Compound Copper Chalcogenide Nanocrystals

Band Structure Engineering and Defect Passivation of Cu x Ag1-x InS2/ZnS Quantum Dots to Enhance Photoelectrochemical Hydrogen Evolution

The AgInS₂ colloidal quantum dot (CQD) is a promising photoanode material with a relatively wide band gap for photoelectrochemical (PEC) solar-driven hydrogen (H₂) evolution. However, the unsuitable energy band structure still forms undesired energy barriers and leads to serious charge carrier recombination with low solar to hydrogen conversion efficiency. Here, we propose to use the ZnS shell for defect passivation and Cu ion doping for band structure engineering to design and synthesize a series of Cu _x Ag_1-x InS₂/ZnS CQDs. ZnS shell-assisted defect passivation suppresses charge carrier recombination because of the formation of the core/shell heterojunction interface, enhancing the performance of PEC devices with better charge separation and stability. More importantly, the tunable Cu doping concentration in AgInS₂ CQDs leads to the shift of the quantum dot band alignment, which greatly promotes the interfacial charge separation and transfer. As a result, Cu _x Ag_1-x InS₂/ZnS CQD photoanodes for PEC cells exhibit an enhanced photocurrent of 5.8 mA cm^-2 at 0.8 V versus the RHE, showing excellent photoelectrocatalytic activity for H₂ production with greater chemical-/photostability.

Phase-Controlled Synthesis and Quasi-Static Dielectric Resonances in Silver Iron Sulfide (AgFeS2 ) Nanocrystals

Ternary metal-chalcogenide semiconductor nanocrystals are an attractive class of materials due to their tunable optoelectronic properties that result from a wide range of compositional flexibility and structural diversity. Here, the phase-controlled synthesis of colloidal silver iron sulfide (AgFeS₂ ) nanocrystals is reported and their resonant light-matter interactions are investigated. The product composition can be shifted selectively from tetragonal to orthorhombic by simply adjusting the coordinating ligand concentration, while keeping the other reaction parameters unchanged. The results show that excess ligands impact precursor reactivity, and consequently the nanocrystal growth rate, thus deterministically dictating the resulting crystal structure. Moreover, it is demonstrated that the strong ultraviolet-visible extinction peak exhibited by AgFeS₂ nanocrystals is a consequence of a quasi-static dielectric resonance (DR), analogous to the optical response observed in CuFeS₂ nanocrystals. Spectroscopic studies and computational calculations confirm that a negative permittivity at ultraviolet/visible frequencies arises due to the electronic structure of these intermediate-band (IB) semiconductor nanocrystals, resulting in a DR consisting of resonant valence-band-to-intermediate-band excitations, as opposed to the well-known localized surface plasmon resonance response typically observed in metallic nanostructures. Overall, these results expand the current library of an underexplored class of IB semiconductors with unique optical properties, and also enrich the understanding of DRs in ternary metal-iron-sulfide nanomaterials.

High-Performance Memristors Based on Ultrathin 2D Copper Chalcogenides

Copper chalcogenides represent a class of materials with unique crystal structures, high electrical conductivity, and earth abundance, and are recognized as promising candidates for next-generation green electronics. However, their 2D structures and the corresponding electronic properties have rarely been touched. Herein, a series of ultrathin copper chalcogenide nanosheets with thicknesses down to two unit cells are successfully synthesized, including layered Cu₂ Te, as well as nonlayered CuSe and Cu₉ S₅ , via van der Waals epitaxy, and their nonvolatile memristive behavior is investigated for the first time. Benefiting from the highly active Cu ions with low migration barriers, the memristors based on ultrathin 2D copper chalcogenide crystals exhibit relatively small switching voltage (≈0.4 V), fast switching speed, high switching uniformity, and wide operating temperature range (from 80 to 420 K), as well as stable retention and good cyclic endurance. These results demonstrate their tangible applications in future low-power, cryogenic, and high temperature harsh electronics.

Microscopic-Scale Examination of the Black and Orange–Yellow Colours of Architectural Glazes from Aššur, Khorsabad and Babylon in Ancient Mesopotamia

Three major corpora of architectural glazed bricks from Ancient Mesopotamia dating to the Neo-Assyrian (Aššur and Khorsabad sites) and the Neo-Babylonian (Babylon site) Periods have been submitted to an in-depth comparative study of the orange–yellow and black glazes. Distinct hues in the orange–yellow range were observed according to the archaeological site. They appear to have been well mastered by the glassmakers, consisting in the ex situ preparation of the antique lead antimonate pigment and its mixing with transparent soda-lime glass frit or with the glass-forming components. The intentional addition of hematite or of Cu2+ colouring ions in a controlled amount is suggested in two cases. SEM-EDX and Raman analysis of the lead antimonate pigments have pointed out different chemical substitutions in their pyrochlore structure, mainly Fe3+ in the Sb5+ site and Ca2+ in the Pb2+ site, the proportion of which being correlated to the pigment shade (from pale yellow to orange–red). Part of these substitutions arises from the chemical reaction of the pigment with the hematite and glass melt during firing. Regarding the black glazes, an unexpected colouring technique involving copper sulphide nanoparticles together with the chromophore Fe3+-S2− is highlighted for Khorsabad (8th century BC) and for Babylon (6th century BC). For Aššur blacks, the study reveals a change in their colouring technique between the 9th and 8th centuries BC, from a colouration with Mn oxides to an enigmatic one that could also have involved copper sulphide nanoparticles.

Ultrathin covalent and cuprophilic interaction-assembled copper-sulfur monolayer in organic metal chalcogenide for oriented photoconductivity

We report the thinnest copper sulfur atomic monolayer in an organic copper chalcogenide [Cu(CMP)]_n (CMP = 5-chloro-2-mercaptopyridine). The layer features a new type of copper sulfur structure woven by both covalent bond and cuprophilic interaction and shows an intriguing oriented photoconductivity.

Two-dimensional copper based colloidal nanocrystals: synthesis and applications

Two-dimensional (2D) semiconductor nanocrystals display unconventional physical and opto-electronic properties due to their ultrathin and unique electronic structures. Since the success of Cd-based photoemissive nanocrystals, the development of sustainable and low-cost nanocrystals with enhanced electronic and physical properties has become a central research theme. In this context, copper-based semiconductor 2D nanocrystals, the cost-effective and eco-friendly alternative, exhibit unique plasmonic resonance, transport properties, and high ionic conductivity beneficial for sensing, energy storage, conversion, and catalytic applications. This review summarizes recent progress in the colloidal synthesis, growth mechanisms, properties, and applications of 2D copper-based nanostructures with tunable compositions, dimensions, and crystal phases. We highlight the growth mechanisms concerning their shape evolution in two dimensions. We analyse the effectiveness of cation exchange as a tool to synthesize multinary nanocrystals. Based on the preparation of Cu-based chalcogenide and non-chalcogenide compositions, we discuss synthesis control achieved via colloidal approaches to allow dimension tunability, phase engineering, and plasmonic and thermoelectric property optimization. Furthermore, their potential in various applications of catalysis, energy storage, and sensing is reviewed. Finally, we address the current challenges associated with 2D Cu-based nanocrystal development and provide an outlook pertaining to unexplored research areas.

