High-Performance Up-Conversion Photodetectors with Zero-Barrier Interconnection via Self-Assembled Surface Dipoles.

The performance of lead sulfide (PbS) quantum-dot-based up-conversion photodetectors is greatly limited owing to a large potential barrier at the interconnection layer between the photodetecting (PD) unit and light-emitting (LED) unit. Thus, very high driving voltage is required, rendering high energy consumption and poor working stability. By introducing azetidinium iodide (AzI) at the PD/LED interface, zero-barrier interconnection was achieved for the PbS-based infrared up-conversion photodetectors. The turn-on voltage under infrared illumination was greatly reduced to 1.2 V and a high photon-to-photon conversion efficiency (ηpp) of ∼3% was obtained at 3 V, showing a 10-fold enhancement compared to those previously reported devices. The mechanism for the regulation of interface energy level alignments was related to the self-assembly of the AzI dipole molecules, resulting from the van der Waals force between the S atoms in the ligands of PbS and the protonated H atoms around N atoms in AzI.

Micromechanism for Copper-Deficiency Enhanced Stability: A Quasi In Situ TEM Study of Electric-Induced Structural Evolution in Cu2-x(S, Se) Liquid-Like Thermoelectric Materials.

Cu-based liquid-like thermoelectric materials have garnered tremendous attention due to their inherent ultralow lattice thermal conductivity. However, their practical application is hampered by stability issues under a large current or temperature gradient. It has been reported that introduction of copper vacancies can enhance the chemical stability, whereas the micromechanism behind this macroscopic improvement still remains unknown. Here, we have established a quasi in situ TEM method to examine and compare the structural evolution of Cu2-xS0.2Se0.8 (x = 0, 0.05) under external electric fields. It is then found that the preset Cu vacancies could favor the electric-induced formation of a more stable intermediate phase, i.e., the hexagonal CuSe-type structure in the form of either lamellar defects (majorly) or long-range order (minorly), in which ordering of S and Se also occurred. Thereby, copper and chalcogen atoms could largely be solidified into the matrix, and the elemental deposition and evaporation process is mitigated under an electric field.

Excellent Nonlinear Optical M[M4 Cl][Ga11 S20 ] (M = A/Ba, A = K, Rb) Achieved by Unusual Cationic Substitution Strategy.

The typical chalcopyrite AgGaQ2 (Q = S, Se) are commercial infrared (IR) second-order nonlinear optical (NLO) materials; however, they suffer from unexpected laser-induced damage thresholds (LIDTs) primairy due to their narrow band gaps. Herein, what sets this apart from previously reported chemical substitutions is the utilization of an unusual cationic substitution strategy, represented by [[SZn4 ]S12 + [S4 Zn13 ]S24 + 11ZnS4 ⇒ MS12 + [M4 Cl]S24 + 11GaS4 ], in which the covalent Sx Zny units in the diamond-like sphalerite ZnS are synergistically replaced by cationic Mx Cly units, resulting in two novel salt-inclusion sulfides, M[M4 Cl][Ga11 S20 ] (M = A/Ba, A = K, 1; Rb, 2). As expected, the introduction of mixed cations in the GaS4 anionic frameworks of 1 and 2 leads to wide band gaps (3.04 and 3.01 eV), which exceeds the value of AgGaS2 , facilitating the improvement of high LIDTs (9.4 and 10.3 × AgGaS2 @1.06 µm, respectively). Furthermore, compounds 1 and 2 exhibit moderate second-harmonic generation intensities (0.84 and 0.78 × AgGaS2 @2.9 µm, respectively), mainly originating from the orderly packing tetrahedral GaS4 units. Importantly, this study demonstrates the successful application of the cationic substitution strategy based on diamond-like structures to provide a feasible chemical design insight for constructing high-performance NLO materials.

Van der Waals Transition Metal Carbo-Chalcogenides: Theoretical Screening and Charge Storage.

