Synthesis of Ligand free CdS Nanoparticles within a Sulfur Copolymer Matrix

Aliphatic ligands are typically used during the synthesis of nanoparticles to help mediate their growth in addition to operating as high temperature solvents. These coordinating ligands help solubilize and stabilize the nanoparticles while in solution, and can influence the resulting size and reactivity of the nanoparticles during their formation. Despite the ubiquity of using ligands during synthesis, the presence of aliphatic ligands on the nanoparticle surface can result in a number of problems during the end use of the nanoparticles, necessitating further ligand stripping or ligand exchange procedures. We have developed a way to synthesize cadmium sulfide CdS nanoparticles using a unique sulfur copolymer. This sulfur copolymer is primarily composed of elemental sulfur, which is a cheap and abundant material. The sulfur copolymer has the advantages of operating both as a high temperature solvent and as a sulfur source, which can react with a cadmium precursor during nanoparticle synthesis, resulting in the generation of ligand free CdS. During the reaction, only some of the copolymer is consumed to produce CdS, while the rest remains in the polymeric state, thereby producing a nanocomposite material. Once the reaction is finished, the copolymer stabilizes the nanoparticles within a solid polymeric matrix. The copolymer can then be removed before the nanoparticles are used, which produces nanoparticles that do not have organic coordinating ligands. This nascent synthesis technique presents a method to produce metal sulfide nanoparticles for a wide variety of applications where the presence of organic ligands is not desired

Inorganic organic interfaces in hybrid solar cells

In this review, we present important concepts to describe inorganic organic interfaces in hybrid solar cells. We discuss the formation of hybrid interfaces, provide an introduction to the ground state electronic structure of the individual components, and detail the overall electronic landscape after combining into a hybrid material for different relevant cases. We then explore the impact of hybrid interfaces on photophysical processes that are crucial for the photovoltaic performance of hybrid solar cells. Within this framework, we discuss methods for hybrid interface modification toward the optimization of hybrid solar cells, such as doping, the application of interlayers, and morphological contro

Co Intercalation Batteries CoIBs Role of TiS2 as Electrode for Storing Solvated Na Ions

The co intercalation of solvent molecules along with Na into the crystal lattice of electrode materials is an undesired process in sodium batteries. An exception is the intercalation of ether solvated alkali ions into graphite, a fast and highly reversible process. Here, reversible co intercalation is shown to also be possible for other layered materials, namely titanium disulfide. Operando X ray diffraction and dilatometry are used to demonstrate different storage mechanisms for different electrolyte solvents. Diglyme is found to co intercalate into the TiS2 leading to a change in the voltage profile and an increase in the interlayer spacing amp; 8776;150 . This behavior is different compared to other solvents, which expand much less during Na storage 24 for tetrahydrofuran [THF] and for a carbonate mixture . For all solvents, specific capacities 2nd cycle exceed 250 mAh g amp; 8722;1 whereas THF exhibited the best stability after 100 cycles. The solvent co intercalation is rationalized by density functional theory and linked to the stability of the solvation shells, which is largest for diglyme. Finally, the TiS2 electrode with diglyme electrolyte is paired with a graphite electrode to realize the first proof of concept solvent co intercalation battery, that is, a battery with two electrodes that both rely on reversible co intercalation of solvent molecule

Spatially resolved X ray absorption spectroscopy investigation of individual cation intercalated multi layered Ti3C2Tx MXene particles

Ti3C2Tx MXene is a two dimensional 2D material possessing highly active hydrophilic surfaces coupled with high metallic conductivity. Cations intercalation between the Ti3C2Tx nanosheets has a significant role in many applications such as water purification, desalination, and electrochemical energy storage. The pseudocapacitive charging mechanism involving surface redox reactions at the Ti3C2Tx surface enables higher energy densities than electrical double layer capacitors, and higher power densities than batteries. In this context, the oxidation state of surface Ti atoms involved in redox reactions has a high impact on the capacitance of Ti3C2Tx MXene and this can be impacted by cation intercalation. Thus, the electronic structure of multi layered Ti3C2Tx particles is investigated by X ray absorption XA spectroscopy, while also benefitting from a high spatial resolution of 30 nm from X ray photoemission electron microscopy. In this work, the XA spectra from multi layered intercalated Ti3C2Tx particles of different thicknesses were recorded at the Ti L and O K edges. The Ti oxidation state in pristine, Li , and Mg intercalated Ti3C2Tx was found to be thickness dependent, while Na and K intercalated Ti3C2Tx particles did not reveal differences upon changing thickness. This work demonstrates thickness dependent modification of the MXene surface chemistry upon cation intercalation in different individual Ti3C2Tx particle

Enhancement of Ti3C2 MXene Pseudocapacitance after Urea Intercalation Studied by Soft X ray Absorption Spectroscopy

