Formation of Zn_1-xMn_xS Nanowires within Mesoporous Silica of Different Pore Sizes

Abstract

Arrays of highly ordered Zn(1-x)MnxS quantum wires with x ranging from 0.01 to 0.3 and with lateral dimensions of 3, 6, and 9 nm were synthesized within mesoporous SiO2 host structures of the MCM-41 and SBA-15 type. The hexagonal symmetry of these arrays (space group p6m) and the high degree of order was confirmed by X-ray diffraction and transmission electron microscopy (TEM) studies. Physisorption measurements show the progressive filling of the pores of the SiO2 host structures, while TEM and Raman studies reveal the wire-like character of the incorporated Zn(1-x)MnxS nanostructures. X-ray absorption near-edge structure, extended X-ray absorption fine structure, photoluminescence excitation (PLE), and electron paramagnetic resonance studies confirm the good crystalline quality of the incorporated Zn(1-x)MnxS guest species and, in particular, that the Mn2+ ions are randomly distributed and are situated on tetrahedrally coordinated cation sites of the Zn(1-x)MnxS wires for all x up to 0.3. The amount of Mn2+ ions loosely bound to the surface of the Zn(1-x)MnxS nanowires is less than 4% of the total Mn content even for the 3 nm nanostructures up to the highest Mn content of x = 0.3. The effects of the reduction of the lateral dimensions on electronic properties of the diluted magnetic semiconductor were studied by PLE spectroscopy. Due to the quantum confinement of the excitons in the wires an increase of the direct band gap with decreasing particle size is observed.

The modification of MoO3 nanoparticles supported on mesoporous SBA-15: characterization using X-ray scattering, N2 physisorption, transmission electron microscopy, high-angle annular darkfield technique, Raman and XAFS spectroscopy

“…In addition, the phase cancellation between the pore walls and the guest species MoO 3 leads to a decrease of the intensity of Bragg reflections, which is more pronounced for higher MoO 3 contents. This phenomenon is well known [17,40] and was also observed in [30].…”

“…For all materials, a type-IV isotherm is observed, which is the typical hysteresis loop of mesoporous materials [41], indicating that the incorporation of Mo species does not destroy the structure of mesoporous SBA-15. The pore sizes were calculated from the desorption branch of the isotherm using the Barrett-Joyner-Halenda (BJH) model, which is an appropriate method for determining changes in the pore-size distribution [17,18,42] and the BarrettEmmett-Teller (BET) equation was applied for calculation of specific surface areas. The isotherms have the following characteristic features: (1) the capillary condensation step, which is caused by the decrease of the pore sizes, typically at the relative pressure p/p 0 = 0.6-0.7 for pristine SBA-15, shifts to lower relative pressure p/p 0 = 0.4-0.6 after introduction of MoO 3 particles into the pores (Fig.…”

“…In addition to the studies of the formation of metal nanoparticles and nanowires, such as Pt [3][4][5], Pd [6][7][8][9], Au [3-5, 10, 11], Ag [3], and Ti [12], the formation of binary nanomaterials such as PbS [13], CdS [14], TiN [15], and GaN [16] within the nanoscale channels of these mesoporous materials have been explored. More recently, highly ordered quantum wires of Zn 1-x Mn x S [17] and Cd 1-x Mn x S [18] have been successfully synthesized within the mesopores of SBA-15.…”

Magnetic MnxGe1-x Dots for Spintronics Applications

“…The above results are supported by modeling results (Wang and Qian, 2006) although carrier mediated exchange has not yet to be experimentally verified in nanowires. Similarly, high Curie temperatures have been observed in other transition metal doped semiconductor nanostructures such as II-VI (including ZnO (Chang et al, 2003, Cui and Gibson, 2005, Baik and Lee, 2005, ZnS (Brieler et al, 2004, Radovanovic et al, 2005, CdS (Radovanovic et al, 2005)) and III-V (including GaN (Radovanovic et al, 2005, Choi et al, 2005b, GaAs (Jeon et al, 2004)), but only inconclusive reports have been published on the magneto-electric transport in these nanostructures. It could be attributed to the complicated ferromagnetic properties caused by precipitates, second-phase alloys and nanometer-scale clusters.…”

Synthesis of solid solutions of Cd1−xZnxS nanocrystals in the channels of mesostructured silica films

“…Using various approaches, CdS, ZnS, Zn 12x Mn x S, and Cd 12x Mn x S nanoparticles have also been synthesized in the channels of mesoporous silica. [7][8][9][10]12,[15][16][17][18] In this article, we focus on the TLCT approach that uses C n EO m non-ionic surfactants in a lyotropic liquid crystalline (LLC) mesophase as the templating agent. 11 A mixture of surfactant, acid (as a catalyst), tetramethylorthosilicate (TMOS, as silica source) and water first produces a liquid mixture that undergoes a transformation, with hydrolysis and condensation, of the silica source to form an LC mesophase and then with further polymerization a solid phase.…”