Pressure-induced bandgap engineering and photoresponse enhancement of wurtzite CuInS2 nanocrystals

Wurtzite CuInS₂ exhibits great potential for optoelectronic applications because of its excellent optical properties and good stability. However, exploring effective strategies to simultaneously optimize its optical and photoelectrical properties remains a challenge. In this study, the bandgap of wurtzite CuInS₂ nanocrystals is successfully extended and the photocurrent is enhanced synchronously using external pressure. The bandgap of wurtzite CuInS₂ increases with pressure and reaches an optimal value (1.5 eV) for photovoltaic solar energy conversion at about 5.9 GPa. Surprisingly, the photocurrent simultaneously increases nearly 3-fold and reaches the maximum value at this critical pressure. Theoretical calculation indicates that the pressure-induced bandgap extention in wurtzite CuInS₂ may be attributed to an increased charge density and ionic polarization between the In-S atoms. The photocurrent preserves a relatively high photoresponse even at 8.8 GPa, but almost disappears above 10.3 GPa. The structural evolution demonstrates that CuInS₂ undergoes a phase transformation from the wurtzite phase (P6₃mc) to the rock salt phase (Fm3̄m) at about 10.3 GPa, which resulted in a direct to indirect bandgap transition and fianlly caused a dramatic reduction in photocurrent. These results not only map a new route toward further increase in the photoelectrical performance of wurtzite CuInS₂, but also advance the current research of A^I-B^III-CVI2 materials.

Modification of metallic and non-metallic sites in pentasupertetrahedral chalcogenidometalate clusters for third-order nonlinear optical response

Four isomorphic P2 chalcogenide clusters named [Sn₁₁In₉Cu₆S₄₄]·11(H⁺DBU) (1) (DBU = 1,8-diazabicyclo[5.4.0] undec-7-ene), [Sn₁₀In₁₀Cu₆Se₄₄]·6(H₂²⁺DMAPA)·2(DMAPA)·9EG (2) (DMAPA = 3-dimethylaminopropylamine, EG = ethylene glycol), [Sn₁₀In₁₀Cu₆S₄₀O₄]·6[H₂²⁺PMDETA]·10EG (3) (PMDETA = pentamethyldiethylenetriamine), [Sn₁₀Ga₁₀Cu₆S₄₀O₄]·6(H₂²⁺DMAPA)·7EG (4) have been isolated via organotin precursor and mixed-metal strategy. These clusters exhibit excellent solubility in organic solvents. The continuous-regulation of optical band and optical limiting performance have been realized through precise controlled substituting engineering of cationic and anionic elements.

Recent Progress in the Synthesis and Applications of Composite Photocatalysts: A Critical Review

Photocatalysis is an advanced technique that transforms solar energy into sustainable fuels and oxidizes pollutants via the aid of semiconductor photocatalysts. The main scientific and technological challenges for effective photocatalysis are the stability, robustness, and efficiency of semiconductor photocatalysts. For practical applications, researchers are trying to develop highly efficient and stable photocatalysts. Since the literature is highly scattered, it is urgent to write a critical review that summarizes the state-of-the-art progress in the design of a variety of semiconductor composite photocatalysts for energy and environmental applications. Herein, a comprehensive review is presented that summarizes an overview, history, mechanism, advantages, and challenges of semiconductor photocatalysis. Further, the recent advancements in the design of heterostructure photocatalysts including alloy quantum dots based composites, carbon based composites including carbon nanotubes, carbon quantum dots, graphitic carbon nitride, and graphene, covalent-organic frameworks based composites, metal based composites including metal carbides, metal halide perovskites, metal nitrides, metal oxides, metal phosphides, and metal sulfides, metal-organic frameworks based composites, plasmonic materials based composites and single atom based composites for CO₂ conversion, H₂ evolution, and pollutants oxidation are discussed elaborately. Finally, perspectives for further improvement in the design of composite materials for efficient photocatalysis are provided.

Indium(II) Chloride as a Precursor in the Synthesis of Ternary (Ag-In-S) and Quaternary (Ag-In-Zn-S) Nanocrystals

A new indium precursor, namely, indium(II) chloride, was tested as a precursor in the synthesis of ternary Ag-In-S and quaternary Ag-In-Zn-S nanocrystals. This new precursor, being in fact a dimer of Cl2In-InCl2 chemical structure, is significantly more reactive than InCl3, typically used in the preparation of these types of nanocrystals. This was evidenced by carrying out comparative syntheses under the same reaction conditions using these two indium precursors in combination with the same silver (AgNO3) and zinc (zinc stearate) precursors. In particular, the use of indium(II) chloride in combination with low concentrations of the zinc precursor yielded spherical-shaped (D = 3.7-6.2 nm) Ag-In-Zn-S nanocrystals, whereas for higher concentrations of this precursor, rodlike nanoparticles (L = 9-10 nm) were obtained. In all cases, the resulting nanocrystals were enriched in indium (In/Ag = 1.5-10.3). Enhanced indium precursor conversion and formation of anisotropic, longitudinal nanoparticles were closely related to the presence of thiocarboxylic acid type of ligands in the reaction mixture. These ligands were generated in situ and subsequently bound to surfacial In(III) cations in the growing nanocrystals. The use of the new precursor of enhanced reactivity facilitated precise tuning of the photoluminescence color of the resulting nanocrystals in the spectral range from ca. 730 to 530 nm with photoluminescence quantum yield (PLQY) varying from 20 to 40%. The fabricated Ag-In-S and Ag-In-Zn-S nanocrystals exhibited the longest, reported to date, photoluminescence lifetimes of ∼9.4 and ∼1.4 μs, respectively. It was also demonstrated for the first time that ternary (Ag-In-S) and quaternary (Ag-In-Zn-S) nanocrystals could be applied as efficient photocatalysts, active under visible light (green) illumination, in the reaction of aldehydes reduction to alcohols.

Nanoscale Metal−Organic Frameworks and Their Nanomedicine Applications

Abundant connectivity among organic ligands and inorganic metal ions makes the physical and chemical characters of metal-organic frameworks (MOFs) could be precisely devised and modulated for specific applications. Especially nanoscale MOFs (NMOFs), a unique family of hybrid nanomaterials, with merits of holding the nature as the mainstay MOFs and demonstrating particle size in nanoscale range which enable them prospect platform in clinic. Adjustability of composition and structure allows NMOFs with different constituents, shapes, and characteristics. Oriented frameworks and highly porous provide enough space for packing therapeutic cargoes and various imaging agents efficiently. Moreover, the relatively labile metal-ligand bonds make NMOFs biodegradable in nature. So far, as a significant class of biomedically relevant nanomaterials, NMOFs have been explored as drug carriers, therapeutic preparation, and biosensing and imaging preparation owing to their high porosity, multifunctionality, and biocompatibility. This review provides up-to-date developments of NMOFs in biomedical applications with emphasis on size control, synthetic approaches, and surfaces functionalization as well as stability, degradation, and toxicity. The outlooks and several crucial issues of this area are also discussed, with the expectation that it may help arouse widespread attention on exploring NMOFs in potential clinical applications.

