Dandan Hu

Intrinsic “Vacancy Point Defect” Induced Electrochemiluminescence from Coreless Supertetrahedral Chalcogenide Nanocluster

A deep understanding of distinct functional differences of various defects in semiconductor materials is conducive to effectively control and rationally tune defect-induced functionalities. However, such research goals remain a substantial challenge due to great difficulties in identifying the defect types and distinguishing their own roles, especially when various defects coexist in bulk or nanoscale material. Hereby, we subtly selected a molecular-type semiconductor material as structural mode composed of supertetrahedral chalcogenide Cd-In-S nanoclusters (NCs) with intrinsic vacancy point defect at the core site and antisite point defects at the surface of supertetrahedron and successfully established the correlation of those point defects with their own electrochemiluminescence (ECL) behaviors. The multichannel ECL properties were recorded, and the corresponding reaction mechanisms were also proposed. The predominant radiation recombination path of ECL emission peak at 585 nm was significantly distinguished from asymmetrically broad PL emission with a peak at 490 nm. In addition, the ECL performance of the coreless supertetrahedral chalcogenide nanocluster can be modulated by atomically precise doping of monomanganese ion at the core vacant site. A relatively high ECL efficiency of 2.1% was also gained. Actually, this is the first investigation of ECL behavior of semiconductor materials based on supertetrahedral chalcogenide nanocluster in aqueous solution. Current research may open up a new avenue to probe the roles of various different defects with defined composition and position in the NC. The versatile and bright ECL properties of Cd-In-S NC combined with tunable ECL potential and ECL peak suggest that the new kind of NC-based ECL material may hold great promising for its potential applications in electrochemical analysis, sensing, and imaging.

PCU-type copper-rich open-framework chalcogenides: pushing up the length limit of the connection mode and the first mixed-metal [Cu7GeSe13] cluster

We report four new copper-rich open-framework chalcogenides (COCs) with the formulas [Cu8Ge6Se19](C5H12N)6 (1a), [Cu8Sn6Se19](C6H12N2)4(H2O)13 (1b), [Cu16Ge12S36][Ni(en)3]4(en)xCl1.5 (1c), and [Cu7Ge4Se13](C6H21N4) (2). Single-crystal X-ray diffraction analyses suggest that all of these compounds with pcu-type topology are completely built on icosahedral clusters. Of particular interest, the connection units linking the icosahedral clusters in 1a–1c are pure dimeric units in three axial directions. Such a case is unprecedented among previously reported COCs and pushes up the length limit of the connection mode, thereby resulting in the largest solvent-accessible space in COCs. Compound 2 is built on an intriguing and unprecedented mixed-metal Cu7GeSe13 cluster. The copper-rich nature of these compounds gives rise to a narrow band gap in the near-infrared range, making them hold promise for photoelectric applications.

Cation-Exchanged Zeolitic Chalcogenides for CO2 Adsorption

We report here the intrinsic advantages of a special family of porous chalcogenides for CO2 adsorption in terms of high selectivity of CO2/N2, large uptake capacity, and robust structure due to their first-ever unique integration of the chalcogen-soft surface, high porosity, all-inorganic crystalline framework, and the tunable charge-to-volume ratio of exchangeable cations. Although tuning the CO2 adsorption properties via the type of exchangeable cations has been well-studied in oxides and MOFs, little is known about the effects of inorganic exchangeable cations in porous chalcogenides, in part because ion exchange in chalcogenides can be very sluggish and incomplete due to their soft character. We have demonstrated that, through a methodological change to progressively tune the host-guest interactions, both facile and nearly complete ion exchange can be accomplished. Herein, a series of cation-exchanged zeolitic chalcogenides (denoted as M@RWY) were studied for the first time for CO2 adsorption. Samples were prepared through a sequential ion-exchange strategy, and Cs+-, Rb+-, and K+-exchanged samples demonstrated excellent CO2 adsorption performance. Particularly, K@RWY has the superior CO2/N2 selectivity with the N2 adsorption even undetected at either 298 or 273 K. It also has the large uptake of 6.3 mmol/g (141 cm3/g) at 273 K and 1 atm with an isosteric heat of 35-41 kJ mol-1, the best among known porous chalcogenides. Moreover, it permits a facile regeneration and exhibits an excellent recyclability, as shown by the multicycling adsorption experiments. Notably, K@RWY also demonstrates a strong tolerance toward water.

