Organometallic halides are great candidates for optoelectronics. As an important family of semiconductors, understanding their thermoelectric transport properties is also important. This has been a challenging task as many of such compounds are highly intrinsic. In this work, we synthesized two halides, CH3NH3PbI3 and (CH3NH3)3Bi2I9, using a solvent-free method. We found an extraordinarily high Seebeck coefficient of +2600 ± 200 μV/K in (CH3NH3)3Bi2I9. For CH3NH3PbI3, our synthesis method led to a negative Seebeck coefficient of −1350 ± 50 μV/K, in contrast to positive values observed in solvent synthesized samples. We also found the thermal conductivity of CH3NH3PbI3 to be 0.38 W/m K, largely independent of temperature from 300 K to 450 K, despite a tetragonal-to-cubic phase transition. (CH3NH3)3Bi2I9 has an even lower thermal conductivity of 0.21 W/m K (also temperature independent) which is due to its soft phonon dispersion and weak bonds.

Transport properties in resonant system PbSe:Tl are now quantitatively explained with Boltzmann transport equations.

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A competitive electrochemical immunoassay for highly sensitive detection of AFB1 is demonstrated using layer-by-layer (LBL) assembled quantum dots (QDs) as labels. To investigate the effects of the higher sensitivity of square wave voltammetric stripping (SWV) and of the LBL technique on the proposed immunoassays, the proposed assay was compared to electrochemical (EC) and fluorescent immunoassays, which did not use LBL technology. Peanut samples were analyzed using the three immunoassays. The limits of detection (LODs) were 0.018, 0.046 and 0.212 ng/mL, respectively, while the sensitivities were 0.308, 1.011 and 4.594 ng/mL, respectively. The proposed electrochemical immunoassay displayed a significant improvement in sensitivity, thereby providing a simple and sensitive alternative strategy for determining AFB1 levels in peanut samples.

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