Organic-inorganic Superlattice Research Articles

An Organic–Inorganic Superlattice with Nanocrystal‐Amorphous Composite Nanolayers for Ultrahigh Thermoelectric Performance

Thermoelectric materials play a crucial role in converting heat into electricity, offering significant potential for applications in waste heat recovery and cooling. Herein, an innovative approach that combines an organic–inorganic hybrid superlattice structure with nanocrystal‐amorphous composite nanolayers is introduced. The nanocrystal‐amorphous composite enhances the Seebeck coefficient resulting in a notable twofold improvement in the power factor. The superlattice, alternating self‐assembled organic monolayers and inorganic nanolayers, effectively reduces lattice thermal conductivity by creating multiple interfaces that scatter phonons effectively. The integration of the nanocrystal‐amorphous composite nanolayers into the superlattice provides a dual advantage, simultaneously boosting the power factor and suppressing thermal conductivity. This synergistic effect leads to exceptional thermoelectric performance in the 4‐mercaptophenol/Sb2Te3 superlattice, with achieved figure of merit (ZT) values of 3.48 at 300 K and reaching a peak ZT value exceeding 4.0 at 400 K while surpassing 2.5 over the temperature range from 300 to 500 K. These results suggest that this innovative approach paves the way for the development of highly efficient thermoelectric materials, propelling efforts toward more energy‐efficient and environmentally friendly solutions.

Interfacial Charge-Transfer Excitonic Insulator in a Two-Dimensional Organic-Inorganic Superlattice.

Excitonic insulators are long-sought-after quantum materials predicted to spontaneously open a gap by the Bose condensation of bound electron-hole pairs, namely, excitons, in their ground state. Since the theoretical conjecture, extensive efforts have been devoted to pursuing excitonic insulator platforms for exploring macroscopic quantum phenomena in real materials. Reliable evidence of excitonic character has been obtained in layered chalcogenides as promising candidates. However, owing to the interference of intrinsic lattice instabilities, it is still debatable whether those features, such as the charge density wave and gap opening, are primarily driven by the excitonic effect or by the lattice transition. Herein, we develop an intercalation chemistry strategy for obtaining a novel charge-transfer excitonic insulator in organic-inorganic superlattice interfaces that serves as an ideal platform to decouple the excitonic effect from the lattice effect. In this system, we observe a narrow excitonic gap, formation of a charge density wave without periodic lattice distortion, and metal-insulator transition, providing visualized evidence of exciton condensation occurring in thermal equilibrium. Our findings identify self-assembly intercalation chemistry as a new strategy for developing novel excitonic insulators.

Titanium‐Based Superlattice with Fe(III)‐Regulable Bandgap and Performance for Optimal and Synergistic Sonodynamic–Chemotherapy Guided by Magnetic Resonance Imaging

AbstractSuperlattices have considerable potential as sonosensitizers for cancer therapy because of their flexible and tunable band gaps, although they have not yet been reported. In this study, a Ti‐based organic–inorganic superlattice with good electron–hole separation was synthesized, which consisted of orderly layered superlattices of 2,2′‐bipyridine‐5,5′‐dicarboxylic acid (BPDC) and Ti−O layers. In addition, the superlattice was coordinated with Fe(III) and encapsulated doxorubicin (DOX) to prepare Ti‐BPDC@Fe@DOX@PEG (TFDP) after biocompatibility modification. TFDP can realize the simultaneous generation of reactive oxygen species and release of DOX under ultrasound irradiation. Moreover, adjusting the Fe(III) content can effectively modulate the band gap of the superlattice and increase the efficiency of sonodynamic therapy (SDT). The mechanisms underlying this modulation were explored. TFDP with Fe(III) can also be used as a contrast agent for magnetic resonance imaging (MRI). Both in vitro and in vivo experiments demonstrated the ability of TFDP to precisely treat cancer using MRI‐guided SDT/chemotherapy. This study expands the applications of superlattices as sonosensitizers with flexible and tailored modifications and indicates that superlattices are promising for precise and customized treatments.

Titanium-Based Superlattice with Fe(III)-Regulable Bandgap and Performance for Optimal and Synergistic Sonodynamic-Chemotherapy Guided by Magnetic Resonance Imaging.

