Ultranarrow ZnSe Nanorods and Nanowires: Structure, Spectroscopy, and One‐Dimensional Properties

Abstract

Zinc selenide is an important wide-bandgap (2.8 eV) material [1] with a broad range of potential applications. It exhibits interesting photophysical phenomena involving green-blue light emission and high transmission in the infrared and the visible electromagnetic spectrum.[2] Nanoparticles of ZnSe, via quantum confinement, shape, size and surface dependent effects, hold promise for tuning the optical properties and for assembling the particles in nanoscale structures. ZnSe has been studied to a lesser extent compared with its 'closest of kin', CdS, CdSe, and ZnS nanoparticles. Spherical ZnSe particles have been produced and studied by several groups. [3][4][5] ZnSe shapes other than spheres have been synthesized and studied to a more limited extent. Several pioneering reports [6][7][8][9][10][11] have described various synthetic routes to produce ZnSe nanowires, and focus on their structural characterization and, occasionally, on their photoluminescence (PL) properties. The nanowires were typically ∼ 10-100 nm wide and several micrometers long. The narrowest reported ZnSe wires were 3-5 nm wide (with an average diameter of 19 nm) [7] and 5-50 nm wide.[8] Except for these narrowest of wires, all the other reported wires are wider than the Bohr diameter of (bulk) ZnSe (9 or 11.4 nm), [12] which limits the expected quantum confinement effects. We have found only one recent allusion to the production of ZnSe nanorods. [13] In a few cases, authors have used the term 'nanorods' for wide ZnSe particles with dimensions of 40-70 nm × 1.5-3 lm, [9] 50-100 nm × 5-15 lm, [10] and 16-20 nm × 120-279 nm, [11] all with relatively large aspect ratios. Here, both of the major dimensions of the particles are larger than the Bohr radius, and quantum confinement effects are expected to be very limited.In this communication, we report the production of uniform wurtzite ZnSe ultranarrow width (1.3 nm), 4.5 nm long nanorods, and 100-200 nm long nanowires with the same width, their characterization and their spectroscopic properties. The development of rods from more spherical nuclei is illustrated. Quantum-confinement effects are manifested in the light absorption and the PL of the particles. The narrow width, ∼ 1 nm, is reflected in the Raman spectrum. The uniformity of the rods and the wires is demonstrated by their spontaneous assembly into highly ordered two-dimensional (2D) supercrystals. This high uniformity and order, together with an intrinsic chemical bipolarity of the rods, is responsible for their one-dimensional growth and for the various unique, essentially one-dimensional processes they undergo, as well as for the polarization properties of their spectra.The synthesis makes use of ligating solvents, i.e., long-chain alkylamines, which enable a low temperature, one step, bench-top reaction of the relatively innocuous zinc acetate and selenourea precursors, to produce wurtzite ZnSe nanorods and nanowires. The nanorods and nanowires are of a uniform width and the nanorods are of a uniform length. The relative amount of r...

Ultrathin Nanowires—A Materials Chemistry Perspective

“…5c). [75] In all the examples mentioned above, very strong quantum confinement effects were observed, testifying to the crystallinity and small diameter of the wires. While it is true that oriented attachment is easier to obtain on structures possessing an anisotropic lattice, such as wurtzite, recent experiments have demonstrated that cubic structures can also undergo oriented attachment in spectacular ways.…”

“…[73] c) HRTEM image of ZnSe nanowires formed by reacting zinc acetate with selenourea in the presence of octadecylamine. [75] d,e) HRTEM and TEM images of PbSe nanowires formed by reacting lead oleate with trioctylphosphine selenide in the presence of oleic acid, and oleic acid and tetradecylphosphonic acid, respectively. [76] f,g) TEM and HRTEM images of PbS nanowires formed by thermal decomposition of lead hexadecylxanthate in the presence of trioctylamine.…”

“…Copyright 2006Copyright , 2005Copyright , 2007 American Chemical Society. Reproduced with permission from [75]. dipoles are formed, and how those dipoles affect the growth of the nanostructures.…”

The role of glutathione on shape control and photoelectrical property of cadmium sulfide nanorod arrays

“…The performance of the resultant devices may be improved because single crystal nanorod or nanowire arrays can offer direct pathways for carrier and thus accelerate transport rate and charge collection [11,15,16]. Many II-IV group nanorods, such as CdS, CdSe, CdTe, ZnS, ZnSe, and ZnTe, have been successfully synthesized in colloidal solutions [17][18][19][20][21][22]. However, except ZnO [23], there are only a few reports that describe the fabrication of aligned II-IV nanorod or nanowire arrays without involving of catalyst and/or templates [24][25][26][27][28].…”

A Semiconductor‐Nanowire Assembly of Ultrahigh Junction Density by the Langmuir–Blodgett Technique

“…The synthesis makes use of long-chain alkylamines as liganding solvents, which enable a low temperature, one step, bench-top reaction of the relatively innocuous zinc acetate and selenourea precursors, to produce ZnSe nanowires. [24] The nanowires are of very uniform width with an average diameter of 1.3 ± 0.1 nm and length of 100-200 nm (an aspect ratio of ∼ 75-150). The side-byside spacing between the wires is 2.0 ± 0.1 nm as measured from transmission electron microscopy (TEM) images, and can be varied by changing the chain length of the amine ligand.…”