Copper-induced tumor cell death mechanisms and antitumor theragnostic applications of copper complexes

Recent studies found that unbalanced copper homeostasis affect tumor growth, causing irreversible damage. Copper can induce multiple forms of cell death, including apoptosis and autophagy, through various mechanisms, including reactive oxygen species accumulation, proteasome inhibition, and antiangiogenesis. Hence, copper in vivo has attracted tremendous attention and is in the research spotlight in the field of tumor treatment. This review first highlights three typical forms of copper's antitumor mechanisms. Then, the development of diverse biomaterials and nanotechnology allowing copper to be fabricated into diverse structures to realize its theragnostic action is discussed. Novel copper complexes and their clinical applications are subsequently described.

Electrochemiluminescent emission potential tunable Cu-Zn-In-S/ZnS nanocrystals for multiplex microRNAs potential-resolved detection

The development of a multi-target simultaneous detection electrochemiluminescence (ECL) strategy remains a great research interest, however, the limited choice of ECL luminophores is the main limitation holding the field back. In this study, a band gap tunable Cu-Zn-In-S/ZnS nanocrystals (CZIS/ZnS NCs) was synthesized and applied to a potential-resolved ECL detection strategy. By changing the Cu ratio in the precursor, the CZIS/ZnS NCs ECL emission spectrum and emission potential were tuned from 480 to 750 nm and -2.10 to -1.11 V, respectively. In addition, an ECL biosensor was fabricated with CZIS/ZnS NCs as signal reporters to detect three types of microRNAs, which could sensitively and selectively determine microRNA-21, microRNA-141, and microRNA-155 in a single cathodic ECL process. The results showed that the ECL intensity was directly linear to the logarithm of the concentration of microRNA-21, microRNA-141, and microRNA-155 from 0.00001 to 10 nM with detection limits of 2.2, 2.6, and 2.7 fM, respectively. This study demonstrates that the emission potential tunable CZIS/ZnS NCs can be employed as a promising alternative to the toxic II-V and II-V NCs to simultaneously detect multiple disease markers, and can guide the further rational design of both ECL luminophores and multi-analyte ECL sensors.

Precisely synthesized LiF-tipped CoF2-nanorod heterostructures improve energy storage capacities

A facile but robust method to precisely synthesize well-defined LiF-tipped CoF2-nanorod heterostructures is established.

Colloid synthesis of AgGa(S1-xSex)2 solid solution nanocrystals with composition-dependent crystal phase for efficient photocatalytic degradation of methyl violet

A series of homogeneous AgGa(S1-xSex)2 solid solutions nanocrystals with controllable composition (0 ≤ x ≤ 1) have been successfully prepared through a facile colloidal synthesis approach. Remarkably, they exhibit an...

Sample preparation induced phase transitions in solution deposited copper selenide thin films

Thin films of CuSe were deposited onto GaAs substrate. XRD showed that the as-deposited films were of the Klockmannite (CuSe – P6₃/mmc 194) phase with lattice parameters a₀ = b₀ = 0.3939 nm, c₀ = 1.7250 nm; however, electron diffraction in the TEM surprisingly indicated the β-Cu_2−xSe phase (Cu_1.95Se – R3̄m 166) with lattice parameters a₀ = b₀ = 0.412 nm, c₀ = 2.045 nm. The discrepancy originated from the specimen preparation method, where the energy of the focused ion beam resulted in loss of selenium which drives a phase transition to β-Cu_2−xSe in this system. The same phase transition was observed also upon thermal treatment in vacuum, as well as when the 200 keV electron beam was focused on a powder sample in the TEM. The initial phase can be controlled to some extent by changing the composition of the reactants in solution, resulting in thin films of the cubic α-Cu_2−xSe (Cu_1.95Se – Fm3̄m) phase co-existing together with the β-Cu_2−xSe phase.

Ion beam irradiation causes Klockmannite CuSe to lose Se and transform into β-Cu₂Se. Caution must be taken when using the dual beam FIB for preparing TEM specimen.

Synergetic Optimization of Electrical and Thermal Transport Properties by Cu Vacancies and Nanopores in Cu2Se

In this study, a series of Cu_2+x-yIn_ySe (-0.3 ≤ x ≤ 0.2 and 0 ≤ y ≤ 0.05) samples were prepared by melting and the spark plasma sintering method. X-ray diffraction measurements indicate that the Cu-deficient samples (x = -0.3 y = 0 and x = -0.2 y = 0) prefer to form the cubic phase (β-Cu₂Se). Adding excessive Cu or introducing In atoms into the Cu₂Se matrix triggers a phase transition from the β to α phase. Positron lifetime measurements confirm the reduction in Cu vacancy concentration by adding excessive Cu or introducing In atoms into Cu₂Se, which causes a dramatic decrease in carrier concentration from 1.59 × 10²¹ to 5.0 × 10¹⁹ cm^-3 at room temperature. The samples with In contents of 0.01 and 0.03 show a high power factor of about 1 mW m^-1 K^-2 at room temperature due to the optimization of the carrier concentration. Meanwhile, the excess Cu content and doping of In atoms also favor the formation of nanopores. These pores have strong interaction with phonons, leading to remarkable reduction in lattice thermal conductivity. Finally, a high ZT value of about 1.44 is achieved at 873 K in the Cu_1.99In_0.01Se (x = 0 and y = 0.01) sample, which is about twice that of the Cu-deficient sample (Cu_1.7Se). Our work provides a viable insight into tuning vacancy defects to improve efficiently the electrical and thermal transport performance for copper-based thermoelectric materials.

Lenvatinib and Cu2-xS nanocrystals co-encapsulated in poly(D,L-lactide-co-glycolide) for synergistic chemo-photothermal therapy against advanced hepatocellular carcinoma

Lenvatinib (LT) is gradually replacing sorafenib as an alternative targeted drug against advanced hepatocellular carcinoma (HCC). However, the anticancer effects of LT are still limited because of its low cytotoxicity, multidrug resistance (MDR), and tumor relapse. Herein, we constructed a smart biophotonic nanoplatform to overcome the barriers preventing high performance. LT and copper sulfide nanocrystals (Cu_2-xS NCs) with excellent photothermal properties in the near-infrared-II (NIR-II) zone were co-encapsulated in poly(D,L-lactide-co-glycolide) (PLGA) through nanoprecipitation. Both in vitro and in vivo evaluations demonstrated that Cu_2-xS NCs enhanced the anticancer efficacy of LT, without recurrence. In addition, the presence of copper ions could allow glutathione (GHS) to be consumed and oxygen to be produced, likely suppressing the expression of P-glycoprotein (P-gp) and overcoming the issue of MDR relating to LT. More importantly, synergistic chemo-photothermal therapy with LT and Cu_2-xS NCs was more effective than any single therapy or theoretical combination. This nanoplatform is promising for advancing future LT-based treatment strategies for HCC therapy.

