Herein, a simple approach based on tailoring the surface charge of nanoparticles, NPs, during the preparation to boost the electrostatic attraction between NPs and the organic pollutant was investigated. In this study, chargeable titania nanoparticles (TiΟ2 NPs) were synthesized via a hydrothermal route under different pH conditions (pH = 1.6, 7.0 and 10). The prepared TiΟ2 NPs were fully characterized via various techniques including; transmission electron microscopy (TEM), X-ray diffraction (XRD), N2 adsorption/desorption, X-ray photoelectron spectroscopy (XPS), Ultraviolet–visible spectroscopy (UV-Vis) and dynamic light scattering (DLS). The influence of the preparation pH on the particle size, surface area and band gap was investigated and showed pH-dependent behavior. The results revealed that upon increasing the pH value, the particle size decreases and lead to larger surface area with less particles agglomeration. Additionally, the effect of pH on the surface charge was monitored by XPS to determine the amount of hydroxyl groups on the TiO2 NPs surface. Furthermore, the photocatalytic activity of the prepared TiΟ2 NPs towards methylene blue (MB) photodegradation was manifested. The variation in the preparation pH affected the point of zero charge (pHPZC) of TiO2 NPs, subsequently, different photocatalytic activities based on electrostatic interactions were observed. The optimum efficiency obtained was 97% at a degradation rate of 0.018 min−1 using TiO2 NPs prepared at pH 10.

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We explored the applicability of different metal oxide nanoparticles (NPs; ZnO, TiO, FeO, and CeO) for the optical imaging and mass spectrometric determination of small drug molecules in latent fingerprints (LFPs). Optical imaging was achieved using a dry method-simply dusting the LFPs with a minute amount of NP powder-and still images were captured using a digital microscope and a smartphone camera. Mass spectrometric determination was performed using the NPs as substrates for surface-assisted laser desorption ionization/mass spectrometry (SALDI-MS), which enabled the detection of small drug molecules with high signal intensities. The reproducibility of the results was studied by calculating the % error, SD, and RSD in the results obtained with the various metal oxide NPs. Collectively, the findings showed that using NPs can boost the intensity of the detected signal while minimizing background noise which is an issue predominantly associated with conventional organic matrices of MALDI-MS. Among the four metal oxide NPs, utilization of the FeO NPs led to the best SALDI performance and the highest detection sensitivity for the analytes of interest. The study was then extended by investigating the influence of time elapsed since the generation of the LFP on the detection of drug molecules in the LFP. The results demonstrated that this method allows the analysis of drug molecules after as long as one week at low and intermediate temperatures (0 and 25 °C). Therefore, the SALDI analysis of small molecules using inorganic NPs, which can be implemented in forensic laboratories for screening and detection purposes, as a powerful alternative to the use of organic matrices. Graphical abstract ᅟ.

Water pollution from the continuous disposal of hazardous substances has become a serious issue and a global concern for the environment and public health. Removal of these pollutants from water is an ongoing challenge, and several approaches have been proposed and applied for this purpose. Adsorption is one of the common and most efficient approaches often used because it is simple, quick processing, inexpensive, and eco-friendly. Polyoxometalates (POMs) are a well-known class of metal–oxygen cluster compounds with tunable structure and size and highly electronegative and oxo-enriched surfaces. Owing to their electronic and physical properties, they have attracted considerable attention in the field of pollutants removal from wastewater. This review discusses the advances made over the last 10 years in the removal of toxic pollutants from wastewater using POMs-based materials. Furthermore, we summarize the recent synthetic strategies used to modify POMs-based materials and their applications in adsorption of pollutants. Knowledge gaps and current challenges in this research area are also discussed to support the development prospect of these materials for industrial use.

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