We report on the high thermoelectric performance of p-type polycrystalline BiCuSeO, a layered oxyselenide composed of alternating conductive (Cu 2 Se 2 ) 2 À and insulating (Bi 2 O 2 ) 2 þ layers. The electrical transport properties of BiCuSeO materials can be significantly improved by substituting Bi 3 þ with Ca 2 þ . The resulting materials exhibit a large positive Seebeck coefficient of B þ 330 lV K À1 at 300 K, which may be due to the 'natural superlattice' layered structure and the moderate effective mass suggested by both electronic density of states and carrier concentration calculations. After doping with Ca, enhanced electrical conductivity coupled with a moderate Seebeck coefficient leads to a power factor of B4.74 lW cm À1 K À2 at 923 K. Moreover, BiCuSeO shows very low thermal conductivity in the temperature range of 300 (B0.9 W m À1 K À1 ) to 923 K (B0.45 W m À1 K À1 ). Such low thermal conductivity values are most likely a result of the weak chemical bonds (Young's modulus, EB76.5 GPa) and the strong anharmonicity of the bonding arrangement (Gruneisen parameter, cB1.5). In addition to increasing the power factor, Ca doping reduces the thermal conductivity of the lattice, as confirmed by both experimental results and Callaway model calculations. The combination of optimized power factor and intrinsically low thermal conductivity results in a high ZT of B0.9 at 923 K for Bi 0.925 Ca 0.075 CuSeO.

Thermoelectric materials have potential applications in energy harvesting and electronic cooling devices, and bismuth antimony telluride (BiSbTe) alloys are the state-of-the-art thermoelectric materials that have been widely used for several decades. It is demonstrated that mixing SiC nanoparticles into the BiSbTe matrix effectively enhances its thermoelectric properties; a high dimensionless fi gure of merit ( ZT ) value of up to 1.33 at 373 K is obtained in Bi 0.3 Sb 1.7 Te 3 incorporated with only 0.4 vol% SiC nanoparticles. SiC nanoinclusions possessing coherent interfaces with the Bi 0.3 Sb 1.7 Te 3 matrix can increase the Seebeck coeffi cient while increasing the electrical conductivity, in addition to its effect of reducing lattice thermal conductivity by enhancing phonon scattering. Nano-SiC dispersion further endows the BiSbTe alloys with better mechanical properties, which are favorable for practical applications and device fabrication.

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A significant enhancement of thermoelectric performance in layered oxyselenides BiCuSeO was achieved. The electrical conductivity and Seebeck coefficient of BiCu(1-x)SeO (x = 0-0.1) indicate that the carriers were introduced in the (Cu(2)Se(2))(2-) layer by Cu deficiencies. The maximum of electrical conductivity is 3 × 10(3) S m(-1) for Bicu(0.975)Seo at 650 °C, much larger than 470 S m(-1) for pristine BiCuSeO. Featured with very low thermal conductivity (∼0.5 W m(-1) K(-1)) and a large Seebeck coefficient (+273 μV K(-1)), ZT at 650 °C is significantly increased from 0.50 for pristine BiCuSeO to 0.81 for BiCu(0.975)SeO by introducing Cu deficiencies, which makes it a promising candidate for medium temperature thermoelectric applications.

The layered oxyselenide BiCuSeO system is known as one of the high‐performance thermoelectric materials with intrinsically low thermal conductivity. By employing atomic, nano‐ to mesoscale structural optimizations, low thermal conductivity coupled with enhanced electrical transport properties can be readily achieved. Upon partial substitution of Bi3+ by Ca2+ and Pb2+, the thermal conductivity can be reduced to as low as 0.5 W m−1 K−1 at 873 K through dual‐atomic point‐defect scattering, while a high power factor of ≈1 × 10−3 W cm−1 K−2 is realized over a broad temperature range from 300 to 873 K. The synergistically optimized power factor and intrinsically low thermal conductivity result in a high ZT value of ≈1.5 at 873 K for Bi0.88Ca0.06Pb0.06CuSeO, a promising candidate for high‐temperature thermoelectric applications. It is envisioned that the all‐scale structural optimization is critical for optimizing the thermoelectricity of quaternary compounds.

