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Efficient thermoelectric power conversion and cooling requires materials with high electrical conductivity s, high Seebeck coefficient a, and low thermal conductivity k.[1–3] Theory predicts that nanostructuring can increase the figure of merit ZT (¼ sa2T/k) beyond the bulk value, owing to k decrease from enhanced phonon scattering at nanostructure boundaries,[4] and increase in s and a from quantum confinement.[1, 5] The promise of higher ZT in nanowires and nanoparticles owing to a greater degree of confinement than in 2D quantum wells [1] has stimulated the exploration of new approaches to synthesize nanostructures of bismuth telluride (Bi2Te3-based thermoelectric materials have the highest reported ZT in the bulk form [1, 6]) and its alloys.[7–9] Nanorods are of particular interest because they are suitable for building heat-pumping circuits for device cooling, and allow the study of thermal and electrical properties of individual nanostructures through contact formation. Aligned Bi2Te3 nanorods can be obtained by electrochemical deposition in porous alumina templates,[10, 11] but are typically polycrystalline and exhibit low charge-carrier mobility.[1] Soft-templating approaches utilizing molecular agents are attractive for synthesizing single-crystal nanorods,[12] which are more conducive for high ZT. Moreover, soft-templating can facilitate template removal during processing and harvest template–nanostructure interactions for passivation or doping.[12]

Here, we demonstrate a new approach to obtain core/shell bismuth telluride/bismuth sulfide nanorods with shell branching by using a biomolecular surfactant, L-glutathionic acid (LGTA). We …