Quantitative X-ray Absorption and Emission Spectroscopies: Electronic Structure Elucidation of Cu2S and CuS

Polyphosphate-Mediated Crystallographic and Colloidal Stabilization of CuS Nanoparticles: Enhanced NIR-Responsive Chemo-Photothermal Efficacy

Photothermal therapy (PTT) is an emerging treatment modality for cancer management. However, the photothermal agents (PTAs) used in PTT should have sufficient biocompatibility, water dispersibility, and good photoresponsive. In this aspect, water-dispersible and biocompatible linear polyphosphate (LP)-functionalized CuS nanoparticles (LP-CuS NPs) were developed using sodium tripolyphosphate (LP molecule) as a surface passivating agent. The successful formation of the green covellite CuS phase was confirmed by X-ray diffraction and TEM analyses, and its surface functionalization with the LP ligand was evident from X-ray photoelectron spectroscopy, Fourier transform infrared, thermogravimetric analysis, and light scattering measurements. It has been found that the use of LP not only stabilizes the crystallographic covellite CuS phase by overcoming the requirement of a soft ligand but also provides long-term aqueous colloidal stability, which is essential for PTT applications. The aqueous suspension of LP-CuS NPs showed excellent heating efficacy under near infrared (NIR) light irradiation (980 nm) and has a strong binding affinity towards anticancer drug, doxorubicin hydrochloride (DOX). The drug-loaded systems (DOX@LP-CuS NPs) revealed a pH-dependent drug release behavior with higher concentrations in a mild acidic environment. The in vitro studies showed substantial cellular uptake of DOX-loaded systems in cancer cell lines and enhanced toxicity towards them upon irradiation of NIR light through apoptotic induction, suggesting their potential application in chemo-photothermal therapy.

Tumor Metabolism Aiming Cu2-xS Nanoagents Mediate Photothermal-Derived Cuproptosis and Immune Activation

Cuproptosis is an emerging form of cell death that relies on the targeted delivery of copper ions to lipoylated tricarboxylic acid cycle proteins. However, a major challenge associated with cuproptosis is its potential to kill both normal and tumor cells without discrimination. Therefore, it is crucial to develop strategies for precise intracellular delivery and redox control of copper to create effective cuproptosis-based tumor therapies. We have introduced a class of nanoagents called metabolism aiming Cu2-xS (MACuS) through a glucose-mediated biomineralization approach. MACuS nanoagents can be specifically targeted to tumors via the glucose transport receptor 1, and we found that NIR-II irradiation can not only result in direct hyperthermia ablation of tumor cells but also facilitate efficient cuproptosis and enhance reactive oxygen species-induced cytotoxicity in tumor cells. As a result, the triple effect of MACuS treatment induced immunogenic cell death, which triggered systemic antitumor immune responses and demonstrated potent efficacy in inhibiting growth, metastasis, and recurrence in mouse and rabbit breast cancer models. The precise intracellular delivery and redox control of copper provided by MACuS hold great potential for the development of highly efficient cuproptosis-based tumor therapies with minimal off-target effects.

Assemble of porous heterostructure thin film through CuS passivation for efficient electron transport in dye-sensitized solar cells

Three different modified solar cells have been passivated with copper sulfide (CuS) on a TiO2 electrode and manganese sulfide (γ-MnS) hexagonal as photon absorbers. The MnS were prepared using (a-c) bis(N-Piperl-N-p-anisildithiocarbamato)Manganese(II) Complexes Mn[N-Piper-N-p-Anisdtc] as (MnS_1), N-p-anisidinyldithiocarbamato Mn[N-p-anisdtc] as (MnS_2) and N-piperidinyldithiocarbamato Mn[N-piperdtc] as (MnS_3). The corresponding passivated films were denoted as CM-1, CM-2, and CM-3. The influence of passivation on the structural, optical, morphological, and photochemical properties of the prepared devices has been investigated. Raman spectra show that the combination of this heterostructure is triggered by the variation in particle size and surface effect, thus resulting in good electronic conductivity. The narrow band gaps could be attributed to good interaction between the passivative materials on the TiO2 surface. CM-2 cells, stability studies show that the cell is polarized and current flows due to electron migration across the electrolyte and interfaces at this steady state. The cyclic voltammetry (CV) curve for the CM-3 with the highest current density promotes the electrocatalytic activity of the assembled solar cell. The catalytic reactions are further confirmed by the interfacial electron lifetimes in the Bode plots and the impedance spectra. The current-voltage (J-V) analysis suggests that the electrons in the conduction band of TiO2/CuS recombine with the semiconductor quantum dots (QDs) and the iodolyte HI-30 electrolyte, resulting in 5.20-6.85% photo-conversions.

Solid phase speciation controls copper mobilisation from marine sediments by methanobactin

Although marine environments represent huge reservoirs of the potent greenhouse gas methane, they currently contribute little to global net methane emissions. Most of the methane is oxidized by methanotrophs, minimizing escape to the atmosphere. Aerobic methanotrophs oxidize methane mostly via the copper (Cu)-bearing enzyme particulate methane monooxygenase (pMMO). Therefore, aerobic methane oxidation depends on sufficient Cu acquisition by methanotrophs. Because they require both oxygen and methane, aerobic methanotrophs reside at oxic-anoxic interfaces, often close to sulphidic zones where Cu bioavailability can be limited by poorly soluble Cu sulphide mineral phases. Under Cu-limiting conditions, certain aerobic methanotrophs exude Cu-binding ligands termed chalkophores, such as methanobactin (mb) exuded by Methylosinus trichosporium OB3b. Our main objective was to establish whether chalkophores can mobilise Cu from Cu sulphide-bearing marine sediments to enhance Cu bioavailability. Through a series of kinetic batch experiments, we investigated Cu mobilisation by mb from a set of well-characterized sulphidic marine sediments differing in sediment properties, including Cu content and phase distribution. Characterization of solid-phase Cu speciation included X-ray absorption spectroscopy and a targeted sequential extraction. Furthermore, in batch experiments, we investigated to what extent adsorption of metal-free mb and Cu-mb complexes to marine sediments constrains Cu mobilisation. Our results are the first to show that both solid phase Cu speciation and chalkophore adsorption can constrain methanotrophic Cu acquisition from marine sediments. Only for certain sediments did mb addition enhance dissolved Cu concentrations. Cu mobilisation by mb was not correlated to the total Cu content of the sediment, but was controlled by solid-phase Cu speciation. Cu was only mobilised from sediments containing a mono-Cu-sulphide (CuSx) phase. We also show that mb adsorption to sediments limits Cu acquisition by mb to less compact (surface) sediments. Therefore, in sulphidic sediments, mb-mediated Cu acquisition is presumably constrained to surface-sediment interfaces containing mono-Cu-sulphide phases.

