Mesoporous Alumina Films: Effect of Oligomer Formation toward Mesostructural Ordering

Alumina films with <i>Im</i>3̅<i>m</i>, <i>Ia</i>3<i>d</i>, and onion-like mesopores have been synthesized using a single sol composition derived from an modified alumina precursor (MAP), partial acetylacetone (acac) chelated aluminum secondary butoxide (ASB/acac = 1:0.5). We observed that MAP undergoes oligomerization with aging time and the differently aged MAP generates different micellar structures in the presence of P123 in alumina sols, and forms differently ordered mesostructured coatings. The time-dependent changes in the chemical nature of the MAP have been studied through ATR-FTIR spectroscopy. The nature of micellar transformations in the sols have been studied by transmission SAXS investigations. It has been observed that the size of the micelles gradually increases with time. On aging, MAP contains more bridging alkoxide groups with lesser hydrophilic characteristics; this reduces its interaction with the hydrophilic groups in the P123 micelle. Therefore, a mesostructure with low curvature is gradually formed in the sol due to the rigid nature of cross-linked MAP. Low angle XRD and TEM studies of the coatings obtained from the above sols have confirmed the generation of three distinctly different types of ordered mesoporous arrangements after heat treatments. The time-induced mesophase transformation mechanism has been proposed based upon the experimental results. The study reveals transformation of a modified Al alkoxide solution with respect to time and its successful use to obtain mesoporous alumina films of different ordered structures on glass

Synthesis of Equimolar Pd–Ru Alloy Nanoparticles Incorporated Mesoporous Alumina Films: A High Performance Reusable Film Catalyst

We report the synthesis of equimolar Pd–Ru alloy nanoparticles (NPs) incorporated mesoporous alumina films (Pd–Ru/MAF) by the sol–gel route. The synthetic strategy involves homogeneous mixing of the Pd²⁺ and Ru³⁺ ions in the alumina sol containing P123 micelles. Dip-coated films, prepared on ordinary glass substrates, were thermally reduced at a relatively lower temperature (500 °C) to generate equimolar Pd–Ru/MAF with a nominal molar composition of Pd:Ru:AlO_1.5 = 2:2:96. Electron microscopy studies revealed uniformly distributed Pd–Ru alloy NPs in a mesoporous alumina–alumina sphere composite film matrix. The P123/alumina nanocomposite acted as an excellent breeding medium to form Pd–Ru (∼1:1) alloy NPs despite the poor miscibility of the two metals. Pd–Ru/MAF showed excellent catalytic performances with highest normalized rate constant values (5.43 × 10¹⁴ min^–1 mol^–2) and possessed good reusability compared to the corresponding monometallic analogues in the reduction of aqueous 4-nitrophenol in the presence of NaBH₄ at 25 °C

Low Temperature Fabrication of Photoactive Anatase TiO₂ Coating and Phosphor from Water–Alcohol Dispersible Nanopowder

Low temperature fabrication of durable photoactive anatase TiO₂ coatings (on glass and plastic substrates) has been accomplished using the synthesized water and water-EtOH dispersible organic-free TiO₂ nanopowder. This nanopowder has been synthesized by refluxing the mixture of Ti­(OiPr)₄, EtOH, and H₂O in the presence of excess NO₃^– ion as a stabilizer at 80 °C for 24 h. The nanopowder has a small crystallite size (∼5 nm) and a high specific surface area of about 268 m²g^–1. It is highly dispersible in water (up to 20 wt %), and the water–EtOH mixture (10 wt %) and the resulting dispersions are very stable. The water–EtOH (1:3 w/w) dispersion of the TiO₂ nanopowder (4–5 wt %) has been used to prepare transparent coatings on glass and flexible plastic (polypropylene and polycarbonate) substrates with a surface hardness of ∼2–3 and 1–2 H, respectively, and good adhesion (5B; high quality). The reasons behind good adhesion and hardness of these coatings have been discussed. Such coatings on plastic and glass substrates have been used as reusable photocatalysts for degradation of toxic dye (methylene blue) to show the self-cleaning property under UV (365 nm) and visible light (Xenon source; 1 sun) sources. Further, by using this TiO₂ powder, a fluorescent ZnS:Mn/TiO₂ phosphor can be easily prepared at a much lower temperature

Correction to “Size Evolution of Protein-Protected Gold Clusters in Solution: A Combined SAXS-MS Investigation”

Correction to “Size Evolution of Protein-Protected Gold Clusters in Solution: A Combined SAXS-MS Investigation

Size Evolution of Protein-Protected Gold Clusters in Solution: A Combined SAXS–MS Investigation

We report a combined small-angle X-ray scattering (SAXS) and mass spectrometric (MS) study of the growth of gold clusters within proteins, in the solution state. Two different proteins, namely, lysozyme (Lyz) and bovine serum albumin (BSA), were used for this study. SAXS study of clusters grown in Lyz shows the presence of a 0.8 nm gold core, which is in agreement with the Au₁₀ cluster observed in MS. Dynamic light scattering suggests the size of the cluster core to be 1.2 nm. For BSA, however, a bigger core size was observed, comparable to the Au₃₃ core obtained in MS. Concentration- and time-dependent data do not show much change in the core size in both SAXS and MS investigations. When metal–protein adducts were incubated for longer time in solution, nanoparticles were formed and protein size decreased, possibly due to the fragmentation of the latter during nanoparticle formation. The data are in agreement with dynamic light scattering studies. This work helps to directly visualize cluster growth within protein templates in solution