High-rate lithium/sodium ion batteries or capacitors are the most promising functional units to achieve fast energy storage that highly depends on charge host materials. Host materials with lamellar structures are a good choice for hybrid charge storage hosts (capacitor or redox type). Emerging layered transition metal carbo-chalcogenides (TMCC) with homogeneous sulfur termination are especially attractive for charge storage. Using density functional theory calculations, six of 30 potential TMCC are screened to be stable, metallic, anisotropic in electronic conduction and mechanical properties due to the lamellar structures. Raman, infrared active modes and frequencies of the six TMCC are well assigned. Interlayer coupling, especially binding energies predict that the bulk layered materials can be easily exfoliated into 2D monolayers. Moreover, Ti2S2C, Zr2S2C are identified as the most gifted Li+/Na+ anode materials with relatively high capacities, moderate volume expansion, relatively low Li+/Na+ migration barriers for batteries or ion-hybrid capacitors. This work provides a foundation for rational materials design, synthesis, and identification of the emerging 2D family of TMCC.

Base-Stabilized Gallium Sulfides and Selenides Supported by a Bis(oxazolinyl)(phenyl)methanide Ligand.

Gallylene supported by a bis(oxazolinyl)(phenyl)methanide (Boxm) ligand was synthesized and structurally characterized. The reaction of this gallylene with triphenylphosphine sulfide/selenide yielded dimeric gallium sulfide and selenide. These compounds could be converted to monomeric terminal sulfide and selenide by coordination of an external Lewis base such as an N-heterocyclic carbene (NHC or IMe4) and 4-dimethylaminopyridiene (DMAP). These doubly-base-stabilized gallium sulfide/selenide reacted with phenyl isocyanate to give the corresponding cycloadducts by releasing the Lewis base, indicating the formation of a single-base-stabilized gallium sulfide/selenide intermediate.

Overriding Cage Effect in Electron Donor-Acceptor Photoactivation of Diaryliodonium Reagents: Synthesis of Chalcogenides.

In recent times, diaryliodonium reagents (DAIRs) have witnessed a resurgence as arylating reagents, especially under photoinduced conditions. However, reactions proceeding through electron donor-acceptor (EDA) complex formation with DAIRs are restricted to electron-rich reacting partners serving as donors due to the well-known cage effect. We discovered a practical and high-yielding visible-light-induced EDA platform to generate aryl radicals from the corresponding DAIRs and use them to synthesize key chalcogenides. In this process, an array of DAIRs and dichalcogenides react in the presence of 1,4 diazabicyclo[2.2.2]octane (DABCO) as a cheap and readily available donor, furnishing a variety of di(hetero)aryl and aryl/alkyl chalcogenides in good yields. The method is scalable, features a broad scope with good yields, and operates under open-to-air conditions. The photoinduced chalcogenation technology is suitable for late-stage functionalizations and disulfide bioconjugations and facilitates access to biologically relevant thioesters, dithiocarbamates, sulfoximines, and sulfones. Moreover, the method applies to synthesizing diverse pharmaceuticals, such as vortioxetine, promazine, mequitazine, and dapsone, under amenable conditions.

Dimers and 2D Networks of Adamantane-Related Ternary Organosilicon Coinage Metal Sulfide Clusters.

Adamantane-type organotin sulfide clusters were recently shown to react with coinage metal phosphine complexes under replacement of an organic substituent by a metal-phosphine unit. An extension of such studies involving the silicon-based congener [(PhSi)4S6] (A) revealed that the cluster core will be partly disassembled and a {PhSi} moiety is replaced by a coinage metal phosphine complex to form [(Et3PAg)3(PhSi)3S6] (B) and [Na2(thf)2.33][(Me3PCu)(PhSi)3S6] (C). Herein, we present an extension of this work upon variation of the reactants and reaction conditions. Besides the isolation of crystalline precursor complexes [CuCl(PMe2Ph)3] (1) and [AgCl(PMe2Ph)2]2 (2), the study addresses reactions of A with AgCl and a phosphine ligand in CH2Cl2, upon which A is completely disassembled to form [(Ph3P)3Ag(µ-S)SiCl2Ph] (3). In another case a CH2 group, most likely stemming from CH2Cl2, was attached to the ligand, thus generating [{PhCl(S)SiSCH2P(Ph2)CH2CH2}2] (4). Upon using CuCl and 1,4-bis(diphenylphosphino)butane (dppb) we isolated the phosphine-bridged analog of B, [{(dppbCu2)CuP(Ph2)(CH2CH2)(PhSi)3S6}2] (5). In order to receive the yet elusive silver homolog of C, we used PMe2Ph as a bulkier ligand. This way we generated a 2D coordination polymer of the desired composition, [Na2(thf)1.5][(Me2PhPAg)(PhSi)3S6] (6). UV-visible spectra of 6 indicated a bandgap of 3.89 eV, thus blue-shifted in regards to B and C.