Effect of PVP Molecular Weights on the Synthesis of Ultrasmall Cus Nanoflakes: Synthesis, Properties, and Potential Application for Phototheranostics

Copper sulfide nanoparticles (CuS) hold tremendous potential for applications in photothermal therapy (PTT) and photoacoustic imaging (PAI). However, the conventional chemical coprecipitation method often leads to particle agglomeration issues. To overcome this challenge, we utilized polyvinylpyrrolidone (PVP) as a stabilizing agent, resulting in the synthesis of small PVP-CuS nanoparticles named PC10, PCK30, and PC40. Our study aimed to investigate how different molecular weights of PVP influence the nanoparticles' crystalline characteristics and essential properties, especially their photoacoustic and photothermal responses. While prior research on PVP-assisted CuS nanoparticles has been conducted, our study delves deeper into this area, providing insights into optical properties. Remarkably, all synthesized nanoparticles exhibited a crystalline structure, were smaller than 10 nm, and featured an absorbance peak at 1020 nm, indicating their robust photoacoustic and photothermal capabilities. Among these nanoparticles, PC10 emerged as the standout performer, displaying superior photoacoustic properties. Our photothermal experiments demonstrated significant temperature increases in all cases, with PC10 achieving an impressive efficiency of 51%. Moreover, cytotoxicity assays revealed the nanoparticles' compatibility with cells, coupled with an enhanced incidence of apoptosis compared to necrosis. These findings underscore the promising potential of PVP-stabilized CuS nanoparticles for advanced cancer theranostics.

A Full-Spectrum ZnS Photocatalyst with Gradient Distribution of Atomic Copper Dopants and Concomitant Sulfur Vacancies for Highly Efficient Hydrogen Evolution

A rarely discussed phenomenon in the realm of photocatalytic materials involves the presence of gradient distributed dopants and defects from the interior to the surface. This intriguing characteristic has been successfully achieved in the case of ZnS through the incorporation of atomic monovalent copper ions (Cu+) and concurrent sulfur vacancies (Vs), resulting in a photocatalyst denoted as G-CZS1-x. Through the cooperative action of these atomic Cu dopants and Vs, G-CZS1-x significantly extends its photoabsorption range to encompass the full spectrum (200-2100 nm), which improves the solar utilization ability. This alteration enhances the efficiency of charge separation and optimizes Δ(H*) (free energy of hydrogen adsorption) to approach 0 eV for the hydrogen evolution reaction (HER). It is noteworthy that both surface-exposed atomic Cu and Vs act as active sites for photocatalysis. G-CZS1-x exhibits a significant H2 evolution rate of 1.01 mmol h-1 in the absence of a cocatalyst. This performance exceeds the majority of previously reported photocatalysts, exhibiting approximately 25-fold as ZnS, and 5-fold as H-CZS1-x with homogeneous distribution of equal content Cu dopants and Vs. In contrast to G-CZS1-x, the H adsorption on Cu sites for H-CZS1-x (ΔG(H*) = -1.22 eV) is excessively strong to inhibit the H2 release, and the charge separation efficiency for H-CZS1-x is relatively sluggish, revealing the positive role of a gradient distribution model of dopants and defects on activity enhancement. This work highlights the synergy of atomic dopants and defects in advancing photoactivity, as well as the significant benefit of the controllable distribution model of dopants and defects for photocatalysis.

Insights into the SILAR Processing of CuxZn1-xS Thin Films via a Chemical, Structural, and Optoelectronic Assessment

Careful analysis of the chemical state of CuxZn1-xS thin films remains an underdeveloped topic although it is key to a better understanding of the phase transformations and the linking between structural and optoelectronic properties needed for tuning the performance of CuxZn1-xS-based next-generation energy devices. Here, we propose a chemical formulation and formation mechanism, providing insights into the successive ionic layer adsorption and reaction (SILAR) processing of CuxZn1-xS, in which the copper concentration directly affects the behavior of the optoelectronic properties. Via chemical, optoelectronic, and structural characterization, including quantitative X-ray photoelectron spectroscopy, we determine that the CuxZn1-xS thin films at low copper concentration are composed of ZnS, metastable CuxZn1-xS, and CuS, where the evidence suggests that a depth compositional gradient exists, which contrasts with homogeneous films reported in the literature. The oxidation states for copper and sulfide species indicate that the films grow following a formation mechanism governed by ionic exchange and diffusion processes. At high copper concentrations, the CuxZn1-xS thin films are covellite CuS that grew on a ZnS seed layer. Hence, this work reiterates that future research related to fine-tuning the application of this material requires a careful analysis of the depth-profile compositional and structural characteristics that can enable high conductivity and transparency.

Electronic Properties of Transition and Alkaline Earth Metal Doped CuS: A DFT Study

CuS is a unique semiconductor with potential in optoelectronics. Its unusual electronic structure, including a partially occupied valence band, and complex crystal structure with an S-S bond offer unique opportunities and potential applications. In this work, the use of doping to optimize the properties of CuS for various applications is investigated by density functional theory (DFT) calculations. Among the dopants studied, Ni, Zn, and Mg may be the most practical due to their lower formation energies. Doping with Fe, Ni, or Ca induces significant distortion, which may be beneficial for achieving materials with high surface areas and active states. Significantly, doping alters the conductor-like behavior of CuS, opening a band gap by increasing bond ionicity and reducing the S-S bond covalency. Thus, doping CuS can tune the plasmonic properties and transform it from a conductor to an intrinsic fluorescent semiconductor. Ni and Fe doping give the lowest band gaps (0.35 eV and 0.39 eV, respectively), while Mg doping gives the highest (0.86 eV). Doping with Mg, Ca, and Zn may enhance electron mobility and charge separation. Most dopants increase the anisotropy of electron-to-hole mass ratios, enabling device design that exploits directional-dependence for improved performance.