Heat-Up Colloidal Synthesis of Shape-Controlled Cu-Se-S Nanostructures-Role of Precursor and Surfactant Reactivity and Performance in N2 Electroreduction

Copper selenide-sulfide nanostructures were synthesized using metal-organic chemical routes in the presence of Cu- and Se-precursors as well as S-containing compounds. Our goal was first to examine if the initial Cu/Se 1:1 molar proportion in the starting reagents would always lead to equiatomic composition in the final product, depending on other synthesis parameters which affect the reagents reactivity. Such reaction conditions were the types of precursors, surfactants and other reagents, as well as the synthesis temperature. The use of 'hot-injection' processes was avoided, focusing on 'non-injection' ones; that is, only heat-up protocols were employed, which have the advantage of simple operation and scalability. All reagents were mixed at room temperature followed by further heating to a selected high temperature. It was found that for samples with particles of bigger size and anisotropic shape the CuSe composition was favored, whereas particles with smaller size and spherical shape possessed a Cu2-xSe phase, especially when no sulfur was present. Apart from elemental Se, Al2Se3 was used as an efficient selenium source for the first time for the acquisition of copper selenide nanostructures. The use of dodecanethiol in the presence of trioctylphosphine and elemental Se promoted the incorporation of sulfur in the materials crystal lattice, leading to Cu-Se-S compositions. A variety of techniques were used to characterize the formed nanomaterials such as XRD, TEM, HRTEM, STEM-EDX, AFM and UV-Vis-NIR. Promising results, especially for thin anisotropic nanoplates for use as electrocatalysts in nitrogen reduction reaction (NRR), were obtained.

Consolidation of 2D Frameworks Based on Corner-Shared Supertetrahedral T5 Clusters via M2OS2 Units for Tunable Photoluminescent and Semiconductor Properties

Introducing transition metals into the intercluster linkers has been considered an important strategy for the rapid development of metal chalcogenide supertetrahedral (Tn) cluster-based open frameworks with excellent properties. However, using this strategy for achieving the structure and property tunability in the cluster-based framework of Tn (n ≥ 5) is still a great challenge. Herein, we report on three new sulfide and oxosulfide open frameworks of T5 clusters, i.e., T5-ZnMnInOS ([In₃₀Zn₅Mn₄O₂S₅₈]^12-), T5-MnInOS ([In₃₄Mn₅O₂S₅₈]^8-), and T5-MnInS ([In₂₈Mn₆S₅₄]^12-). Interestingly, transition metals Zn and Mn are successfully introduced into T5-ZnMnInOS and T5-MnInOS via the consolidation of corner-shared Zn₂OS₂ and Mn₂OS₂ units, respectively. Under the photoexcitation of UV light, three compounds can emit bright-orange-red light closely associated with the Mn²⁺ ions, and the compounds containing M₂OS₂ units exhibit better photoluminescence (PL) lifetimes. Variable-temperature PL spectra demonstrate that the introduced M₂OS₂ units are favorable for weakening the deformation of the skeleton structure and decreasing the red shifts of the emission peaks at low temperatures. Moreover, the experimental results exhibit that the three compounds are wide-band-gap semiconductors and that the photogenerated electron separation efficiency can be doubly increased because the intercluster linkers are fixed by the M₂OS₂ units. This work paves a new way for enriching the content and distribution types of transition-metal sites in the supertetrahedral cluster-based metal chalcogenide open frameworks.

Gram-Scale Production of Photothermally Active Tetrahedrite Nanoparticles for Solar-Driven Water Evaporation

Pristine and substituted tetrahedrite nanoparticles have shown immense potential as low-cost and sustainable materials for energy conversion applications. However, the commonly used synthetic methods for their production are cumbersome and are not easily scalable. In this work, we report a facile colloidal synthetic protocol for the preparation of phase-pure samples of pristine (Cu₁₂ Sb₄ S₁₃ ) and Zn-substituted (Cu₁₁ ZnSb₄ S₁₃ ) tetrahedrite nanoparticles on the gram scale. Both tetrahedrite compositions were found to be photothermally responsive, enabling their use in solar-driven water evaporation.

Starch Capped Atomically Thin CuS Nanocrystals for Efficient Photothermal Therapy

Photothermal therapy requires efficient plasmonic nanomaterials with small size, good water dispersibility, and biocompatibility. This work reports a one-pot, 2-min synthesis strategy for ultrathin CuS nanocrystals (NCs) with precisely tunable size and localized surface plasmon resonance (LSPR), where a single-starch-layer coating leads to a high LSPR absorption at the near-IR wavelength 980 nm. The CuS NC diameter increases from 4.7 (1 nm height along [101]) to 28.6 nm (4.9 nm height along [001]) accompanied by LSPR redshift from 978 to 1200 nm, as the precursor ratio decreases from 1 to 0.125. Photothermal temperature increases by 38.6 °C in 50 mg L^-1 CuS NC solution under laser illumination (980 nm, 1.44 W cm^-2 ). Notably, 98.4% of human prostate cancer PC-3/Luc+ cells are killed by as little as 5 mg L^-1 starch-coated CuS NCs with 3-min laser treatment, whereas CuS NCs without starch cause insignificant cell death. LSPR modeling discloses that the starch layer enhances the photothermal effect by significantly increasing the free carrier density and blue-shifting the LSPR toward 980 nm. This study not only presents a new type of photothermally highly efficient ultrathin CuS NCs, but also offers in-depth LSPR modeling investigations useful for other photothermal nanomaterial designs.

Optothermal properties of plasmonic inorganic nanoparticles for photoacoustic applications

Plasmonic systems are becoming a favourable alternative to dye molecules in the generation of photoacoustic signals for spectroscopy and imaging. In particular, inorganic nanoparticles are appealing because of their versatility. In fact, as the shape, size and chemical composition of nanoparticles are directly correlated with their plasmonic properties, the excitation wavelength can be tuned to their plasmon resonance by adjusting such traits. This feature enables an extensive spectral range to be covered. In addition, surface chemical modifications can be performed to provide the nanoparticles with designed functionalities, e.g., selective affinity for specific macromolecules. The efficiency of the conversion of absorbed photon energy into heat, which is the physical basis of the photoacoustic signal, can be accurately determined by photoacoustic methods. This review contrasts studies that evaluate photoconversion in various kinds of nanomaterials by different methods, with the objective of facilitating the researchers' choice of suitable plasmonic nanoparticles for photoacoustic applications.

Dual Plasmonic Au-Cu2-x S Nanocomposites: Design Strategies and Photothermal Properties

Coupling two different materials to create a hybrid nanostructured system is a powerful strategy for achieving synergistically enhanced properties and advanced functionalities. In the case of Au and Cu_2-x S, their combination on the nanoscale results in dual plasmonic Au-Cu_2-x S nanocomposites that exhibit intense photon absorption in both the visible and the near-infrared spectral ranges. Their strong light-absorbing properties translate to superior photothermal transduction efficiency, making them attractive in photothermal-based applications. There are several nanostructure configurations that are possible for the Au-Cu_2-x S system, and the successful fabrication of a particular architecture often requires a carefully planned synthetic strategy. In this Minireview, the different synthetic approaches that can be employed to produce rationally designed Au-Cu_2-x S nanocomposites are presented, with a focus on the experimental protocols that can lead to heterodimer, core-shell, reverse core-shell, and yolk-shell configurations. The photothermal behavior of these materials is also discussed, providing a glimpse of their potential use as photothermally active agents in therapeutic and theranostic applications.