Superlattices have considerable potential as sonosensitizers for cancer therapy because of their flexible and tunable band gaps, although they have not yet been reported. In this study, a Ti-based organic-inorganic superlattice with good electron-hole separation was synthesized, which consisted of orderly layered superlattices of 2,2'-bipyridine-5,5'-dicarboxylic acid (BPDC) and Ti-O layers. In addition, the superlattice was coordinated with Fe(III) and encapsulated doxorubicin (DOX) to prepare Ti-BPDC@Fe@DOX@PEG (TFDP) after biocompatibility modification. TFDP can realize the simultaneous generation of reactive oxygen species and release of DOX under ultrasound irradiation. Moreover, adjusting the Fe(III) content can effectively modulate the band gap of the superlattice and increase the efficiency of sonodynamic therapy (SDT). The mechanisms underlying this modulation were explored. TFDP with Fe(III) can also be used as a contrast agent for magnetic resonance imaging (MRI). Both in vitro and in vivo experiments demonstrated the ability of TFDP to precisely treat cancer using MRI-guided SDT/chemotherapy. This study expands the applications of superlattices as sonosensitizers with flexible and tailored modifications and indicates that superlattices are promising for precise and customized treatments.

Organic-SnSe2 Hybrid Superlattice toward Synergistic Electrical Transport Optimization and Thermal Conductance Suppression.

Recently, layered SnSe2 has drawn broad research interest as a promising thermoelectric material that possesses great potential for application in energy conversion. However, extensive efforts have been devoted to optimizing the thermoelectric performance of SnSe2, but the ZT value is still far from satisfactory. Therefore, we developed an organic-inorganic superlattice hybrid by intercalating organic cations into SnSe2 interlayers in an attempt to enhance the thermoelectric properties. Organic intercalants can enlarge the basal spacing and decouple the SnSe2 layers, bringing about synergistic electrical transport modification and phonon softening. Thus, by simultaneously improving the electrical conductivity and reducing the thermal conductivity, a ZT value of 0.34 is achieved at 342 K in tetrabutylammonium-intercalated SnSe2, approximately two orders of magnitude higher than that of pristine SnSe2 single crystals. In addition, by opening van der Waals gaps via organic cations, outstanding flexibility of organic-intercalated SnSe2 is realized, with a superior figure of merit for flexibility of approximately 0.068. This work demonstrates a general and facile strategy to fabricate organic-inorganic superlattice hybrids with a considerable improvement in the thermoelectric performance via organic cation intercalation, which is promising for flexible thermoelectrics.

Interfacial modulation of organic-inorganic two-dimensional superlattices for efficient electromagnetic wave absorption

Conventional strategies used to develop broadband electromagnetic wave (EMW) absorbing materials have mainly focused on multi-component hybrid materials. In these materials, attenuation of EMW absorption is achieved through strong interfacial polarization at heterogeneous interfaces. However, these interfaces have most often been on the micron scale and, therefore, they have many inherent defects. Herein, we devised a new approach in which an organic-inorganic superlattice structure composite is employed to achieve hyperpolarization loss by modulating the heterogeneous interface between a V2O5 layer and PANI at the molecular scale. Amplification of interfacial polarization effects at heterogeneous interfaces between materials by exploiting large differences in physical properties between the non-conducting V2O5 phase and the conducting PANI phase. Synergy between conductive losses and polarization losses is achieved by optimizing the thickness of the conductive phase PANI layer, which contributes to an effective absorption bandwidth (EAB) of 6.40 GHz at a thickness of 2.1 mm. The results of experimental and theoretical studies clearly show that the superlattice structure is responsible for the unique microwave absorption properties. Thus, the construction of heterogeneous interfaces at the molecular scale will serve as the basis for designing future broadband absorbing materials.

Electrical defect passivation of nanocrystalline In-Ga-O thin film transistor with organic-inorganic superlattice structure

ABSTRACT Metal oxide thin film transistors have received tremendous attention due to various advantages over the conventional Si-based TFT for the next-generation wearable electronics. However, the surface of a metal oxide thin film is very sensitive to ambient molecules such as moisture and oxygen, degrading the device performance after long-term operation. In this work, we report on utilizing the passivation effect from various phosphonic acids (PAs) to suppress the adsorption of ambient chemical species and the oxygen vacancy defect in the superlattice (SL) structure prepared by insertion of PA between two nanocrystalline In-Ga-O (nc-IGO) layers (7.5% atomic percentage). The most effective stabilization of SL structure is successfully realized with 1,10-decyl diphosphonic acid (P10) treatment. Very impressively, the reference device with pristine nc-IGO film around 10 nm shows a large threshold voltage (Vth) shift of 11.80 V after 10,000 s of PBS (VG = 50 V, VDS = 25 V), but the optimized device with P10 SL structure with similar thickness shows a negligible Vth of 1.21 V with same stress condition. Furthermore, the oxygen vacancy defect suppression also resulted in a small Vth shift of 2.94 V after 10,000 s NBS (VG = −50 V, VDS = −25 V).

