Anion/Cation Co-Doping to Improve the Thermoelectric Performance of Sn-Enriched n-Type SnSe Polycrystals with Suppressed Lattice Thermal Conductivity.

Enhancing the thermoelectric performance of n-type polycrystalline SnSe is essential, addressing challenges posed by elevated thermal conductivity and compromised power factor inherent in its intrinsic p-type characteristics. This investigation utilized solid-state reactions and spark plasma sintering techniques for the synthesis of n-type SnSe. A significant improvement in the figure of merit (ZT) is achieved through strategic reduction in Se concentration and optimization of crystal orientation. The co-doping with Br and Ge further improves the material; Br amplifies carrier concentration, enhancing electrical conductivity, while Ge introduces effective phonon scattering centers. In the Br/Ge co-doped SnSe sample, thermal conductivity dropped to 0.38 Wm⁻¹K⁻¹, yielding a remarkable power factor of 662 µW mK- 2 at 773 K, culminating in a ZT of 1.34. This signifies a noteworthy 605% improvement over the pristine sample, underscoring the pivotal role of Ge doping in enhancing n-type material thermoelectric properties. The enhancement is attributed to Br doping introducing additional electronic states near the valence band, and Ge doping modifying the band structure, fostering resonant states near the conduction band. The Br/Ge co-doping further transforms the band structure, influencing electrical conductivity, Seebeck coefficient, and thermal conductivity, advancing the understanding and application of n-type SnSe materials for superior thermoelectric performance.

Flexible power generators by Ag2Se thin films with record-high thermoelectric performance.

Exploring new near-room-temperature thermoelectric materials is significant for replacing current high-cost Bi2Te3. This study highlights the potential of Ag2Se for wearable thermoelectric electronics, addressing the trade-off between performance and flexibility. A record-high ZT of 1.27 at 363 K is achieved in Ag2Se-based thin films with 3.2 at.% Te doping on Se sites, realized by a new concept of doping-induced orientation engineering. We reveal that Te-doping enhances film uniformity and (00l)-orientation and in turn carrier mobility by reducing the (00l) formation energy, confirmed by solid computational and experimental evidence. The doping simultaneously widens the bandgap, resulting in improved Seebeck coefficients and high power factors, and introduces TeSe point defects to effectively reduce the lattice thermal conductivity. A protective organic-polymer-based composite layer enhances film flexibility, and a rationally designed flexible thermoelectric device achieves an output power density of 1.5 mW cm-2 for wearable power generation under a 20 K temperature difference.

Porous In2O3 Hollow Tube Infused with g-C3N4 for CO2 Photocatalytic Reduction.

Converting CO2 into energy-rich fuels by using solar energy is a sustainable solution that promotes a carbon-neutral economy and mitigates our reliance on fossil fuels. However, affordable and efficient CO2 conversion remains an ongoing challenge. Here, we introduce polymeric g-C3N4 into the pores of a hollow In2O3 microtube. This architecture results in a compact and staggered arrangement between g-C3N4 and In2O3 components with an increased contact interface for improved charge separation. The hollow interior further contributes to strengthening light absorption. The resulting g-C3N4-In2O3 hollow tubes exhibit superior activity (274 µmol·g-1·h-1) toward CO2 to CO conversion in comparison with those of pure In2O3 and g-C3N4 (5.5 and 93.6 µmol·g-1·h-1, respectively), underlining the role of integrating g-C3N4 and In2O3 in this advanced system. This work offers a strategy for the advanced design and preparation of hollow heterostructures for optimizing CO2 adsorption and conversion by integrating inorganic and organic semiconductors.

Construction of site-specific magnetic Z-scheme CdS/Fe3O4@N-doped graphene aerogel microtube/N-doped TiO2 with porous structure: enhanced catalytic performance in photo-Fenton reaction.