Controlled Synthesis of CuS and Cu9S5 and Their Application in the Photocatalytic Mineralization of Tetracycline

Pure-phase Cu2−xS (x = 1, 0.2) nanoparticles have been synthesized by the thermal decomposition of copper(II) dithiocarbamate as a single-source precursor in oleylamine as a capping agent. The compositions of the Cu2−xS nanocrystals varied from CuS (covellite) through the mixture of phases (CuS and Cu7.2S4) to Cu9S5 (digenite) by simply varying the temperature of synthesis. The crystallinity and morphology of the copper sulfides were studied using X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM), which showed pure phases at low (120 °C) and high (220 °C) temperatures and a mixture of phases at intermediate temperatures (150 and 180 °C). Covellite was of a spherical morphology, while digenite was rod shaped. The optical properties of these nanocrystals were characterized by UV−vis–NIR and photoluminescence spectroscopies. Both samples had very similar absorption spectra but distinguishable fluorescence properties and exhibited a blue shift in their band gap energies compared to bulk Cu2−xS. The pure phases were used as catalysts for the photocatalytic degradation of tetracycline (TC) under visible-light irradiation. The results demonstrated that the photocatalytic activity of the digenite phase exhibited higher catalytic degradation of 98.5% compared to the covellite phase, which showed 88% degradation within the 120 min reaction time using 80 mg of the catalysts. The higher degradation efficiency achieved with the digenite phase was attributed to its higher absorption of the visible light compared to covellite.

The Preparation of CuInS2-ZnS-Glutathione Quantum Dots and Their Application on the Sensitive Determination of Cytochrome c and Imaging of HeLa Cells

Cytochrome c (Cyt c), one of the most significant proteins acting as an electron transporter, plays an important role during the transferring process of the energy in cells. Apoptosis, one of the major forms of cell death, has been associated with various physiological regularity and pathological mechanisms. It was found that Cyt c can be released from mitochondria to cytosol under different pathological conditions, triggering subsequent cell apoptosis. Herein, we developed a fluorescence nanoprobe based on negatively charged CuInS₂-ZnS-GSH quantum dots (QDs) for the sensitive determination of Cyt c. CuInS₂-ZnS-GSH QDs with high photochemical stability and favorable hydrophilicity were prepared by a simple hot reflux method and emit a bright orange-red light. The electron-deficient heme group in Cyt c is affiliated with the electron-rich CuInS₂-ZnS-GSH QDs through the photo-induced electron transfer process, resulting in a large decrease in fluorescence intensity of QDs. A good linearity for concentration of Cyt c in the range of 0.01-7 μmol L^-1 is obtained, and the detection limit of Cyt c is as low as 1.1 nM. The performance on the detection of Cyt c in spiked human serum and fetal bovine serum samples showed good recoveries from 85.5% to 95.0%. Furthermore, CuInS₂-ZnS-GSH QDs were applied for the intracellular imaging in HeLa cells showing an extremely lower toxicity and excellent biocompatibility.

Covalent SO Bonding Enables Enhanced Photoelectrochemical Performance of Cu2 S/Fe2 O3 Heterojunction for Water Splitting

The severe charge recombination and the sluggish kinetic for oxygen evolution reaction have largely limited the application of hematite (α-Fe₂ O₃ ) for water splitting. Herein, the construction of Cu₂ S/Fe₂ O₃ heterojunction and discover that the formation of covalent SO bonds between Cu₂ S and Fe₂ O₃ can significantly improve the photoelectrochemical performance and stability for water splitting is reported. Compared with bare Fe₂ O₃ , the heterostructure of Cu₂ S/Fe₂ O₃ endows the resulting electrode with enhanced charge separation and transfer, extended range for light absorption, and reduced charge recombination rate. Additionally, due to the photothermal properties of Cu₂ S, the heterostructure exhibits locally a higher temperature under illumination, profitable for increasing the rate of oxygen evolution reaction. Consequently, the photocurrent density of the heterostructure is enhanced by 177% to be 1.19 mA cm^-2 at 1.23 V versus reversible hydrogen electrode. This work may provide guideline for future in the design and fabrication of highly efficient photoelectrodes for various reactions.

Tunable structural and optical properties of CuInS2 colloidal quantum dots as photovoltaic absorbers

Facile phase selective synthesis of CuInS₂ (CIS) nanostructures has been an important pursuit because of the opportunity for tunable optical properties of the phases, and in this respect is investigated by hot-injection colloidal synthesis in this study. Relatively monodispersed colloidal quantum dots (3.8–5.6 nm) of predominantly chalcopyrite structure synthesized at 140, 180 and 210 °C over 60 minutes from copper(ii) hexafluoroacetylacetonate hydrate and indium(iii) diethyldithiocarbamate precursors exhibit temperature-dependent structural variability. The slightly off-stoichiometric quantum dots are copper-deficient in which copper vacancies , indium interstitials , indium–copper anti-sites and surface trapping states are likely implicated in broad photoluminescence emission with short radiative lifetimes, τ₁, τ₂, and τ₃ of 1.5–2.1, 7.8–13.9 and 55.2–70.8 ns and particle-size dependent tunable band gaps between 2.25 and 2.32 eV. Further structural and optical tunability (E_g between 2.03 and 2.28 eV) is achieved with possible time-dependent wurtzite to chalcopyrite phase transformation at 180 °C likely involving a dynamic interplay of kinetic and thermodynamic factors.

We report the facile hot-injection colloidal synthesis of near-stoichiometric CuInS₂ quantum dots at varying reaction times and temperatures which exhibit both optical and structural tunability with implications for enhanced photovoltaic utility.

Stoichiometric Doping of Highly Coupled Cu2-xS Nanocrystal Assemblies

The hole density of individual copper sulfide nanocrystals (Cu_2-xS NCs) is determined from the stoichiometric mismatch (x) between copper and sulfide atoms. Consequently, the electronic properties of the material vary over a range of x. To exploit Cu_2-xS NCs in devices, assemblies of NCs are typically required. Herein, we investigate the influence of x, referred to as the stoichiometric doping effect, on the structural, optical, electrical, and thermoelectric properties of electronically coupled Cu_2-xS NC assemblies. The doping process is done by immersing the solid NC assemblies into a solution containing a Cu(I) complex for different durations (0-10 min). As Cu⁺ gradually occupied the copper-deficient sites of Cu_2-xS NCs, x could be controlled from 0.9 to less than 0.1. Consequently, the near-infrared (NIR) absorbance of Cu_2-xS NC assemblies changes systematically with x. With increasing x, electrical conductivity increased and the Seebeck coefficient decreased systematically, leading to the maximal thermoelectric power factor from a film of Cu_2-xS NCs at an optimal doping condition yielding x = 0.1. The physical characteristics of the Cu_2-xS NC assemblies investigated herein will provide guidelines for exploiting this emerging class of nanocrystal system based on doping.

