Design of Metal@Titanium Oxide Nano-heterodimers by Laser-Driven Photodeposition: Growth Mechanism and Modeling

Abstract

In order to circumvent the usual nucleation of randomly distributed tiny metallic dots photodeposited on TiO2 nanoparticles (NPs) induced by conventional UV lamps, we propose to synthesize well-controlled nanoheterodimers (NHDs) using lasers focused inside microfluidic reactors to strongly photoactivate redox reactions of active ions flowing along with nanoparticles in water solution. Since the flux of photons issued from a focused laser may be orders of magnitude higher than that reachable with classical lamps, the

Hole Scavenging and Electron–Hole Pair Photoproduction Rate: Two Mandatory Key Factors to Control Single-Tip Au–CdSe/CdS Nanoheterodimers

“…Concomitantly, Figure e (see also Figure S8) shows that the presence of DT and MS Au-DRs decreases, raising the important role of light intensity, through the electron–hole production rate, in ST photodeposition. It also corroborates the results obtained in photodeposition experiments using lamps (or LEDs) emitting typically around 10 mW/cm 2 , known to produce MS deposition; this behavior is retrieved here at low laser intensity …”

“…This ratio still increases and maintains at a value higher than 80% beyond I = 177 mW/cm 2 ( P L = 100 mW). This beam intensity threshold may be a signature of the crossover between the low and the high field growth regimes previously demonstrated in laser-deposition of silver and gold onto TiO 2 NPs as strongly beneficial for ST deposition . This shows the importance of the laser irradiation for the ST deposition at a given hole scavenger concentration and the existence of a concentration threshold necessary to reach such high yields.…”

“…In order to properly control this hole scavenging and since the reaction takes place in an organic phase, we chose methanol to play this role as it is fully miscible with toluene. Additionally, its scavenging efficiency in the presence of TiO 2 under UV excitation has been widely demonstrated, , motivating us to explore its role in CdSe/CdS DRs systems. To check the scavenging effect of methanol, we chose to keep constant all the other parameters involved in the reaction: beam intensity inside the cuvette I = 355 mW/cm 2 , [KAuCl 4 ] = 40 μM, [DR] = 2.5 nM, deposition time t = 8 min.…”

“…Most of the research concerning single-tip NHDs has been performed under the following conditions: low temperature, , long alkyl amine ligands, anaerobic conditions, or/and high reactivity gold precursors (AuCl 3 , AuCl), all of them mainly set to reduce the defect deposition, thereby improving the ratio of single-tip NHDs. Moreover, even if the presence of a hole scavenger has been shown to play a vital role in the photodeposition process of semiconductors (such as TiO 2 ), − it has rarely been mentioned as such in the photodeposition on a cadmium chalcogenide semiconductor. ,,, This is probably linked to the fact that even without the presence of a dedicated hole scavenger the chalcogenide anions forming the rods participate to the reduction of Au 3+ ions with a concomitant etching of the rods , or didodecyl dimethylammonium bromide (DDAB) and dodecylamine (DDA) a primary amine claimed to act not only as a reducing and stabilizing agent, but most probably also as a hole scavenger. ,, We should also mention that Kalisman et al commented on the necessary presence of a hole scavenger to favor the hydrogen yield during the photocatalytic reaction . Moreover, as far as we are aware, there is still no methodical research on the various parameters affecting the single-tip production, especially concerning the systematic variation of the ratios of single-tip (ST), double-tip (DT), and multiple-site (MS) hybrid nanoparticles (HNPs) even if the sites and size control have a great impact in catalysis and chirality .…”

Preparation and in vivo bacteriostatic application of PPDO-coated Ag loading TiO2 nanoparticles

“…Both the lattice size and crystallite size of Ag@TiO 2 nanoparticles were larger than those of pure anatase TiO 2 , indicating that Ag was definitely embedded into the crystal defects of TiO 2 37 . Characteristic 2θ peaks between 20° and 25° that belong to PPDO macromolecules could be observed in the XRD spectra of Ag@TiO 2 -PPDOs, and characteristic 2θ peaks of Ag and TiO 2 could also be observed 38 . The This indicates that PPDO macromolecules were grafted successfully onto the surface of Ag@TiO 2 nanoparticles.…”