Jahan Zeb Hassan

Bio: Jahan Zeb Hassan is an academic researcher from Riphah International University. The author has contributed to research in topics: Intercalation (chemistry) & Rational design. The author has an hindex of 2, co-authored 2 publications receiving 10 citations.

Rational Design and Advance Applications of Transition Metal Oxides

Abstract: An attractive class of transition metal oxides (TMOs) have been freshly concerned with increasing research interest worldwide concerning stoichiometric and non-stoichiometric configurations as well, that usually exhibits a spinel structure. These TMOs will contribute substantial roles in the production of eco-friendly and low-cost energy conversion (storage) devices owing to their outstanding electrochemical properties. The current chapter involves the summary of the latest research and fundamental advances in the effectual synthesis and rational design of TMOs nanostructures with meticulous size, composition, shape, and micro as well as nanostructures. Also applications of TMOs such as effective photocatalyst, gas sensing, biomedical, and as an electrode material that can be utilized for lithium-ion batteries, and photovoltaic applications. Additionally, certain future tendencies and visions for the development of next-generation advanced TMOs for electrochemical energy storage methods are also displayed.

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

Abstract: 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.

Chemical unzipping of WS2 nanotubes

Abstract: 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.

Liquid-phase exfoliated MoS2 nanosheets doped with p-type transition metals: a comparative analysis of photocatalytic and antimicrobial potential combined with density functional theory.

Abstract: MoS2 nanosheets were developed by undertaking the liquid-phase exfoliation of bulk counterparts. In order to enhance its photocatalytic properties, the host material was doped with p-type transition metals (i.e., Ag, Co, Bi, and Zr). The hydrothermal technique was used to produce samples doped with 7.5 wt% transition metals (TM). X-ray diffraction detected the existence of 2H-phase by mirroring its reflection at 2θ ∼ 14°, while the peak distribution revealed the degree of exfoliation in samples. Low PL intensities indicated a lower recombination of electron-hole pairs, as corroborated by a high degree of photocatalytic action. Raman analysis was undertaken to identify molecular vibrations. The A1g mode in Raman spectra consistently showed a blueshift in all samples and the E12g mode was only slightly affected, which is evidence of the p-type doping in the MoS2 nanosheets. In the XPS spectrum, two characteristic peaks of Mo 3d appeared at 229.87 and 233.03 eV assigned to Mo-3d5/2 and Mo-3d3/2, respectively. Furthermore, a microstructural examination with HR-TEM and FESEM divulged a thin-layered structure of MoS2 consisting of flat, gently curved or twisted nanosheets. Diverse morphologies were observed with a non-uniform distribution of the dopant. Photocatalytic action of the TM-doped products effectively degraded methylene blue (MB) concentrations of up to 94 percent (for Ag-MoS2). The synergistic effect of doped MoS2 nanosheets against S. aureus in comparison to E. coli bacteria was also evaluated. The efficacy % age improved from (0-31.7%) and (23.5-55.2%) against E. coli, and (0-34.2%) and (8.3-69.23%) against S. aureus. Moreover, results from first principles calculations indicate that substitutional doping of TM atoms is indeed advantageous. Theoretical calculations confirmed that doping with Ag, Co, Bi, and Zr leads to a decrease in the band gap to a certain degree, in which the conduction band edge shifts toward lower energy, while the valence band shifts closer to the high energy end. It can be concluded that Ag, Co, and Bi impurities can lead to beneficial p-type doping in MoS2 monolayered structures. With regards to doping with Zr, the acceptor levels are formed above the edge of the valence band, revealing an introduction of the p-type character.

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

Abstract: 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.