Inorganic Molecular Crystals Research Articles

First principles study on interactions in inorganic molecular crystals at zero dimensions

Inorganic molecular crystals (IMCs) are attracting significant scientific interest due to their distinctive anisotropic crystal structure. The molecular units in the form of cages are the fundamental unit of these materials and most of their properties are dependent on the geometry, their arrangement and the interactions present in between these cages. This work is carried out to shed light on the structural arrangement and the interaction properties of three IMCs including antimony oxide (Sb2O3), phosphorous tri-selenium (P4Se3) and phosphorous trioxide (P4O6) in zero dimensions. The reported calculations were carried out using density Functional Theory (DFT) to investigate the interactions between the cages based on ETS-NOCV, NBO, Wiberg bond indices and QTAIM analysis. The results revealed weak VdWs association along the inter-cages and significant covalent bonding within the cage. The investigation shows that Sb2O3 and P4Se3 IMCs have potential applications in high-pressure and stress-bearing materials.

Polarization‐directed nanophotonic routers based on two‐dimensional inorganic molecular crystals

AbstractPhotonic and plasmonic hybrid nanostructures are the key solution for integrated nanophotonic circuits with ultracompact size but relative low loss. However, the poor tunability and modulability of conventional waveguides makes them cumbersome for optical multiplexing. Here we make use of two‐dimensional molecular crystal, α‐Sb2O3 as a dielectric waveguide via total internal reflection, which shows polarization‐sensitive modulation of the propagating beams due to its large polarization mode dispersion. Both experiments and simulations are performed to verify such concept. These Sb2O3 nanoflakes can be coupled with plasmonic nanowires to form nanophotonic beam splitters and routers which can be easily modulated by changing the polarization of the incidence. It thus provides a robust, exploitable and tunable platform for on‐chip nanophotonics.image

Emergence of Two-Dimensional Inorganic Molecular Crystals

Emergence of Two-Dimensional Inorganic Molecular Crystals

Large‐Scale Ultrastable 2D Inorganic Molecular Crystal BiBr3 and Heterostructures with Superior Photoluminescence Enhancement

AbstractIn contrast to conventional atomic crystals, two‐dimensional inorganic molecular crystals (2DIMCs) possess a unique crystal structure composed of small molecules held together by van der Waals force. Such distinctive structure grants them specific chemical and physical properties highly suitable for electronic and optoelectronic applications. However, the synthesis of 2DIMCs has posed significant challenges due to the inherent issues such as uncontrollable growth orientation stemming from their natural crystalline isotropy and poor stability resulting from the weak intermolecular connections. Addressing these obstacles, the preparation of large‐scale and highly‐stable 2DIMC BiBr3, and its heterostructure are reported here by developing crystallization orientation engineering strategies. This approach has successfully yielded centimeter‐scale 2DIMC BiBr3 with a clean and dense surface, showcasing exceptional long‐term air‐stability exceeding 80 days. Furthermore, the universal growth of large‐scale 2DIMC BiBr3 is demonstrated on diverse substrates, including SiO2, Al2O3, and MoS2 monolayers. Notably, the resultant 2D BiBr3/MoS2 heterostructure exhibits remarkable photoluminescence enhancement. This contribution paves a universal avenue for the mature synthesis of large‐scale 2DIMCs with superior stability, holding great promise for prompting their integration in practical electronic and optoelectronic devices.

Enhanced charge transport in 2D inorganic molecular crystals constructed with charge‐delocalized molecules

AbstractOutstanding charge transport in molecular crystals is of great importance in modern electronics and optoelectronics. The widely adopted strategies to enhance charge transport, such as restraining intermolecular vibration, are mostly limited to organic molecules, which are nearly inoperative in 2D inorganic molecular crystals currently. In this contribution, charge transport in 2D inorganic molecular crystals is improved by integrating charge‐delocalized Se8 rings as building blocks, where the delocalized electrons on Se8 rings lift the intermolecular orbitals overlap, offering efficient charge transfer channels. Besides, α‐Se flakes composed of charge‐delocalized Se8 rings possess small exciton binding energy. Benefitting from these, α‐Se flake exhibits excellent photodetection performance with an ultrafast response rate (~5 μs) and a high detectivity of 1.08 × 1011 Jones. These findings contribute to a deeper understanding of the charge transport of 2D inorganic molecular crystals composed of electron‐delocalized inorganic molecules and pave the way for their potential application in optoelectronics.