Sulfur Vacancy-Rich CuS for Improved Surface-Enhanced Raman Spectroscopy and Full-Spectrum Photocatalysis

There are growing interests in the development of bifunctional semiconducting nanostructures for photocatalysis and real-time monitoring of degradation process on catalysts. Defect engineering is a low-cost approach to manipulating the properties of semiconductors. Herein, we prepared CuS nanoplates by a hydrothermal method at increasing amounts of thioacetamide (CS-1, CS-2, and CS-3) and investigated the influence of sulfur vacancy (V_s) on surface-enhanced Raman spectroscopy (SERS) and photocatalysis performance. SERS intensity of 4-nitrobenzenethiol on CS-3 is 346 and 17 times that of CS-1 and CS-2, respectively, and enhancement factor is 1.34 × 10⁴. Moreover, SERS is successfully applied to monitor the photodegradation of methyl orange. In addition, CS-3 also exhibited higher efficiency of Cr(VI) photoreduction than CS-1 and CS-2, and removal rate is 88%, 96%, and 73% under 2 h UV, 4 h visible, and 4 h near-infrared illumination, respectively. A systematic study including electron paramagnetic resonance spectra, photoelectrochemical measurements, and nitrogen adsorption isotherms were conducted to investigate the underlying mechanism. This work may help to understand the impact of vacancy defect on SERS and photocatalysis, and provide an effective and low-cost approach for the design of multifunctional materials.

Periplasmic Bacterial Biomineralization of Copper Sulfide Nanoparticles

Metal sulfides are a common group of extracellular bacterial biominerals. However, only a few cases of intracellular biomineralization are reported in this group, mostly limited to greigite (Fe3 S4 ) in magnetotactic bacteria. Here, a previously unknown periplasmic biomineralization of copper sulfide produced by the magnetotactic bacterium Desulfamplus magnetovallimortis strain BW-1, a species known to mineralize greigite (Fe3 S4 ) and magnetite (Fe3 O4 ) in the cytoplasm is reported. BW-1 produces hundreds of spherical nanoparticles, composed of 1-2 nm substructures of a poorly crystalline hexagonal copper sulfide structure that remains in a thermodynamically unstable state. The particles appear to be surrounded by an organic matrix as found from staining and electron microscopy inspection. Differential proteomics suggests that periplasmic proteins, such as a DegP-like protein and a heavy metal-binding protein, could be involved in this biomineralization process. The unexpected periplasmic formation of copper sulfide nanoparticles in BW-1 reveals previously unknown possibilities for intracellular biomineralization that involves intriguing biological control and holds promise for biological metal recovery in times of copper shortage.

The bond valence model as a prospective approach: examination of the crystal structures of copper chalcogenides with Cu bond valence excess

Bond valence analysis has been applied to various copper chalcogenides with copper valence excess, i.e. where the formal valence of copper exceeds 1. This approach always reveals a copper bond valence excess relative to the unit value, correlated to an equivalent ligand bond valence deficit. In stoichiometric chalcogenides, this corresponds to one ligand electron in excess per formula unit relative to the valence equilibrium considering only Cu^I. This ligand electron in excess is 50/50 shared between all or part of the Cu-atom positions, and all or part of the ligand-atom positions. In Cu₃Se₂, only one of the two Cu positions is involved in this sharing. It would indicate a special type of multicentre bonding (`one-electron co-operative bonding'). Calculated and ideal structural formulae according to this bond valence distribution are presented. At the crystal structure scale, Cu-ligand bonds implying the single electron in excess form one-, two- or three-dimensional subnetworks. Bond valence distribution according to two two-dimensional subnets is detailed in covellite, CuS. This bond valence description is a formal crystal-chemical representation of the metallic conductivity of holes (mixing between Cu 3d bands and ligand p bands), according to published electronic band structures. Bond valence analysis is a useful and very simple prospective approach in the search for new compounds with targeted specific physical properties.

Djurleite Copper Sulfide-Coupled Cobalt Sulfide Interface for a Stable and Efficient Electrocatalyst

Transition metal sulfides (TMS) exhibit proliferated edge sites, facile electrode kinetics, and improved intrinsic electrical conductivity, which demand low potential requirements for total water splitting application. Here, we have propounded copper sulfide-coupled cobalt sulfide nanosheets grown on 3D nickel as an electrocatalyst for hydrogen (HER) and oxygen evolution (OER) reactions. The formation of djurleite copper sulfide with a Cu vacancy enables faster H⁺ ion transport and shows improved HER activity with a remarkably lower overpotential of 164 mV at 10 mA/cm², whereas cobalt-incorporated copper sulfide undergoes cation exchange during synthesis and shows elevated OER activity with a lower overpotential of 240 mV at 10 mA/cm² for the OER. Moreover, Cu_2-xS/Co is said to have a hybrid CoS-CoS₂ interface and provide Co²⁺ active sites on the surface and enable the fast adsorption of intermediate species (OH*, O*, and OOH*), which lowers the potential requirement. The copper vacancy and cation exchange with a hybrid CoS-CoS₂ structure are helpful in supplying more surface reactive species and faster ion transport for the HER and OER, respectively. The full-cell electrolyzer requires a very low potential of 1.58 V to attain a current density of 10 mA/cm², and it shows excellent stability for 50 h at 100 mA/cm² as confirmed by the chronopotentiometry test.

CuS Nanoparticles Trigger Sulfite for Fast Degradation of Organic Dyes under Dark Conditions

CuS nanoparticles (CuS NPs) were synthesized by a simple precipitation method using rice starch water as a capping and reducing agent. The phase composition, morphology, absorbance, chemical bonds, and chemical states of the CuS NPs were investigated systematically and then examined for dye degradation catalytic activity with or without sulfite (SO3 2-) under dark conditions. Herein, we observed two reaction trends after the addition of SO3 2- in a CuS NPs/dye system, first substantially enhanced dye degradation and second greater degradation activity between reaction time interval "t" 0-12 min. The redox cycling of Cu(II)/Cu(I) and oxidized sulfur (SO x 2-) species on the surface of CuS NPs played a major role for the activation of SO3 2- and generation and transformation of a sulfite radical (•SO3 -) into a sulfate radical (•SO4 -). Scavenging studies of reactive oxygen species (ROS) revealed that •SO4 - was major reactive species involved in dye degradation. Our study showed that SO3 2- acted as a source and CuS NP surface acted as an SO3 2- activating agent for the generation of •SO4 -, which degrades the dyes. The activation pathway of SO3 2- and generation pathway of relevant ROS were proposed.

