Results show that nanoparticles (NPs) can be biosynthesized at room temperature on the reductive and chelating surfaces of Portobello mushroom spores (PMS). Using this green approach TiOx, Ag, Au, Ag-TiOx and Au-TiOx NPs have been prepared. These were characterized by TEM, SIMS and μFTIR-FTIR. TiOx/PMS, Ag-TiOx/PMS, Au-TiOx/PMS and Ag/PMS were active in bacterial inhibition towards Eschericia coli and Staphylococcus aureus, but Au/PMS was not active (suggesting a strong Au-PMS interaction). TiOx/PMS, Ag/PMS and Ag-TiOx/PMS were equally active in an antibacterial and an antifungal sense when tested against Asperillus and Candide. All samples (except Ag-TiOx/PMS and Au-TiOx/PMS) showed an interesting interaction with DNA. We report on the process of fine-tuning these antibacterial properties, progress on making these nanomaterials optically self-indicating and movement towards optical control of their antibacterial activity. Au-TiOx/PMS shows a surface plasmon resonance (SPR) with a maximum at 518 nm that might be useful in following its anti-bacterial properties (i.e. making the bionanomaterial self-indicating). The future of such green bio-nanomaterials is strong.
The potential for nanoengineering hybrid PVA hydrogel and hydrogel microsphere optical coatings is demonstrated with fine-tuning by the addition of (i) PNIPAm domains, (ii) water-hunting humectant CaCl2, and (ii) polystyrene or SiO2 colloidal crystals. The design and application onto substrates of the hydrogel scaffold is described. The addition of a temperature-triggered component as well as humectant and NIR reflectors are reported. The hybrid hydrogels appeared effective in sustainable adsorption cooling technology (ACT) over sustained periods. It is shown that the thermoresponsive (PNIPAm) domains act as an extra reserve, sweating water above 305K, prolonging the controlled release of water. It is also reported that the addition of humectant is crucial for the natural re-hydration of the hydrogels. For the moment PNIPAm microspheres have only short- lived ACT properties. Finally, coating with microspheres (MSs) in hydrogels produces a visible-NIR reflector effect that may allow optical feedback on ACT.
The surfaces of Portobello mushroom spores (PMS) have been used to produce Au and Ag nanoparticles, which are held thereon. They have then been overcoated with TiOx. These adsorbed more methyl orange (MO) pollutant from water than commercial P25 TiO2. After calcination they form biomimetic TiO2 (PMS) and removal of the biotemplate, they catalyse faster rates of MO from water (molecules/mg/s) than P25 anataserutile. Other biotemplates are now anticipated that will yield biomimetic photocatalysts with higher turnover number (s-1) removal of endocrine disrupters from water.
At the first ICF conference some of the present authors described advances towards low-index silica AR coatings and high-index zirconia HR coatings on fused silica for use at 1.06 micrometers , where silica and zirconia coatings showed good laser-induced damage thresholds. Here progress towards full 3(omega) mirrors at 351 nm using well defined sol-gels to produce the necessary SiO2-ZrO2 stacks is described in detail. Results suggest that these SiO2-ZrO2 stacks have higher laser damage resistance than previous ones and that MgF2 and Sc2O3 alternatives may improve the mirrors still further. The nature of damage caused to these coatings by Nd-YAG laser at 355 nm operating with pulses of 11 ns duration and a beam 1 mm in diameter is also reported.
Tantala and zirconia sol gel coatings, with simple preparation methods and high single layer laser damage thresholds at 1064 nm and 355 nm have been investigated. The sols are ethanol based and the coatings have high refractive indices and abrasion resistance. In situ microscopy and interferometric image suggest a thermal mechanism for damage at 1064 nm and inter- particle bonding, high strength and low porosity are linked to the high damage thresholds observed. The absence of exothermic reactions in the coatings at high temperatures and the closeness of absorption band edges to the laser wavelength are also considered to be factors influencing damage thresholds.
Silica sol-gel anti-reflective (AR) coatings have been investigated with particular reference to their laser induced damage threshold (LIDT) when subjected to irradiation from a Nd pulse laser at 1064 nm. Coatings (whose thickness was optimized for minimum reflection at 1064 nm) were deposited by spinning silica sols (average particle size 15 nm) formed by the base (ammonium hydroxide) catalyzed hydrolysis/condensation of TEOS in ethanol. Addition of polyethyleneglycols (PEGs) increased the size of the colloidal silica particles and also induced some particle aggregation in the sol, unlike a similar chain length diol. Increases in the LIDT of the coatings possibly depend upon the impurity levels, the wettability of the substrate, and the presence of PEG. LIDT improvements may be obtained by control of substrate and coating surface wettability, hydrophilicity, and surface chemistry.
Aqueous-inorganic (AIZ) and organic (OZ) zirconia sols have been synthesized by hydrothermal and alcothermal techniques. The size and structure of the ZrO2 nanoparticles of which the sols are composed are dependent on the reaction precursors and the synthesis conditions used. AIZ produced crystallites which are a mixture of monoclinic and metastable tetragonal ZrO2 while the OZ route yielded mainly amorphous particles. ZrO2 coatings deposited from both sols show comparable laser-induced damage thresholds to SiO2 sol-gel anti-reflective (AR) coatings. Thus, they could be candidates for the high index component in alternating SiO2/ZrO2 stacks for highly reflective mirrors. Here we describe sol-gel routes to ZrO2 coatings and the benefits in terms of resistance to laser damage of the addition of polyethylene glycol (PEG). The relevant microchemistry is discussed.
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