Enhanced Photocatalytic Performance under Visible and Near-Infrared Irradiation of Cu1.8Se/Cu₃Se₂ Composite via a Phase Junction

Precursor engineering for soft selective synthesis of phase pure metal-rich digenite (Cu9S5) and djurleite (Cu31S16) nanocrystals and investigation of their photo-switching characteristics

Copper sulfide nanostructures have evolved as one of the most technologically important materials for energy conversion and storage owing to their economic and non-toxic nature and superior performances. This paper presents a direct, scalable synthetic route aided by a single source molecular precursor (SSP) approach to access copper sulfide nanomaterials. Two SSPs, CuX(dmpymSH)(PPh3)2 (where X = Cl or I), were synthesized in quantitative yields and thermolyzed under appropriate conditions to afford the nanostructures. The analysis of the nanostructures through pXRD, EDS and XPS suggested that phase pure digenite (Cu9S5) and djurleite (Cu31S16) nanostructures were isolated from -Cl and -I substituted SSPs, respectively. The morphologies of the as-synthesized nanomaterials were investigated using electron microscopy techniques (SEM and TEM). DRS studies on pristine materials revealed blue shifted optical band gaps, which were found to be optimum for photoelectrochemical application. A prototype photoelectrochemical cell fabricated using the pristine nanostructures exhibited a stable photo-switching property, which presents these materials as suitable economic and environmentally friendly photon absorber materials.

PLGA and PDMS-based in situ forming implants loaded with rosuvastatin and copper-selenium nanoparticles: a promising dual-effect formulation with augmented antimicrobial and cytotoxic activity in breast cancer cells

Breast cancer is among the most prevalent tumors worldwide. In this study, in-situ forming implants (ISFIs) containing rosuvastatin calcium were prepared using three types of poly (D, L-lactic-co-glycolic acid) (PLGA), namely, PLGA 50/50 with ester terminal and PLGA 75/25 with ester or acid terminal. Additionally, polydimethylsiloxane (PDMS) was added in concentrations of 0, 10, 20, and 30% w/v to accelerate matrix formation. The prepared ISFIs were characterized for their rheological behaviors, rate of matrix formation, and in-vitro drug release. All the prepared formulations revealed a Newtonian flow with a matrix formation rate between 0.017 and 0.059 mm/min. Generally, increasing the concentration of PDMS increased the matrix formation rate. The prepared implants' release efficiency values ranged between 46.39 and 89.75%. The ISFI containing PLGA 50/50 with 30% PDMS was selected for further testing, as it has the highest matrix formation rate and a promising release efficiency value. Copper-selenium nanoparticles were prepared with two different particle sizes (560 and 383 nm for CS1 and CS2, respectively) and loaded into the selected formulation to enhance its anticancer activity. The unloaded and loaded implants with rosuvastatin and copper-selenium nanoparticles were evaluated for their antibacterial activity, against Gram-positive and negative microorganisms, and anticancer efficacy, against MCF-7 and MDA-MB-231 cell lines. The results confirmed the potency of rosuvastatin calcium against cancer cells and the synergistic effect when loaded with smaller particle sizes of copper-selenium nanoparticles. This formulation holds a considerable potential for efficient breast cancer therapy.

In situ selective selenization of ZIF-derived CoSe2 nanoparticles on NiMn-layered double hydroxide@CuBr2 heterostructures for high performance supercapacitors

As an emerging energy storage device, the practical application of supercapacitors (SCs) is currently constrained by their low energy density. Enhancing the capacitance of supercapacitors by leveraging the synergistic effect of multiple components in composite electrodes with well-designed structures can effectively increase their energy density. Here, a wire-sheet-particle hierarchical heterostructured CoSe2@NiMn-layered double hydroxide (NiMn-LDH) @Cu1.8Se/Copper foam (CF) electrode is synthesized via phase pseudomorphic transformation process achieved by selective selenization for Cu and Co elements. Benefiting from the stable support structure of CuBr2, the large specific surface area of NiMn-LDH, and the excellent conductivity of CoSe2, the prepared binder-free electrode shows excellent electrochemical properties. The CoSe2@NiMn-LDH@Cu1.8Se hybrid electrode exhibits a superior specific areal capacitance of 7064 mF cm-2 at 2 mA cm-2 and a stable cyclic performance with 80.11 % capacitance retention after 10,000 cycles. Furthermore, the assembled CoSe2@NiMn-LDH@Cu1.8Se/CF//AC (activated carbon) asymmetric supercapacitor (ASC) achieves an energy density of 36.6 Wh kg-1 when the power density is 760.6 W Kg-1 and retains 87.35 % of the initial capacitance after 5000 cycles. Overall, this pioneering research provided new insight for preparing supercapacitor electrode materials by selective selenization and ration design of the structures.