A Combined Theoretical and Experimental Raman Scattering Study of BaZrS3-BaHfS3 Solid Solutions.

Ba(Zr,Hf)S3 solid solutions are proposed for photovoltaic applications and a fast non-destructive measurement of the composition of these solutions and the identification of any possible secondary phases is a prerequisite for understanding their opto-electronic properties. Here we calculate the non-resonant one-phonon Raman spectra of pure BaHfS3 and BaZrS3, which show only subtle differences between them. To test this experimentally, a solution series of BaZr1-xHfxS3 (0≤x≤1) powders was synthesised and free of a secondary phase, HfS3 identified by 633 nm excitation Raman spectroscopy. The veracity of the synthesis method was confirmed by comparing X-ray diffractograms and optical absorption spectra of the BaZr0.5Hf0.5S3 solid solution to a 50:50 mixture of the pure ternary compounds. Experimental non-resonant Raman measurements on the solid solution powders confirm that only slight variations in the spectra are visible, making a solid solution composition determination difficult. However, exciting the solid solutions resonantly, leads to the appearance of new two-phonon modes in the Raman spectrum, which change significantly across the solid solution series. We consequently suggest that a rapid solid solution composition measurement can be made unambiguously by measuring the ratio of the intensities of the 825 cm-1 and 625 cm-1 Raman features.

The Hydrogen Evolution Activity of BaZrS3, BaTiS3, and BaVS3 Chalcogenide Perovskites.

Chalcogenide perovskites are a class of materials with electronic and optoelectronic properties desirable for solar cells, infrared optics, and computing. The oxide counterparts of these chalcogenides have been studied extensively for their electrocatalytic and photoelectrochemical properties. As chalcogenide perovskites are more covalent, conductive, and stable, we hypothesize that they are more viable as electrocatalysts than oxide perovskites. The goal of this synthetic, experimental, and computational study is to examine the hydrogen evolution reaction (HER) activity of three Barium-based chalcogenides in perovskite and related structures: BaZrS3, BaTiS3, and BaVS3. Potential energy surfaces for hydrogen adsorption on surfaces of these materials are calculated using density functional theory and the computational hydrogen electrode model is used to contrast overpotentials with experiment. Although both experiments and computations agree that BaVS3 is the most active of the three materials, high overpotentials of these materials make them less viable than platinum for HER. Our work establishes a framework for future studies in the chemical and electrochemical properties of chalcogenide perovskites.

Synthesis of Phosphine Chalcogenides Using Tetrabutylammonium Chalcogenocyanates.

The new chalcogenylation of phosphines using nBu4N‧XCN (X = S, Se) is described. The reaction in 1,2-dichloroethane at 120 °C provided the corresponding phosphine sulfides in good to high yields. The protocol could be extended to the synthesis of phosphinic acid derivatives as well as sulfurization of poly(styrene-co-4-styryldiphenylphosphine).

Stacked Polarizing Elements for Controlling Parameters of Surface Relief Gratings Written in Photosensitive Materials.

