Michael V. Liga

Bio: Michael V. Liga is an academic researcher from Rice University. The author has contributed to research in topics: Photocatalysis & Adsorption. The author has an hindex of 6, co-authored 6 publications receiving 2306 citations.

Simple route to enhanced photocatalytic activity of p25 titanium dioxide nanoparticles by silica addition.

Abstract: Silica doped TiO2(P25) nanoparticles are tested for its photocatalytic activity in the degradation of bacteriophage MS2. During our studies it was found that treatment of TiO2(P25) in the glass flasks sealed with silicone grease resulted in a significant improvement in the catalytic activity of the titania. Further improvement can be made by the purposeful reaction of TiO2(P25) with 2.5 wt % silica. This non in situ method of incorporating silica to TiO2(P25) nanoparticles is tested for their role in killing of viruses, and it is found that the rate constant is three times higher to kill viruses with the addition of silica. BET measurements show no significant change/increase in the surface area of silica doped TiO2(P25)-SiO2, compared to the undoped TiO2(P25). Further studies show that the addition of silica increases the adsorption of viruses onto the catalyst. There is a significant difference in the activity of the TiO2(P25)-SiO2 samples in the presence of methanol, supporting the notion that hydroxide radical (HO·) is responsible for the antiviral action. The TiO2(P25)-SiO2 either produces more HO· than non silica-doped material, or the enhanced adsorption of MS2 to the catalyst results in greater exposure to the HO·, or both mechanisms may work in concert. XPS studies suggest the formation of silica species on the surface of the TiO2(P25), while UV-visible spectroscopy suggests that the presence of the silica results in a small increase in the measured band gap. We suggest that the enhanced catalytic activity is a result of increased adsorption and/or band bending which can occur at the interface within TiO2(P25)-SiO2. One result of this would be a reduction of the electron-hole recombination, the formation of a greater concentration of OH·, and hence an improved catalytic performance.

Silica decorated TiO2 for virus inactivation in drinking water--simple synthesis method and mechanisms of enhanced inactivation kinetics.

Abstract: A new method of modifying TiO2 photocatalysts with SiO2 is developed in which SiO2 nanoparticles are simply mixed with TiO2 in water under ambient conditions. This method does not require the use of toxic solvents or significant energy input. Although the SiO2 modification slightly reduces hydroxyl free radical production, the composite SiO2–TiO2 nanomaterials have markedly higher photocatalytic inactivation rates for a common surrogate virus, bacteriophage MS2 (up to 270% compared to the unmodified TiO2), due to the greatly improved adsorptive density and dark inactivation of MS2. The Langmuir isotherm describes the adsorption data well and shows that the TiO2 modified with 5% SiO2 has a maximum adsorption density qmax 37 times that of the unmodified TiO2. The Langmuir–Hinshelwood model fits the photocatalytic inactivation kinetic data well. The SiO2–TiO2 material produces a greater maximum initial inactivation rate yet a lower intrinsic surface reaction rate constant, consistent with the reduced hydroxy...

Single walled carbon nanotubes (SWNTs) as templates for the growth of TiO2: the effect of silicon in coverage and the positive and negative synergies for the photocatalytic degradation of Congo red dye

Abstract: Single walled carbon nanotubes (SWNTs) are used as scaffolds to grow titania (TiO2) under a range of different growth conditions. It is found that the titania growth occurring on SWNTs is significantly different in the presence of silica; this is contrary to prior reports, the important controlling factor for obtaining good coverage is not “nanoscopic HF bubbles”. The silica is either sourced from the reaction vessel if made from glass or may be added in the form of fumed silica: the greater the silicon content the greater the coverage of the SWNT. The adsorption and photocatalysis of organic Congo red dye on these hybrid titania covered SWNT materials are studied; while the adsorption of the dye onto the catalyst may be high, it is only in certain cases wherein it results in superior catalytic performance. The synergy between TiO2 and SWNTs with regard to photocatalysis is not always positive. The addition of silica promotes the complete coating of SWNT with TiO2, the resulting materials show very high absorption of Congo red but essentially no catalytic activity. In order to promote catalytic activity, it is necessary to have less full coverage of the SWNTs and the smallest average particle size of the grown titania. Intimate contact between the SWNT and the TiO2 is needed (rather than a physical mixture) for any catalysis, and the electronic properties of the SWNTs are clearly important since multiwalled carbon nanotubes appear to have little effect on altering the photocatalytic activity.

Graphitic Carbon Nitride (g-C3N4)-Based Photocatalysts for Artificial Photosynthesis and Environmental Remediation: Are We a Step Closer To Achieving Sustainability?

Abstract: As a fascinating conjugated polymer, graphitic carbon nitride (g-C3N4) has become a new research hotspot and drawn broad interdisciplinary attention as a metal-free and visible-light-responsive photocatalyst in the arena of solar energy conversion and environmental remediation. This is due to its appealing electronic band structure, high physicochemical stability, and “earth-abundant” nature. This critical review summarizes a panorama of the latest progress related to the design and construction of pristine g-C3N4 and g-C3N4-based nanocomposites, including (1) nanoarchitecture design of bare g-C3N4, such as hard and soft templating approaches, supramolecular preorganization assembly, exfoliation, and template-free synthesis routes, (2) functionalization of g-C3N4 at an atomic level (elemental doping) and molecular level (copolymerization), and (3) modification of g-C3N4 with well-matched energy levels of another semiconductor or a metal as a cocatalyst to form heterojunction nanostructures. The constructi...

Applications of nanotechnology in food packaging and food safety: Barrier materials, antimicrobials and sensors

Abstract: In this article, several applications of nanomaterials in food packaging and food safety are reviewed, including: polymer/clay nanocomposites as high barrier packaging materials, silver nanoparticles as potent antimicrobial agents, and nanosensors and nanomaterial-based assays for the detection of food-relevant analytes (gasses, small organic molecules and food-borne pathogens). In addition to covering the technical aspects of these topics, the current commercial status and understanding of health implications of these technologies are also discussed. These applications were chosen because they do not involve direct addition of nanoparticles to consumed foods, and thus are more likely to be marketed to the public in the short term.