Designing Nanostructured Metal Chalcogenides as Cathode Materials for Rechargeable Magnesium Batteries

Rechargeable magnesium batteries (RMBs) are regarded as promising candidates for beyond-lithium-ion batteries owing to their high energy density. Moreover, as Mg metal is earth-abundant and has low propensity for dendritic growth, RMBs have the advantages of being more affordable and safer than the currently used lithium-ion batteries. However, the commercial viability of RMBs has been negatively impacted by slow diffusion kinetics in most cathode materials due to the high charge density and strongly polarizing nature of the Mg²⁺ ion. Nanostructuring of potential cathode materials such as metal chalcogenides offers an effective means of addressing these challenges by providing larger surface area and shorter migration routes. In this article, a review of recent research on the design of metal chalcogenide nanostructures for RMBs' cathode materials is provided. The different types and structures of metal chalcogenide cathodes are discussed, and the synthetic strategies through which nanostructuring of these materials can be achieved are described. An organized summary of their electrochemical performance is also presented, along with an analysis of the current challenges and future directions. Although particular focus is placed on RMBs, many of the nanostructuring concepts that are discussed here can be carried forward to other next-generation energy storage systems.

Near-Infrared II Thermoplasmonics of Cuprous Selenide Multilayer Nanoshells: The Role of the Plasmonic Core

We present a numerical investigation of the plasmonic and photothermal properties of two different types of cuprous selenide (Cu_2-xSe) concentric multilayer nanoshells (CMNSs), heteroCMNSs and homoCMNSs, comprising an outer Cu_2-xSe nanoshell and an intermediate silica layer but with a different nanoparticle core of either Au or Cu_2-xSe. Numerical calculations of optical absorption, near-field enhancement, and local temperature increase are performed with varied dimensions. The plasmon modes from both types of CMNSs are interpreted by combining the plasmon hybridization theory with the surface charge distribution. The two CMNSs exhibit remarkable near-infrared II (NIR-II) plasmonic properties tunable by controlling the interaction between the inner core and the Cu_2-xSe nanoshell. The distinct temperature increase distributions between the two CMNSs are identified at their NIR-II resonance wavelengths. The correlation between the partial absorption and the temperature increase of the inner core and Cu_2-xSe nanoshell suggests the thermal interplay between the components.

Investigation of dual plasmonic core-shell Ag@CuS nanoparticles for potential surface-enhanced Raman spectroscopy-guided photothermal therapy

Aim: To prepare efficient metal-semiconductor nanoparticles as noninvasive, real-time imaging probes for photothermal therapy (PTT) applications. Materials & methods: A bottom-up approach was used to fabricate core-shell Ag@CuS nanoparticles (NPs). PTT and Raman mapping were done using HeLa cells. Theoretical simulation of electric field enhancement and heat dissipation density of Ag@CuS NPs was performed. Results: PTT-induced hyperthermia was achieved under 940 nm near-infrared light irradiation. Surface-enhanced Raman spectroscopy (SERS) signals of dye molecules were observed when conjugated with Ag@CuS NPs. Conclusion: Ag@CuS NPs are found to be efficient for SERS imaging and localized heating under laser irradiation, making a promising candidate for SERS-guided PTT.

One-Dimensional Superlattice Heterostructure Library

Axially, epitaxially organizing nano-objects of distinct compositions and structures into superlattice nanowires enables full utilization of sunlight, readily engineered band structures, and tunable geometric parameters to fit carrier transport, thus holding great promise for optoelectronics and solar-to-fuel conversion. To maximize their efficiency, the general and high-precision synthesis of colloidal axial superlattice nanowires (ASLNWs) with programmable compositions and structures is the prerequisite; however, it remains challenging. Here, we report an axial encoding methodology toward the ASLNW library with precise control over their compositions, dimensions, crystal phases, interfaces, and periodicity. Using a predesigned, editable nanoparticle framework that offers the synthetic selectivity, we are able to chemically decouple adjacent sub-objects in ASLNWs and thus craft them in a controlled approach, yielding a library of distinct ASLNWs. We integrate therein plasmonic, metallic, or near-infrared-active chalcogenides, which hold great potential in solar energy conversion. Such synthetic capability enables a performance boost in target applications, as we report order-of-magnitude enhanced photocatalytic hydrogen production rates using optimized ASLNWs compared to corresponding solo objects. Furthermore, it is expected that such unique superlattice nanowires could bring out new phenomena.

Large-Scale Synthesis of Semiconducting Cu(In,Ga)Se2 Nanoparticles for Screen Printing Application

During the last few decades, the interest over chalcopyrite and related photovoltaics has been growing due the outstanding structural and electrical properties of the thin-film Cu(In,Ga)Se2 photoabsorber. More recently, thin film deposition through solution processing has gained increasing attention from the industry, due to the potential low-cost and high-throughput production. To this end, the elimination of the selenization procedure in the synthesis of Cu(In,Ga)Se2 nanoparticles with following dispersion into ink formulations for printing/coating deposition processes are of high relevance. However, most of the reported syntheses procedures give access to tetragonal chalcopyrite Cu(In,Ga)Se2 nanoparticles, whereas methods to obtain other structures are scarce. Herein, we report a large-scale synthesis of high-quality Cu(In,Ga)Se2 nanoparticles with wurtzite hexagonal structure, with sizes of 10-70 nm, wide absorption in visible to near-infrared regions, and [Cu]/[In + Ga] ≈ 0.8 and [Ga]/[Ga + In] ≈ 0.3 metal ratios. The inclusion of the synthesized NPs into a water-based ink formulation for screen printing deposition results in thin films with homogenous thickness of ≈4.5 µm, paving the way towards environmentally friendly roll-to-roll production of photovoltaic systems.

Dithiocarbamate Complexes as Single Source Precursors to Nanoscale Binary, Ternary and Quaternary Metal Sulfides

Nanodimensional metal sulfides are a developing class of low-cost materials with potential applications in areas as wide-ranging as energy storage, electrocatalysis, and imaging. An attractive synthetic strategy, which allows careful control over stoichiometry, is the single source precursor (SSP) approach in which well-defined molecular species containing preformed metal-sulfur bonds are heated to decomposition, either in the vapor or solution phase, resulting in facile loss of organics and formation of nanodimensional metal sulfides. By careful control of the precursor, the decomposition environment and addition of surfactants, this approach affords a range of nanocrystalline materials from a library of precursors. Dithiocarbamates (DTCs) are monoanionic chelating ligands that have been known for over a century and find applications in agriculture, medicine, and materials science. They are easily prepared from nontoxic secondary and primary amines and form stable complexes with all elements. Since pioneering work in the late 1980s, the use of DTC complexes as SSPs to a wide range of binary, ternary, and multinary sulfides has been extensively documented. This review maps these developments, from the formation of thin films, often comprised of embedded nanocrystals, to quantum dots coated with organic ligands or shelled by other metal sulfides that show high photoluminescence quantum yields, and a range of other nanomaterials in which both the phase and morphology of the nanocrystals can be engineered, allowing fine-tuning of technologically important physical properties, thus opening up a myriad of potential applications.