Multifunctional Cu-Se Alloy Core Fibers and Micro-Nano Tapers

Cu-Se alloy core fibers with glass cladding were fabricated by a thermal drawing method of a reactive molten core. The composition, crystallography, and photoelectric/thermoelectric performance of the fiber cores were investigated. The X-ray diffraction spectra of the Cu-Se alloy core fibers illustrate the fiber cores being polycrystalline with CuSe and Cu₃Se₂ phases. Interestingly, the fiber cores show a lower electrical conductivity under laser irradiation than under darkness at room temperature. Meanwhile, the fiber cores possess a power factor of ~1.2 mWm^-1K^-2 at room temperature, which is approaching the value of the high thermoelectric performance bulk of Cu₂Se polycrystals. The flexible Cu-Se fibers and their micro-nano tapers have potential multifunctional applications in the field of photoelectric detection and thermoelectric conversion on curved surfaces.

Molecular precursor-mediated facile synthesis of phase pure metal-rich digenite (Cu1.8S) nanocrystals: an efficient anode for lithium-ion batteries

Copper sulfides have gained significant attention as alternative electrodes for rechargeable batteries. A simple and easily scalable synthetic pathway to access these materials is highly desirable. This paper describes the facile synthesis of metal-rich digenite Cu_1.8S nanocrystals from a structurally characterized new single-source molecular precursor in various high boiling solvents of varied polarity. The as-prepared nanostructures were thoroughly characterized by PXRD, Raman spectroscopy, EDS, XPS, electron microscopy techniques and diffuse reflectance spectroscopy to understand the crystal structure, phase purity, elemental composition, morphology and band gap. It was found that the reaction solvent has a profound role on their crystallite size, morphology and band gap, however the crystal structure and phase purity remained unaffected. Pristine Cu_1.8S nanostructures have been employed as an anode material in lithium-ion batteries (LIBs). The cell delivers a high initial charge capacity of ∼462 mA h g^-1 and retains a capacity of 240 mA h g^-1 even after 300 cycles at 0.1 A g^-1. DFT calculations revealed that multi-size polyhedron layers in the direction perpendicular to the two Li movement channels aid in the sustainable uptake of Li atoms with controlled volume expansion. The structure-mediated flexibility of the metal-rich Cu_1.8S lattice during lithiation permits high cyclability with reasonable retention of capacity.

Facile one pot synthesis of highly photoresponsive coinage metal selenides (Cu1.8Se and Ag2Se) achieved through novel Cu and Ag pyridylselenolates as molecular precursors

Copper selenide (Cu_1.8Se) and silver selenide (Ag₂Se) have garnered unprecedented attention as efficient absorber materials for cost-effective and sustainable solar cells. Phase pure preparation of these exotic materials in a nano-regime is highly desirable. This account outlines a simple and easily scalable pathway to Cu_1.8Se and Ag₂Se nanocrystals using novel complexes [Cu{2-SeC₅H₂(Me-4,6)₂N}]₄ (1), [Ag{2-SeC₅H₂(Me-4,6)₂N}]₆ (2) and [Ag{2-SeC₅H₃(Me-5)N}]₆·2C₆H₅CH₃ (3·2C₆H₅CH₃) as single source molecular precursors (SSPs). Structural studies revealed that the Cu and Ag complexes crystallize into tetrameric and hexameric forms, respectively. This observed structural diversity in the complexes has been rationalized via DFT calculations and attributed to metal-metal bond endorsed energetics. The thermolysis at relatively lower temperature in oleylamine of complex 1 afforded cubic berzelianite Cu_1.8Se and complexes 2 and 3 produced orthorhombic naumannite Ag₂Se nanocrystals. The low temperature synthesis of these nanocrystals seems to be driven by the observed preformed Cu₄Se₄ and Ag₆Se₆ core in the complexes which have close resemblance with the bulk structure of the final materials (Cu_1.8Se and Ag₂Se). The crystal structure, phase purity, morphology, elemental composition and band gap of these nanocrystals were determined from pXRD, electron microscopy (SEM and TEM), EDS and DRS-UV, respectively. The band gap of these nanocrystals lies in the range suitable for solar cell applications. Finally, these nanocrystal-based prototype photo-electrochemical cells exhibit high photoresponsivity and stability under alternating light and dark conditions.

Template free-synthesis of cobalt-iron chalcogenides [Co0.8Fe0.2L2, L = S, Se] and their robust bifunctional electrocatalysis for the water splitting reaction and Cr(vi) reduction