The development of composite photocatalysts with high charge transfer efficiency, great visible light absorption, and quick recovery has aroused the interest of many researchers. Herein, based on the hydrothermal assisted vacuum freeze drying method, CdS, Fe3O4, and N-TiO2 were, respectively, fixed in the inner, middle, and outer layers of nitrogen-doped graphene aerogel for preparation of the site-specific magnetic porous Z-scheme CdS/Fe3O4@N-doped graphene aerogel microtube/N-doped TiO2 (CdS/Fe3O4@NGAM/N-TiO2) photocatalyst. For the composite, Fe3O4@NGAM carrier with porous and tubular structure not only helps the recycle and reactants/productions mass transport in the photocatalytic process but also ensures the well-steered transfer of electrons and holes from CdS and N-TiO2 in the Z-type heterojunction system, greatly improving the separation of photogenerated carriers. Besides, Fe3O4 can also work as a Fenton catalyst to activate hydrogen peroxide which is generated in situ by CdS. Thus, the CdS/Fe3O4@NGAM/N-TiO2 composite presents excellent degradation efficiencies towards methyl orange ((MO) 98% removal rate within 50 min), bisphenol A ((BPA) 96% removal rate within 50 min), tetracycline hydrochloride ((TCH) 96% removal rate within 120 min) and strong stabilities after 6 cycles. The free radical removal experiments show that ·O2- and ·OH are the main active substances of catalysis, which further confirms the synergistic effect of photocatalysis and Fenton catalysis.

High-Performance Thermoelectric Flexible Ag2Se-Based Films with Wave-Shaped Buckling via a Thermal Diffusion Method.

Herein, an n-type Ag2Se thermoelectric flexible thin film has been fabricated on a polyimide (PI) substrate via a novel thermal diffusion method, and the thermoelectric performance is well-optimized by adjusting the pressure and temperature of thermal diffusion. All of the Ag2Se films are beneficial to grow (013) preferred orientations, which is conducive to performing a high Seebeck coefficient. By increasing the thermal diffusion temperature, the electrical conductivity can be rationally regulated while maintaining the independence of the Seebeck coefficient, which is mainly attributed to the increased electric mobility. As a result, the fabricated Ag2Se thin film achieves a high power factor of 18.25 µW cm-1 K-2 at room temperature and a maximum value of 21.7 µW cm-1 K-2 at 393 K. Additionally, the thermal diffusion method has resulted in a wave-shaped buckling, which is further verified as a promising structure to realize a larger temperature difference by the simulation results of finite element analysis (FEA). Additionally, this unique surface morphology of the Ag2Se thin film also exhibits outstanding mechanical properties, for which the elasticity modulus is only 0.42 GPa. Finally, a flexible round-shaped module assembled with Sb2Te3 has demonstrated an output power of 166 nW at a temperature difference of 50 K. This work not only introduces a new method of preparing Ag2Se thin films but also offers a convincing strategy of optimizing the microstructure to enhance low-grade heat utilization efficiency.

Shape tunability of copper nanocrystals deposited on nanorods.

The significant role of metal particle geometry in dictating catalytic activity, selectivity, and stability is well established in heterocatalysis. However, this topic is rarely explored in semiconductor-metal hybrid photocatalytic systems, primarily due to the lack of synthetic control over this feature. Herein, we present a new synthetic route for the deposition of metallic Cu nanoparticles with spherical, elliptic, or cubic geometrical shapes, which are selectively grown on one side of the well-established CdSe@CdS nanorod photocatalytic system. An additional multipod morphology in which several nanorod branches are combined on a single Cu domain is presented as well. Cu is an earth-abundant low-cost catalyst known to promote a diverse gallery of organic transformations and is an excellent thermal and electrical conductor with interesting plasmonic properties. Its deposition on cadmium chalcogenide nanostructures is enabled here via mitigation of the reaction kinetics such that the cation exchange reaction is prevented. The structural diversity of these sophisticated nanoscale hybrid systems lays the foundations for shape-activity correlation studies and employment in various applications.

MoS2/polyaniline (PANI)/polyacrylonitrile (PAN)@BiFeO3 bilayer hollow nanofiber membrane: Photocatalytic filtration and piezoelectric effect enhancing degradation and disinfection.