Copper nanoclusters: designed synthesis, structural diversity, and multiplatform applications

Atomically precise metal nanoclusters (MNCs) have gained tremendous research interest in recent years due to their extraordinary properties. The molecular-like properties that originate from the quantized electronic states provide novel opportunities for the construction of unique nanomaterials possessing rich molecular-like absorption, luminescence, and magnetic properties. The field of monolayer-protected metal nanoclusters, especially copper, with well-defined molecular structures and compositions, is relatively new, about two to three decades old. Nevertheless, the massive progress in the field illustrates the importance of such nanoobjects as promising materials for various applications. In this respect, nanocluster-based catalysts have become very popular, showing high efficiencies and activities for the catalytic conversion of chemical compounds. Biomedical applications of clusters are an active research field aimed at finding better fluorescent contrast agents, therapeutic pharmaceuticals for the treatment and prevention of diseases, the early diagnosis of cancers and other potent diseases, especially at early stages. A huge library of structures and the compositions of copper nanoclusters (CuNCs) with atomic precisions have already been discovered during last few decades; however, there are many concerns to be addressed and questions to be answered. Hopefully, in future, with the combined efforts of material scientists, inorganic chemists, and computational scientists, a thorough understanding of the unique molecular-like properties of metal nanoclusters will be achieved. This, on the other hand, will allow the interdisciplinary researchers to design novel catalysts, biosensors, or therapeutic agents using highly structured, atomically precise, and stable CuNCs. Thus, we hope this review will guide the reader through the field of CuNCs, while discussing the main achievements and improvements, along with challenges and drawbacks that one needs to face and overcome.

Synthesis, modification and bioapplications of nanoscale copper chalcogenides

Copper chalcogenides have a simple general formula, variable atomic ratios, and complicated crystal structures, which lead to their wealth of optical, electrical, and magnetic properties with great potential for wide applications ranging from energy conversion to the biomedical field. Herein, we summarize the recent advances in (1) the synthesis of size- and morphology tunable nanostructures by different methods; (2) surface modification and functionalization for different purposes; and (3) bioapplications for diagnosis and treatment of tumors by different imaging and therapy methods, as well as antibacterial applications. We also briefly discuss the future directions and challenges of copper chalcogenide nanoparticles in the biomedical field.

Organic-to-Aqueous Phase Transfer of Alloyed AgInS2-ZnS Nanocrystals Using Simple Hydrophilic Ligands: Comparison of 11-Mercaptoundecanoic Acid, Dihydrolipoic Acid and Cysteine

The exchange of primary hydrophobic ligands for hydrophilic ones was studied for two types of alloyed AgInS₂-ZnS nanocrystals differing in composition and by consequence exhibiting two different emission colors: red (R) and green (G). Three simple hydrophilic ligands were tested, namely, 11-mercaptoundecanoic acid, dihydrolipoic acid and cysteine. In all cases, stable aqueous colloidal dispersions were obtained. Detailed characterization of the nanocrystal surface before and after the ligand exchange by NMR spectroscopy unequivocally showed that the exchange process was the most efficient in the case of dihydrolipoic acid, leading to the complete removal of the primary ligands with a relatively small photoluminescence quantum yield drop from 68% to 40% for nanocrystals of the R type and from 48% to 28% for the G ones.

Effect of the Annealing Atmosphere on Crystal Phase and Thermoelectric Properties of Copper Sulfide

Cu_2-xS has become one of the most promising thermoelectric materials for application in the middle-high temperature range. Its advantages include the abundance, low cost, and safety of its elements and a high performance at relatively elevated temperatures. However, stability issues limit its operation current and temperature, thus calling for the optimization of the material performance in the middle temperature range. Here, we present a synthetic protocol for large scale production of covellite CuS nanoparticles at ambient temperature and atmosphere, and using water as a solvent. The crystal phase and stoichiometry of the particles are afterward tuned through an annealing process at a moderate temperature under inert or reducing atmosphere. While annealing under argon results in Cu_1.8S nanopowder with a rhombohedral crystal phase, annealing in an atmosphere containing hydrogen leads to tetragonal Cu_1.96S. High temperature X-ray diffraction analysis shows the material annealed in argon to transform to the cubic phase at ca. 400 K, while the material annealed in the presence of hydrogen undergoes two phase transitions, first to hexagonal and then to the cubic structure. The annealing atmosphere, temperature, and time allow adjustment of the density of copper vacancies and thus tuning of the charge carrier concentration and material transport properties. In this direction, the material annealed under Ar is characterized by higher electrical conductivities but lower Seebeck coefficients than the material annealed in the presence of hydrogen. By optimizing the charge carrier concentration through the annealing time, Cu_2-xS with record figures of merit in the middle temperature range, up to 1.41 at 710 K, is obtained. We finally demonstrate that this strategy, based on a low-cost and scalable solution synthesis process, is also suitable for the production of high performance Cu_2-xS layers using high throughput and cost-effective printing technologies.

Thrombolysis Combined Therapy Using CuS@SiO2-PEG/uPA Nanoparticles

Massive hemorrhage caused by the uncontrolled release of thrombolysis drugs is a key issue of thrombolysis therapy in clinical practice. In this study, we report a near-infrared (NIR) light-triggered drug delivery system, i.e., CuS@mSiO₂-PEG (CSP) nanoparticles, for the loading of a thrombolytic drug (urokinase plasminogen activators, uPA). CSP nanoparticles with the CuS nanoparticles as photothermal agents and mesoporous SiO₂ for the loading of uPA were synthesized using a facile hydrothermal method. The CSP core-shell nanoparticles were demonstrated to possess excellent photothermal performance, exhibiting a photothermal conversion efficiency of up to 52.8%. Due to the mesoporous SiO₂ coating, the CSP core-shell nanoparticles exhibited appropriate pore size, high pore volume, and large surface area; thus, they showed great potential to be used as drug carriers. Importantly, the release of uPA from CuS@mSiO₂-PEG/uPA (CSPA) carriers can be promoted by the NIR laser irradiation. The drug loading content of uPA for the as-prepared NIR-triggered drug delivery system was calculated to be 8.2%, and the loading efficiency can be determined to be as high as 89.6%. Due to the excellent photothermal effect of CSP nanocarriers, the NIR-triggered drug delivery system can be used for infrared thermal imaging in vivo. The in vivo thrombolysis assessment demonstrated that the NIR-triggered drug delivery system showed excellent thrombolytic ability under the irradiation of an 808 nm laser, showing the combined therapy for thrombolysis. As far as we know, the CSPA core-shell nanoparticles used as NIR-triggered drug delivery systems for thrombolysis have not been reported.

Deterministic synthesis of Cu9S5 flakes assisted by single-layer graphene arrays

The employment of two-dimensional materials, as growth substrates or buffer layers, enables the epitaxial growth of layered materials with different crystalline symmetries with a preferential crystalline orientation and the synthesis of heterostructures with a large lattice constant mismatch. In this work, we employ single crystalline graphene to modify the sulfurization dynamics of copper foil for the deterministic synthesis of large-area Cu₉S₅ crystals. Molecular dynamics simulations using the Reax force-field are used to mimic the sulfurization process of a series of different atomistic systems specifically built to understand the role of graphene during the sulphur atom attack over the Cu(111) surface. Cu₉S₅ flakes show a flat morphology with an average lateral size of hundreds of micrometers. Cu₉S₅ presents a direct band-gap of 2.5 eV evaluated with light absorption and light emission spectroscopies. Electrical characterization shows that the Cu₉S₅ crystals present high p-type doping with a hole mobility of 2 cm² V^-1 s^-1.

