CdSe nanorods

Beneficial electro-optic effects have also been reported for semiconductor quantum dots doped into nematic liquid crystals. Khoo and Mallouck et al. published one of the earlier reports on suspensions of quantum dots in nematic liquid crystals [331], This work, however, focused on CdSe nanorods and will be discussed in a later section on two-dimensional nanomaterials in liquid crystals. 

EDOT) coated CdSe nanorods as a function of the quantity of poly [2-methoxy-5-(3, 7 -dimethy locty loxy)-1,4-phenylenevinylene] (MDMO-PPV) added (solvent CHC13).151 (Reprinted with permission from D. Aldakov et al., Eur. Phys. J. Appl. Phys. 2006, 36, 261-265. Copyright the European Physical Journal.)... 

Figure 18 Absorption (solid line) and PL (dashed line) spectra for medium-length (3.3 x 21 nm) CdSe nanorods, (a) Core nanorods without ZnS shell, (b) (Core)shell nanorods with thin CdS-ZnS shells ( 2 monolayers of shell material, where the CdS buffer shell comprises 35% of the total shell), (c) (Core)shell nanorods with medium CdS-ZnS shells ( 4.5 monolayers of shell material, where the CdS buffer shell comprises 22% of the total shell). PL spectra were recorded following photoannealing of the samples ...

Several polymer/polyelectrolyte-nanocrystal hybrid devices have been fabricated seeking to exploit the electro and photoluminescent properties of such material [179-188]. Device fabrication in all these cases is by low-cost self-assembly based techniques. These devices utilize thin films of these hybrids obtained either by multilayer deposition or drop/spin casting methods. Thus, solar cells have been made from poly(2-hexylthiophene)-CdSe nanorod multilayers, lasers from drop cast films of CdSe-titania composites and an infrared emitter from multilayers... 

Sun B. Q. and Greenham N. C. (2006), Improved efficiency of photovoltaics based on CdSe nanorods and poly(3-hexylthiophene) nanofibers , Phys. Chem. Chent. Phys. 8, 3557-3560. 

Fig. 56 ECE (A) of 7-, 30-, and 60-nm-long CdSe nanorods having a diameter of 7 nm. Current-voltage characteristics in the dark and O.lmW/cm (B) and at AM 1.5 solar spectrum (C) of P3HT CdSe hybrid solar cells. Photocurrent spectra of 60-nm-long nanorods with a diameter of 3 and 7 nm are compared in (D). From [250]. (Reprinted with permission from American Association for the Advancement of Science (AAAS), 2002. http //www.sciencemag.org)...

In a recent pubHcation, Alivisatos and co-workers reported the making of hybrid nanorods-polymer solar cells and their properties [122]. These solar cells were made by spin casting of a solution of both poly(3-hexylthiophene) (hole acceptor) and CdSe nanorods (electron acceptor) onto indium tin oxide glass substrates coated with poly(ethylene dioxythiophene) doped with polystyrene sulfonic acid and aluminum as a top contact. Nanorods have been used in composites so as to improve the carrier mobiHty. Indeed, the latter can be high for some inorganic semiconductors, but it is typically extremely low for conjugated polymers [123]. The use of the nanorods suppHes an interface for the charge transfer as well as a direct path for electrical transport. Also, because of their anisotropy, self-assembly of these nanorods is observed by electron microscopy. It shows... 

ELECTROMODULATION OF PHOTOLUMINESCENCE FROM CdSe NANORODS FILM... 

We studied photoluminescence (PL) properties of CdSe nanorods integrated in a thin film sandwiched between transparent electrodes to which an electric field applied. Nearly 20 % of PL quenching accompanied with the weak Stark shift have been observed. This effect is proposed to be used for PL modulation, in particular in the wavelength range beyond the range that traditional optoelectronic devices may cover. 

In the present paper, we investigate the influence of external electric field onto luminescence properties of chemically synthesized CdSe nanorods. Unlike quantum dots, the nanorods exhibit quantum confinement only in two dimensions. It is suggested that the electric field applied along the nanorods axis may provide an effective exciton dissociation resulting in the strong quenching of PL. 

CdSe/ZnS core-shell nanorods with size ca. 4x25 nm were synthesized according to published procedures [6]. The polymeric polymethylmetacrylate (PMMA) film with CdSe nanorods was placed between two transparent indium-tin oxide (ITO) electrodes sealed with epoxy glue. The electric field influence on the nanorods PL was studied by applying a constant dc voltage between transparent ITO electrodes. The PL was excited by 488 nm Ar-ion laser. The PL spectra at different voltages were measured by a combination of inverted microscope and liquid nitrogen (LN)-cooled CCD camera based spectrometer. 

Fig. 1 shows PL spectra of CdSe nanorods in PMMA film at different applied voltages. 

Figure 2. Differential PL (a) and normalized differential PL (b) spectra of CdSe nanorods vs. electric field applied.

We observed the sensitivity of PL properties of CdSe nanorods to applied electric field. This effect may find applications to make a luminescence modulator in which the incoming beam optically pumps the active part of the device (nanorods) and the resulting PL is electrically switched on and off with an applied voltage (input RF signal). 

Sometimes, nanorods can self-assemble into superlattices that behave like liquid crystals. Examples include the smectic-type superlattices of CU2S nanorods formed on thermal decomposition of copper thiolate at low temperature (140°C to 200°C Reference 78). Under appropriate conditions, nematic-type superlattices of CdSe nanorods are produced from a concentrated solution of the nanorods in a low boding solvent such as cyclohexane (79). When a solution of nanorods is destabilized by adding a nonsolvent, hquid crystal-hke assemblies (nematic, smectic) of a... 

For the preparation of CdSe/ZnS core-shell nanorods (86), first CdSe nanorods are prepared by decomposing a cadmium precursor, Cd(CHs)2, and selenium metal in the... 

Sih, B. C. and Wolf, M. O. (2007) CdSe Nanorods Functionalized with Thiol-Anchored Ohgothiophenes./. Phys. Chem. C, 111, 17184-92. 

Kwon, S., Shim, M., Lee, J.I., Lee, T.-W., Cho, K., Kim, J.K. Ultrahigh density array of CdSe nanorods for CdSe/polymer hybrid solar cells enhancement in short-circuit current density. J. Mato. Chem. 21, 12449 (2011)... 

Q. Zhang, T. P. Russell, T. Emrick, Synthesis and Characterization of CdSe Nanorods Functionahzed with Regioregular Poly(3-Hexylthiophene). Chem. 

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