A novel MoS2/polyaniline (PANI)/polyacrylonitrile (PAN)@BiFeO3 bilayer hollow nanofiber membrane (PPBM-H) was successfully synthesized by coaxial electrospinning technique. In the nanofiber, BiFeO3 nanoparticles (NPs) and MoS2 nanosheets (NSs) were loaded in the middle and outer layers of the PANI/PAN composites, respectively, which constructs a type II heterojunction with spatially separated microtopography, thus significantly improving the charge separation in photocatalysis. Moreover, the hollow structure and the vast number of exposed groups on the surface of PPBM-H help to improve the mass transfer efficiency and pollutant adsorption performance in wastewater treatment. In addition, PPBM-H can generate H2O2 by in-situ activation of BiFeO3/MoS2 for photo-Fenton catalysis, enabling Fe3+ and Fe2+ recycling. Also, PPBM-H can produce piezoelectric polarisation under ultrasonic excitation, which can further enhance the efficiency of electron/hole separation and transfer, and induce the generation of active free radicals. Owing to its wonderful self-cleaning effect, the PPBM-H has good mechanical strength (2.95 Mpa), hydrophilicity (11.6°), water flux (1248 L·m-2·h-1), BSA rejection (98.8 %), and exhibits distinguished photocatalytic filtration efficiencies (99.5 % tetracycline hydrochloride (TCH) and 99.9 % methyl orange (MO) within 60 min), piezo-photocatalysis (99.2 % TCH within 2 h), disinfection performance for Escherichia coli (E. coli) (100 %, within 60 min).

Preparation of site-specific Z-scheme g-C3N4/PAN/PANI@LaFeO3 cable nanofiber membranes by coaxial electrospinning: Enhancing filtration and photocatalysis performance.

The coaxial electrospinning method for preparation of g-C3N4/polyacrylonitrile (PAN)/polyaniline (PANI)@LaFeO3 cable fiber membrane (PC@PL) was designed for adsorption-filtration-photodegradation of pollutants. A series of characterization results show that LaFeO3 and g-C3N4 nanoparticles (NPs) are respectively loaded in the inner and outer layers of PAN/PANI composite fibers to construct the site-specific Z-type heterojunction system with spatially separated morphologies. The PANI in cable not only possesses abundant exposed amino/imino functional groups for adsorption of contaminant molecules but also due to the excellent electrical conductivity works as a redox medium for collecting and consuming the electrons and holes from LaFeO3 and g-C3N4, which can efficiently promote photo-generated charge carriers separation and improve the catalytic performance. Further investigations demonstrate that as a photo-Fenton catalyst LaFeO3 in PC@PL catalyzes/activates the H2O2 generated in situ by LaFeO3/g-C3N4, further enhancing the decontamination efficiency of the PC@PL. The porous, hydrophilic, antifouling, flexible and reusable properties of the PC@PL membrane significantly enhance the mass transfer efficiency of reactants by filtration effect and increase the amount of dissolved oxygen, thus producing massive •OH for degradation of pollutants, which maintains the water flux (1184 L m-2. h-1 (LMH)) and the rejection rate (98.5%). Profiting from its unique synergistic effect of adsorption, photo-Fenton and filtration, PC@PL exhibits wonderful self-cleaning performance and distinguished removal rate for methylene blue (97.0%), methyl violet (94.3%), ciprofloxacin (87.6%) and acetamiprid (88.9%) within 75 min, disinfection (100% Escherichia coli (E. coli) and 80% Staphylococcus aureus (S.aureus) inactivation)) and excellent cycle stability.

Effects of Si Substrates with Variable Initial Orientations on the Growth and Thermoelectric Properties of Bi-Sb-Te Thin Films.

For thermoelectric thin film, the substrate plays an important role during the growing process and produces effects on its thermoelectric properties. Some special kinds of substrates provide an optimal combination of influences on both the structure and thermoelectric properties. In this work, Bi-Sb-Te films are deposited on Si substrates with different initial orientations by magnetron sputtering in two ways: with and without a pre-coating process. The preferred orientations of the Bi-Sb-Te films are greatly affected by the substrates, in which the thin film tends to deposit on Si substrate with (100) initial orientation and high (015)-texture, while the (00l)-textured Bi-Sb-Te film easily deposits on Si substrate with (110) initial orientation. The experimental and theoretical calculation results indicate that Bi-Sb-Te film with (00l)-texture presents good electrical conductivity and a higher power factor than that of film with (015)-texture.

A Dual Fluorescence Assay Enables High-Throughput Screening for Poly(ethylene terephthalate) Hydrolases.