Synthetically Produced Isocubanite as an Anode Material for Sodium-Ion Batteries: Understanding the Reaction Mechanism During Sodium Uptake and Release

Bulk isocubanite (CuFe₂S₃) was synthesized via a multistep high-temperature synthesis and was investigated as an anode material for sodium-ion batteries. CuFe₂S₃ exhibits an excellent electrochemical performance with a capacity retention of 422 mA h g^-1 for more than 1000 cycles at a current rate of 0.5 A g^-1 (0.85 C). The complex reaction mechanism of the first cycle was investigated via PXRD and X-ray absorption spectroscopy. At the early stages of Na uptake, CuFe₂S₃ is converted to form crystalline CuFeS₂ and nanocrystalline NaFe_1.5S₂ simultaneously. By increasing the Na content, Cu⁺ is reduced to nanocrystalline Cu, followed by the reduction of Fe²⁺ to amorphous Fe⁰ while reflections of nanocrystalline Na₂S appear. During charging up to -5 Na/f.u., the intermediate NaFe_1.5S₂ appears again, which transforms in the last step of charging to a new unknown phase. This unknown phase together with NaFe_1.5S₂ plays a key role in the mechanism for the following cycles, evidenced by the PXRD investigation of the second cycle. Even after 400 cycles, the occurrence of nanocrystalline phases made it possible to gain insights into the alteration of the mechanism, which shows that Cu_xS phases play an important role in the region of constant specific capacity.

Study of the Lithium Storage Mechanism of N-Doped Carbon-Modified Cu2 S Electrodes for Lithium-Ion Batteries

Owing to their high specific capacity and abundant reserve, Cu_xS compounds are promising electrode materials for lithium‐ion batteries (LIBs). Carbon compositing could stabilize the Cu_xS structure and repress capacity fading during the electrochemical cycling, but the corresponding Li⁺ storage mechanism and stabilization effect should be further clarified. In this study, nanoscale Cu₂S was synthesized by CuS co‐precipitation and thermal reduction with polyelectrolytes. High‐temperature synchrotron radiation diffraction was used to monitor the thermal reduction process. During the first cycle, the conversion mechanism upon lithium storage in the Cu₂S/carbon was elucidated by operando synchrotron radiation diffraction and in situ X‐ray absorption spectroscopy. The N‐doped carbon‐composited Cu₂S (Cu₂S/C) exhibits an initial discharge capacity of 425 mAh g⁻¹ at 0.1 A g⁻¹, with a higher, long‐term capacity of 523 mAh g⁻¹ at 0.1 A g⁻¹ after 200 cycles; in contrast, the bare CuS electrode exhibits 123 mAh g⁻¹ after 200 cycles. Multiple‐scan cyclic voltammetry proves that extra Li⁺ storage can mainly be ascribed to the contribution of the capacitive storage.

Insights into Nucleation and Growth of Colloidal Quaternary Nanocrystals by Multimodal X-ray Analysis

Copper chalcogenide nanocrystals find applications in photovoltaic inks, bio labels, and thermoelectric materials. We reveal insights in the nucleation and growth during synthesis of anisotropic Cu2ZnSnS4 nanocrystals by simultaneously performing in situ X-ray absorption spectroscopy (XAS) and small-angle X-ray scattering (SAXS). Real-time XAFS reveals that upon thiol injection into the reaction flask, a key copper thiolate intermediate species is formed within fractions of seconds, which decomposes further within a narrow temperature and time window to form copper sulfide nanocrystals. These nanocrystals convert into Cu2ZnSnS4 nanorods by sequentially incorporating Sn and Zn. Real-time SAXS and ex situ TEM of aliquots corroborate these findings. Our work demonstrates how combined in situ X-ray absorption and small-angle X-ray scattering enables the understanding of mechanistic pathways in colloidal nanocrystal formation.

Kβ X-ray Emission Spectroscopy as a Probe of Cu(I) Sites: Application to the Cu(I) Site in Preprocessed Galactose Oxidase

Cu(I) active sites in metalloproteins are involved in O₂ activation, but their O₂ reactivity is difficult to study due to the Cu(I) d¹⁰ closed shell which precludes the use of conventional spectroscopic methods. Kβ X-ray emission spectroscopy (XES) is a promising technique for investigating Cu(I) sites as it detects photons emitted by electronic transitions from occupied orbitals. Here, we demonstrate the utility of Kβ XES in probing Cu(I) sites in model complexes and a metalloprotein. Using Cu(I)Cl, emission features from double-ionization (DI) states are identified using varying incident X-ray photon energies, and a reasonable method to correct the data to remove DI contributions is presented. Kβ XES spectra of Cu(I) model complexes, having biologically relevant N/S ligands and different coordination numbers, are compared and analyzed, with the aid of density functional theory (DFT) calculations, to evaluate the sensitivity of the spectral features to the ligand environment. While the low-energy Kβ_2,5 emission feature reflects the ionization energy of ligand np valence orbitals, the high-energy Kβ_2,5 emission feature corresponds to transitions from molecular orbitals (MOs) having mainly Cu 3d character with the intensities determined by ligand-mediated d-p mixing. A Kβ XES spectrum of the Cu(I) site in preprocessed galactose oxidase (GO_pre) supports the 1Tyr/2His structural model that was determined by our previous X-ray absorption spectroscopy and DFT study. The high-energy Kβ_2,5 emission feature in the Cu(I)-GO_pre data has information about the MO containing mostly Cu 3d_x²-y² character that is the frontier molecular orbital (FMO) for O₂ activation, which shows the potential of Kβ XES in probing the Cu(I) FMO associated with small-molecule activation in metalloproteins.

Insights into Copper Sulfide Formation from Cu and S K edge XAS and DFT studies

An understanding of the fundamentals of the reaction between CuO with trace amounts of H₂S to form CuS products is critical for the optimal utilization of this process in sulfur removal applications. Unfortunately, CuS is a complex material, featuring various Cu_2-xS compounds (with 0 ≤ x ≤ 1), distorted crystal phases, and varying electronic structures and coordination environments of Cu and S ions. In this work, we combine ex situ and in situ X-ray absorption spectroscopy (XAS) at S and Cu K edges, fixed bed sorption experiments, DFT simulations, and other characterization techniques to speciate the CuS products formed at different temperatures (298-383 K) and from CuO sorbents with different crystallite sizes (2.8-40 nm). The results of our analysis identify the formation of a distorted CuS layer at the surface of CuO crystals with disulfide groups with shorter Cu-S bonds and higher delocalization of the positive charge of the Cu center into (S^1-)₂. This distorted CuS layer dominates the XAS signal at lower temperatures (298-323 K) and at the initial stages of sulfidation at higher temperatures (353 and 383 K) where conversion is low (<40%). First-principles atomistic simulations confirm the thermodynamic favorability of the formation of surface (S^1-)₂ on both CuO (111) and (1̅11) surfaces, providing further support for our experimental observations. Furthermore, these simulations reveal that the presence of disulfide bonds stabilized surface hydroxyl groups, leading to lower Gibbs Free Energies of their surface migration.

