Near-Infrared Active Lead Chalcogenide Quantum Dots: Preparation, Post-Synthesis Ligand Exchange, and lications in Solar Cells

Quantum dots (QDs) of lead chalcogenides (e.g. PbS, PbSe, and PbTe) are attractive near‐infrared (NIR) active materials that show great potential in a wide range of applications, such as, photovoltaics (PV), optoelectronics, sensors, and bio‐electronics. The surface ligand plays an essential role in the production of QDs, post‐synthesis modification, and their integration to practical applications. Therefore, it is critically important that the influence of surface ligands on the synthesis and properties of QDs is well understood for their applications in various devices. In this Review we elaborate the application of colloidal synthesis techniques for the preparation of lead chalcogenide based QDs. We specifically focus on the influence of surface ligands on the synthesis of QDs and their solution‐phase ligand exchange. Given the importance of lead chalcogenide QDs as potential light harvesters, we also pay particular attention to the current progress of these QDs in photovoltaic applications.This work was financially supported by the Australian Research Council Discovery Projects DP110102877 and DP140104062, DP150101939 and Discovery Early Career Award DE16010056

Functionalized large pore mesoporous silica nanoparticles for gene delivery featuring controlled release and co-delivery

Novel mesoporous silica nanoparticles (LPMSNs) functionalised with degradable poly(2-dimethylaminoethyl acrylate) (PDMAEA) have been developed (PDMAEA–LPMSNs) as nano-carriers for gene delivery. The unique design of PDMAEA–LPMSNs has endowed this system with multiple functions derived from both the organic and inorganic moieties. The cationic polymer unit binds to genetic molecules and undergoes a self-catalyzed hydrolysis in water to form a non-toxic anionic polymer poly(acrylic acid), allowing controlled release of siRNA in the cells. The nanopores of the LPMSNs provide a reservoir for storage and release of chloroquine to facilitate endosomal escape. The PDMAEA–LPMSN composites were characterized by elemental analysis (EA), X-ray photoelectron spectroscopy (XPS), solid-state 13C magic-angle spinning nuclear magnetic resonance (MAS-NMR), thermogravimetric analysis (TGA), and nitrogen sorption techniques. Their siRNA delivery performance was tested in a KHOS cell line, showing promising potential for co-delivery of genes and drugs

Mesoporous hybrid material composed of Mn3O4 nanoparticles on nitrogen-doped graphene for highly efficient oxygen reduction reaction

The hybrid material composed of Mn3O4 nanoparticles on nitrogendoped graphene was prepared via a solvothermal process and investigated for the first time as a catalyst for oxygen reduction reaction (ORR). Its high ORR activity, excellent durability and tolerance to methanol make this hybrid material a promising candidate for highly efficient ORR in fuel cells and metal-air batteries.Jingjing Duan, Yao Zheng, Sheng Chen, Youhong Tang, Mietek Jaroniec and Shizhang Qia

Study of multicomponent adsorption equilibrium and kinetics of hydrocarbons on activated carbon

Comprehensive theoretical and experimental study of multicomponent adsorption equilibrium and kinetics of hydrocarbons on activated carbon are carried out in this thesis. The multicomponent adsorption isotherm and kinetics models based on micropore size distribution concept are proposed to identify the competitive adsorption and the intraparticle mass transfer process. The models assume the micropore size distribution as the source of surface heterogeneity. The adsorbate-adsorbent interaction energy is related to the pore size by the Lennard-Jones potential relationship and the energy matching of different species on heterogeneous surfaces is related to their own interaction strength with the local micropore by the adsorbate-pore interaction mechanism. The pore size exclusion is considered on both adsorption equilibrium and kinetics models. The local adsorbed phase concentration is calculated from the extended Langmuir equation or ideal adsorbed solution theory (IAST). In the kinetics model, the diffusions of both free and adsorbed species are considered and the chemical potential gradient is used as the driving force for the diffusion of adsorbed species, so the concentration dependence of the surface diffusivity can be explained. By using only information of single component equilibrium and mass transfer, the proposed models can be used to predict the multicomponent adsorption equilibrium and dynamics. In the experimental study, adsorption equilibrium data of pure component on activated carbon were collected by a high accuracy volumetric measurement rig. The binary adsorption equilibrium and all kinetics data were measured using a differential adsorption bed (DAB) rig. The extensive experimental adsorption equilibrium and dynamics data of methane, ethane, propane and carbon dioxide on Ajax or Norit activated carbons at different temperatures and concentration conditions were utilized to validate the proposed models. The results show that the models developed in this study can correctly predict the single and binary component adsorption equilibria and kinetics. In addition, the model parameters and micropore size distribution shape were demonstrated to play significant roles in affecting the model performance. The potential of the kinetics models are further tested by predicting simultaneous desorption and displacement dynamics of ethane and propane. Comparing the prediction results of adsorption kinetics between the micropore size distribution method and the energy distribution method shows that the model based on adsorbate-adsorbent interaction concept is more fundamental and has clear physical significance and provides better prediction for binary desorption kinetics

Using local IAST with micropore size distribution to predict desorption and displacement kinetics of mixed gases in activated carbon

A mathematical model utilizing ideal adsorbed solution theory (IAST) and micropore size distribution (MPSD) concept to describe the adsorption equilibrium and surface energetic heterogeneity is used to predict the desorption and displacement kinetics of mixed gases in activated carbon. The model takes into account the intraparticle diffusion in both pore volume and adsorbed phase. The driving force for surface diffusion is the chemical potential gradient, and the apparent surface diffusivity is a function of the adsorbed concentration. The adsorbate-adsorbent interaction energy is related to the micropore size by the Lennard-Jones potential, and the matching energies between different species in the adsorbed phase are therefore described by this adsorbate-pore interaction mechanism in both equilibrium and diffusion of the adsorbed species. The overall adsorption isotherm and the diffusion flux of the adsorbed species are the integrals of their corresponding local values over all MPSD range accessible by the adsorbate molecules. The size exclusion effect is taken into account in the competition of the different gases for the given pore. The model parameters are obtained using only information of pure gas equilibrium and mass transfer. The model predictions are tested with the desorption and displacement kinetics data of binary gases on Ajax activated carbon and found to be in good agreement with the experimental data. (C) 2002 Elsevier Science B.V. All rights reserved

Study of isosteric heat of adsorption and activation energy for surface diffusion of gases on activated carbon using equilibrium and kinetics information

Pure component adsorption equilibria and kinetics of ethane and propane were measured on two activated carbon samples at various temperatures. The isosteric heat of adsorption was derived from the equilibrium information using the Clapeyron equation, while the activation energy for surface diffusion was derived from the surface diffusivity, which was extracted from the kinetics data using the macropore and surface diffusion (MSD) model. Two isotherm models, Unilan and Toth equations are used in the analysis of equilibrium and kinetics data. It is found that the choice of adsorption isotherm has a significant influence on the calculated values of isosteric heat of adsorption, but has less influence on the activation energy for surface diffusion. The ratio of activation energy to isosteric heat of adsorption is found between 0.25 and 0.6 for ethane and propane on the two carbons, depending on the choice of isotherm equation. This ratio is a weak function of surface loading. (C) 2003 Elsevier B.V. All rights reserved