Double perovskites are attractive candidates for addressing the main challenges associated with efficient single perovskites, such as low stability and the presence of heavy metals in their ...composition. However, the double perovskite structure is complex and presents unique synthesis challenges. Furthermore, fine-tuning the synthesis parameters to obtain precise control of the nanoparticle size is necessary. To tackle these issues, we combined machine learning with a multioutput model, allowing us to simultaneously generate multiple outcomes within a single regression while considering interactions among all targets in a complex reaction. As a result, we built a specific data set with relevant parameters for the synthesis of double perovskite, using the hot injection method considering lead-free double and single perovskites. We then developed three different multioutput machine learning models based on decision trees, random forests, and neural networks. These models were trained to predict optimal synthesis conditions for double perovskites, including reagent amounts, time of reaction, and bandgap. The selection of the best model was based on MAE, RMSE, and R 2 metrics. We utilize this model to predict the synthesis condition of a double perovskite, which we subsequently synthesized, specifically Cs2AgInCl6, hence validating our model with experimental results. Our approach enables us to achieve accurate predictions and gain a deeper understanding of the intricate relationships between synthesis parameters and material properties.
In order to allow quantum dots with the desired physical and chemical properties, the fine control and prediction of size during chemical syntheses is a challenge that must be addressed. In this ...work, we applied machine learning algorithms, with information extracted from scientific papers, to identify the most important variables in the synthesis of CdSe, CdS, PbS, PbSe, and ZnSe quantum dots. From the random forest and gradient boosting machine algorithms, the most influential parameters on the final diameter of the quantum dots were the time of reaction, temperature, and metal precursors. Our models were applied to suggest the best reaction parameters for a desired quantum dot size. This methodology shall contribute to the quantum dot community to save time and money while reaching the proper material conditions for their applications.
In this work, we show the effect of the thermal treatment temperature on the photoelectrochemical (PEC) activity of CdSe/TiO
2
nanocomposites. TiO
2
nanotubes (NTs) were synthesized by anodization ...and the nanocomposites were obtained by depositing CdSe clusters
via
magnetron sputtering. A two-step thermal treatment was performed: heating the TiO
2
NTs at different temperatures prior to CdSe deposition and further heating the CdSe/TiO
2
nanocomposites. The nanocomposites were characterized by Rutherford backscattering spectroscopy (RBS), scanning electron microscopy (SEM), scanning transmission electron microscopy (STEM), high-resolution transmission electron microscopy (HRTEM), energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), UV-Vis spectrophotometry, and electrochemical impedance spectroscopy (EIS). To compare the PEC performance of the CdSe/TiO
2
nanocomposites and pristine TiO
2
NTs, linear sweep voltammetry (LSV) curves were obtained under visible light and under 1 sun illumination. It was observed that CdSe incorporation into the TiO
2
template enhances the visible light absorbance thereby improving the PEC performance of the nanocomposites. We have found that the optical, structural and PEC properties of the CdSe/TiO
2
nanocomposites are dependent on the thermal treatment temperature of the TiO
2
nanotubular substrate, prior to CdSe deposition. Moreover, a three-fold improvement in photocurrent was observed upon further thermal treatment of the obtained nanocomposite.
Effect of the thermal treatment temperature on the photoelectrochemical (PEC) activity of CdSe/TiO
2
nanocomposites.
The sustainable synthesis of macromolecules with control over sequence and molar mass remains a challenge in polymer chemistry. By coupling mechanochemistry and electron‐transfer processes (i.e., ...mechanoredox catalysis), an energy‐conscious controlled radical polymerization methodology is realized. This work explores an efficient mechanoredox reversible addition‐fragmentation chain transfer (RAFT) polymerization process using mechanical stimuli by implementing piezoelectric barium titanate and a diaryliodonium initiator with minimal solvent usage. This mechanoredox RAFT process demonstrates exquisite control over poly(meth)acrylate dispersity and chain length while also showcasing an alternative to the solution‐state synthesis of semifluorinated polymers that typically utilize exotic solvents and/or reagents. This chemistry will find utility in the sustainable development of materials across the energy, biomedical, and engineering communities.
Coupling mechanochemistry and single‐electron transfer processes in a ball mill facilitates an efficient reversible addition‐fragmentation chain transfer polymerization reaction. A versatile mechanoredox process is developed to synthesize macromolecules with good molar mass control. This method serves as an alternative to access complex polymers that may be difficult to access using traditional solution‐state processes.
