Comparative Study of Bulk and Nanoengineered Doped ZnSe

Chromium- and cobalt-doped zinc selenide nanoparticles were synthesized using a low-temperature reactive solution growth method. The morphological and optical characteristics were compared to those of doped zinc selenide (ZnSe) bulk crystals grown by the physical vapor transport (PVT) method. We observed agglomeration of particles; however, the thioglycerol capping agent has been shown to limit particle grain growth and agglomeration. This process enables doping by addition of chromium and cobalt salts in the solution. A slightly longer refluxing time was required to achieve cobalt doping as compared with chromium doping due to lower refluxing temperature. The nanoparticle growth process showed an average particle size of approximately 300 nm for both Cr- and Co-doped zinc selenide. The optical characterization of Co:ZnSe is ongoing; however, preliminary results showed a very high bandgap compared to that of pure ZnSe bulk crystal. Additionally, Co:ZnSe has an order of magnitude higher fluorescence intensity compared to bulk Cr:ZnSe samples.

Effects of oligomerization and decomposition on the nanoparticle growth: a model study

The rate at which freshly formed secondary aerosol particles grow is an important factor in determining their climate impacts. The growth rate of atmospheric nanoparticles may be affected by particle-phase oligomerization and decomposition of condensing organic molecules. We used the Model for Oligomerization and Decomposition in Nanoparticle Growth (MODNAG) to investigate the potential atmospheric significance of these effects. This was done by conducting multiple simulations with varying reaction-related parameters (volatilities of the involved compounds and reaction rates) using both artificial and ambient measured gas-phase concentrations of organic vapors to define the condensing vapors. While our study does not aim at providing information on any specific reaction, our results indicate that particle-phase reactions have significant potential to affect the nanoparticle growth. In simulations in which one-third of a volatility basis set bin was allowed to go through particle-phase reactions, the maximum increase in growth rates was 71 % and the decrease 26 % compared to the base case in which no particle-phase reactions were assumed to take place. These results highlight the importance of investigating and increasing our understanding of particle-phase reactions.

MnO, Co and Ni Nanoparticle Synthesis by Oleylamie and Oleic Acid

Background: Magnetic nanoparticles are attracting much attention toward easy operation and size controlable synthesis methods. We develop a method to synthesize MnO, Co, CoO, and Ni nanoparticles by thermal decomposition of metal 2,4-pentanedionates in the presence of oleylamine (OLA), oleic acid (OA), and 1‐octadecene (ODE). Methods: Similar experimental conditions are used to prepare nanoparticles except for the metal starting materials (manganese 2,4-pentanedionate, nickel 2,4-pentanedionate, and cobalt 2,4-pentanedionate), leading to different products. For the manganese 2,4-pentanedionate starting material, MnO nanoparticles are always obtained as the reaction is controlled with different temperatures, precursor concentrations, ligand ratios, and reaction time. For the cobalt 2,4-pentanedionate starting material, only three experimental conditions can produce pure phase CoO and Co nanoparticles. For the nickel 2,4-pentanedionate starting material, only three experimental conditions lead to the production of pure phase Ni nanoparticles. Results: The nanoparticle sizes increase with the increase of reaction temperatures. It is observed that the reaction time affects nanoparticle growth. The nanoparticles are studied by XRD, TEM, and magnetic measurements. Conclusion: This work presents a facile method to prepare nanoparticles with different sizes, which provides a fundamental understanding of nanoparticle growth in solution.

A New in-situ Exsolution Supporting Framework for Metal Nanoparticle Growth

Catalysts made of in-situ exsolved metal nanoparticles often demonstrate promising activity and high stability in many applications. However, the design of these catalysts is greatly constrained by the classic exsolution mechanism, which occurs almost exclusively through substitutional metal-doping in perovskites. Here we show that metal nanoparticles can also be in-situ exsolved from interstitially doped metal cations in a NiOOH supporting framework with the guidance of theoretical calculation. The exsolution can be conducted swiftly at room temperature. A novel copper nanocatalyst prepared with this approach have a quasi-uniform size of 4 nm delivering an exceptional CO faradaic efficiency of 95.6% with a notable durability for the electrochemical reduction of CO2. This design principle is further proven to be generally applicable to other metals and foregrounded for guiding the development of advanced catalytic materials.

