Biomolecule‐Assisted Reduction in the Synthesis of Single‐Crystalline Tellurium Nanowires

Abstract

are both localized on the substituted side fluorene groups), a sizeable increase in electron affinity (by~0.91 eV) is achieved in poly-S-m-Br-methoxy in comparison to S-methoxy. Such donor±acceptor molecular systems might not be appropriate for blue-light emission: the triplet energy is indeed bounded upwards by that of the substituted units, which itself relates to the donor/acceptor strengths (hence only weak electroactive groups, translating into small changes in HOMO±LUMO energies, will ensure high singlet±triplet energy separations); however, they yield the smallest bandgap among all investigated hosts for green-light emission.To summarize, we have performed DFT calculations in order to design molecular hosts suitable for efficient colortunable triplet emission. Focusing on the carbazole and spiro building blocks, the influence of molecular topology on the triplet excited-state properties has been explored.The DFT results indicate the following:d host materials suitable for blue-light-emitting devices can be designed by interconnecting CBZ and spiro monomers through their meta (3,6) positions. In this case, the triplet wavefunction is mostly localized over 2 phenyl rings and the calculated S 0 ±T 1 energy gap amounts to~3 eV.d sequential interconnection in para (2,7) and meta positions causes the triplet to be more delocalized (typically over 3 phenyl rings), which considerably lowers the triplet energy. This route can be used to prepare hosts that are suitable for green-light-emitting devices.d interconnecting monomers in para positions leads to the triplet being delocalized over~4 phenyl rings and further lowers the singlet-triplet energy gap. Such compounds, which are characterized by the lowest ionization potentials and highest electron affinities, are the best candidates to be used as hosts in red-light-emitting devices. To further improve charge injection while maintaining a constant singlet±triplet gap, a series of oligomers substituted with electroactive groups on the side fluorene moieties of their spiro units have been investigated. This approach was found to be successful in the case of molecular architecture involving para connections between the spiro units, as in these molecules the triplet is confined to the main backbone while the HOMO and LUMO are localized on the side fluorenes. In contrast, the lowest triplet state of the oligomers with interconnections in meta positions is localized on the side segments, because in this case the energy gain caused by the substitution overwhelms that due to the interactions along the backbone. Therefore, the highest triplet energy that can be achieved in such configuration is bounded by the S 0 ±T 1 energy difference in the isolated substituted chromophore. For both para and meta inter-connected oligomers, the proposed strategy enables the dramatic improvement of hole and electron injection in hosts for green-and red-light emission. ExperimentalComputational Details: Density functional theory (DFT) [10] calculations were performed using the B3LYP hybrid f...

Synthesis of Single Crystalline Tellurium Nanotubes with Triangular and Hexagonal Cross Sections

“…23 Komarneni and co-workers demonstrated a biomolecule, alginic acid, assisted synthesis of Te nanowires. 24 Zhu et al reported the microwave assisted synthesis of Te nanorods and nanowires. 25 Recently, He et al demonstrated the growth of shuttlelike scrolled tellurium nanotubes and nanowires in a wet chemical method using amino acids as a growth assisting agent.…”

“…This anisotropic structure induces Te toward 1D growth. 3,[21][22][23][24][25][26][27][28][29][30][31][32] Mayer and Xia reported the synthesis of Te nanotubes with hexagonal cross sections by reducing orthotelluric acid in ethylene glycol. 3 Wei et al synthesized Te nanotubes by a solvothermal process using N,N-dimethylformamide as a solvent and porous silica (MCM-41) as a growth assisting agent.…”

“…Most of the reported synthetic schemes for 1D tellurium nanostructures to date have used hydrazine, surfactant, biomolecules, other precursors, or some special experimental techniques. 3,[21][22][23][24][25][26][27][28][29][30][31][32] The present method used only tellurium metal powder for the growth of the nanotubes. We will discuss the influence of deposition temperature, pressure, the flow rate of argon gas, and the substrates used for the synthesis on the morphology of the 1D tellurium nanostructures in this work.…”

“…It has been considered to be an excellent candidate for use in future high-efficiency photoconductors, thermoelectric, and piezoelectric devices. 3,[21][22][23][24][25][26][27][28][29][30][31][32] Many functional materials can be easily synthesized by the reaction of tellurium with other elements. The crystal structure of Te is highly anisotropic with covalently bonded atoms forming unique helical chains.…”

Hydrothermal synthesis of selenium and tellurium nanorods

“…Nanoparticles exhibit significantly different properties relative to those of their corresponding bulk materials. Recently, much effort has been focused on preparing t-Se and t-Te nanorods [12,13], nanowires [14][15][16][17][18], nanobelts [19,20] and nanotubes [21,22]. In this article, we report a simple hydrothermal method for direct growth of selenium and tellurium nanorods by using glucose as a green reducing agent, Na 2 SeO 3 and Na 2 TeO 3 as selenium and tellurium source, and cationic surfactant cetyltrimethylammonium bromide (CTAB) as a structure-directing agent.…”