Zn-Cu-In-S-Se Quinary "Green" Alloyed Quantum-Dot-Sensitized Solar Cells with a Certified Efficiency of 14.4

The photoelectronic properties of quantum dots (QDs) have a critical impact on the performance of quantum-dot-sensitized solar cells (QDSCs). Currently, I-III-VI group QDs have become the mainstream light-harvesting materials in high-performance QDSCs. However, it is still a great challenge to achieve satisfactory efficiency for light-harvesting, charge extraction, and charge collection simultaneously in QDSCs. We design and prepare Zn_0.4 Cu_0.7 In_1.0 S_x Se_2-x (ZCISSe) quinary alloyed QDs by cation/anion co-alloying strategy. The critical photoelectronic properties of target QDs, including band gap, conduction band energy level, and density of defect trap states, can be conveniently tailored. Experimental results demonstrate that the ZCISSe quinary alloyed QDs can achieve an ideal balance among light-harvesting, photogenerated electron extraction, and charge-collection efficiencies in QDSCs compared to its single anion or cation quaternary alloyed QD counterparts. Consequently, the quinary alloyed QDs boost the certified efficiency of QDSCs to 14.4 %, which is a new efficiency record for liquid-junction QD solar cells.

Binary and Ternary Colloidal Cu-Sn-Te Nanocrystals for Thermoelectric Thin Films

Recent advances in copper chalcogenide-based nanocrystals (NCs), copper sulfide, and copper selenide derived nanostructures, have drawn considerable attention. However, reports of crystal phase and shape engineering of binary or ternary copper telluride NCs remain rare. Here, a colloidal hot-injection approach for producing binary copper/tin telluride, and ternary copper tin telluride NCs with controllable compositions, crystal structures, and morphologies is reported. The crystal phase and growth behavior of these tellurides are systematically studied from both experimental and theoretical perspectives. The morphology of Cu_1.29 Te NCs is modified from 1D nanorods with different aspect ratios to 2D nanosheets and 3D nanocubes, by controlling the preferential growth of specific crystalline facets. A controllable phase transition from Cu_1.29 Te to Cu_1.43 Te NCs is also demonstrated. The latter can be further converted into Cu₂ SnTe₃ and SnTe through Sn incorporation. Temperature dependent thermoelectric properties of metal (Cu and Sn) telluride nanostructure thin films are also studied, including Cu_1.29 Te, Cu_1.43 Te, Cu₂ SnTe₃ , and SnTe. Cu₂ SnTe₃ is a low carrier density semimetal with compensating electron and hole Fermi surface pockets. The engineering of crystal phase and morphology control of colloidal copper tin telluride NCs opens a path to explore and design new classes of copper telluride-based nanomaterials for thermoelectrics and other applications.

Preparation of Cu cluster catalysts by simultaneous cooling-microwave heating: application in radical cascade annulation

One of the hallmarks of microwave irradiation is its selective heating mechanism. In the past 30 years, alternative designs of chemical reactors have been introduced, where the microwave (MW) absorber occupies a limited reactor volume but the surrounding environment is MW transparent. This advantage results in a different heating profile or even the possibility to quickly cool down the system. Simultaneous cooling-microwave heating has been largely adopted for organic chemical transformations. However, to the best of our knowledge there are no reports of its application in the field of nanocluster synthesis. In this work, we propose an innovative one-pot procedure for the synthesis of Cu nanoclusters. The cluster nucleation was selectively MW-activated inside the pores of a highly ordered mesoporous substrate. Once the nucleation event occurred, the crystallization reaction was instantaneously quenched, precluding the growth events and favoring the production of Cu clusters with a homogenous size distribution. Herein, we demonstrated that Cu nanoclusters could be successfully adopted for radical cascade annulations of N-alkoxybenzamides, resulting in various tricyclic and tetracyclic isoquinolones, which are widely present in lots of natural products and bioactive compounds. Compared to reported homogeneous methods, supported Cu nanoclusters provide a better platform for a green, sustainable and efficient heterogeneous approach for the synthesis of tricyclic and tetracyclic isoquinolones, avoiding a variety of toxic waste/byproducts and metal contamination in the final products.

Colloidal Nanocrystals as Precursors and Intermediates in Solid State Reactions for Multinary Oxide Nanomaterials

ConspectusPolyelemental compounds with dimensions in the nanosized regime are desirable in a large variety of applications, yet their synthesis remains a general challenge in chemistry. One of the major bottlenecks to obtaining multinary systems is the complexity of the synthesis itself. As the number of elements to include in one single nano-object increases, different chemical interactions arise during nucleation and growth, thus challenging the formation of the targeted product. Choosing the reaction conditions and identifying the parameters which ensure the desired reaction pathway are of the uttermost importance. When, in addition to composition, the simultaneous control of size and shape is sought after, the development of new synthetic strategies guided by the fundamental understanding of the formation mechanisms becomes crucial.In this Account we discuss the use of colloidal chemistry to target multinary oxide nanomaterials, with focus on light absorbers which can drive chemical reactions. We propose the combination of soft and solid-state chemistries as one successful strategy to target this family of polyelemental compounds with control on composition and morphological features. To start with, we highlight studies where in situ forming nanoparticles act as reaction intermediates, which we found in both oxide (i.e., Bi-V-O) and sulfide (Cu-M-S, with M = V, Cr, Mn) nanocrystals (NCs). Examples of ternary sulfides are mentioned only with the purpose of showing that similar mechanisms can apply to different families of multinary nanomaterials. Using this new knowledge, we demonstrate that reacting pre-synthesized NCs with well-defined composition and size with molecular precursors allows significant control of these same property-dictating features (i.e., composition and grain size) in the resulting ternary and quaternary compounds. For example, nanostructured BiV_1-xSb_xO₄ thin films with tunable composition and nanostructured β-Cu₂V₂O₇ with tunable grain size were accessed from colloidally synthesized Bi_1-xSb_x NCs (0 < x < 1) and size-controlled Cu NCs reacted with a vanadium molecular precursor, respectively. The analysis of reaction aliquots revealed that the formation of these materials occurs via a solid-state reaction between the NC precursors and V-containing amorphous nanoparticles, which form in situ from the molecular precursors. With the aim to achieve better control on the reaction product, we finally propose the use of colloidally synthesized NCs as reactants in solid state reactions. As the first proof of concept, ternary metal oxide NCs, including CuFe₂O₄, CuMn₂O₄, and CuGa₂O₄ with defined size and shape regulated by the NC precursors were obtained. Considering the huge library of single component and binary NCs accessible by colloidal chemistry, the extension of this synthetic concept, which combines soft and solid-state chemistries, to a larger variety of polyelemental nanomaterials is foreseen. Such an approach will contribute to facilitate a more rapid translation of design principles to materials with the desired composition and structural features.