Photosensitive materials are widely used for the direct fabrication of surface relief gratings (SRGs) without the selective etching of the material. It is known that the interferometric approach makes it possible to fabricate SRGs with submicron and even subwavelength periods. However, to change the period of the written SRGs, it is necessary to change the convergence angle, shift a sample, and readjust the interferometric setup. Recently, it was shown that structured laser beams with predetermined, periodically modulated polarization distributions can also be used to fabricate SRGs. A structured laser beam with the desired polarization distribution can be formed with just one polarizing optical element-for example, the so-called depolarizer, a patterned micro-retarder array. The use of such stacked elements makes it possible to directly control the modulation period of the polarization of the generated laser beam. We show that this approach allows one to fabricate SRGs with submicron periods. Moreover, the addition of q-plates, elements effectively used to generate cylindrical vector beams with polarization singularities, allows the efficient formation of fork polarization gratings (FPGs) and the fabrication of higher-order fork-shaped SRGs. Full control of the parameters of the generated FPGs is possible. We demonstrate the formation of FPGs of higher orders (up to 12) by only adding first- and second-order q-plates and half-wave plates to the depolarizers. In this work, we numerically and experimentally study the parameters of various types of SRGs formed using these stacked polarizing elements and show the significant potential of this method for the laser processing of photosensitive materials, which often also serve as polarization sensors.

Integrated Reconfigurable Photon-Pair Source Based on High-Q Nonlinear Chalcogenide Glass Microring Resonators.

Chalcogenide glasses (ChGs) have recently emerged as enabling materials for building reconfigurable nanophotonic devices by employing their refractive index changes associated with photosensitive effects. In particular, the availability of low-loss thin-film ChGs and the realization of high-Q microresonators provide exciting opportunities for integrated photonics. So far, the ChG photonic devices are predominately operated in the classical optics regime. In this work, we present the realization on-chip bright photon-pair quantum light sources via spontaneous four-wave mixing in a high-Q microring resonator fabricated on the newly developed ChG Ge25Sb10S65 platform. The emission wavelength of the photon-pair source can be continuously tuned across a double-free spectral range in a reconfigurable manner. Our work serves as a starting point to fully unleash the potential of exploiting ChGs for developing reconfigurable integrated quantum photonic devices.

3D Lead-Organoselenide-Halide Perovskites and their Mixed-Chalcogenide and Mixed-Halide Alloys.

We incorporate Se into the 3D halide perovskite framework using the zwitterionic ligand: SeCYS (+NH3(CH2)2Se-), which occupies both the X- and A+ sites in the prototypical ABX3 perovskite. The new organoselenide-halide perovskites: (SeCYS)PbX2 (X = Cl, Br) expand upon the recently discovered organosulfide-halide perovskites. Single-crystal X-ray diffraction and pair distribution function analysis reveal the average structures of the organoselenide-halide perovskites, whereas the local lead coordination environments and their distributions were probed through solid-state 77Se and 207Pb NMR, complemented by theoretical simulations. Density functional theory calculations illustrate that the band structures of (SeCYS)PbX2 largely resemble those of their S analogs, with similar band dispersion patterns, yet with a considerable bandgap decrease. Optical absorbance measurements indeed show bandgaps of 2.07 and 1.86 eV for (SeCYS)PbX2 with X = Cl and Br, respectively. We further demonstrate routes to alloying the halides (Cl, Br) and chalcogenides (S, Se) continuously tuning the bandgap from 1.86 to 2.31 eV-straddling the ideal range for tandem solar cells or visible-light photocatalysis. The comprehensive description of the average and local structures, and how they can fine-tune the bandgap and potential trap states, respectively, establishes the foundation for understanding this new perovskite family, which combines solid-state and organo-main-group chemistry.

Lattice Distortions and Multiple Valence Band Convergence Contributing to High Thermoelectric Performance in MnTe.

Here, a new route is proposed for the minimization of lattice thermal conductivity in MnTe through considerable increasing phonon scattering by introducing dense lattice distortions. Dense lattice distortions can be induced by Cu and Ag dopants possessing large differences in atom radius with host elements, which causes strong phonon scattering and results in extremely low lattice thermal conductivity. Density functional theory (DFT) calculations reveal that Cu and Ag codoping enables multiple valence band convergence and produces a high density of state values in the electronic structure of MnTe, contributing to the large Seebeck coefficient. Cu and Ag codoping not only optimizes the Seebeck coefficient but also substantially increases the carrier concentration and electrical conductivity, resulting in the significant enhancement of power factor. The maximum power factor reaches 11.36 µW cm-1 K-2 in Mn0.98 Cu0.04 Ag0.04 Te. Consequently, an outstanding ZT of 1.3 is achieved for Mn0.98 Cu0.04 Ag0.04 Te by these synergistic effects. This study provides guidelines for developing high-performance thermoelectric materials through the rational design of effective dopants.