Robust Lithium–Sulfur Batteries Enabled by Highly Conductive WSe2‐Based Superlattices with Tunable Interlayer Space

AbstractSuperlattices are rising stars on the horizon of energy storage and conversion, bringing new functionalities; however, their complex synthesis limits their large‐scale production and application. Herein, a simple solution‐based method is reported to produce organic–inorganic superlattices and demonstrate that the pyrolysis of the organic compound enables tuning their interlayer space. This strategy is exemplified here by combining polyvinyl pyrrolidone (PVP) with WSe2within PVP/WSe2superlattices. The annealing of such heterostructures results in N‐doped graphene/WSe2(NG/WSe2) superlattices with a continuously adjustable interlayer space in the range from 10.4 to 21 Å. Such NG/WSe2superlattices show a metallic electronic character with outstanding electrical conductivities. Both experimental results and theoretical calculations further demonstrate that these superlattices are excellent sulfur hosts at the cathode of lithium–sulfur batteries (LSB), being able to effectively reduce the lithium polysulfide shuttle effect by dual‐adsorption sites and accelerating the sluggish Li–S reaction kinetics. Consequently, S@NG/WSe2electrodes enable LSBs characterized by high sulfur usages, superior rate performance, and outstanding cycling stability, even at high sulfur loadings, lean electrolyte conditions, and at the pouch cell level. Overall, this work not only establishes a cost‐effective strategy to produce artificial superlattice materials but also pioneers their application in the field of LSBs.

High-Yield Exfoliation of Monolayer 1T'-MoTe2 as Saturable Absorber for Ultrafast Photonics.

Liquid-phase exfoliation can be developed for the large-scale production of two-dimensional materials for photonic applications. Although atomically thin 2D transition metal dichalcogenides (TMDs) show enhanced nonlinear optical properties or photoluminescence quantum yield relative to the bulk phase, these properties are weak in the absolute sense due to the ultrashort optical path, and they are also sensitive to layer-dependent symmetry properties. Another practical issue is that the chemical stability of some TMDs (e.g., Weyl semimetals) decreases dramatically as the thickness scales down to monolayer, precluding application as optical components in air. To address these issues, a way of exfoliating TMDs that ensures instantaneous passivation needs to be developed. Here, we employed a polymer-assisted electrochemical exfoliation strategy to synthesize PVP-passivated TMDs monolayers that could be spin coated and restacked into organic-inorganic superlattices with well-defined X-ray diffraction patterns. The segregation of restacked TMDs (e.g., MoS2) by PVP allows the inversion asymmetry of individual layers to be maintained in these superlattices, which allows second harmonic generation and photoluminescence to be linearly scaled with thickness. PVP-passivated monolayer 1T'-MoTe2 saturable absorber fabricated from these flakes exhibits fast response and recovery time (<150 fs) and pulse stability. Continuous-wave mode-locking based on 1T'-MoTe2 saturable absorber in a fiber ring laser cavity has been realized, attaining a fundamental repetition rate of 3.15 MHz and pulse duration as short as 867 fs at 1563 nm.

Advances in Atomic Layer Deposition (ALD) Nanolaminate Synthesis of Thermoelectric Films in Porous Templates for Improved Seebeck Coefficient.

Thermoelectrics is a green renewable energy technology which can significantly contribute to power generation due to its potential in generating electricity out of waste heat. The main challenge for the development of thermoelectrics is its low conversion efficiency. One key strategy to improve conversion efficiency is reducing the thermal conductivity of thermoelectric materials. In this paper, the state-of-the-art progresses made in improving thermoelectric materials are reviewed and discussed, focusing on phononic engineering via applying porous templates and ALD deposited nanolaminates structure. The effect of nanolaminates structure and porous templates on Seebeck coefficient, electrical conductivity and thermal conductivity, and hence in figure of merit zT of different types of materials system, including PnCs, lead chalcogenide-based nanostructured films on planar and porous templates, ZnO-based superlattice, and hybrid organic-inorganic superlattices, will be reviewed and discussed.