Emerging van der Waals Dielectrics of Inorganic Molecular Crystals for 2D Electronics.

In the landscape of continuous downscaling metal-oxide-semiconductor field-effect transistors, two-dimensional (2D) semiconductors with atomic thinness emerge as promising channel materials for ultimate scaled devices. However, integrating compatible dielectrics with 2D semiconductors, particularly in a scalable way, remains a critical challenge that hinders the development of 2D devices. Recently, 2D inorganic molecular crystals (IMCs), which are free of dangling bonds and possess excellent dielectric properties and simplicity for scalable fabrication, have emerged as alternatives for gate dielectric integration in 2D devices. In this Perspective, we start with the introduction of structure and synthesis methods of IMCs and then discuss the explorations of using IMCs as the dielectrics, as well as some remaining relevant issues to be unraveled. Moreover, we look at the future opportunities of IMC dielectrics in 2D devices both for practical applications and fundamental research.

Impacts of structural downscaling of inorganic molecular crystals - A DFT study of Sb2O3

Impacts of structural downscaling of inorganic molecular crystals - A DFT study of Sb2O3

Structural diversity and topological property of I-based two-dimensional inorganic molecular crystals

Structural diversity and topological property of I-based two-dimensional inorganic molecular crystals

An Ultrathin Inorganic Molecular Crystal Interfacial Layer for Stable Zn Anode.

Zn metal anode suffers from dendrite growth and side reactions during cycling, significantly deteriorating the lifespan of aqueous Zn metal batteries. Herein, we introduced an ultrathin and ultra-flat Sb2O3 molecular crystal layer to stabilize Zn anode. The in-situ optical and atomic force microscopes observations show that such a 10nm Sb2O3 thin layer could ensure uniform under-layer Zn deposition with suppressed tip growth effect, while the traditional WO3 layer undergoes an uncontrolled up-layer Zn deposition. The superior regulation capability is attributed to the good electronic-blocking ability and low Zn affinity of the molecular crystal layer, free of dangling bonds. Electrochemical tests exhibit Sb2O3 layer can significantly improve the cycle life of Zn anode from 72 h to 2800 h, in contrast to the 900 h of much thicker WO3 even in 100 nm. This research opens up the application of inorganic molecular crystals as the interfacial layer of Zn anode.

An Ultrathin Inorganic Molecular Crystal Interfacial Layer for Stable Zn Anode

AbstractZn metal anode suffers from dendrite growth and side reactions during cycling, significantly deteriorating the lifespan of aqueous Zn metal batteries. Herein, we introduced an ultrathin and ultra‐flat Sb2O3 molecular crystal layer to stabilize Zn anode. The in situ optical and atomic force microscopes observations show that such a 10 nm Sb2O3 thin layer could ensure uniform under‐layer Zn deposition with suppressed tip growth effect, while the traditional WO3 layer undergoes an uncontrolled up‐layer Zn deposition. The superior regulation capability is attributed to the good electronic‐blocking ability and low Zn affinity of the molecular crystal layer, free of dangling bonds. Electrochemical tests exhibit Sb2O3 layer can significantly improve the cycle life of Zn anode from 72 h to 2800 h, in contrast to the 900 h of much thicker WO3 even in 100 nm. This research opens up the application of inorganic molecular crystals as the interfacial layer of Zn anode.

Recent Advances in Growth, Properties and Applications of 2D Inorganic Molecular Crystals†

Comprehensive SummarySince the concept of 2D inorganic molecular crystals (2DIMCs) was introduced, intensive attentions have been gradually devoted to this field. Herein, the very recent advances in growth, properties, and applications of 2D inorganic molecular crystals are comprehensively reviewed. Firstly, the newly emerged 2DIMCs are classified into three categories. Then the two typical production methods are present, thus leading to discrepancy in size, distribution, morphology and structures of 2DIMCs. Moreover, the unique physicochemical properties of 2DIMCs are demonstrated on the basis of the as‐obtained 2DIMCs, the various applications are exhibited, demonstrating significant potential in related fields. Finally, the perspective and prospects are outlooked to offer insights in further development of 2DIMCs.