Three-in-One Strategy Constructing the First High-Performance Nonlinear Optical Sulfide Crystallizing with the P43 Space Group.

The balance between large nonlinear optical (NLO) effect and wide bandgap is the key scientific issue for the exploration of infrared NLO materials. Targeting this issue, two new pentanary chalcogenides KGaGe1.37 Sn0.63 S6 (1) and KGaGe1.37 Sn0.63 Se6 (2) are obtained by the three-in-one strategy, viz. three types of fourfold-coordinated metal elements co-occupying the same site. They crystallize in the tetragonal P43 (1) and monoclinic Cc (2) space group. Their structures can be evolved from benchmark AgGaS2 (AGS) by suitable substitution. Remarkably, 1 is the first NLO sulfide crystallizing with the P43 space group, representing a new structure-type NLO material. The structural relationship between 1 and 2 and the evolution from 1, 2 to AGS are also analyzed. Both 1 and 2 show balanced NLO properties. Specifically, 1 exhibits phase-matchable SHG response of 0.6 × AGS, a wide bandgap of 3.50 eV, and a high laser damage threshold of 6.24 × AGS. Theoretical calculation results suggest that the Ga/Ge/Sn element ratios of the co-occupied sites of 1 and 2 are the most appropriate for stabilizing the structures. The strategy adopted here will provide some inspiration for exploring new high-performance NLO materials.

Photothermal Ferrotherapy - Induced Immunogenic Cell Death via Iron-Based Ternary Chalcogenide Nanoparticles Against Triple-Negative Breast Cancer.

Triple-negative breast cancer (TNBC) is highly malignant and prone to recurrence and metastasis. Patients with TNBC have limited therapeutic options, often resulting in poor prognosis. Some new treatments for TNBC have been considered in the past decade, such as immunotherapy, photothermal therapy (PTT), and ferroptosis therapy, that allow the rapid and minimally invasive ablation of cancer. However, a multifunctional nanodrug system with more potent efficacy for TNBC is still needed. The use of iron-based ternary chalcogenide nanoparticles (NPs), namely AgFeS2 , is reported, which synergistically combines photothermal therapy, ferrotherapy, and immunotherapy in one system for the treatment of TNBC. AgFeS2 possesses excellent photothermal conversion performance for tumor near-infrared (NIR) phototherapy. Upon photoirradiation, these NPs generate heat, accelerate the release of iron ions, and effectively catalyze the Fenton reaction, resulting in cell apoptosis and ferroptosis. Additionally, AgFeS2 promotes the release of tumor-specific antigens and triggers an immune response via immunogenic cell death (ICD), thereby providing unique synergistic mechanisms for cancer therapy. The present study demonstrates the great potential of iron-based ternary chalcogenide as a new therapeutic platform for a combination of photothermal therapy, ferrotherapy, and immunotherapy for the suppression of TNBC.

Nonlinear Optical Sulfides LiMGa8 S14 (M = Rb/Ba, Cs/Ba) Created by Li+ Driven 2D Centrosymmetric to 3D Noncentrosymmetric Transformation.