Effects of oligomerization and decomposition to the nanoparticle growth, a model study

The rate at which freshly formed secondary aerosol particles grow is an important factor in determining their climate impacts. The growth rate of atmospheric nanoparticles may be affected by particle phase oligomerization and decomposition of condensing organic molecules. We used Model for Oligomerization and Decomposition in Nanoparticle Growth (MODNAG) to investigate the potential atmospheric significance of these effects. This was done by conducting multiple simulations with varying reaction-related parameters (volatilities of the involved compounds and reaction rates) using both artificial and ambient measured gas phase concentrations of organic vapors to define the condensing vapors. While our study does not aim at providing information on any specific reaction, our results indicate that particle phase reactions have significant potential to affect the nanoparticle growth. In simulations where one-third of a volatility basis set bin was allowed to go through particle phase reactions the maximum increase in growth rates was 71 % and decrease 26 % compared to base case where no particle phase reactions were assumed to take place. These results highlight the importance of investigating and increasing our understanding of particle phase reactions.

Computational Study of Quenching Effects on Growth Processes and Size Distributions of Silicon Nanoparticles at a Thermal Plasma Tail

In this paper, quenching effects on silicon nanoparticle growth processes and size distributions at a typical range of cooling rates in a thermal plasma tail are investigated computationally. We used a nodal-type model that expresses a size distribution evolving temporally with simultaneous homogeneous nucleation, heterogeneous condensation, interparticle coagulation, and melting point depression. The numerically obtained size distributions exhibit similar size ranges and tendencies to those of experiment results obtained with and without quenching. In a highly supersaturated state, 40–50% of the vapor atoms are converted rapidly to nanoparticles. After most vapor atoms are consumed, the nanoparticles grow by coagulation, which occurs much more slowly than condensation. At higher cooling rates, one obtains greater total number density, smaller size, and smaller standard deviation. Quenching in thermal plasma fabrication is effectual, but it presents limitations for controlling nanoparticle characteristics.

Photodetectors for Weak Signal Conditions from Au/Cu co-doped ZnO

Here, we have used a simple method for polyol synthesis, analysis, and testing of Au/Cu-doped ZnO Ultraviolet (UV) photodetectors (PD). Our results are reported and discussed by X-ray diffraction (XRD) to ensure that the manufactured samples show a hexagonal wurtzite ZnO structure. Transmission electron microscopy (TEM) confirmed the nanoparticle growth in the hexagonal sample on the surface, which is the key to improving the light response. Our prepared UV PD Au/Cu codoped ZnO showed a rapid time at a power density of 7.6 mW. the highest responsivity of R = 575 mA/W and sensitivity 103 obtained at 7.6 mW with an applied voltage of 1V. Our results demonstrate the obvious substitution of Au and Cu in ZnO, thereby improving the UV-sensing light response.

Synthesis of Magnetic Mno, Co and Ni Nanoparticle by Oleylamie and Oleic Acid

Magnetic MnO, Co, CoO, and Ni nanoparticles are synthesized by thermal decomposition of metal 2,4-pentanedionates in the presence of oleylamine (OLA), oleic acid (OA), and 1-octadecene (ODE). Similar experimental conditions are used to prepare nanoparticles except for the metal starting materials (manganese 2,4-pentanedionate, nickel 2,4-pentanedionate, and cobalt 2,4-pentanedionate). MnO nanoparticles are always obtained as the reaction is controlled with different temperatures, precursor concentrations, ligand ratios, and reaction time. Only three experimental conditions can produce pure phase CoO and Co nanoparticles. The same three experimental conditions lead to the production of pure phase Ni nanoparticles. Other experimental conditions produce mixture phase nanomaterials. The nanoparticle sizes increase with the increase of reaction temperatures. The influence of reaction precursor concentrations on the sizes of the nanoparticles is also studied. The ratio of ligand OLA to OA is used to control the reaction in terms of nanoparticle sizes. It is observed that the reaction time affects nanoparticle growth. The nanoparticles are studied by XRD, TEM, and magnetic measurements. This work presents a facile method to prepare nanoparticles with different sizes, which provides a fundamental understanding of nanoparticle growth in solution.