CuS nanoparticles in humid environments: adsorbed water enhances the transformation of CuS to CuSO4

Covellite copper sulfide nanoparticles (CuS NPs) have attracted immense research interest due to their widespread use in a range of biological and energy applications. As such, it is crucial to understand the transformations of these nanomaterials and how these transformations influence the behavior of these nanoparticles in environmental and biological systems. This study specifically focuses on understanding the role of water vapor and adsorbed water in the transformation of CuS NP surfaces to CuSO4 in humid environments. Surface sulfide ions are oxidized to sulfate by oxygen in the presence of water vapor, as detected by atomic force microscopy based photothermal infrared spectroscopy (AFM-PTIR) and in situ attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy. These results show that the transformation of CuS to CuSO4 is highly dependent on relative humidity (RH). While sulfide to sulfate conversion is not observed to a great extent at low RH (<20%), there is significant conversion at higher RH (>80%). X-ray photoelectron spectroscopy (XPS) analysis confirms that sulfide is irreversibly oxidized to sulfate. Furthermore, it shows that initially, the Cu ions possess the original oxidation state similar to the original covellite, i.e. Cu+, but they are oxidized to Cu2+ at higher RH. The formation of CuSO4 has also been confirmed by HRTEM. These analyses show that adsorbed water on the NP surfaces enhances the conversion of sulfide to sulfate and the oxidation of Cu+ to Cu2+ in the presence of molecular oxygen.

Biomineralization of Cu2S Nanoparticles by Geobacter sulfurreducens

Dissimilatory metal-reducing bacteria are ubiquitous in soils and aquifers and are known to utilize a wide range of metals as terminal electron acceptors. These transformations play an important role in the biogeochemical cycling of metals in pristine and contaminated environments and can be harnessed for bioremediation and metal bioprocessing purposes. However, relatively little is known about their interactions with Cu. As a trace element that becomes toxic in excess, Cu can adversely affect soil biota and fertility. In addition, biomineralization of Cu nanoparticles has been reported to enhance the mobilization of other toxic metals. Here, we demonstrate that when supplied with acetate under anoxic conditions, the model metal-reducing bacterium Geobacter sulfurreducens can transform soluble Cu(II) to Cu₂S nanoparticles. This study provides new insights into Cu biomineralization by microorganisms and suggests that contaminant mobilization enhanced by Cu biomineralization could be facilitated by Geobacter species and related organisms.

Biomineralization of Cu has been shown to control contaminant dynamics and transport in soils. However, very little is known about the role that subsurface microorganisms may play in the biogeochemical cycling of Cu. In this study, we investigate the bioreduction of Cu(II) by the subsurface metal-reducing bacterium Geobacter sulfurreducens. Rapid removal of Cu from solution was observed in cell suspensions of G. sulfurreducens when Cu(II) was supplied, while transmission electron microscopy (TEM) analyses showed the formation of electron-dense nanoparticles associated with the cell surface. Energy-dispersive X-ray spectroscopy (EDX) point analysis and EDX spectrum image maps revealed that the nanoparticles are rich in both Cu and S. This finding was confirmed by X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) analyses, which identified the nanoparticles as Cu₂S. Biomineralization of Cu_xS nanoparticles in soils has been reported to enhance the colloidal transport of a number of contaminants, including Pb, Cd, and Hg. However, formation of these Cu_xS nanoparticles has only been observed under sulfate-reducing conditions and could not be repeated using isolates of implicated organisms. As G. sulfurreducens is unable to respire sulfate, and no reducible sulfur was supplied to the cells, these data suggest a novel mechanism for the biomineralization of Cu₂S under anoxic conditions. The implications of these findings for the biogeochemical cycling of Cu and other metals as well as the green production of Cu catalysts are discussed.

IMPORTANCE Dissimilatory metal-reducing bacteria are ubiquitous in soils and aquifers and are known to utilize a wide range of metals as terminal electron acceptors. These transformations play an important role in the biogeochemical cycling of metals in pristine and contaminated environments and can be harnessed for bioremediation and metal bioprocessing purposes. However, relatively little is known about their interactions with Cu. As a trace element that becomes toxic in excess, Cu can adversely affect soil biota and fertility. In addition, biomineralization of Cu nanoparticles has been reported to enhance the mobilization of other toxic metals. Here, we demonstrate that when supplied with acetate under anoxic conditions, the model metal-reducing bacterium Geobacter sulfurreducens can transform soluble Cu(II) to Cu₂S nanoparticles. This study provides new insights into Cu biomineralization by microorganisms and suggests that contaminant mobilization enhanced by Cu biomineralization could be facilitated by Geobacter species and related organisms.

First-principles study of electronic structure and fermiology of covellite mineral and its B1, B3 phases

We present the first-principles calculations under the framework of density functional theory to explore the Fermi surface and electronic properties of covellite mineral. The correlation effects are considered applying the +U correction in the density functional theory. Lattice parameters are determined and the possibility of pressure induced phase transitions to the hypothetical B1 and B3 crystals is examined. All calculations show impending B18 → B1 and B3 → B1 phase transitions. Using generalized gradient approximation these are found to occur at 7.4 and 6.48 GPa, respectively. Electronic bands structures of the three crystals highlight metallic properties. Two copper atoms situated at distinct locations in covellite exhibit a distinct role. The Fermi surfaces of all phases are presented. The calculations of B18 map out corrugated cylindrical Fermi surface signifying inter-layer interaction mediated by the S(II)-S(II) bond. The +U correction shows anisotropy in the Fermi surface noted in experiment. It also indicates stronger inter-layer interaction. Applying Debye-Slater and the Debye-Grüneisen models the thermal expansion coefficient, heat capacity and entropy are found and their temperature dependence is discussed.

