From 1D Chain to 3D Network:  Tuning Hybrid II-VI Nanostructures and Their Optical Properties

Abstract

In an effort to make semiconductor nanomaterials with tunable properties, we have deliberately designed and synthesized a family of novel organic-inorganic hybrid nanocomposites based on II-VI semiconductors with structures ranging from one-dimensional (1-D) chain to two-dimensional layer (2-D) to three-dimensional (3-D) framework. All nanostructures exhibit strong quantum confinement effect (QCE), while possessing a perfectly periodic arrangement. The optical absorption experiments show that all compounds generate a very large blue shift in the absorption edge (1.0-2.0 eV) due to the strong QCE. More significantly, their band edge shift and optical properties can be tuned by changing the dimensionality of inorganic motifs as well as overall crystal structures. Raman studies reveal that not only do these structures have distinctly different vibrational signatures from those of the II-VI host semiconductors, but they also differ significantly from each other as a result of changes in dimensionality. The crystal structures of these nanocomposite materials have been characterized by single crystal and/or powder X-ray diffraction methods. [ZnTe(pda)] (1; pda = propanediamine) is composed of 1-D chains of [ZnTe] with pda chelating to Zn atoms. [ZnTe(N(2)H(4))] (2; N(2)H(4) = hydrazine) and [ZnTe(ma)] (3; ma = MeNH(2) = methylamine) are two-dimensional (2-D) layered structures containing [ZnTe] slabs and terminal hydrazine (2) or methylamine (3) molecules. The crystal structures of [CdSe(en)(0.5)] (4; en = ethylenediamine) and [CdSe(pda)(0.5)] (5) are 3-D networks containing [CdSe] slabs bridged by bidentate organic diamine molecules. Crystal data for 1: Orthorhombic, space group Pbcm, a = 9.997(2), b = 6.997(1), c = 10.332(2) A, Z = 4. For 2: Monoclinic, space group P2(1), a = 4.2222(6), b = 6.9057(9), c = 7.3031(10) A, beta = 98.92(8) degrees, Z = 2. For 3: Orthorhombic, Pbca, a = 7.179(1), b = 6.946(1), c = 18.913(4) A, Z = 8. For 4: Orthorhombic, Pbca, a = 7.0949(3), b = 6.795(3), c = 16.7212(8) A, Z = 8. For 5: Orthorhombic, Cmc2(1), a = 20.6660(12), b = 6.8900(4), c = 6.7513(4) A, Z = 8.

Synthesis of Semiconducting Functional Materials in Solution: From II‐VI Semiconductor to Inorganic–Organic Hybrid Semiconductor Nanomaterials

“…8). [121][122][123][124] While possessing uniform and periodic crystal structures, the resultant threedimensional networks [MQ(L) 0.5 ] (M ¼ Mn, Zn, Cd; Q ¼ S, Se, Te; L ¼ diamine, deta) hybrid structures, exhibit a very large blue shift in their optical adsorption edge due to a strong quantum confinement effect (QCE) induced by the internal sub-nanostructures. [17,18,121] These compounds exhibit significantly enhanced electronic and optical properties, [121,[125][126][127][128][129][130] including tunable band gap as a result of strong quantum confinement effect (blue shifts up to $2 eV) and high bandedge absorption (e.g., 10-20 times higher in 3D-ZnTe(en) 0.5 compared to bulk GaAs) (Fig.…”

Tetraethylenepentamine‐Directed Controllable Synthesis of Wurtzite ZnSe Nanostructures with Tunable Morphology

“…That is, [ZnSe]-A C H T U N G T R E N N U N G (TEPA) 0.5 could serve as the precursor to ZnSe, similar to those of previous structures. [13] If the reaction time was prolonged to 6 h, the wurtzite ZnSe could be detected in the XRD pattern (Figure 4e-v). The characteristic peaks of ZnSe were remarkably intensified and those of the precursor were weakened and finally disappeared when the reaction time extended to 10 h (Figure 4e).…”

Hydrazine-cadmium tellurite hybrid microcrystals: An efficient precursor to porous cadmium telluride and tellurium architectures through its thermal decomposition

“…For example, a variety of organoamine-metal chalcogenide organic-inorganic hybrid materials have been synthesized and shown to have novel optical, electrical, and thermal expansion properties [2][3][4][5][6][7][8][9][10][11][12]. In particular, various hydrazinebased hybrid materials can be synthesized by using hydrazine as both solvent and reagent because of its high solubility and reducing capability toward chalcogenide elements.…”