Thermoelectric Property in Orthorhombic-Domained SnSe Film

A singular plasmonic-thermoelectric hollow nanostructure inducing apoptosis and cuproptosis for catalytic cancer therapy

Thermoelectric technology has recently emerged as a distinct therapeutic modality. However, its therapeutic effectiveness is significantly limited by the restricted temperature gradient within living organisms. In this study, we introduce a high-performance plasmonic-thermoelectric catalytic therapy utilizing urchin-like Cu2-xSe hollow nanospheres (HNSs) with a cascade of plasmonic photothermal and thermoelectric conversion processes. Under irradiation by a 1064 nm laser, the plasmonic absorption of Cu2-xSe HNSs, featuring rich copper vacancies (VCu), leads to a rapid localized temperature gradient due to their exceptionally high photothermal conversion efficiency (67.0%). This temperature gradient activates thermoelectric catalysis, generating toxic reactive oxygen species (ROS) targeted at cancer cells. Density functional theory calculations reveal that this vacancy-enhanced thermoelectric catalytic effect arises from a much more carrier concentration and higher electrical conductivity. Furthermore, the exceptional photothermal performance of Cu2-xSe HNSs enhances their peroxidase-like and catalase-like activities, resulting in increased ROS production and apoptosis induction in cancer cells. Here we show that the accumulation of copper ions within cancer cells triggers cuproptosis through toxic mitochondrial protein aggregation, creating a synergistic therapeutic effect. Tumor-bearing female BALB/c mice are used to evaluate the high anti-cancer efficiency. This innovative approach represents the promising instance of plasmonic-thermoelectric catalytic therapy, employing dual pathways (membrane potential reduction and thioctylated protein aggregation) of mitochondrial dysfunction, all achieved within a singular nanostructure. These findings hold significant promise for inspiring the development of energy-converting nanomedicines.

Constructing quasi-layered and self-hole doped SnSe oriented films to achieve excellent thermoelectric power factor and output power density

Thermoelectric (TE) technology can achieve the mutual conversion between electric energy and waste heat, and it has exhibited great prospects in multifunctional energy applications to alleviate the energy crisis. In the recent decade, SnSe has been explored widely because of its potentially high energy harvesting efficiency, green nature, and low cost. However, the relatively poor power factor (PF) derived from the intrinsic low carrier concentration (∼1017 cm-3) limits the output power density of the stoichiometric SnSe devices. Therefore, the advancement of novel optimization strategies for controlling carrier concentration is of utmost importance. Besides, compared with 3D bulks, 2D thin films are more compatible with modern semiconductor technology and have unique advantages in the construction and application of TE micro- and nano-devices. In this study, post-selenization technology were applied to increase the carrier concentration of the a-axis oriented SnSe epitaxial films utilizing the charge transfer and self-hole doped effects. The quasi-layered and self-hole doped films exhibited a high power factor of ∼5.9 µW cm-1 K-2 at 600 K along the in-plane direction when the carrier concentration is enhanced to ∼1018 cm-3 by increasing the selenization time to ∼20 min. The TE generator composed of four P-type film legs demonstrated the ultrahigh maximum power density of ∼83, ∼838 µW cm-2 at the temperature difference of ∼50 and ∼90 K, respectively. Post-selenization can effectively optimize the carrier concentration of SnSe-based materials, which is also feasible to other anion deficient TE films.

Stepwise Alloying in Liquid-like Solid Solutions to Achieve Crystallographic Distortion for Regulating Thermoelectric Transport Behavior

With the surge of energy consumption, environmental-protection Cu2-xSe thermoelectric materials are increasingly attracting attention. In this work, multilayered structures are constructed in Cu2-xSe solid solutions by alloying (SnSe)0.75(AgBiSe2)0.25, which strongly scatters full-wavelength phonons by carefully regulating the crystallographic distortion. By using the stepwise alloying strategies, crystallographic distortion and the resultant strain fields presented in microstructure were strengthened markedly, which enhanced the phonon scattering. Meanwhile, by adjusting the coalloying content of Ag, Bi, and Sn elements, the carrier and phonon transports were well decoupled in p-type Cu2-xSe, and the thermoelectric performance was significantly enhanced. By optimized power factor as well as depressed heat transport originating from the moderate coalloying, the maximum zT of 1.23 at 750 K was achieved in Cu1.9Se - 1 wt % (SnSe)0.75(AgBiSe2)0.25. This study indicated that the stepwise alloying strategy was a suitable method for optimizing zT of Cu2-xSe.

Recent Advances in 2D Material Theory, Synthesis, Properties, and Applications

Two-dimensional (2D) material research is rapidly evolving to broaden the spectrum of emergent 2D systems. Here, we review recent advances in the theory, synthesis, characterization, device, and quantum physics of 2D materials and their heterostructures. First, we shed insight into modeling of defects and intercalants, focusing on their formation pathways and strategic functionalities. We also review machine learning for synthesis and sensing applications of 2D materials. In addition, we highlight important development in the synthesis, processing, and characterization of various 2D materials (e.g., MXnenes, magnetic compounds, epitaxial layers, low-symmetry crystals, etc.) and discuss oxidation and strain gradient engineering in 2D materials. Next, we discuss the optical and phonon properties of 2D materials controlled by material inhomogeneity and give examples of multidimensional imaging and biosensing equipped with machine learning analysis based on 2D platforms. We then provide updates on mix-dimensional heterostructures using 2D building blocks for next-generation logic/memory devices and the quantum anomalous Hall devices of high-quality magnetic topological insulators, followed by advances in small twist-angle homojunctions and their exciting quantum transport. Finally, we provide the perspectives and future work on several topics mentioned in this review.

