to higher binding energy after heating. These are interpreted in the light of ligand removal and size evolution of Au particles upon heating of the clusters on titania. The important outcome of the present work is that defects introduced at the ALD titania surface via sputtering and heating strongly reduce the agglomeration of the Au clusters adsorbed to the surface.

Triphenylphosphine ligand-protected Au9 clusters deposited onto titania nanosheets show three different atomic configurations as observed by scanning transmission electron microscopy. The configurations observed are a 3-dimensional structure, corresponding to the previously proposed Au9 core of the clusters, and two pseudo-2-dimensional (pseudo-2D) structures, newly found by this work. With the help of density functional theory (DFT) calculations, the observed pseudo-2D structures are attributed to the low energy, de-ligated structures formed through interaction with the substrate. The combination of scanning transmission electron microscopy with DFT calculations thus allows identifying whether or not the deposited Au9 clusters have been de-ligated in the deposition process.

Au 9 (PPh 3 ) 8 )](NO 3 ) 3 (Au 9 ) clusters were deposited onto sputtered ALD titania surfaces. Atomic force microscopy (AFM) was used to determine the height and distributions of the Au 9 clusters over the titania surface fabricated using atomic layer deposition (ALD). Synchrotron X-ray photoelectron spectroscopy (XPS) was used to derive information about the degree of agglomeration of the Au 9 clusters due to the annealing process. Both AFM and XPS show that the Au 9 clusters deposited on ALD titania are partially agglomerated after annealing. Deposition of the [Au 9 (PPh 3 ) 8 )](NO 3 ) 3 clusters on sputtered ALD titania is compared with deposition of the same cluster on titania nanosheets of previous work.

Metal oxide titanium dioxide (TiO2) nanoparticles were synthesized by using a simple and economical sol-gel method. The prepared nanoparticles were used to evaluate methylene blue dye degradation and as catalysts in the oxidation of benzaldehyde. The crystallite size of the titanium dioxide nanoparticle was 18.3 nm, which was confirmed by X-ray diffraction analysis. The spherical morphology was confirmed by scanning electron microscopy (SEM), and the elemental composition of the nanoparticle was found by energy dispersive X-ray (EDAX) analysis. The anatase form of the nanoparticle was confirmed by the bandgap 3.2 eV, which was measured using UV–DRS analysis. The bond between metal and oxygen was confirmed by the peaks at 485 and 606 cm–1 analyzed by Fourier transform infrared analysis (FTIR). The efficiency of the catalyst in dye degradation was 60.08, 68.38, and 80.89% with respect to 50, 75, and 100 mg catalyst weight. The yield % of benzoic acid was 94%, and the reduction efficiency against 4-nitrophenol was 98.44%.

Au9 clusters forming groups of clusters on titania nanosheets at least partially consist of individual clusters both before and after annealing. Au9 clusters also can attach as individual clusters.

The current study aims to synthesize bimetal oxide nanoparticles (zinc and manganese ions) using the carica papaya leaf extract. The crystallite size of the nanoparticle from X-ray diffraction method was found to be 19.23 nm. The nanosheet morphology was established from Scanning Electron Microscopy. Energy-dispersive X-ray diffraction was used to determine the elemental content of the synthesized material. The atomic percentage of Mn and Zn was found to be 15.13 and 26.63. The weight percentage of Mn and Zn was found to be 7.08 and 10.40. From dynamic light scattering analysis, the hydrodynamic diameter and zeta potential was found to be 135.1 nm and −33.36 eV. The 1,1-diphenyl-2-picryl hydroxyl radical, hydroxyl radical, FRAP, and hydrogen peroxide scavenging tests were used to investigate the antioxidant activity of Mn-Zn NPs. Mn-Zn NPs have substantial antioxidant properties. The photocatalytic activity of the Mn-Zn NPs was assessed by their ability to degrade Erichrome black T (87.67%), methyl red dye (78.54%), and methyl orange dye (69.79%). Additionally, it had significant antimicrobial action S. typhi showed a higher zone of inhibition 14.3 ± 0.64 mm. Mn-Zn nanoparticles were utilized as a catalyst for p-nitrophenol reduction. The bimetal oxide Mn-Zn NPs synthesized using C. papaya leaf extract exhibited promising dye degradation activity in wastewater treatment. Thus, the aforementioned approach will be a novel, low cost and ecofriendly approach.

Polymers are long-chain, highly molecular weight molecules containing large numbers of repeating units within their backbone derived from the product of polymerization of monomeric units. The materials exhibit unique properties based on the types of bonds that exist within their structures. Among these, some behave as rubbers because of their excellent bending ability, lightweight nature, and shape memory. Moreover, their tunable chemical, structural, and electrical properties make them promising candidates for their use as sensing materials. Polymer-based sensors are highly utilized in the current scenario in the public health sector and environment control due to their rapid detection, small size, high sensitivity, and suitability in atmospheric conditions. Therefore, the aim of this review article is to highlight the current progress in polymer-based sensors. More importantly, this review provides general trends and challenges in sensor technology based on polymer materials.