CdTe Nanorods Research Articles

Energetics of Photoinduced Electron-Transfer Reactions Decided by Quantum Confinement

The photophysics of linear CdSe−CdTe nanorod heterostructures are reported. Charge-transfer emission and absorption bands are identified. Analysis of these bands reveals the factors governing photoinduced electron transfer from CdTe to CdSe, and it is thereby shown how quantum confinement effects decide the thermodynamic parameters of the Marcus−Hush theory. An important finding is the very small reorganization energy associated with the nuclear degrees of freedom (∼20 meV in toluene), which seems to be a characteristic of these nanoscale donor−acceptor systems and differentiates them from most analogous molecular systems. Therefore Marcus “inverted region” behavior is found to be typical for these systems. By analyzing the mixing between the CdTe exciton and the charge-transfer states for one sample, we find the electronic coupling matrix element that promotes the charge separation to be ∼50 meV.

Synthesis and Characterization of Wavelength-Tunable, Water-Soluble, and Near-Infrared-Emitting CdHgTe Nanorods

Water-soluble alloyed CdHgTe nanorods were synthesized in aqueous media using CdTe nanorods as a template. Their emission spectra were in the near-infrared and tunable according to material compositions (red-shifted with increased Hg content).

Electric-Field-Driven Accumulation and Alignment of CdSe and CdTe Nanorods in Nanoscale Devices

Local electric fields generated by nanopatterned electrodes were used to control the position and orientation of well-isolated as well as closely packed colloidal semiconducting CdTe and CdSe nanorods (NRs) drop-cast from solution. Postdeposition imaging using transmission-electron microscopy and atomic-force microscopy revealed strong NR alignment to the direction of the applied field and dense accumulation around and onto voltage-biased electrodes when deposited from dilute and concentrated solutions, respectively. The degree of alignment under the applied electric field is characterized by a nematic order parameter S approximately 0.8 in contrast to the zero-field case when S approximately 0.1.

The selective synthesis of water-soluble highly luminescent CdTe nanoparticles and nanorods: The influence of the precursor Cd/Te molar ratio

In this report, we initially systematically investigated the influence of the precursor Cd/Te molar ratio on the morphology of water-soluble thiol-stabilized CdTe nanocrystals. By only changing the precursor Cd/Te molar ratio, highly luminescent CdTe nanoparticles (NPs) and nanorods (NRs) can be prepared selectively in the presence of the same concentration single ligand ( l-cysteine or thioglycolic acid) system. A high precursor Cd/Te molar ratio leads to isotropic spherical growth, whereas a low Cd/Te molar ratio promotes the linear self-assembly of NPs into NRs. Thus, a new efficient strategy has been developed in aqueous phase to prepare selectively highly luminescent dot- or rod-shaped CdTe nanocrystals in single ligand system. Then, we further explored the influence of the properties of initial CdTe dispersions with different luminescence maxima on the formation of NRs. The experiment results revealed that the formation of CdTe NRs is also dependent on the properties of initial CdTe dispersions. CdTe NPs with short wavelength emission (∼520–550 nm) can self-assemble directly into high quality CdTe NRs after storage at room temperature.

A controllable synthesis of multi-armed CdTe nanorods

A simple, productive and low-cost route has been developed to synthesize multi-armedCdTe nanorods using myristic acid (MA) as a complex agent. The yield of this approachcan reach 75%. The dimension of the multi-armed nanorods can be controlled bytuning the molar ratios of Cd/Te and Cd/MA; the diameter can be changedfrom 2 to 7 nm while the length from 15 to 60 nm. The hexagonal structure wasconfirmed in x-ray diffraction analysis. However, it was assumed that one crystal iscomposed of the dominant hexagonal structure along with a cubic structure in thecore.

Hybrid solar cells with vertically aligned CdTe nanorods and a conjugated polymer

Vertically aligned CdTe nanorods were fabricated by electrodeposition and were applied for the active layer of solar cells after being combined with poly(3-octylthiophene) (P3OT), a conjugated polymer. The electrodeposited CdTe showed an n-type behavior with the electric resistivity and the electron density of 2×106Ωcm, 1.3×1010cm−3, respectively. Quantum efficiency curve of the hybrid solar cells exhibited a peak at the same wavelength as the optical absorption for CdTe nanorods. The hybrid solar cells demonstrated a power conversion efficiency of 1.06%, whereas the efficiency was only 0.0006% without the nanorods.

Luminescent CdTe quantum dots and nanorods as metal ion probes

Water-soluble luminescent thiol-capped CdTe QDs and nanorods have been synthesized and used to investigate the effect on their photoluminescence (PL) responses to divalent metal ions, such as zinc, calcium, magnesium, manganese, nickel, and cobalt ions. The change trends of PL were nearly similar for both CdTe QDs and nanorods. The zinc ions enhanced the photoluminescence, while the manganese, nickel, and cobalt ions quenched the PL. The effect on the PL response of CdTe QDs to divalent metal ions could be described by Langmuir-type binding model or Stern–Volmer-type equation. The CdTe nanorods were more sensitive to metal cations than QDs, and their enhancement mechanisms are different. CdTe QDs and nanorods maybe used as selective ion probes and developed as fluorescence sensors.

Preparation of Asymmetric Nanostructures through Site Selective Modification of Tetrapods

CdTe tetrapods have been deposited on a substrate and partially coated with a protective polymer layer, exposing just one arm. The exposed arm was then decorated with Au nanoparticles in a site selective fashion. The modified arms were readily broken off from the remainder of the tetrapods and released from the substrate, yielding CdTe nanorods asymmetrically modified with Au nanoparticles. These nanostructures with reduced symmetry may show interesting optoelectronic properties.

Hexagonal CdTe nanorods in spray deposited CdTe nanoparticle thin films

Nanoparticle CdTe thin films were deposited by spraying CdTe nanoparticles, synthesized by the solvothermal method and dispersed in 1-butanol, on glass substrates at a temperature of 200 °C. Films were deposited with and without a voltage applied to the nozzle during the deposition. X-ray diffraction of the film deposited without voltage showed cubic CdTe dominant peaks, while the films deposited with a voltage of 700 V showed hexagonal CdTe dominant peaks. TEM studies of the films deposited with an applied voltage of 700 V revealed the formation of nanorods having widths varying from 20 nm to 100 nm and being up to few microns long. Electron diffraction patterns for the films deposited with 700 V showed the formation of hexagonal CdTe nanorods with lattice parameters a =0.454 nm and c = 0.745 nm. The films deposited without voltage showed uniformly distributed spherical nanoparticles (average size ∼10 nm), and the lattice parameter a was found to be 0.645 nm. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

A Facile Synthesis of CdSe and CdTe Nanorods Assisted by Myristic Acid

Abstract A simple, productive, low-cost route has been developed to synthesize the high-quality 1-D nanorods of CdE (E = Se, Te) with 3–8 nm in diameter and 5–40 nm in length using myristic acid as a complexing agent. Moreover, the reaction is performed under mild conditions and relatively low temperatures. The X-ray powder diffraction patterns confirmed the CdE nanorods with wurtzite structure.

Mixed ligand system of cysteine and thioglycolic acid assisting in the synthesis of highly luminescent water-soluble CdTe nanorods.

Highly luminescent water-soluble CdTe nanorods were prepared with the assistance of the mixed ligand system of cysteine and thioglycolic acid; the aspect ratio and photoluminescence of the CdTe nanorods could be controlled by the refluxing time.