The drastically increasing consumption of petroleum-derived plastics hasserious environmental impacts and raises public concerns. Poly(ethylene terephthalate) (PET) is amongst the most extensively produced synthetic polymers. Enzymatic hydrolysis of PET recently emerged as an enticing path for plastic degradation and recycling. In-lab directed evolution has revealed the great potential of PET hydrolases (PETases). However, the time-consuming and laborious PETase assays hinder the identification of effective variants in large mutant libraries. Herein, we devise and validate a dual fluorescence-based high-throughput screening (HTS) assay for a representative IsPETase. The two-round HTS of a pilot library consisting of 2850 IsPETase variants yields six mutant IsPETases with 1.3-4.9 folds improved activities. Compared to the currently used structure- or computational redesign-based PETase engineering, this HTS approach provides a new strategy for discovery of new beneficial mutation patterns of PETases.

Post-Electric Current Treatment Approaching High-Performance Flexible n-Type Bi2Te3 Thin Films.

Inorganic n-type Bi2Te3 flexible thin film, as a promising near-room temperature thermoelectric material, has attracted extensive research interest and application potentials. In this work, to further improve the thermoelectric performance of flexible Bi2Te3 thin films, a post-electric current treatment is employed. It is found that increasing the electric current leads to increased carrier concentration and electric conductivity from 1874 S cm−1 to 2240 S cm−1. Consequently, a high power factor of ~10.70 µW cm−1 K−2 at room temperature can be achieved in the Bi2Te3 flexible thin films treated by the electric current of 0.5 A, which is competitive among flexible n-type Bi2Te3 thin films. Besides, the small change of relative resistance <10% before and after bending test demonstrates excellent bending resistance of as-prepared flexible Bi2Te3 films. A flexible device composed of 4 n-type legs generates an open circuit voltage of ~7.96 mV and an output power of 24.78 nW at a temperature difference of ~35 K. Our study indicates that post-electric current treatment is an effective method in boosting the electrical performance of flexible Bi2Te3 thin films.

Optimized Thermoelectric Properties of Sulfide Compound Bi2SeS2 by Iodine Doping.

The Te-free compound Bi2SeS2 is considered as a potential thermoelectric material with less environmentally hazardous composition. Herein, the effect of iodine (I) substitution on its thermoelectric transport properties was studied. The electrical conductivity was enhanced due to the increased carrier concentration caused by the carrier provided defect Ise. Thus, an enhanced power factor over 690 µWm−1K−2 was obtained at 300 K by combining a moderate Seebeck coefficient above 150 µV/K due to its large effective mass, which indicated iodine was an effective n-type dopant for Bi2SeS2. Furthermore, a large drop in the lattice thermal conductivity was observed due to the enhanced phonon scattering caused by nanoprecipitates, which resulted in a low total thermal conductivity (<0.95 Wm−1K−1) for all doped samples. Consequently, a maximum ZT value of 0.56 was achieved at 773 K for a Bi2Se1−xIxS2 (x = 1.1%) sample, a nearly threefold improvement compared to the undoped sample.

Achieving High Thermoelectric Performance of Eco-Friendly SnTe-Based Materials by Selective Alloying and Defect Modulation.

Recently, rock-salt lead-free chalcogenide SnTe-based thermoelectric (TE) materials have been considered an alternative to PbTe because of the nontoxic properties of Sn as compared to Pb. However, high carrier concentration that originated from intrinsic Sn vacancies and relatively high thermal conductivity of pristine SnTe lead to poor TE efficiency, which makes room for improving its TE properties. In this study, we present that the Na incorporation into the SnTe matrix is helpful for modifying the electronic band structure, optimization of carrier concentration, introducing dislocations, and kink planes; benefiting from these synergistic effects obviates the disadvantages of SnTe and makes a significant improvement in TE performance. We reveal that Na favorably impacts the structure of electronic bands by valence, conduction band engineering, leading to a nice enhancement in the Seebeck coefficient, which exhibits the highest power factor value of 37.93 µWcm-1 K-2 at 898 K, representing the best result for the SnTe material system. Moreover, a broader phonon spectrum is introduced by new phonon-scattering centers, scattered by dislocations and kink planes which suppressed lattice thermal conductivity to 0.57 Wm-1 K-1 at 898 K, which is much lower than that of pristine SnTe. Ultimately, a maximum ZT of 1.26 at 898 K is achieved in the Sn1.03Te + 3% Na sample, which is 97% higher than that of the pristine SnTe, suggesting that SnTe-based materials are a robust candidate for TE applications specifically, an ideal alternative of lead chalcogenides for TE power generation at high temperatures.

