The ability to tune material properties using gating by electric fields is at the heart of modern electronic technology. It is also a driving force behind recent advances in two-dimensional systems, such as the observation of gate electric-field-induced superconductivity and metal-insulator transitions. Here, we describe an ionic field-effect transistor (termed an iFET), in which gate-controlled Li ion intercalation modulates the material properties of layered crystals of 1T-TaS2. The strong charge doping induced by the tunable ion intercalation alters the energetics of various charge-ordered states in 1T-TaS2 and produces a series of phase transitions in thin-flake samples with reduced dimensionality. We find that the charge-density wave states in 1T-TaS2 collapse in the two-dimensional limit at critical thicknesses. Meanwhile, at low temperatures, the ionic gating induces multiple phase transitions from Mott-insulator to metal in 1T-TaS2 thin flakes, with five orders of magnitude modulation in resistance, and superconductivity emerges in a textured charge-density wave state induced by ionic gating. Our method of gate-controlled intercalation opens up possibilities in searching for novel states of matter in the extreme charge-carrier-concentration limit.

http://absimage.aps.org/image/MAR15/MWS_MAR15-2014-020259.pdf

Gate-tunable phase transitions in thin flakes of 1T-TaS$_{2}$

WS2 nanoribbons have been synthesized by chemical unzipping of WS2 nanotubes. Lithium atoms are intercalated in WS2 nanotubes by a solvothermal reaction with n-butyllithium in hexane. The lithiated WS2 nanotubes are then reacted with various solvents--water, ethanol, and long chain thiols. While the tubes break into pieces when treated with water and ethanol, they unzip through longitudinal cutting along the axes to yield nanoribbons when treated with long chain thiols, 1-octanethiol and 1-dodecanethiol. The slow diffusion of the long chain thiols reduces the aggression of the reaction, leading to controlled opening of the tubes.

Chemical unzipping of WS2 nanotubes

A review of photocatalytic characterization, and environmental cleaning, of metal oxide nanostructured materials

Photocatalytic solar energy harvesting is considered as an excellent pathway to address the environmental energy dilemma. Due to the unique layered and band structure of bismuth oxyhalide (BiOX), it is an emergent class of photocatalysts which display adequate properties that promote the robust light response and may result in amplification of solar energy conversion. The current review will summarize the recent revolution in BiOX-based energy applications such as H2 and O2 evolution, as well as N2 fixation, and will present structural engineering and design solutions for improving energy conversion. Particularly, the preparation and structure tailoring of BiOX materials, as well as some other advanced techniques such as the building of Moire superlattices, heterojunctions, and tailoring the internal electric field, may boost the photocatalysis of BiOX materials. Additionally, various composite frameworks are discussed, emphasizing the importance of BiOX-based nanocomposites. Finally, the primary problems and potential for the material based on BiOX are discussed in terms of their future development. This review will provide a link between structural engineering and environmental applications and will provide a preferred path toward the novel material design based on BiOX for environmental and in particular, energy-related applications.

Recent advances in structural tailoring of BiOX-based 2D composites for solar energy harvesting

Recent advances in carbonaceous sustainable nanomaterials for wastewater treatments

Advances in Liquid-Phase and Intercalation Exfoliations of Transition Metal Dichalcogenides to Produce 2D Framework

In the current era according to the floating industrial ratings the top most industry of Pakistan is the cement industry. This sector has been able to earn high returns over the investment which has created more interest to determine major factors which are needed to be focused on while evaluating the profitability of the cement companies. DuPont Model was one of the most significant equation presented in 70’s which stated that Returns on Assets (ROA) is to be considered for evaluating firm’s performance but later the researchers figured out that Return on Equity (ROE) is the major factor which should be considered for assessing profitability and growth of the company. The purpose of the study is to investigate the most influencing factors which affect the Returns on Equity (ROE) for the cement sector of Pakistan. Data from 2006 to 2015 is taken for the analysis from annual reports of 03 listed cement companies in Pakistan Stock Exchange. Regressions model with the Panel Least Squares method and Period random effects will be used for the measurement of the data. The results of this research will be beneficial for future researchers who aim to focus on investigating the determinants of the Return on Equity (ROE). The study will also describe the impact of various financial ratios on ROE which will also assist cement companies to work on their full potential and acquire large market share which will ultimately result in better profitability. The research is concluded with the recommendations and suggestions for the selected companies and this study provides tool for companies to identify the main factors of the return on equity.

Umer Farooq

Papers

Advances in Liquid-Phase and Intercalation Exfoliations of Transition Metal Dichalcogenides to Produce 2D Framework

Determinants of Return on Equity: Evidence from the Cement Industry of Pakistan