Chalcogenide semiconductor nanoparticles and their self-assembly structures have become the most explored group of semiconductor nanomaterials due to the interesting physics involved in quantum confinement, surface chemistry and variety of applications. In the last couple of decades, facile routes for their synthesis and strategies for controlling the size, shape and morphology have been reported. In the present review, synthesis strategies of size and shape controlled nanoparticles belonging to II-VI group of semiconductor chalcogenides are presented and each method for preparation of nanoparticles is critically analysed. Role of various factors that affect the nucleation and growth of nanoparticles is discussed at length. Nanoparticles and self-assemblies of CdSe, CdTe, HgTe and ZnSe are synthesized using new and facile single molecular precursor based noble route by our group that uses non-pyrophoric, low temperature and non-toxic chemicals, their properties and synthesis scheme are discussed as future development in this field. Some recent applications of chalcogenides QDs in the fields of solar cell, optical fibre amplifiers, biosensing and bo-imaging are discussed and reviewed.

CdTe nanorods are synthesized by solvothermal decomposition, using single source molecular precursors (SSMP) cadmium (II), complex of bis-(aminopropyl telluride) (SSMP-I) and cadmium (II) bis-(isopropyl telluro) propane (SSMP-II) and quinoline as solvent at relatively low temperature (210°C). As synthesized nanomaterials are structurally characterized by XRD and SEM, SEM micrographs revealed formation of rod shapes structures whose dimensions change with the source precursor molecule. The average crystallite size estimated from XRD data is 29.78 and 28.94 nm respectively using Precursors I and II. The average size of nanorods is 1.237 μm and 0.15μm respectively, estimated from SEM micrographs. These are much larger than the average crystallite size estimated from XRD data. This is attributed to the agglomeration of nanocrystallites as quinoline is not a good capping agent.

Semiconducting CdSe nanoparticles of a few nanometers in size were synthesised by solvothermal decomposition of novel, single-source molecular precursor Cd(II) complex of bis(aminoethyl)selenide ((NH2CH2CH2)2Se.CdCl2)) using quinoline as coordinating agent at 200°C. Particle size, structural phase, elemental compositions, morphology and optical bandgap of as-synthesised nanoparticles were characterised using X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDAX), transmission electron microscopy (TEM) and UV–Vis spectroscopy. The XRD pattern revealed that hexagonal CdSe nanocrystallites of ≈7 nm average size can be obtained by the solvothermal decomposition of ((NH2CH2CH2)2Se.CdCl2)) in quinoline. Elemental composition ratio of Cd:Se reveals non-stochiometric phase as confirmed standard less ZAF quantification, where Z, A and F are the matrix correction parameters, describing the atomic number effect (stopping power and backscatter effect), the absorption effect, and the fluorescence effect, respectively, in EDAX. Absorption spectra show blue shift in the absorption in nano particles with respect to their bulk counterpart and the calculated optical bandgap is estimated at 3·94 eV. This method has several advantages such as non-toxic and non-pyroforic single-source precursor, relatively low temperature and avoids the need for inert environment. However, quinoline used as coordinating agent has proved ineffective in capping and dispersing the nanoparticles and need to be further investigated.

Background: Metal chalcogenide nanomaterials represent an important group of efficient materials, in which the subtle variations in shape, size and phase of nano-powders resulted in physical properties (e.g., electronic and optical) differing from their bulk counterparts, which makes them useful materials for various technological devices. Objective: Synthesis and growth of chalcogenide nano powders from novel single source molecular precursors (i.e., Cd(II) bis-(aminopropane) selenide, Cd(II) bis-(aminoethane) telluride) for the production of cadmium chalcogenide (CdE, E= Se/Te) at nano scale. Method: Single source molecular precursor inserted in quinoline, acting as a coordinating solvent at suitable temperature, yielded vacuum dried powders of CdSe and CdTe nanomaterials. Results: The average particle size was estimated as CdSe ≈ 3 nm, and CdTe ≈ 29 nm from powder X-ray diffraction pattern of synthesized nanoparticles. The produced nanomaterials possess optical properties and calculated energy band gap of nanoparticles as CdTe = 5.2 eV and CdSe = 4.0 eV from UV-Visible spectra. Conclusion: The economical, harmless single source molecular method may be a striking technique to fabricate metal chalcogenide nanoparticles.