Novel Thermal Diffusion Temperature Engineering Leading to High Thermoelectric Performance in Bi2 Te3 -Based Flexible Thin-Films.

Flexible Bi2 Te3 -based thermoelectric devices can function as power generators for powering wearable electronics or chip-sensors for internet-of-things. However, the unsatisfied performance of n-type Bi2 Te3 flexible thin films significantly limits their wide application. In this study, a novel thermal diffusion method is employed to fabricate n-type Te-embedded Bi2 Te3 flexible thin films on flexible polyimide substrates, where Te embeddings can be achieved by tuning the thermal diffusion temperature and correspondingly result in an energy filtering effect at the Bi2 Te3 /Te interfaces. The energy filtering effect can lead to a high Seebeck coefficient ≈160 µV K-1 as well as high carrier mobility of ≈200 cm2 V-1 s-1 at room-temperature. Consequently, an ultrahigh room-temperature power factor of 14.65 µW cm-1 K-2 can be observed in the Te-embedded Bi2 Te3 flexible thin films prepared at the diffusion temperature of 623 K. A thermoelectric sensor is also assembled through integrating the n-type Bi2 Te3 flexible thin films with p-type Sb2 Te3 counterparts, which can fast reflect finger-touch status and demonstrate the applicability of as-prepared Te-embedded Bi2 Te3 flexible thin films. This study indicates that the thermal diffusion method is an effective way to fabricate high-performance and applicable flexible Te-embedded Bi2 Te3 -based thin films.

Homo-composition and hetero-structure nanocomposite Pnma Bi2SeS2 - Pnnm Bi2SeS2 with high thermoelectric performance.

Nanocomposite engineering decouples the transport of phonons and electrons. This usually involves the in-situ formation or ex-situ addition of nanoparticles to a material matrix with hetero-composition and hetero-structure (heC-heS) interfaces or hetero-composition and homo-structure (heC-hoS) interfaces. Herein, a quasi homo-composition and hetero-structure (hoC-heS) nanocomposite consisting of Pnma Bi2SeS2 - Pnnm Bi2SeS2 is obtained through a Br dopant-induced phase transition, providing a coherent interface between the Pnma matrix and Pnnm second phase due to the slight structural difference between the two phases. This hoC-heS nanocomposite demonstrates a significant reduction in lattice thermal conductivity (~0.40 W m-1 K-1) and an enhanced power factor (7.39 µW cm-1 K-2). Consequently, a record high figure-of-merit ZTmax = 1.12 (at 773 K) and a high average figure-of-merit ZTave = 0.72 (in the range of 323-773 K) are achieved. This work provides a general strategy for synergistically tuning electrical and thermal transport properties by designing hoC-heS nanocomposites through a dopant-induced phase transition.

Photoinduced Self-Assembly of Carbon Nitride Quantum Dots.

The study of nanocrystal self-assembly into superlattices or superstructures is of great significance in nanoscience. Carbon nitride quantum dots (CNQDs), being a promising new group of nanomaterials, however, have hardly been explored in their self-organizing behavior. Here we report of a unique irradiation-triggered self-assembly and recrystallization phenomenon of crystalline CNQDs (c-CNQDs) terminated by abundant oxygen-containing groups. Unlike the conventional self-assembly of nanocrystals into ordered superstructures, the photoinduced self-assembly of c-CNQDs resembles a "click reaction" process of macromolecules, in which the activated -OH and -NH2 functional groups along the perimeters initiate cross-linking of adjacent QDs through a photocatalytic effect. Our findings unveil fundamental physiochemical features of CNQDs and open up new possibilities of manipulating carbon nitride nanomaterials via controlled assembly. Prospects for potential applications are discussed as well.

New type of borneol-based fluorine-free superhydrophobic antibacterial polymeric coating.