Copper aluminum sulfide has been explored as an interesting low-toxicity material for application in optoelectronics and biological labeling. Herein, we have applied design of experiments (DOE) and ...density functional theory simulations (DFT) to investigate the effect of experimental conditions on the optical properties of copper aluminum sulfide nanoparticles synthesized through the heat-up method. The resulting material was characterized by UV–vis-NIR absorption, photoluminescence spectroscopy, X-ray diffractometry (XRD), Raman spectroscopy, and transmission electron microscopy (TEM). XRD and Raman spectroscopy revealed the formation of copper aluminum sulfide alongside byproducts such as covellite, atacamite, paratacamite, and clinoatacamite. DOE revealed the concentration of aluminum precursor as the most important parameter to affect the photoluminescence (PL) intensity. This finding can be correlated to a donor–acceptor pair formed by a copper vacancy and copper substituted by aluminum as the responsible for PL emission. DFT simulations performed for different possible defects reproduced the role of the donor–acceptor pair and provided an insight on their role on PL. The potential application of the nanoparticles for fluorescence biological labeling was confirmed by confocal microscopy assay showing strong fluorescence under excitation at 405, 473, and 559 nm.
Ternary sulfide nanostructures are small band gap materials that combine relatively low toxicity with useful optical properties for several applications, including photovoltaics. A systematic ...experimental study on the synthesis and mechanism of formation of copper thioantimonates (Cu3SbS4) and thioantimonides (CuSbS2) nanoparticles is presented. Antimony oxide (Sb2O3) was formed in an initial step by hydrolysis with oleylamine. The injection of a sulfur precursor led to the conversion to Cu3SbS4 driven by an excess of sulfur in oleylamine medium and at high temperatures (>200 °C). The sulfur excess was depleted as the reaction progressed, causing the reduction of the antimony(V) of the Cu3SbS4 back to antimony(III). Consequently, the Cu3SbS4 was converted to CuSbS2. In addition, the rate of antimony reduction increased with the reaction temperature. The formation mechanism unveiled here provides important insights toward the synthesis of analogous materials.
Several copper chalcogenide nanoparticles have been investigated as attractive candidates for replacing toxic (lead and cadmium based) and expensive (indium based) semiconductors. Among these ...materials, copper antimony sulfides present promising physical properties and reduced costs. Despite many works have dealt with the synthesis of these materials, fewer advanced on the formation mechanisms of the nanoparticles. Herein, we use the design of experiments as a tool to identify the role of each synthesis parameter on the composition, particle size, and optical properties of the obtained material. We evaluated synthesis time and temperature, solvent mixture, and two methods: heat up and hot injection. The nanoparticles were characterized by transmission electron microscopy, Raman spectroscopy, X-ray diffraction, UV-vis-NIR absorption spectroscopy and photoluminescence spectroscopy. The reaction time and synthesis method were found as the main factors governing phase compositions and nanoparticle size.
Design of experiments to find the main factors governing phase compositions and nanoparticle size.
The growth dynamics of zinc selenide quantum dots (ZnSe QDs) using oleic acid as stabilizer was addressed in this work. The QDs were synthesized by hot-injection method, using 2:1 and 10:1 oleic ...acid/zinc acetate ratio at 170, 190, and 210 °C. The syntheses were carried out for 30 min, 1, 2, and 3 h and the samples were characterized by transmission electron microscopy, high-resolution transmission electron microscopy, X-ray diffraction, and UV-Vis spectroscopy. The QDs diameter was evaluated by Effective Mass Approximation theory from the optical band gap. Lower oleic acid/zinc acetate molar ratio resulted in smaller particles and narrower size distribution. These results, evaluated under the light of Classical Nucleation and Growth Theory, were attributed to a smaller solubility of the monomers in the oleic acid solution. This effect leads to an increased supersaturation, promoting faster nucleation and, eventually, diffusion controlled growth, resulting in particles with narrower size distribution.
We report the transformation of several metal selenide nanocrystals (NCs), including PbSe, CdSe, ZnSe, and PbSe/CdSe core/shell NCs, in dimethyl sulfoxide (DMSO) in acidic solutions at room ...temperature. In this study, the DMSO solution of metal selenide NCs was mixed with nitric acid, which was used to adjust the pH of the solution. Upon mixing, the metal selenide NCs readily transformed into crystalline selenium (trigonal structure) nano- or microwires under ambient light, whereas little or no transformation occurred in the dark. Photocorrosion, where the photogenerated carriers within the NCs participate in the cleavage of the metal and selenium atoms, turns out to be responsible for the transformation. DMSO removes organic ligands on the NC surface and creates surface trap sites for photoinduced charge carriers. Then, nitric acid helps shift the reduction potentials, thereby promoting a “cathodic reduction”. In this sense, the photocorrosion rate can be controlled by several parameters, such as the absorption cross section of the selenide NCs and the pH. The diameter and shape of the resulting selenium wires help gauge the transformation rate and thus unveil the transformation mechanism.
We report ripening of metal particles anchored on pyramid-shaped heterostructure nanocrystals. The 'intra-particle' ripening results in a large metal tip at one corner with the other three tips ...vanishing. Investigation reveals that the ripening and core/shell formation affects photocatalytic activities via the Fermi level change.
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