N-Type Flexible Films and a Thermoelectric Generator of Single-Walled Carbon Nanotube-Grafted Tin Selenide Nanocrystal Composites

Despite the significant progress in thermoelectric composites in recent years, the enhancement of thermoelectric performance is mainly based on weak interfacial interactions, although strong interactions (such as covalent-bonding grafting) are expected to display a more significant effect. In this study, the thermoelectric composites are prepared using a covalent-bond grafting method between tin selenide (SnSe) and single-walled carbon nanotubes (SWCNTs) via a simple solvothermal process. The as-prepared highly flexible composite film shows an n-type thermoelectric characteristic. An optimized power factor of 58.86 μW m^-1 K^-2 at room temperature has been realized for the composite film with 16 wt % SWCNT loading. Finally, a flexible thermoelectric generator (TEG) consisting of three couples of p/n films is assembled, which can generate an open-circuit voltage of 15.55 μV and a maximum output power of 1.38 μW at a temperature gradient of 60 K. The results open a new avenue for the fabrication of n-type flexible films and TEG based on covalent-bonding-grafted composites and will benefit the design strategy of high-performance thermoelectric composites and flexible TEGs.

One-Dimensional Vanadium(III) Chalcogenidostannates Incorporating [V(tepa)]3+ Complexes as Bridging Groups

Two new one-dimensional (1D) vanadium(III) chalcogenidostannates, [H₂tepa]_0.5n[V^III(tepa)(μ-Sn₂Q₆)]_n [Q = S (1), Se (2); tepa = tetraethylenepentamine], were achieved by solvothermal methods, which offer the first examples of organic hybrid polymeric chalcogenidostannates incorporating [V(tepa)]³⁺ complexes as bridging groups. Both 1 and 2 feature the 1D sinusoidal chains of [V^III(tepa)(μ-Sn₂Q₆)]_n containing two types of novel bridging modes of the [μ-Sn₂Q₆]^4- anion. Their magnetic, photocurrent response, and optical properties are also studied.

Dynamic Epitaxial Crystallization of SnSe2 on the Oxidized SnSe Surface and Its Atomistic Mechanisms

Surface oxidation of SnSe sharply reduces its thermoelectric properties though the bulk single-crystalline materials of SnSe claim the record high zT values. Investigation on the oxidation behaviors of SnSe together with the subsequent phase transition and element migration is fundamentally important to maintaining the ultrahigh zT values, with a potential for further improvement. In this work, we disclose the dynamic epitaxial crystallization of SnSe2 on the amorphous surface of partially oxidized SnSe crystals and the corresponding atomistic mechanisms via transmission electron microscopy (TEM). It is revealed that the thermally annealed amorphous surface crystallized to SnO2 and SnSe2 in the outermost and secondary layers, respectively, forming distinctive SnSe/SnSe2/SnO2 multilayer heterostructures with specific orientation relationships between the two selenides. By means of in situ scanning TEM (STEM), the dynamic epitaxial crystallization process of SnSe2 was revealed when the oxidized SnSe surface was subjected to electron beam irradiation. Through the atomic-scale characterization and modeling analysis, we find that the exposed dangling Se diatoms on the SnSe surface serve as nucleation sites for lateral epitaxial crystallization of SnSe2. The same valence and similar coordination configuration of Se atoms in these two phases are supposed to facilitate the sharing of Se atoms, with lattice distortions in the SnSe2/SnSe interface. These findings are valuable for understanding the surface oxidation behavior of SnSe and revealing the interface structures of SnSe2/SnSe heterojunctions and also offering new routes for SnSe-related multilayer or heterostructure system design.

High-Performance Thermoelectric SnSe: Aqueous Synthesis, Innovations, and Challenges

Tin selenide (SnSe) is one of the most promising candidates to realize environmentally friendly, cost-effective, and high-performance thermoelectrics, derived from its outstanding electrical transport properties by appropriate bandgaps and intrinsic low lattice thermal conductivity from its anharmonic layered structure. Advanced aqueous synthesis possesses various unique advantages including convenient morphology control, exceptional high doping solubility, and distinctive vacancy engineering. Considering that there is an urgent demand for a comprehensive survey on the aqueous synthesis technique applied to thermoelectric SnSe, herein, a thorough overview of aqueous synthesis, characterization, and thermoelectric performance in SnSe is provided. New insights into the aqueous synthesis-based strategies for improving the performance are provided, including vacancy synergy, crystallization design, solubility breakthrough, and local lattice imperfection engineering, and an attempt to build the inherent links between the aqueous synthesis-induced structural characteristics and the excellent thermoelectric performance is presented. Furthermore, the significant advantages and potentials of an aqueous synthesis route for fabricating SnSe-based 2D thermoelectric generators, including nanorods, nanobelts, and nanosheets, are also discussed. Finally, the controversy, strategy, and outlook toward future enhancement of SnSe-based thermoelectric materials are also provided. This Review guides the design of thermoelectric SnSe with high performance and provides new perspectives as a reference for other thermoelectric systems.