Two-dimensional organic–inorganic superlattice-like heterostructures for energy storage applications

Recent progress in 2D organic–inorganic superlattices by alternate stacking of organic layers and inorganic sheets is reviewed.

Boosting superconductivity in organic-inorganic superlattices

Boosting superconductivity in organic-inorganic superlattices

Solvent-Dependent Intercalation and Molecular Configurations in Metallocene-Layered Crystal Superlattices.

Organic-inorganic superlattices are a class of artificial structures of significant scientific and technological importance. Forming these hybrid materials can be achieved via controlled intercalation of organic molecules into inorganic layered hosts, which is a complex course involving multiple physicochemical processes. In solution phase, it is further complicated by interaction of solvent molecules with the intercalant and/or host. Here we describe an intercalation system exhibiting strong solvent-dependent kinetics and phase evolution. In revisiting intercalation of ferrocene into layered VOPO4·2H2O material by taking into account the influence of solvent, we are able to unravel molecular configurations of ferrocene molecules. An exclusive orientation of ferrocene but different arrangements among the layers are concluded in two model solvents. Resolving this complicated structure is possible thanks to a combined experimental and theoretical approach. Our study provides new insights into understanding molecular configurations and controlling intercalation kinetics in creating organic-inorganic superlattices, which may offer unprecedented properties beyond conventional materials.

Molecule-Confined Engineering toward Superconductivity and Ferromagnetism in Two-Dimensional Superlattice.

Superconductivity is mutually exclusive with ferromagnetism, because the ferromagnetic exchange field is often destructive to superconducting pairing correlation. Well-designed chemical and physical methods have been devoted to realize their coexistence only by structural integrity of inherent superconducting and ferromagnetic ingredients. However, such coexistence in freestanding structure with nonsuperconducting and nonferromagnetic components still remains a great challenge up to now. Here, we demonstrate a molecule-confined engineering in two-dimensional organic-inorganic superlattice using a chemical building-block approach, successfully realizing first freestanding coexistence of superconductivity and ferromagnetism originated from electronic interactions of nonsuperconducting and nonferromagnetic building blocks. We unravel totally different electronic behavior of molecules depending on spatial confinement: flatly lying Co(Cp)2 molecules in strongly confined SnSe2 interlayers weaken the coordination field, leading to spin transition to form ferromagnetism; meanwhile, electron transfer from cyclopentadienyls to the Se-Sn-Se lattice induces superconducting state. This entirely new class of coexisting superconductivity and ferromagnetism generates a unique correlated state of Kondo effect between the molecular ferromagnetic layers and inorganic superconducting layers. We anticipate that confined molecular chemistry provides a newly powerful tool to trigger exotic chemical and physical properties in two-dimensional matrixes.

Tailoring a compact and stable Langmuir bi-dimensional PbX-based layered perovskite film at the air-water interface and on solid support.

The present work studies the stability of Langmuir organic-inorganic superlattice materials thin films consisting of layered perovskite-based films with controlled 2D framework as well as to design experimental conditions for increasing the efficiency of the organic-inorganic perovskite motif by mechanical stimulus. Therefore, a whole covering of the air/water interface by a compact and stable lead-based layered perovskite structure is pursued. A 2D layered perovskite-type hybrid structure of the form [(CH3(CH2)19NH3)2(PbX4)], X=Cl, and Br, in which, two-dimensional sheets stabilized by a inner bilayer of organic monoammonium cation matrix, is mechanically tailored by successive compression-expansion cycles. The formation of 2D molecular patterns has been characterized by ΔR, BAM, XRD and XPS.

Hydroquinone-ZnO nano-laminate deposited by molecular-atomic layer deposition

In this study, we have deposited organic-inorganic hybrid semiconducting hydroquinone (HQ)/zinc oxide (ZnO) superlattices using molecular-atomic layer deposition, which enables accurate control of film thickness, excellent uniformity, and sharp interfaces at a low deposition temperature (150 °C). Self-limiting growth of organic layers is observed for the HQ precursor on ZnO surface. Nano-laminates were prepared by varying the number of HQ to ZnO cycles in order to investigate the physical and electrical effects of different HQ to ZnO ratios. It is indicated that the addition of HQ layer results in enhanced mobility and reduced carrier concentration. The highest Hall mobility of approximately 2.3 cm2/V·s and the lowest n-type carrier concentration of approximately 1.0 × 1018/cm3 were achieved with the organic-inorganic superlattice deposited with a ratio of 10 ZnO cycles to 1 HQ cycle. This study offers an approach to tune the electrical transport characteristics of ALD ZnO matrix thin films using an organic dopant. Moreover, with organic embedment, this nano-laminate material may be useful for flexible electronics.

