Photocatalytic water treatment using nanocrystalline titanium dioxide (NTO) is a well-known advanced oxidation process (AOP) for environmental remediation. With the in situ generation of electron-hole pairs upon irradiation with light, NTO can mineralize a wide range of organic compounds into harmless end products such as carbon dioxide, water, and inorganic ions. Photocatalytic degradation kinetics of pollutants by NTO is a topic of debate and the mostly reporting Langmuir-Hinshelwood kinetics must accompanied with proper experimental evidences. Different NTO morphologies or surface treatments on NTO can increase the photocatalytic efficiency in degradation reactions. Wisely designed photocatalytic reactors can decrease energy consumption or can avoid post-separation stages in photocatalytic water treatment processes. Doping NTO with metals or non-metals can reduce the band gap of the doped catalyst, enabling light absorption in the visible region. Coupling NTO photocatalysis with other water-treatment technologies can be more beneficial, especially in large-scale treatments. This review describes recent developments in the field of photocatalytic water treatment using NTO.

The temperature dependence of the crystal structure and electronic properties of brownmillerite-like Ca(2.5)Sr(0.5)GaMn(2)O(8) has been studied by neutron powder diffraction and muSR spectroscopy. The results show that short-range 2D magnetic order begins to develop within the perovskite-like bilayers of MnO(6) octahedra approximately 50 K above the 3D Néel temperature of approximately 150 K. The bilayers show a structural response to the onset of magnetism throughout this temperature range whereas the GaO(4) layers that separate the bilayers only respond below the 3D ordering temperature. XANES spectroscopy shows that the sample contains Mn(3+) and Mn(4+) cations in a 1:1 ratio, and the behavior in the region of the Néel transition is interpreted as a local charge ordering. Electron diffraction and high-resolution electron microscopy have been used to show that the local microstructure is more complex than the average structure revealed by neutron diffraction, and that microdomains exist in which the GaO(4) tetrahedra show different orientations. It is argued that the bonding requirements of diamagnetic gallium control the electronic behavior within the perovskite-like bilayers.

BackgroundGold nanoparticles (AuNP) are extensively used as biophysical tools in the area of medicine and technology due to their distinct properties. However, vivid understanding of the consequences of biomolecule-nanomaterial interactions is still lacking. In this context, we explore the affect of conjugation of Gαi1 subunit (of heterotrimeric G-proteins) to AuNP and examine its consequences. We consider two bio-conjugation strategies covalent and non-covalent binding.ResultsAffinity of the AuNP to the Gαi1 is 7.58 × 10 12 M-1. AuNP conjugated Gαi1 exhibits altered kinetics of activation, non-covalent bio-conjugates displays retarded kinetics, up to 0.88 fold when GTPγS was used as ligand, of protein activation contrary to covalent conjugates which accelerates it to ~ 5 fold. Conjugation influence intrinsic Gαi1 GTPase function in conflicting modes. Non-covalent conjugation inhibits GTPase function (decrease in activity upto 0.8 fold) whilst covalent conjugation drastically accelerates it (12 fold increase in activity). Altered basal nucleotide uptake in both types of conjugates and GTPase function in non-covalent conjugate are almost comparable except for GTPase property of covalent conjugate. The effect is despite the fact that conjugation does not change global conformation of the protein.ConclusionThese findings provide clear evidence that nanoparticles, in addition to ‘passive interaction’ with protein (biomolecule), can interact “actively” with biomolecule and modify its function. This concept should be considered while engineering nanoparticle based delivery systems in medicine.

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