Giant Tunability of Charge Transport in 2D Inorganic Molecular Crystals by Pressure Engineering.

The unique intermolecular van der Waals force in emerging two-dimensional inorganic molecular crystals (2DIMCs) endows them with highly tunable structures and properties upon applying external stimuli. Using high pressure to modulate the intermolecular bonding, here we reveal the highly tunable charge transport behavior in 2DIMCs for the first time, from an insulator to a semiconductor. As pressure increases, 2D α-Sb2 O3 molecular crystal undergoes three isostructural transitions, and the intermolecular bonding enhances gradually, which results in a considerably decreased band gap by 25 % and a greatly enhanced charge transport. Impressively, the in situ resistivity measurement of the α-Sb2 O3 flake shows a sharp drop by 5 orders of magnitude in 0-3.2 GPa. This work sheds new light on the manipulation of charge transport in 2DIMCs and is of great significance for promoting the fundamental understanding and potential applications of 2DIMCs in advanced modern technologies.

Giant Tunability of Charge Transport in 2D Inorganic Molecular Crystals by Pressure Engineering

AbstractThe unique intermolecular van der Waals force in emerging two‐dimensional inorganic molecular crystals (2DIMCs) endows them with highly tunable structures and properties upon applying external stimuli. Using high pressure to modulate the intermolecular bonding, here we reveal the highly tunable charge transport behavior in 2DIMCs for the first time, from an insulator to a semiconductor. As pressure increases, 2D α‐Sb2O3 molecular crystal undergoes three isostructural transitions, and the intermolecular bonding enhances gradually, which results in a considerably decreased band gap by 25 % and a greatly enhanced charge transport. Impressively, the in situ resistivity measurement of the α‐Sb2O3 flake shows a sharp drop by 5 orders of magnitude in 0–3.2 GPa. This work sheds new light on the manipulation of charge transport in 2DIMCs and is of great significance for promoting the fundamental understanding and potential applications of 2DIMCs in advanced modern technologies.

Fabrication of Sb2O3 by an improved chemical reaction assisted vertical micro sublimation method and its saturable absorber performance

Two-dimensional molecular crystals (2DMCs) are emerging ideal materials for future high-performance optoelectronic devices. People are constantly exploring new methods to solve the problem of difficult growth. Here, we design an improved chemical reaction-assisted vertical micro sublimation method based on vertical micro sublimation for the growth of two-dimensional Sb2O3 inorganic molecular crystals for the first time. The saturation absorption characteristics of the self-made Sb2O3 2DMCs were systematically tested, and the Q-switched laser output characteristics of Sb2O3 2DMCs at 1 µm were verified by using Nd: GYAP mixed crystal. The maximum average output power of 231 mW was achieved at 1080.6 nm, corresponding shortest pulse with a duration of 472 ns and maximum pulse repetition rate of 376 kHz. The maximum single pulse energy and the maximum peak power of the laser output were 0.614 µJ and 1.3 W, respectively. The growth of other 2DMCs would be motivated and its potential applications in the field of ultrafast photonics would be expanded with our findings.

Emerging Two-Dimensional Inorganic Molecular Crystals: The Concept and Beyond.

The concept of two-dimensional (2D) inorganic molecular crystals (IMCs) was first introduced by Zhai and coauthors in 2019. In contrast to the layered structures of graphene-like 2D materials, 2D IMCs consist of tiny inorganic molecules bonded together through all-around van der Waals (vdW) interactions. Their structural peculiarities lead to some special behaviors and appealing properties in their synthesis and applications. In this Perspective, we first introduce the concept of 2D IMCs and present the very first synthesis of 2D IMCs using a surface-passivated growth approach. The special intermolecular effects between the inorganic molecules are also summarized. In addition, because of its molecular structure, a vdW film of IMCs can be facilely fabricated, which exhibits appealing potential in integrated 2D devices. More importantly, we give a general outlook for the further development of 2D IMCs with the goal of attracting more attention to this emerging research frontier.