Electric conduction of PbBr-based layered perovskite organic–inorganic superlattice having carbazole chromophore-linked ammonium molecule as an organic layer

We have successfully prepared thin films of PbBr-based layered perovskite having hole-transporting carbazole chromophore-linked ammonium molecules as an organic layer by a simple spin-coating from the N,N-dimethylformamide solution in which the stoichiometric amount of lead bromide and carbazole-linked ammonium bromides was dissolved. Their X-ray diffraction profiles exhibited that their layer structure formed (00n)-orientation, where c-axis is perpendicular to the substrate plane. Their layer structure depended on the alkyl chain length of ammonium molecules. When methylene length of C5H10 was employed in the carbazole-linked ammonium molecules, highest orderliness of the layer structure was attained; higher-order X-ray diffraction peaks were observed in the layered perovskite films. In the layered pervskite film, in-plane conduction, namely conduction in the direction of the stacking of carbazole chromophore, was measured. For comparison, conductivity of poly(N-vinylcarbazole) (PVCBz) thin film was also measured. The conductivity of the layered perovskite thin film (1.8×10−10Scm−1 at 303K) was about three order of magnitude larger than that of the PVCBz thin film (5.3×10−14Scm−1 at 303K). Despite the much higher conductivity of the layered peroskite thin film, the activation energy of the conductivity of the layered perovskite thin film (1.44eV) was about 2.4 times larger than that of the PVCBz thin film (0.61eV). This phenomenon is probably due to difference in film morphology through considering the results of AFM observation.

Thermoelectric Properties of Hybrid Organic–Inorganic Superlattices

We theoretically evaluate the thermoelectric transport coefficients of hybrid thiophene/SiGe superlattices and the effect of their chemical tuning via phenyl groups. Owing to the interplay between alloy scattering and phonon transmission at the molecular layers, very low thermal conductivities under 1 W/(m K) and values of ZT more than twice as large as those of bulk SiGe can be attained. These results highlight exciting possibilities of organic–inorganic hybrid systems, as compared to traditional inorganic thermoelectrics.

Active glass–polymer superlattice structure for photonic integration

We propose an all-laser processing approach allowing controlled growth of organic–inorganic superlattice structures of rare-earth ion doped tellurium-oxide-based glass and optically transparent polydimethyl siloxane (PDMS) polymer; the purpose of which is to illustrate the structural and thermal compatibility of chemically dissimilar materials at the nanometer scale. Superlattice films with interlayer thicknesses as low as 2 nm were grown using pulsed laser deposition (PLD) at low temperatures (100 °C). Planar waveguides were successfully patterned by femtosecond-laser micro-machining for light propagation and efficient Er3+-ion amplified spontaneous emission (ASE). The proposed approach to achieve polymer–glass integration will allow the fabrication of efficient and durable polymer optical amplifiers and lossless photonic devices. The all-laser processing approach, discussed further in this paper, permits the growth of films of a multitude of chemically complex and dissimilar materials for a range of optical, thermal, mechanical and biological functions, which otherwise are impossible to integrate via conventional materials processing techniques.

PbBr-based layered perovskite organic–inorganic superlattice having hole-transporting carbazole chromophore in organic layer

Oriented thin films of lead bromide-based layered perovskite having an organic–inorganic superlattice structure, which is combined with a lead bromide semiconductor layer and an organic layer of carbazole-linked ammonium molecules, were successfully prepared by spin-coating from dimethylformamide solution in which stoichiometric amounts of PbBr2 and carbazolelinked ammonium bromides were dissolved. The thin films exhibited sharp exciton absorption around 400 nm which is characteristic of PbBr-based layered perovskite in addition to absorptions due to carbazole chromophore peaking around 350 and 300 nm. X-ray diffraction measurement demonstrated that the layer structure was oriented parallel to the film plane: the spin-coated films exhibited only (0 0 n) reflections, where c-axis is in the stacking direction of the layer structure. 2004 Elsevier B.V. All rights reserved.