Tuning the efficiency of multi-step energy transfer in a host–guest antenna system based on a chalcogenide semiconductor zeolite through acidification and solvation of guests

We report a new multi-step energy transfer process in a host–guest antenna system based on a chalcogenide semiconductor zeolite (coded as RWY). The multi-step vectorial energy transfer assay was fabricated by encapsulating both proflavine ions (PFH+) and pyronine ions (Py+) into the RWY porous framework, serving as a UV-vis light-harvesting host. The ultraviolet high-energy excitation absorbed by the RWY host was channeled to the PFH+ ions and then onto the Py+ ions to give rise to visible-light emission. The steady-state fluorescence and fluorescent dynamics of emission revealed successfully the process of multi-step vectorial energy transfer occurring in the RWY⊃(PFH+&Py+) host–guest antenna system. Moreover, the post treatment of guest ions, such as further acidification of the PFH+ ions and solvation of the guests, was also investigated to tune energy transfer efficiency in such host–guest antenna systems. The current study shows that deep protonation of PFH+ as well as solvation of guest ions can dramatically enhance energy transfer efficiency between the RWY host and PFH+, and even between PFH+ and Py+, much higher than that in an untreated host–guest antenna system.

Pushing up the Size Limit of Metal Chalcogenide Supertetrahedral Nanocluster

The cubic ZnS structure type and the size-dependent properties of related nanoparticles are of both fundamental and technological importance. Yet, it remains a challenge to synthesize large atom-precise clusters of this structure type. Currently, only supertetrahedral clusters with 4, 10, 20, and 35 metal sites (denoted as T2, T3, T4, and T5, respectively) are known. Because the synthesis of T5 in 2002, numerous synthetic efforts targeting larger clusters only resulted in T2-T5 clusters in various compositions and intercluster connectivity, with T6 (56 metal and 84 anion sites) being elusive. Here, we report the so-far largest supertetrahedral cluster (T6, [Zn25In31S84]25-). New T6 clusters can serve as the host matrix for optically active centers. Mn-doped variants of T4 and T6 have also been made, allowing the investigation of site-dependent Mn emission. The results lead to the elucidation of the mechanism regulating Mn emission via size-dependent crystal lattice strain and provide new insight into Mn-doping chemistry in cluster-based chalcogenides at the atomic level.

Two Unique Crystalline Semiconductor Zeolite Analogues Based on Indium Selenide Clusters

Developing the structural diversity of microporous zeolitic frameworks with integrated semiconducting properties is promising but remains a challenge. Reported here are two unique crystalline semiconductor zeolite analogues constructed from two kinds of indium selenide clusters with augmented ctn and zeolite-type sod networks. The intrinsic semiconducting nature in these In-Se domains gives rise to pore-size-dependent and visible-light-driven photocatalytic activity for organic dye degradation.

Assembly of supertetrahedral clusters into a Cu–In–S superlattice via an unprecedented vertex–edge connection mode

We demonstrated here the first case of a vertex–edge connection mode in a three-dimensional open-framework chalcogenide built from the largest known T5 cluster. Such connection relies on a tri-coordinated edge sulfur atom, which serves as the linkage to bridge two adjacent T5 clusters. The architecture of the resulting structure can be classified as the infinite order of super-supertetrahedral T5 clusters (T5, ∞).

Hybrid Assembly of Different-Sized Supertetrahedral Clusters into a Unique Non-Interpenetrated Mn–In–S Open Framework with Large Cavity

Reported here is a unique crystalline semiconductor open-framework material built from the large-sized supertetrahedral T4 and T5 clusters with the Mn-In-S compositions. The hybrid assembly between T4 and T5 clusters by sharing terminal μ2-S2- is for the first time observed among the cluster-based chalcogenide open frameworks. Such three-dimensional structure displays non-interpenetrated diamond-type topology with extra-large nonframework volume of 82%. Moreover, ion exchange, CO2 adsorption, as well as photoluminescence properties of the title compound are also investigated.

An Unusual Metal Chalcogenide Zeolitic Framework Built from the Extended Spiro-5 Units with Supertetrahedral Clusters as Nodes

Reported here is a new metal chalcogenide semiconductor with the double-interpenetrated zeolitic nabesite framework, which is constructed by the rare extended spiro-5 units with supertetrahedral clusters serving as building units. Different from the TO4-based simple spiro-5 unit frequently observed in oxide-based zeolites, the extended spiro-5 unit composed of five supertetrahedral T3-InSnS clusters is for the first time observed in the family of open-framework metal chalcogenides. Such secondary building units finally assemble into a rare NAB topological framework with large external space. In addition, the title semiconductor material also displays good properties in photocurrent response and electrocatalytic oxygen reduction reaction.

Substituent-Modulated Assembly Formation: An Approach to Enhancing the Photostability of Photoelectric-Sensitive Chalcogenide-Based Ion-Pair Hybrids.

A series of electronically active viologen dications (RV) with tunable substituent groups were utilized to hybridize with [Ge4S10]4- (T2 cluster) to form the hybrids of T2@RV. These hybrids exhibited variable supermolecular assembly formation, tunable optical absorption properties, and different photoelectric response under the influence of different RV dications. Raman testing and time-dependent photocurrent response indicated that the photosensitivity and photostability of T2@RV could be integrated while choosing suitable RV dications. Current research provides a general method to build a tunable hybrid system based on crystalline metal chalcogenide compounds through the replacement of photoinactive cationic organic templates with photoactive ones with different substituent groups.