The ease of production of materials and showing multiple applications are appealing in this modern era of advanced technology. This paper reports the synthesis of a pair of novel cobalt-iron chalcogenides [Co0.8Fe0.2S2 and Co0.8Fe0.2Se2] with enhanced electro catalytic activities. These ternary metal chalcogenides were synthesized by a one-step template-free approach via a hexamethyldisilazane (HMDS)-assisted synthetic method. Transient photocurrent (TPC) studies and electrochemical impedance spectra (EIS) of these materials showed free electron mobility. Their bifunctional activities were verified in both the electrochemical oxygen evolution reaction (OER) and in the electrochemical reduction of toxic inorganic heavy metal ions [Cr(vi)] in polluted water. The materials showed robust catalytic ability in the oxygen evolution reaction with minimum possible over potential (345 and 350 mV @ η10) as determined by linear sweep voltammetry and the lower Tafel values (52.4 and 84.5 mV dec-1) for Co0.8Fe0.2Se2 and Co0.8Fe0.2S2 respectively. Surprisingly, both the materials also showed an excellent activity towards electrochemical Cr(vi) reduction to Cr(iii). Besides the maximum current achieved for Co0.8Fe0.2S2, a minimum value for the Limit of detection (LOD) was obtained for Co0.8Fe0.2S2 (0.159 μg L-1) compared to Co0.8Fe0.2Se2 (0.196 μg L-1). We tested the durability of catalysts, the critical factor for the prolonged use of catalysts, through the recyclability measurements of these materials as catalysts. Both the catalysts presented outstanding durability and balanced electro catalytic activities for up to 1500 CV cycles, and chronoamperometry studies also confirmed exceptional stability. The enhanced catalytic activities of these materials are ascribed to the free electron movement, evidenced by the increased TPC measured and EIS. Therefore, the template-free synthesis of these electro catalysts containing non-noble metal illustrates the practical approach to develop such types of catalysts for multiple functions.

Heavily Doped Semiconductor Colloidal Nanocrystals as Ultra-Broadband Switches for Near-Infrared and Mid-Infrared Pulse Lasers

Heavily self-doped semiconductors can be designed to be used in advanced photonics due to both fabrication and functional advantages. Ultrafast response, strong optical nonlinearity, broadband wavelength range, and accessibility of integration are major challenges for ultrafast all-optical photonics to operate in the infrared wavelength range. Here, solution-processed Cu_1.8Se semiconductor nanocrystals (NCs) demonstrate an ultrafast response (about 360-520 fs), strong optical nonlinearity (as large as -1.4 × 10³ cm GW^-1), and broadband (from 800 to 3000 nm) nonlinear optical absorption in the near-infrared and mid-infrared wavelength ranges. The ultrafast response and larger optical nonlinearity may be triggered by the plasma ground-state bleaching in the strong surface electromagnetic filed. Stable Q-switched lasers in Er-doped fiber laser, Tm-doped fiber laser, and Ho/Pr-codoped ZBLAN fiber laser are operated, respectively. These findings indicate that Cu_1.8Se NCs are prospective nonlinear materials for ultrafast response and broadband pulse laser.

Ultrasonically aided selective stabilization of pyrrolic type nitrogen by one pot nitrogen doped and hydrothermally reduced Graphene oxide/Titania nanocomposite (N-TiO2/N-RGO) for H2 production

Herein, we report the simultaneous doping of nitrogen on TiO₂ and reduced graphene oxide (N-TiO₂/N-RGO) with exclusive stabilization of pyrrolic type nitrogen on RGO network by ultrasonic conditions followed by hydrothermal method for efficient photocatalytic H₂ production. Interestingly, during synthesis of N-TiO₂/N-RGO composite, pyrrolic type nitrogen in RGO has been exclusively stabilized as confirmed by XPS analysis. The exclusive stabilization of pyrrolic nitrogen changed the optical and electronic properties of N-TiO₂/N-RGO nanocomposites by giving two π-electrons to the system for extended conjugation, which enhanced the optical absorption and charge carrier separation efficiency as confirmed by UV-Vis DRS and PL studies. Notably, N-TiO₂/N-RGO nanocomposite demonstrated. This enhanced photocatalytic activity can be ascribed to synergetic action of N-TiO₂ and N-RGO in optical and photogenerated charge carrier separation. Moreover, the plausible mechanism for exclusive stabilization of pyrrolic type nitrogen and enhanced photocatalytic activity were also proposed.

Curcumin-Functionalized Ag/Ag2 O Nanocomposites: Efficient Visible-Light Z-scheme Photocatalysts

Curcumin-functionalized Ag/Ag₂ O (c-Ag/Ag₂ O) nanocomposites with varying proportions of curcumin and Ag/Ag₂ O were prepared by a simple one pot green synthesis protocol in aqueous medium. The plasmonic band undergoes slight redshift, broadening and decrease in intensity with increase in the proportion of Ag₂ O formed. These composite nanoparticles were found to be efficient visible-light photocatalysts for aerobic oxidation of methyl orange and rhodamine B (RhB). Functionalization by curcumin significantly enhanced the photocatalytic activity with good reusability. The photocatalytic oxidation rate showed super linear increase with light intensity because of localized surface plasmon resonance (LSPR)-induced strong near field. The trapping experiments confirmed that superoxide radicals were the main active species responsible for the degradation reaction. A plasmonic Z-scheme photocatalytic mechanism is proposed to explain the possible charge transfer and separation behavior of electron-hole pairs among Ag, Ag₂ O and curcumin under visible-light irradiation.