Scalable Van der Waals Encapsulation by Inorganic Molecular Crystals (Adv. Mater. 7/2022)

2D Materials Van der Waals (vdW) encapsulation is one of the most promising approaches to improve the stability and reliability of 2D-materials-based devices. So far, a scalable vdW encapsulation approach through complementary metal–oxide-semiconductor (CMOS)-compatible processes still remains elusive. In article number 2106041, Kailang Liu, Tianyou Zhai, and co-workers present a scalable vdW encapsulation method based on inorganic molecular crystals, through which the ambient stability of a series of 2D materials is significantly improved by tens of times.

Inorganic molecular crystals for 2D electronics

Inorganic molecular crystals for 2D electronics

Effect of Strong Intermolecular Interaction in 2D Inorganic Molecular Crystals.

Strong intermolecular interactions in 2D organic molecular crystals arising from π-π stacking have been widely explored to achieve high thermal stability, high carrier mobility, and novel physical properties, which have already produced phenomenal progress. However, strong intermolecular interactions in 2D inorganic molecular crystals (2DIMCs) have rarely been investigated, severely limiting both the fundamental research in molecular physics and the potential applications of 2DIMCs for optoelectronics. Here, the effect of strong intermolecular interactions induced by unique short intermolecular Se-Se and P-Se contacts in 2D α-P4Se3 nanoflakes is reported. On the basis of theoretical calculations of the charge density distribution and an analysis of the thermal expansion and plastic-crystal transition, the physical picture of strong intermolecular interactions can be elucidated as a higher charge density between adjacent P4Se3 molecules, arising from an orderly and close packing of P4Se3 molecules. More importantly, encouraged by the strong intermolecular coupling, the in-plane mobility of α-P4Se3 nanoflakes is first calculated with a quantum nuclear tunneling model, and a competitive hole mobility of 0.4 cm2 V-1 s-1 is obtained. Our work sheds new light on the intermolecular interactions in 2D inorganic molecular crystals and is highly significant for promoting the development of molecular physics and optoelectronics.

2D van der Waals Molecular Crystal β-HgI2 : Economical, Rapid, and Substrate-Free Liquid-Phase Synthesis and Strong In-Plane Optical Anisotropy.

2D materials have a great potential for wide-range applications due to their adjustable bandgap characteristics and special crystal structures. β-HgI2 is a new 2D van der Waals inorganic molecular crystal material with a wide bandgap of 4.03 eV, on whose preparation and properties there are few relevant reports due to the feature of instability of molecular crystals. Here, an economical method to control the synthesis of large-size 2D β-HgI2 single crystal by using a mineralizer-assisted solution is reported. According to angle-resolved polarization Raman spectroscopy and first-principles optical absorption calculation, 2D β-HgI2 flake has a strong in-plane anisotropic light scattering characteristic and high optical absorption dichroism (az /ay = 3.4), which is due to a low in-plane symmetry of the orthorhombic structure of β-HgI2 . More importantly, due to the molecular crystal structure of β-HgI2 , its sensitivity to temperature is less than that of 2D materials such as MoS2 , which has been confirmed by temperature-dependent Raman spectroscopy. In the work, more 2D inorganic molecular crystals are studied in the aspect of growth, which provides a theoretical basis for 2D molecular crystal optoelectronic devices' potential applications.

2D Inorganic Materials: from Atomic Crystals to Molecular Crystals

Prof. Zhai Tianyou and co-workers introduce the concept of 2D inorganic molecular crystals, which are different from traditional 2D atomic crystals, such as graphene, MoS2, black phosphorus, MXene, etc. The materials system is unique, and completely new to the community. Another research boom on 2D molecular materials may thus be drawn in the scope of electronics, energy and environment. This work has been published online in the Nature Communications in October 17, 2019.