Taking a snapshot of the triplet excited state of an OLED organometallic luminophore using X-rays

OLED technology beyond small or expensive devices requires light-emitters, luminophores, based on earth-abundant elements. Understanding and experimental verification of charge transfer in luminophores are needed for this development. An organometallic multicore Cu complex comprising Cu–C and Cu–P bonds represents an underexplored type of luminophore. To investigate the charge transfer and structural rearrangements in this material, we apply complementary pump-probe X-ray techniques: absorption, emission, and scattering including pump-probe measurements at the X-ray free-electron laser SwissFEL. We find that the excitation leads to charge movement from C- and P- coordinated Cu sites and from the phosphorus atoms to phenyl rings; the Cu core slightly rearranges with 0.05 Å increase of the shortest Cu–Cu distance. The use of a Cu cluster bonded to the ligands through C and P atoms is an efficient way to keep structural rigidity of luminophores. Obtained data can be used to verify computational methods for the development of luminophores.

OLED materials based on thermally activated delayed fluorescence have promising efficiency. Here, the authors investigate an organometallic multicore Cu complex as luminophore, by pump-probe X-ray techniques at three different facilities deriving a complete picture of the charge transfer in the triplet excited state.

An Innovative Lithium Ion Battery System Based on a Cu2S Anode Material

Cu₂S is considered as one of the potential anode paradigms for advanced rechargeable batteries because of its high theoretical capacity (∼335 mAh·g^-1), high and flat charge/discharge voltage plateaus (∼1.7 V vs Li⁺/Li), stable cycling performance, and its elemental abundance. However, many studies have shown that Cu₂S exhibits a dramatic capacity fade in carbonate-based electrolytes, which has precluded its commercialization when paired with high voltage cathodes in state-of-the-art lithium ion batteries. Here, we report on a fundamental mechanistic study of the electrochemical processes of Cu₂S in both ether- and carbonate-based electrolytes employing operando synchrotron X-ray methods. Based on our findings, we developed a Cu₂S/C composite material that suppresses its failure mechanism in carbonate-based electrolytes and further demonstrated its feasibility in lithium ion full cells for the first time. Our experiment provides the basis for the utilization of Cu₂S in industrial-scale applications for large-scale electrical energy storage.

A Possible Prebiotic Ancestry of Porphyrin-Type Protein Cofactors

In previous experiments that simulated conditions on primordial volcanic islands, we demonstrated the abiotic formation of hydrophobic porphyrins. The present study focused on the question whether such porphyrins can be metalated by prebiotically plausible metal ion sources. We used water-insoluble octaethylporphyrin (H2oep) as a model compound. Experiments were conducted in a nitrogen atmosphere under cyclic wet-dry conditions in order to simulate the fluctuating environment in prebiotic rock pools. Wetting-drying proved to be a crucial factor. Significant yields of the metalloporphyrins (20-78% with respect to H2oep) were obtained from the soluble salts MCl2 (M = Mg, Fe, Co, Ni and Cu) in freshwater. Even almost insoluble minerals and rocks metalated the porphyrin. Basalt (an iron source, 11% yield), synthetic jaipurite (CoS, 33%) and synthetic covellite (CuS, 57%) were most efficient. Basalt, magnetite and FeCl2 gave considerably higher yields in artificial seawater than in freshwater. From iron sources, the highest yields, however, were obtained in an acidic medium (hydrochloric acid with an initial pH of 2.1). Under these conditions, iron meteorites also metalated the porphyrin. Acidic conditions were considered because they are known to occur during eruptions on volcanic islands. Octaethylporphyrinatomagnesium(II) did not form in acidic medium and was unstable towards dissolved Fe2+. It is therefore questionable whether magnesium porphyrins, i.e. possible ancestors of chlorophyll, could have accumulated in primordial rock pools. However, abiotically formed ancestors of the modern cofactors heme (Fe), B12 (Co), and F430 (Ni) may have been available to hypothetical protometabolisms and early organisms.

Copper sulfide nanosheets with shape-tunable plasmonic properties in the NIR region

2D copper sulfide nanocrystals are promising building blocks of plasmonic materials in the near-infrared (NIR) spectral region. We demonstrate precise shape and size control (hexagonal/triangle) of colloidal plasmonic copper sulfide (covellite) nano-prisms simply by tuning the precursor concentration without the introduction of additional ligands. The ultra-thin 2D nanocrystals possess sizes between 13 and 100 nm and triangular or hexangular shapes. We also demonstrate CuS nanosheets (NSs) with lateral sizes up to 2 microns using a syringe pump. Based on the experimental findings and DFT simulations, we propose a qualitative and quantitative mechanism for the formation of different shapes. The analysis of the spectral features in the NIR region of the synthesized CuS nanocrystals has been performed with respect to the shape and the size of particles by the discrete dipole approximation method and the Drude-Sommerfeld theory.

Raman characterization of Cu2ZnSnS4 nanocrystals: phonon confinement effect and formation of Cu x S phases

A Raman spectroscopic study of Cu2ZnSnS4 (CZTS) nanocrystals (NCs) produced by a "green" synthesis in aqueous solutions is reported. Size-selected CZTS NCs reveal phonon confinement that manifests itself in an upward shift of the main phonon peak by about 3-4 cm-1 by varying the NC diameter from 3 to 2 nm. A non-monotonous shift and narrowing of the main peak are attributed to the special shape of the phonon dispersion in this material. Moreover, the method of sample preparation, the nature of the supporting substrate and the photoexcitation regime are found to crucially influence the Raman spectra of the CZTS samples. Particularly, the possible oxidation and hydrolysis of CZTS NCs with the concomitant formation of a Cu-S phase are systematically investigated. The nature of the film support is found to strongly affect the amount of admixture copper sulfide phases with the Cu2-x S/CuS content being the highest for oxidized silicon and glass and notably lower for ITO and even less for gold supports. The effect is assumed to originate from the different hydrophilicity of the supporting surfaces, resulting in a different morphology and surface area of the NC film exposed to the atmosphere, as well as the degree of the NC oxidation/hydrolysis. The amount of copper sulfide increases with the laser power. This effect is interpreted as a result of photochemical/photocatalytic transformations of the CZTS NCs.

