Search

Bismuth oxides were synthesized from bismuth carbonate using the sol-gel method. Studies have described the formation of Bi 2 O 3 , as a precursor of HNO 3 dissolution, and intermediate oxides, such as Bi x O y when using H 2 SO 4 and H 3 PO 4 . The average size of the crystallite calculated from Scherrer's formula ranged from 9 to 19 nm, according to X-ray diffraction. The FTIR analysis showed the presence of specific Bi 2 O 3 bands when using HNO 3 and of crystalline phases of "bismuth oxide sulphate" when using H 2 SO 4 and "bismuth phosphate" when using H 3 PO 4 . The TG curves showed major mass losses and specific thermal effects, delimited in four temperature zones for materials synthesized with HNO 3 (with loss of mass between 24% and 50%) and H 2 SO 4 (with loss of mass between 45% and 76%), and in three temperature zones for materials synthesized with H 3 PO 4 (with loss of mass between 13% and 43%). Further, the thermal stability indicates that materials have been improved by the addition of a polymer or polymer and carbon. Confocal laser scanning microscopy showed decreased roughness in the series, [Bi x O y ] N > [Bi x O y -6% PVA] N > [Bi x O y -C-6% PVA] N , and increased roughness for materials [Bi x O y ] S , [Bi x O y -6% PVA] S , [Bi x O y -C-6% PVA] S , [Bi x O y ] P , [Bi x O y -6% PVA] P and [Bi x O y -C-6% PVA] P . The morphological analysis (electronic scanning microscopy) of the synthesized materials showed a wide variety of forms: overlapping nanoplates ([Bi x O y ] N or [Bi x O y ] S ), clusters of angular forms ([Bi x O y -6% PVA] N ), pillars ([Bi x O y -6% PVA] S -Au), needle particles ([Bi x O y -Au], [Bi x O y -6% PVA] S -Au, [Bi x O y -C-6% PVA] S -Au), spherical particles ([Bi x O y -C-6% PVA] P -Pt), 2D plates ([Bi x O y ] P -Pt) and 3D nanometric plates ([Bi x Oy-C-6% PVA] S -Au). For materials obtained in the first synthesis stage, antimicrobial activity increased in the series [Bi x O y ] N > [Bi x O y ] S > [Bi x O y ] P . For materials synthesized in the second synthesis stage, when polymer (polyvinyl alcohol, PVA) was added, maximum antimicrobial activity, regardless of the microbial species tested, was present in the material [Bi x O y -6% PVA] S . For the materials synthesized in the third stage, to which graphite and 6% PVA were added, the best antimicrobial activity was in the material [Bi x O y -C-6% PVA] P . Materials synthesized and doped with metal ions (gold or platinum) showed significant antimicrobial activity for the tested microbial species.

Active and stable materials that utilize solar radiation for promoting different reactions are critical for emerging technologies. Two of the most common polymeric carbon nitrides were prepared by the thermal polycondensation of melamine. The scope of this work is to investigate possible structural degradation before and after photoelectrochemical testing. The materials were characterized using synchrotron radiation and lab-based techniques, and subsequently degraded photoelectrochemically, followed by post-mortem analysis. Post-mortem investigations reveal: (1) carbon atoms bonded to three nitrogen atoms change into carbon atoms bonded to two nitrogen atoms and (2) the presence of methylene terminals in post-mortem materials. The study concludes that polymeric carbon nitrides are susceptible to photoelectrochemical degradation via ring opening.

Polymer electrolyte membrane fuel cells require cheap and active electrocatalysts to drive the oxygen reduction reaction. Nitrogen-doped carbons have been extensively studied regarding their oxygen reduction reaction. The work at hand looks beyond the nitrogen chemistry and brings to light the role of oxygen. Nitrogen-doped nanocarbons were obtained by a radio-frequency plasma route at 0, 100, 250, and 350 W. The lateral size of the graphitic domain, determined from Raman spectroscopy, showed that the nitrogen plasma treatment decreased the crystallite size. Synchrotron radiation photoelectron spectroscopy showed a similar nitrogen chemistry, albeit the nitrogen concentration increased with the plasma power. Lateral crystallite size and several nitrogen moieties were plotted against the onset potential determined from oxygen reduction reaction curves. There was no correlation between the electrochemical activity and the sample structure, as determine from Raman and synchrotron radiation photoelectron spectroscopy. Near-edge X-ray absorption fine structure (NEXAFS) was performed to unravel the carbon and nitrogen local structure. A difference analysis of the NEXAFS spectra showed that the oxygen surrounding the pyridinic nitrogen was critical in achieving high onset potentials. The work shows that there were more factors at play, other than carbon organization and nitrogen chemistry.

Pharmaceuticals and pesticides are emerging contaminants problematic in the aquatic environment because of their adverse effects on aquatic life and humans. In order to remove them from water, photocatalysis is one of the most modern technologies to be used. First, newly synthesized photocatalysts were successfully prepared using a sol-gel method and characterized by different techniques (XRD, FTIR, UV/Vis, BET and SEM/EDX). The photocatalytic properties of TiO 2 , ZnO and MgO nanoparticles were examined according to their removal from water for two antibiotics (ciprofloxacin and ceftriaxone) and two herbicides (tembotrione and fluroxypyr) exposed to UV/simulated sunlight (SS). TiO 2 proved to be the most efficient nanopowder under UV and SS. Addition of (NH 4 ) 2 S 2 O 8 led to the faster removal of both antibiotics and herbicide fluroxypyr. The main intermediates were separated and identified for the herbicides and antibiotic ciprofloxacin. Finally, the toxicity of each emerging pollutant mixture and formed intermediates was assessed on wheat germination and biomass production.

A facile sol-gel route has been applied to synthesize hybrid silica-PVA-iron oxide nanocomposite materials. A step-by-step calcination (processing temperatures up to 400 °C) was applied in order to oxidize the organics together with the iron precursor. Transmission electron microscopy, X-ray diffraction, small angle neutron scattering, and nitrogen porosimetry were used to determine the temperature-induced morpho-textural modifications. In vitro cytotoxicity assay was conducted by monitoring the cell viability by the means of MTT assay to qualify the materials as MRI contrast agents or as drug carriers. Two cell lines were considered: the HaCaT (human keratinocyte cell line) and the A375 tumour cell line of human melanoma. Five concentrations of 10 µg/mL, 30 µg/mL, 50 µg/mL, 100 µg/mL, and 200 µg/mL were tested, while using DMSO (dimethylsulfoxid) and PBS (phosphate saline buffer) as solvents. The HaCaT and A375 cell lines were exposed to the prepared agent suspensions for 24 h. In the case of DMSO (dimethyl sulfoxide) suspensions, the effect on human keratinocytes migration and proliferation were also evaluated. The results indicate that only the concentrations of 100 μg/mL and 200 μg/mL of the nanocomposite in DMSO induced a slight decrease in the HaCaT cell viability. The PBS based in vitro assay showed that the nanocomposite did not present toxicity on the HaCaT cells, even at high doses (200 μg/mL agent)., Competing Interests: The authors declare no conflict of interest.