Synthesis of hybrid polymethacrylate–noble metal (M = Au, Pd) nanoparticles for the growth of metal-oxide semiconductor nanowires

Abstract

Metal-oxide semiconductor nanowires (NWs) such as ZnO, b-Ga 2 O 3 and SnO 2 with diameters of tens of nanometres and lengths of many micrometres have been grown using micellar nanohybrids consisting of methacrylate-based diblock copolymers and noble metal nanoparticles (MNPs). Micellar Au and Pd MNPs with diameters as small as 2.3 ¡ 0.3 nm were deposited on Si(001) by spin coating or drop casting and metal-oxide NWs were grown by reactive vapor transport. A high yield of b-Ga 2 O 3 NWs with diameters of approximately 40 nm, lengths . 10 mm and a monoclinic crystal structure were obtained at 900 uC with the largest MNPs. These exhibited a broad, symmetric photoluminescence (PL) spectrum centred at 2.3 eV attributed to defect states situated energetically in the energy band gap of b-Ga 2 O 3 . We find that a reduction in the size of the MNPs below 10 nm leads to the formation of necklace like b-Ga 2 O 3 NWs via the encapsulation of the MNPs which act as catalytic centres for the formation of branched nanostructures along the length of the b-Ga 2 O 3 NWs that are also responsible for a blue shift in the PL at 2.8 eV as a result of quantum confinement. This was not observed upon reducing the density of MNPs or in the case of ZnO or SnO 2 NWs grown with the smallest of MNPs probably due to differences in surface energy. We show that polymethacrylatenoble MNPs may be patterned directly by electron beam lithography and may be exploited for the selective location growth of semiconductor NWs while we also discuss the difference between the sizes of the hybrid polymer-MNPs and MO NWs which is attributed to agglomeration.

Structural properties of SnO2 nanowires and the effect of donor like defects on its charge distribution

“…The top region of an NW showed lattice fringes of the {1–10} SnO 2 planes (0.335 nm). It should be noted that the amorphous like‐interfacial area between the SnO 2 NWs and Si occurs most likely due to the lateral spread and coalescence of the SnO 2 NWs during the initial stages of growth which has been clearly shown when using hybrid polymer coated Au metal nanoparticles 7.…”

“…More importantly SnO 2 NWs do not grow on plain Si(001) via a self‐catalytic mechanism like ZnO and Ga 2 O 3 . This permits selective area location growth on lithographically patterned Au on Si(001) via a vapour–liquid–solid (VLS) like mechanism 7. Furthermore, indium tin oxide (ITO) NWs belong to the class of transparent conducting oxides which are useful for solar cells, displays and sensors 8–10.…”

Low temperature and cost-effective growth of vertically aligned carbon nanofibers using spin-coated polymer-stabilized palladium nanocatalysts

“…the molar ratio of the vinyl pyridine units to the palladium salt was 18:1 and 38:1. The Pd-containing LauMA x -b-AEMA y micellar hybrids have been prepared in n -hexane by following a previously reported methodology [ 20 , 22 ]. Exemplarily, the procedure followed for the synthesis of the LauMA 120 -b-AEMA 67 /Pd micellar nanohybrids is described as follows: LauMA 120 -b-AEMA 67 (20 mg, 0.03 mmoles of AEMA units) was dissolved in n -hexane (5 mL).…”

“…The resulting solution was left to stir for 24 h at room temperature. The size of the palladium NPs generated within the micellar cores has been already reported [ 22 ]. The average diameter of the palladium NPs is 2.3 ± 0.3 nm for the LauMA 50 -b-AEMA 9 /Pd(solution A) and 8.8 ± 1.7 nm for LauMA 120 -b-AEMA 67 /Pd(solution B).…”