Stability enhancement of Cu2S against Cu vacancy formation by Ag alloying

As a potential solar absorber material, Cu₂S has proved its importance in the field of renewable energy. However, almost all the known minerals of Cu₂S suffer from spontaneous Cu vacancy formation in the structure. The Cu vacancy formation causes the structure to possess very high p-type doping that leads the material to behave as a degenerate semiconductor. This vacancy formation tendency is a major obstacle for this material in this regard. A relatively new predicted phase of Cu₂S which has an acanthite-like structure was found to be preferable than the well-known low chalcocite Cu₂S. However, the Cu-vacancy formation tendency in this phase remained similar. We have found that alloying silver with this structure can help to reduce Cu vacancy formation tendency without altering its electronic property. The band gap of silver alloyed structure is higher than pristine acanthite Cu₂S. In addition, Cu diffusion in the structure can be reduced with Ag doped in Cu sites. In this study, a systematic approach is presented within the density functional theory framework to study Cu vacancy formation tendency and diffusion in silver alloyed acanthite Cu₂S, and proposed a possible route to stabilize Cu₂S against Cu vacancy formations by alloying it with Ag.

Localized Surface Plasmon Resonance in Semiconductor Nanocrystals

Localized surface plasmon resonance (LSPR) in semiconductor nanocrystals (NCs) that results in resonant absorption, scattering, and near field enhancement around the NC can be tuned across a wide optical spectral range from visible to far-infrared by synthetically varying doping level, and post synthetically via chemical oxidation and reduction, photochemical control, and electrochemical control. In this review, we will discuss the fundamental electromagnetic dynamics governing light matter interaction in plasmonic semiconductor NCs and the realization of various distinctive physical properties made possible by the advancement of colloidal synthesis routes to such NCs. Here, we will illustrate how free carrier dielectric properties are induced in various semiconductor materials including metal oxides, metal chalcogenides, metal nitrides, silicon, and other materials. We will highlight the applicability and limitations of the Drude model as applied to semiconductors considering the complex band structures and crystal structures that predominate and quantum effects that emerge at nonclassical sizes. We will also emphasize the impact of dopant hybridization with bands of the host lattice as well as the interplay of shape and crystal structure in determining the LSPR characteristics of semiconductor NCs. To illustrate the discussion regarding both physical and synthetic aspects of LSPR-active NCs, we will focus on metal oxides with substantial consideration also of copper chalcogenide NCs, with select examples drawn from the literature on other doped semiconductor materials. Furthermore, we will discuss the promise that LSPR in doped semiconductor NCs holds for a wide range of applications such as infrared spectroscopy, energy-saving technologies like smart windows and waste heat management, biomedical applications including therapy and imaging, and optical applications like two photon upconversion, enhanced luminesence, and infrared metasurfaces.

Active Manipulation of NIR Plasmonics: the Case of Cu2-xSe through Electrochemistry

Active control of nanocrystal optical and electrical properties is crucial for many of their applications. By electrochemical (de)lithiation of Cu_2-xSe, a highly doped semiconductor, dynamic and reversible manipulation of its NIR plasmonics has been achieved. Spectroelectrochemistry results show that NIR plasmon red-shifted and reduced in intensity during lithiation, which can be reversed with perfect on-off switching over 100 cycles. Electrochemical impedance spectroscopy reveals that a Faradaic redox process during Cu_2-xSe (de)lithiation is responsible for the optical modulation, rather than simple capacitive charging. XPS analysis identifies a reversible change in the redox state of selenide anion but not copper cation, consistent with DFT calculations. Our findings open up new possibilities for dynamical manipulation of vacancy-induced surface plasmon resonances and have important implications for their use in NIR optical switching and functional circuits.

Facile fabrication of CuS microflower as a highly durable sodium-ion battery anode

CuS micro-flower was synthesized by dealloying and adopted as an anode in SIB with high rate and stable cycle performances.

Thermoelectric properties of Ag-doped CuS nanocomposites synthesized by a facile polyol method

Single crystalline hexagonal nanodisks (NDs) of covellite CuS and temperature dependent thermoelectric figure of merit of Ag-doped CuS nanocomposites.

Operando Multi-modal Synchrotron Investigation for Structural and Chemical Evolution of Cupric Sulfide (CuS) Additive in Li-S battery

Conductive metal sulfides are promising multi-functional additives for future lithium-sulfur (Li-S) batteries. These can increase the sulfur cathode's electrical conductivity to improve the battery's power capability, as well as contribute to the overall cell-discharge capacity. This multi-functional electrode design showed initial promise; however, complicated interactions at the system level are accompanied by some detrimental side effects. The metal sulfide additives with a chemical conversion as the reaction mechanism, e.g., CuS and FeS₂, can increase the theoretical capacity of the Li-S system. However, these additives may cause undesired parasitic reactions, such as the dissolution of the additive in the electrolyte. Studying such complex reactions presents a challenge because it requires experimental methods that can track the chemical and structural evolution of the system during an electrochemical process. To address the fundamental mechanisms in these systems, we employed an operando multimodal x-ray characterization approach to study the structural and chemical evolution of the metal sulfide-utilizing powder diffraction and fluorescence imaging to resolve the former and absorption spectroscopy the latter-during lithiation and de-lithiation of a Li-S battery with CuS as the multi-functional cathode additive. The resulting elucidation of the structural and chemical evolution of the system leads to a new description of the reaction mechanism.

High-index faceted CuFeS2 nanosheets with enhanced behavior for boosting hydrogen evolution reaction

A rational design of highly active and robust catalysts based on earth-abundant elements for hydrogen evolution reaction (HER) is essential for future renewable energy applications. Herein, we report the synthesis of a new class of ultrathin metallic CuFeS₂ nanosheets (NSs) with abundant exposed high-index {02[combining macron]4} facets. They serve as a robust catalyst for the HER with a lower onset potential of 28.1 mV, an overpotential of only 88.7 mV (at j = 10 mA cm^-2) and remarkable long-term stability in 0.5 M H₂SO₄, which make them the best system among all the reported non-noble metal catalysts. The theoretical calculations reveal that the mechanistic origin for such a high HER activity should be attributed to the excess S^2- active sites on the exposed {02[combining macron]4} high-index facets of CuFeS₂ NSs, which have a rather favorable Gibbs free energy for atomic hydrogen adsorption. The present work highlights the importance of designing ultrathin metallic chalcopyrite nanosheets with high-index facets in order to increase the number of active sites for boosting the HER performance.

