Light Emission in 2D Silver Phenylchalcogenolates

Inorganic-Organic Hybrid Layered Semiconductor AgSePh: Quasi-Solution Synthesis, Optical Properties, and Thermolysis Behavior

Two-dimensional inorganic-organic hybrid layered semiconductors are actively studied because of their naturally formed multiquantum well (MQW) structures and associated optical, photoelectric, and quantum optics characteristics. Silver benzeneselenolate (AgSePh, Ph = C6H5) is a new member of such hybrid layered materials, but has not fully been exploited. Herein, we present a quasi-solution method to prepare high quality free-standing AgSePh flake-like microcrystals by reacting diphenyl diselenide (Ph2Se2) with silver nanoparticles. The resultant AgSePh microflakes exhibit room-temperature (RT) resolvable MQW-induced quasi-particle quantization and interesting optical properties, such as three distinct excitonic resonance absorptions X1 (2.67 eV), X2 (2.71 eV), and X3 (2.83 eV) in the visible region, strong narrow-line width blue photoluminescence at ∼2.64 eV (470 nm) from the radiative recombination of the X1 exciton state, and a large exciton binding energy (∼0.35 eV). Furthermore, AgSePh microcrystals show high stability under water, oxygen, and heat environments, while above 220 °C, they will thermally decompose to silver and Ph2Se2 as evidenced by a combination of thermogravimetry and differential scanning calorimetry and pyrolysis-coupled gas chromatography-mass spectrometry studies. Finally, a comparison is extended between AgSePh and other metal benzeneselenolates, benzenethiolates, and alkanethiolates to clarify differences in their solubility, decomposition/melting temperature, and pyrolytic products.

MOCHAs: An Emerging Class of Materials for Photocatalytic H2 Production

Production of green hydrogen (H2) is a sustainable process able to address the current energy crisis without contributing to long-term greenhouse gas emissions. Many Ag-based catalysts have shown promise for light-driven H2 generation, however, pure Ag-in its bulk or nanostructured forms-suffers from slow electron transfer kinetics and unfavorable Ag─H bond strength. It is demonstrated that the complexation of Ag with various chalcogenides can be used as a tool to optimize these parameters and reach improved photocatalytic performance. In this work, metal-organic-chalcogenolate assemblies (MOCHAs) are introduced as effective catalysts for light-driven hydrogen evolution reaction (HER) and investigate their performance and structural stability by examining a series of AgXPh (X = S, Se, and Te) compounds. Two catalyst-support sensitization strategies are explored: by designing MOCHA/TiO2 composites and by employing a common Ru-based photosensitizer. It is demonstrated that the heterogeneous approach yields stable HER performance but involves a catalyst transformation at the initial stage of the photocatalytic process. In contrast to this, the visible-light-driven MOCHA-dye dyad shows similar HER activity while also ensuring the structural integrity of the MOCHAs. The work shows the potential of MOCHAs in constructing photosystems for catalytic H2 production and provides a direct comparison between known AgXPh compounds.

Dimensionality Engineering of Lead Organic Chalcogenide Semiconductors

Two-dimensional (2D) metal organic chalcogenides (MOCs) such as silver phenylselenolate (AgSePh) have emerged as a new class of 2D materials due to their unique optical properties. However, these materials typically exhibit large band gaps, and their elemental and structural versatility remain significantly limited. In this work, we synthesize a new family of 2D lead organic chalcogenide (LOC) materials with excellent structural and dimensionality tunability by designing the bonding ability of the organic molecules and the stereochemical activity of the Pb lone pair. The introduction of electron-donating substituents on the benzenethiol ligands results in a series of LOCs that transition from 1D to 2D, featuring reduced band gaps (down to 1.7 eV), broadband emission, and strong electron-phonon coupling. We demonstrated a prototypical single crystal photodetector with 2D LOC that showed the dimensionality engineering on the transport property of LOC semiconductors. This study paves the way for further development of the synthesis and optical properties of novel organic-inorganic hybrid 2D materials.

Controlled Assembly of CdSe Nanoplatelet Thin Films and Nanowires

We assemble semiconductor CdSe nanoplatelets (NPs) at the air/liquid interface into 2D monolayers several micrometers wide, distinctly displaying nematic order. We show that this configuration is the most favorable energetically and that the edge-to-edge distance between neighboring NPs can be tuned by ligand exchange without disrupting film topology and nanoparticle orientation. We explore the rich assembly phase space by using depletion interactions to direct the formation of 1D nanowires from stacks of NPs. The improved control and understanding of the assembly of semiconductor NPs offers opportunities for the development of cheaper optoelectronic devices that rely on 1D or 2D charge delocalization throughout the assembled monolayers and nanowires.

1D Hybrid Semiconductor Silver 2,6-Difluorophenylselenolate

Organic-inorganic hybrid materials present new opportunities for creating low-dimensional structures with unique light-matter interaction. In this work, we report a chemically robust yellow emissive one-dimensional (1D) semiconductor, silver 2,6-difluorophenylselenolate─AgSePhF₂(2,6), a new member of the broader class of hybrid low-dimensional semiconductors, metal-organic chalcogenolates. While silver phenylselenolate (AgSePh) crystallizes as a two-dimensional (2D) van der Waals semiconductor, introduction of fluorine atoms at the (2,6) position of the phenyl ring induces a structural transition from 2D sheets to 1D chains. Density functional theory calculations reveal that AgSePhF₂ (2,6) has strongly dispersive conduction and valence bands along the 1D crystal axis. Visible photoluminescence centered around λ_p ≈ 570 nm at room temperature exhibits both prompt (110 ps) and delayed (36 ns) components. The absorption spectrum exhibits excitonic resonances characteristic of low-dimensional hybrid semiconductors, with an exciton binding energy of approximately 170 meV as determined by temperature-dependent photoluminescence. The discovery of an emissive 1D silver organoselenolate highlights the structural and compositional richness of the chalcogenolate material family and provides new insights for molecular engineering of low-dimensional hybrid organic-inorganic semiconductors.