Effect of CdSe Nanoparticles on the Growth of Te Nanowires: Greater Length and Tortuosity and Nonmonotonic Concentration Effect

Abstract

Improved control over nanowire (NW) geometry and composition offers multiple benefits for design material and devices, including uses in complex nanoelectronic circuits, facilitating their organization on substrates, providing more efficient charge transport over large distances, and greater mechanical strength. Te NWs have many interesting thermoelectric, piezoelectric, conducting, and photoconducting properties and are highly reactive with numerous chemicals, allowing Te NWs to be used as templates for NWs of other compositions. Te NWs are made in this work from CdTe nanoparticles (NPs) by slow oxidation. Te NWs with average lengths of 6.63 ( 1.07 µm and aspect ratios of 50 were initially formed. Unexpectedly, the presence of CdSe NPs results in a drastic increase in the length, aspect ratio, and tortuosity of the Te NWs. We believe that Se 2is being incorporated into the Te seeds as elemental Se, fouling them and reducing the number of viable Te seeds, which allows longer Te NWs to form. Excessive amount of CdTe NPs stops the growth of Te NWs completely making the concentration dependence strongly nonmonotonic. The longest tortuous NWs grown in this fashion have lengths of 15.56 ( 4.16 µm and aspect ratios 103. This work reveals a novel process taking place between growing NW and NPs. These finding indicate advantages of using NPs for reaction control for preparation of NW with high practical relevance.

Nanoparticle Assemblies into Luminescent Dendrites in Shrinking Microdroplets

“…Decrease of the long-range electrostatic repulsion by increasing ionic strength caused compaction of the assemblies whereas reducing interparticle attraction by irradiation with light triggered NP dis-assembly. Complementing the previous data on solvent effects, the data demonstrate that the microscale NP environment can alter the NP assembly patterns. The experimental set up is simple and should be adaptable for modulating the self-assembly of many NPs.…”

“…The fluorescence spectrum of the extended dendrites exhibits a distinct blue shift (λ em = 515 nm), whereas the spectrum of the compact dendrite shows a red shift of a few nanometers (λ em = 555 nm) compared with the as-prepared CdTe solution (λ em = 550 nm) (Figure S6A). The previously reported NP dentritic structures showed only red shift (refs and ) and, to the best of our knowledge, this is the first observation of blue shifts in dentritic structures although it is common for other NP assemblies when CdTe transforms into CdS …”

Controlled transformation of aqueous CdTe quantum dots → Te-rich CdTe nanorods → second CdTe QDs

“…attributed to the introduction of L-cys. In previous studies, [24][25][26] the addition of EDTA (a strong complexing agent for Cd 2+ ions) has been proven to induce the fast decomposition of CdTe QDs and the resulting complete transformation of CdTe to Te (Te 22 anions released from the decomposition of CdTe QDs could be easily oxidized to Te in water (i.e., 2Te 22 + O 2 + 2H 2 O A 2Te + 4OH 2 ; the redox potential is 21.14 V for Te 22 /Te; 0.401 for O 2 / OH 2 )). Here, similar to EDTA, L-cys can also destabilize CdTe QDs to release Te 22 anions due to the strong complexing ability, whereas different from EDTA, L-cys, a thiol molecule, can act as the stabilizer the synthesis of water-soluble CdTe nanocrystals simultaneously (the complexing ability of L-cys with Cd 2+ ions might be weaker than that of EDTA).…”

“…Using existing QDs as the starting point for making other nanomaterials is receiving increasing attention. 13,[18][19][20][21][22][23][24][25][26][27][28] This method allows one to easily and independently control the chemical compositions, structures and morphologies of nanostructured materials. Hence, in this study, using aqueous CdTe QDs as the starting material, Te-rich CdTe NRs were synthesized following a method modified from those of previous works for water-soluble CdTe nanorods (see the Experimental section).…”

“…[14][15][16][17] To our knowledge, the shape transformation of aqueous CdTe nanocrystals from QDs to nanorods, initiated by Kotov et al in 2002, 18 is probably the most successful example. [19][20][21][22] Subsequently, they further prepared other inorganic nanomaterials, such as nanosheets, 23 Se nanowires, Te nanowires 24,25 and angled Te nanocrystals 26 using CdSe or CdTe QDs as the starting material of the synthesis. Here, it should be mentioned that spontaneous CdTe A alloy A CdS transition of stabilizer-depleted CdTe nanoparticles induced by EDTA was found for the first time in 2006.…”