A new type of superhydrophobic borneol-based polymeric coating has been prepared. The chemical composition of the polymer particles was analyzed by Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy, which showed that the polymer did not contain fluorine, which can effectively avoid the cytotoxic risk of fluorine. By dynamic light scattering, scanning electron microscopy, and static contact angle measurement, the contact angle of the prepared coating gradually increased with increasing diameter of the polymer particles, and a superhydrophobic coating surface was finally obtained. Interestingly, after dissolving the superhydrophobic sample with tetrahydrofuran and making it a normal hydrophobic sample, the antiadhesion performance for E. coli was greatly reduced, and it could not effectively prevent E. coli adhesion. In addition, a long-term antiadhesion study of bacteria was performed. The superhydrophobic borneol-based polymer coating showed long-term resistance to E. coli adhesion. Therefore, the excellent antibacterial properties and cell compatibility mean that this series of polymer materials has great potential in the field of biomedicine.

Selenium mitigates salt-induced oxidative stress in durum wheat (Triticum durum Desf.) seedlings by modulating chlorophyll fluorescence, osmolyte accumulation, and antioxidant system.

Hydroponic experiments were conducted to investigate the effects of different concentrations of sodium selenate (Na2SeO4) and sodium selenite (Na2SeO3) on durum wheat seed germination and seedling growth under salt stress. The treatments used were 0 and 50 mM NaCl solutions, each supplemented with Na2SeO4 or Na2SeO3 at 0, 0.1, 1, 2, 4, 8, or 10 µM. Salt alone significantly inhibited seed germination and reduced seedling growth. Addition of low concentrations (0.1-4 µM) of Na2SeO4 or Na2SeO3 mitigated the adverse effects of salt stress on seed germination, biomass accumulation, and other physiological attributes. Among them, 1 µM Na2SeO4 was most effective at restoring seed germination rate, germination energy, and germination index, significantly increasing these parameters by about 12.35, 24.17, and 11.42%, respectively, compared to salt-stress conditions. Adding low concentrations of Na2SeO4 or Na2SeO3 to the salt solution also had positive effects on chlorophyll fluorescence indices, decreased the concentrations of free proline and malondialdehyde, as well as electrolyte leakage, and increased catalase, superoxide dismutase, and peroxidase activities in roots and shoots. However, high concentrations (8-10 µM) of Na2SeO4 or Na2SeO3 disrupted seed germination and seedling growth, with damage caused by Na2SeO3 being more severe than that by Na2SeO4. It is thus clear that exogenous selenium can improve the adaptability of processing wheat to salt stress and maintain higher photosynthetic rate by decreasing the accumulation of reactive oxygen species and alleviating the degree of membrane lipid peroxidation. Na2SeO4 was more effective than Na2SeO3 at all given concentrations.

Two-Dimensional Platinum Diselenide: Synthesis, Emerging Applications, and Future Challenges.

In recent years, emerging two-dimensional (2D) platinum diselenide (PtSe2) has quickly attracted the attention of the research community due to its novel physical and chemical properties. For the past few years, increasing research achievements on 2D PtSe2 have been reported toward the fundamental science and various potential applications of PtSe2. In this review, the properties and structure characteristics of 2D PtSe2 are discussed at first. Then, the recent advances in synthesis of PtSe2 as well as their applications are reviewed. At last, potential perspectives in exploring the application of 2D PtSe2 are reviewed.

Recent Progress of Two-Dimensional Thermoelectric Materials.

Thermoelectric generators have attracted a wide research interest owing to their ability to directly convert heat into electrical power. Moreover, the thermoelectric properties of traditional inorganic and organic materials have been significantly improved over the past few decades. Among these compounds, layered two-dimensional (2D) materials, such as graphene, black phosphorus, transition metal dichalcogenides, IVA-VIA compounds, and MXenes, have generated a large research attention as a group of potentially high-performance thermoelectric materials. Due to their unique electronic, mechanical, thermal, and optoelectronic properties, thermoelectric devices based on such materials can be applied in a variety of applications. Herein, a comprehensive review on the development of 2D materials for thermoelectric applications, as well as theoretical simulations and experimental preparation, is presented. In addition, nanodevice and new applications of 2D thermoelectric materials are also introduced. At last, current challenges are discussed and several prospects in this field are proposed.