The effect of Ca substitution on microstructure and thermoelectric transport properties of BiCuSeO oxyselenide has been studied. The substitution of Ca 2+ for Bi 3+ reduces both electrical resistivity and Seebeck coefficient due to an increased carrier concentration. However, the enhanced electrical conductivity compensates for the decrease of Seebeck coefficient, and consequently the power factor is greatly improved in the whole temperature range from 300 to 773 K, exceeding 600 mW m À1 K À2 in the Bi 1Àx Ca x CuSeO samples with 0.075 # x # 0.125. Additionally, the lattice thermal conductivity is significantly reduced due to the refined grains and the introduced point defects that limit the phonon mean free path, resulting in a total thermal conductivity lower than 1.0 W m À1 K À1 in all the doped samples. Benefiting from the enhanced electrical conductivity and the reduced thermal conductivity, high ZT values, both at low and medium temperatures, 0.3 at 300 K and 0.8 at 773 K, are achieved for the Bi 0.925 Ca 0.075 CuSeO composition.

Inspired by the enhanced photoluminescence of Au nanoclusters (AuNCs)with arigid shell, the formation of rigid host-guest assemblies on AuNC surfaces was employed to screen novel electrochemiluminophores with 6-aza-2thiothymine(ATT)-protected AuNCs (ATT-AuNCs) and larginine (ARG) as models for the first time.T he rigid hostguest assemblies formed between ARG and ATTont he ATT-AuNC surface enabled aqueous-soluble ARG/ATT-AuNCs with ad ramatically enhanced electrochemiluminescence (ECL) compared to ATT-AuNCs.T his includes one cathodic ECL process (À1.30 V) and three anodic ECL processes (+ 0.78, 0.90, and 1.05 V) in as o-called half-scan experiment without aco-reactant, as well as a70-fold enhanced oxidativereduction ECL at + 0.78 Vw ith tri-n-propylamine as ac oreactant. Importantly,t he ECL of the ARG/ATT-AuNCs is highly monochromatic with an emission maximum around 532 nm and afull width at half-maximum of 36 nm, whichisof great interest for color-selective ECL assays.

Screening a novel electrochemiluminescence (ECL) system is crucial to ECL evolution. Herein, an efficient ECL system with less interference and environmental concern under physiological condition is developed via a unique internal Cu­(I)/Cu­(II) couple cycling amplified strategy by employing the glutathione- and citrate-capped copper indium sulfide (CIS)/ZnS nanocrystals (NCs) as electro­chemiluminophore and N2H4·H2O as co-reactant. CIS/ZnS NCs can be electrochemically injected with valence band (VB) hole at 0.46 and 0.87 V (vs Ag/AgCl), and then achieve the same hole-injected states by relocalizing VB holes with the Cu­(I) species inside of CIS/ZnS NCs to form internal Cu­(II) defects, while each N2H4·H2O molecule can be successively oxidized to two more reducing species N2H3 • and N2H2 around 0.10 V, and inject conduction band (CB) electron onto CIS/ZnS NCs for triple times. The internal Cu­(I)/Cu­(II) couple cycling involved radiative-charge recombination between these VB hole and CB electron eventually enables two efficient near-infrared ECL processes (around 731 nm) at 0.55 and 0.87 V, in which each single nanocrystal may participate in multiple ECL reaction cycles to produce multiple photons for amplified ECL, similar to the tris­(bipyridyl)­ruthenium­(III) based ECL system. The low-triggering-potential ECL process at 0.55 V can be utilized to selectively determine Cu­(II) with a wide linear range from 10 and 1500 nM and a limit of detection of 5 nM (S/N = 3). This work presents a NCs engineering and co-reactant selecting combined strategy for further ECL evolution.