Compound Copper Chalcogenide Nanocrystals

This review captures the synthesis, assembly, properties, and applications of copper chalcogenide NCs, which have achieved significant research interest in the last decade due to their compositional and structural versatility. The outstanding functional properties of these materials stems from the relationship between their band structure and defect concentration, including charge carrier concentration and electronic conductivity character, which consequently affects their optoelectronic, optical, and plasmonic properties. This, combined with several metastable crystal phases and stoichiometries and the low energy of formation of defects, makes the reproducible synthesis of these materials, with tunable parameters, remarkable. Further to this, the review captures the progress of the hierarchical assembly of these NCs, which bridges the link between their discrete and collective properties. Their ubiquitous application set has cross-cut energy conversion (photovoltaics, photocatalysis, thermoelectrics), energy storage (lithium-ion batteries, hydrogen generation), emissive materials (plasmonics, LEDs, biolabelling), sensors (electrochemical, biochemical), biomedical devices (magnetic resonance imaging, X-ray computer tomography), and medical therapies (photochemothermal therapies, immunotherapy, radiotherapy, and drug delivery). The confluence of advances in the synthesis, assembly, and application of these NCs in the past decade has the potential to significantly impact society, both economically and environmentally.

Synergistic activating effect of promoter and oxidant in single step conversion of methane into methanol over a tailored polymer-Ag coordination complex

Single-step conversion of methane to its oxygenated derivatives, such as methanol, is a challenging topic in C1 chemistry.

Tuning plasmonic properties of CuS thin films via valence band filling

Tuning plasmonic properties of CuS thin films via electrochemical reduction by decreasing hole concentration in the valence band.

XDS: a flexible beamline for X-ray diffraction and spectroscopy at the Brazilian synchrotron

The majority of the beamlines at the Brazilian Synchrotron Light Source Laboratory (LNLS) use radiation produced in the storage-ring bending magnets and are therefore currently limited in the flux that can be used in the harder part of the X-ray spectrum (above ∼10 keV). A 4 T superconducting multipolar wiggler (SCW) was recently installed at LNLS in order to improve the photon flux above 10 keV and fulfill the demands set by the materials science community. A new multi-purpose beamline was then installed at the LNLS using the SCW as a photon source. The XDS is a flexible beamline operating in the energy range between 5 and 30 keV, designed to perform experiments using absorption, diffraction and scattering techniques. Most of the work performed at the XDS beamline concentrates on X-ray absorption spectroscopy at energies above 18 keV and high-resolution diffraction experiments. More recently, new setups and photon-hungry experiments such as total X-ray scattering, X-ray diffraction under high pressures, resonant X-ray emission spectroscopy, among others, have started to become routine at XDS. Here, the XDS beamline characteristics, performance and a few new experimental possibilities are described.

Synergetic inhibition of thermochemical formation of chlorinated aromatics by sulfur and nitrogen derived from thiourea: Multielement characterizations

Nitrogen and sulfur (N/S)-containing compounds inhibit the formation of polychlorinated dibenzo-p-dioxins (PCDDs) and furans (PCDFs) in thermal processes. However, few studies have examined the inhibition mechanisms of N/S-containing compounds. In the present study, we focused on thiourea [(NH2)2CS] as such a compound and investigated its inhibition effects and mechanisms. The production of PCDD/Fs, polychlorinated biphenyls (PCBs), and chlorobenzenes (CBzs) were inhibited by >99% in the model fly ash in the presence of 1.0% thiourea after heating at 300 °C. Experimental results using real fly ash series were indicative of the thermal destruction of these chlorinated aromatics by thiourea. Multielement characterization using K-edge X-ray absorption fine structures of copper, chlorine, sulfur, nitrogen, and carbon revealed three possible inhibition paths, namely, (a) sulfidization of the copper catalyst to CuS, Cu2S, and CuSO4; (b) blocking the chlorination of carbon via the reaction of chlorine with N-containing compounds to generate ammonium chloride and other minor compounds; and (c) changing the carbon frame involved in attacking the carbon matrix by sulfur and nitrogen. Thus, thiourea plays a role as a sulfur and nitrogen donor to achieve multiple and synergistic inhibition of chlorinated aromatics. Our results suggest that other N/S-containing inhibitors function based on similar mechanisms.

Preparation and characterization of colloidal copper xanthate nanoparticles

Colloids formed by the direct interaction of aqueous Cu²⁺ ions and xanthates were characterized along with their precipitates incorporating dixanthogen.

Nanoporous CuS with excellent photocatalytic property

We present the rational synthesis of nanoporous CuS for the first time by chemical dealloying method. The morphologies of the CuS catalysts are controlled by the composition of the original amorphous alloys. Nanoporous Cu₂S is firstly formed during the chemical dealloying process, and then the Cu₂S transforms into CuS. The nanoporous CuS exhibits excellent photocatalytic activity for the degradation of the methylene blue (MB), methyl orange (MO) and rhodamine B (RhB). The excellent photocatalytic activity of the nanoporous CuS is mainly attributed to the large specific surface area, high adsorbing capacity of dyes and low recombination of the photo generated electrons and holes. In the photo degradation process, both chemical and photo generated hydroxyl radicals are generated. The hydroxyl radicals are favor in the oxidation of the dye molecules. The present modified dealloying method may be extended for the preparation of other porous metal sulfide nanostructures.

Ultrafast Hole Trapping and Relaxation Dynamics in p-Type CuS Nanodisks

CuS nanocrystals are potential materials for developing low-cost solar energy conversion devices. Understanding the underlying dynamics of photoinduced carriers in CuS nanocrystals is essential to improve their performance in these devices. In this work, we investigated the photoinduced hole dynamics in CuS nanodisks (NDs) using the combination of transient optical (OTA) and X-ray (XTA) absorption spectroscopy. OTA results show that the broad transient absorption in the visible region is attributed to the photoinduced hot and trapped holes. The hole trapping process occurs on a subpicosecond time scale, followed by carrier recombination (~100 ps). The nature of the hole trapping sites, revealed by XTA, is characteristic of S or organic ligands on the surface of CuS NDs. These results not only suggest the possibility to control the hole dynamics by tuning the surface chemistry of CuS but also represent the first time observation of hole dynamics in semiconductor nanocrystals using XTA.

Heterovalent-Doping-Enabled Efficient Dopant Luminescence and Controllable Electronic Impurity Via a New Strategy of Preparing II-VI Nanocrystals

Substitutional heterovalent doping represents an effective method to control the optical and electronic properties of nanocrystals (NCs). Highly monodisperse II-VI NCs with deep substitutional dopants are presented. The NCs exhibit stable, dominant, and strong dopant fluorescence, and control over n- and p-type electronic impurities is achieved. Large-scale, bottom-up superlattices of the NCs will speed up their application in electronic devices.