Cations that can regulate the configuration of anion group are greatly important but regularly unheeded. Herein, the structural transformation from 2D CS to 3D noncentrosymmetric (NCS, which is the prerequisite for second-order NLO effect) is rationally designed to newly afford two sulfides LiMGa8 S14 (M = Rb/Ba, 1; Cs/Ba, 2) by introducing the smallest alkali metal Li+ cation into the interlamination of 2D centrosymmetric (CS) RbGaS2 . The unusual frameworks of 1 and 2 are constructed from C2 -type [Ga4 S11 ] supertetrahedrons in a highly parallel arrangement. 1 and 2 display distinguished NLO performances, including strong phase-matchable second-harmonic generation (SHG) intensities (0.8 and 0.9 × AgGaS2 at 1910 nm), wide optical band gaps (3.24 and 3.32 eV), and low coefficient of thermal expansion for favorable laser-induced damage thresholds (LIDTs, 4.7, and 7.6 × AgGaS2 at 1064 nm), which fulfill the criteria of superior NLO candidates (SHG intensity >0.5 × AGS and band gap >3.0 eV). Remarkably, 1 and 2 melt congruently at 873.8 and 870.5 °C, respectively, which endows them with the potential of growing bulk crystals by the Bridgeman-Stockbarge method. This investigated system provides a new avenue for the structural evolution from layered CS to 3D NCS of NLO materials.

Zn2 HgP2 S8 : A Wide Bandgap Hg-Based Infrared Nonlinear Optical Material with Large Second-Harmonic Generation Response.

Hg-based chalcogenides, as good candidates for the exploration of high-performance infrared (IR) nonlinear optical (NLO) materials, usually exhibit strong NLO effects, but narrow bandgaps. Herein, an unprecedented wide bandgap Hg-based IR NLO material Zn2 HgP2 S8 (ZHPS) with diamond-like structure is rationally designed and fabricated by a tetrahedron re-organization strategy with the aid of structure and property predictions. ZHPS exhibits a wide bandgap of 3.37 eV, which is the largest one among the reported Hg-based chalcogenide IR NLO materials and first breaks the 3.0 eV bandgap "wall" in this system, resulting in a high laser-induced damage threshold (LIDT) of ≈2.2 × AgGaS2 (AGS). Meanwhile, it shows a large NLO response (1.1 × AGS), achieving a good balance between bandgap (≥3.0 eV) and NLO effect (≥1 × AGS) for an excellent IR NLO material. DFT calculations uncover that, compared to normal [HgS4 ]n , highly distorted [HgS4 ]d tetrahedral units are conducive to generating wide bandgap, and the wide bandgap in ZHPS can be attributed to the strong s-p hybridization between Hg─S bonding in distorted [HgS4 ]d , which gives some insights into the design of Hg-based chalcogenides with excellent properties based on distorted [HgS4 ]d tetrahedra.

Synthesis, Structural Characterization, and Bonding of Molecular Heavier Beryllium Chalcogenides.

The reactions of a cyclic alkyl(amino)carbene (CAAC)-stabilized beryllium radical with E2 Ph2 (E=S, Se, Te) and of a beryllole with HEPh (E=S, Se) yield the corresponding beryllium phenylchalcogenides, including the first structurally authenticated beryllium selenide and telluride complexes. Calculations show that their Be-E bonds are best described by the interaction between the Be+ and E- fragments, with Coulombic forces accounting for ca. 55 % of the attraction and orbital interactions dominated by the σ component.

Recent developments in Chalcogenide phase change material-based nanophotonics.

There is now a deep interest in actively reconfigurable nanophotonics as they will enable the next generation of optical devices. Of the various alternatives being explored for reconfigurable nanophotonics, Chalcogenide phase change materials (PCMs) are considered highly promising owing to the nonvolatile nature of their phase change. Chalcogenide PCM nanophotonics can be broadly classified into integrated photonics (with guided wave light propagation) and Meta-optics (with free space light propagation). Despite some early comprehensive reviews, the pace of development in the last few years has shown the need for a topical review. Our comprehensive review covers recent progress on nanophotonic architectures, tuning mechanisms, and functionalities in tunable PCM Chalcogenides. In terms of integrated photonics, we identify novel PCM nanoantenna geometries, novel material utilization, the use of nanostructured waveguides, and sophisticated excitation pulsing schemes. On the meta-optics front, the breadth of functionalities has expanded, enabled by exploring design aspects for better performance. The review identifies immediate, and intermediate-term challenges and opportunities in (1) the development of novel chalcogenide PCM, (2) advance in tuning mechanism, and (3) formal inverse design methods, including machine learning augmented inverse design, and provides perspectives on these aspects. The topical review will interest researchers in further advancing this rapidly growing subfield of nanophotonics.