MXenes have shown outstanding properties due to their highly active hydrophilic surfaces coupled with high metallic conductivity. Many applications rely on the intercalation between Ti3C2Tx Tx describes the OH, F and O surface terminations flakes by ions or molecules, which in turn might alter the Ti3C2Tx surface chemistry and electrochemical properties. In this work, we show that the capacitance, rate capability, and charge carrier kinetics in Ti3C2Tx MXene electrodes are remarkably enhanced after urea intercalation u Ti3C2Tx . In particular, the areal capacitance increased to 1100 mF cm2, which is 56 higher than that of pristine Ti3C2Tx electrodes. We attribute this dramatic improvement to changes in the Ti3C2Tx surface chemistry upon urea intercalation. The oxidation state and the oxygen bonding of individual Ti3C2Tx flakes before and after urea intercalation are probed by soft X ray absorption spectroscopy XAS at the Ti L and O K edges with 30 nm spatial resolution in vacuum. After urea intercalation, a higher Ti oxidation state is observed across the entire flake compared to pristine Ti3C2Tx. Additionally, in situ XAS of u Ti3C2Tx aqueous dispersions reveal a higher Ti oxidation similar to dry samples, while for pristine Ti3C2Tx the Ti atoms are significantly reduced in water compared to dry sample

Crystallinity and Size Control of Colloidal Germanium Nanoparticles from Organogermanium Halide Reagents

Germanium Ge nanoparticles are gaining increasing interest due to their properties that arise in the quantum confinement regime, such as the development of the band structure with changing size. While promising materials, significant challenges still exist related to the development of synthetic schemes allowing for good control over size and morphology in a single step. Herein, we investigate a synthetic method that combines sulfur and primary amines to promote the reduction of organometallic Ge IV precursors to form Ge nanoparticles at relatively low temperatures 300 C . We propose a reaction mechanism and examine the effects of solvents, sulfur concentration, and organogermanium halide precursors. Hydrosulfuric acid H2S produced in situ acts as the primary reducing species, and we were able to increase the particle size more than 2 fold by tuning both the reaction time and quantity of sulfur added during the synthesis. We found that we are able to control the crystalline or amorphous nature of the resulting nanoparticles by choosing different solvents and propose a mechanism for this interaction. The reaction mechanism presented provides insight into how one can control the resulting particle size, crystallinity, and reaction kinetics. While we demonstrated the synthesis of Ge nanoparticles, this method can potentially be extended to other members of the group IV famil

Understanding the Effects of Primary and Secondary Doping via Post Treatment of P Type and N Type Hybrid Organic Inorganic Thin Film Thermoelectric Materials

Hybrid organic inorganic materials have emerged as promising thermoelectric TE materials since they inherit the individual strengths of each component, enabling rational materials design with enhanced TE performance. The doping of hybrid TE materials via post treatment processes is used to improve their performance, but there is still an incomplete understanding of the elicited effects. Here, the impact of different doping methods on the thin film TE performance of p type Te poly 3,4 ethylenedioxythiophene poly styrenesulfonate PEDOT PSS and n type Ag2Te PEDOT PSS hybrid materials is investigated. Primary doping through acid base and charge transfer processes using H2SO4 and tetrakis dimethylamino ethylene, respectively, and the effects of secondary doping using ethylene glycol is examined. Through a combination of Hall effect measurements, hard X ray photoelectron spectroscopy, and Raman spectroscopy, variations in the charge carrier concentration, mobility, and overall TE performance are related to the morphological and chemical structure of the hybrid materials. This study provides an improved understanding of the effects that different post treatments have on hybrid materials and shows that the impact of these post treatments on pure PEDOT PSS does not always apply to hybrid systems. These new insights into post treatment effects on hybrid materials is expected to facilitate further enhancement of their performance as electronic materials in general and thermoelectric materials in particula

Structural Study of Carbon Coated TiO2 Anatase Nanoparticles as High Performance Anode Materials for Na Ion Batteries

In this work, we study the electronic and atomic structural modifications occurring in TiO2 anatase nanoparticles as anode materials in Na ion batteries upon sodiation and desodiation. The structural investigation is performed over both long and short range order by combining a comprehensive extended X ray absorption fine structure EXAFS characterization with X ray diffraction XRD . The evolution of the electronic structure upon cycling is qualitatively investigated by X ray absorption near edge structure XANES analysis. The goal of this work is to correlate the outstanding electrochemical performance of carbon coated TiO2 anatase nanoparticles in sodium batteries with the electronic and structural modifications induced during the sodiation and desodiation processes upon cycling. This work also demonstrates for the first time a coherent explanation of the structural changes observed, where an electrochemically induced short range ordering is revealed upon cyclin