Supramolecular Interaction Controlled Diffusion Mechanism and Improved Mechanical Behavior of Hybrid Hydrogel Systems of Zwitterions and CNT

Hashmi, Saud,GhavamiNejad, Amin,Obiweluozor, Francis O.,Vatankhah-Varnoosfaderani, Mohammad,Stadler, Florian J. American Chemical Society 2012 Macromolecules Vol.45 No.24

<P>Hybrid hydrogels of poly(<I>N</I>-isopropylacrylamide) (pNIPAM) containing carboxylate carbon nanotubes (CNTs) and/or zwitterions are synthesized by free radical polymerization. The supramolecular interactions among zwitterionic monomers and CNTs influence the mechanical properties and diffusion mechanism in hybrid hydrogel systems. These supramolecular interactions and response behavior of hybrid hydrogels were tested mechanically and with respect to their swelling characteristics. Hybrid hydrogels of pNIPAM and CNT or pNIPAM, zwitterions, and CNT follow a Fickian diffusion behavior, while adding zwitterions leads to an anomalous triple-stage swelling behavior and stiffening of the gel due to the interactions of the zwitterions with each other, which significantly increase the viscous dissipation and change the microscopic structure. While CNT itself stiffens the gel and slightly increases the diffusion speed, it complexes zwitterions, which leads to a novel property profile that is both potentially antibiotic and electrically conductive. CNT affords a relaxation process at long relaxation times, while zwitterion attachment and detachment lead to dissipation predominantly at high frequencies. Dynamic rheological measurements were performed during swelling of these complex materials.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/mamobx/2012/mamobx.2012.45.issue-24/ma301366h/production/images/medium/ma-2012-01366h_0014.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/ma301366h'>ACS Electronic Supporting Info</A></P>

Two-dimensional honeycomb hafnene monolayer: stability and magnetism by structural transition

Hashmi, Arqum,Umar Farooq, M.,Khan, Imran,Hong, Jisang Royal Society of Chemistry 2017 Nanoscale Vol.9 No.28

<P>A few years ago, it was claimed that the two-dimensional ferromagnetic planar Hf monolayer could be synthesized on Ir(111). However, several questions remained unanswered. Herein, we unravel the structural stability of the HF monolayer and its influence on magnetism using first principles calculations. Despite the ferromagnetic state in the planar free-standing Hf layer, extensive systematic calculations with phonon spectra reveal that the planar free-standing Hf layer is unstable and it has a non-magnetic high-buckled structure in the ground state. We also find a structural transition from buckled to flat honeycomb geometry on the Ir(111) substrate. Nonetheless, 2D hafnene has no magnetic state due to strong hybridization with the Ir(111) surface. The evolution from the non-magnetic to the ferromagnetic state combined with structural transition is observed by adding BN as a spacer layer on the Ir(111) substrate (BN/Ir(111)). In addition, we find that 2D Hf on BN/Ir(111) has a giant perpendicular magnetic anisotropy of 3.41 meV.</P>

Band gap and effective mass of multilayer BN/graphene/BN: van der Waals density functional approach

Hashmi, Arqum,Hong, Jisang American Institute of Physics 2014 Journal of Applied Physics Vol.115 No.19

Using the van der Waals density functional theory method (DFT-D2), we have investigated thickness dependent energy band gaps and effective masses of multilayer BN/graphene/BN structures by changing the stacking order. The band gap is substantially dependent on the stacking order. For instance, the calculated band gap in ABA stacking is about 150 meV, whereas it becomes 31 meV in ABC stacking. No significant thickness dependent band gap is observed in both ABA and ABC stackings although the band gap is gradually increasing with the BN thickness in ABA stacking. In addition, the effective mass is found to be strongly dependent on the stacking order. The effective mass in ABA stacking is much larger than that found in ABC stacking. On the other hand, the effective mass along K-M direction is smaller than that along K-Gamma direction in ABA stacking. However, it is independent on the band direction in ABC stacking. We have found that the inclusion of van der Waals interaction alters thickness dependent band gap and effective mass of BN/graphene/BN multilayer systems compared with those found with standard density functional theory. (C) 2014 AIP Publishing LLC.

Establishing National Science and Technology Park in Pakistan

Hashmi, Amer,Shah, Ali World Technopolis Association 2013 World Technopolis Review Vol.1 No.4

This paper presents the concept of the National Science and Technology Park (NSTP) in Islamabad, Pakistan. Keeping in line with Karl Popper's Piecemeal Social Engineering theory, a critical-pragmatic approach is adopted in shedding light on the strategic thrusts and expected outcomes of this knowledge-driven, entrepreneurially-spirited, multi-industry project. Based on Triple-Helix perspectives, we investigate the role of the National University of Sciences and Technology, Islamabad in efforts aimed at developing NSTP as an intermediary hybrid organization that enhances industry-academia-government linkages, with the potential to serve as an engine for regional and national economic growth and competitiveness.

Ultra-high capacity hydrogen storage in a Li decorated two-dimensional C2N layer

Hashmi, A.,Farooq, M. U.,Khan, I.,Son, J.,Hong, J. Royal Society of Chemistry 2017 Journal of Materials Chemistry A Vol.5 No.6

<P>Owing to naturally existing uniform periodic pores in two-dimensional (2D) C2N layers, they can be an ideal candidate for hydrogen storage materials among other 2D materials. Here, we explored the potential application of ultra-high capacity hydrogen storage using the first principles method. Remarkably, Li was strongly bonded with the C2N layer via a Kubas-type interaction with a large binding energy of 3-5 eV. This unique interaction does not exist in graphene or other 2D materials, and it rules out the possibility of Li alkali metal cluster formations. We found that the Li-decorated C2N could show a very high theoretical gravimetric density of 13 weight percentage (wt%). Very interestingly, this gravimetric density is not only 40% and 30% higher than those found in MgH2 and C-60 but also significantly higher than the values obtained in alkali metal decorated graphene, MoS2 and phosphorene. Irrespective of the theoretical capacity, the most important physical quantity is the practical capacity (the difference in the number of adsorbed and desorbed hydrogen molecules) under ambient conditions of pressure and temperature. Our thermodynamic analysis showed that 75% of the adsorbed hydrogen molecules could be released under practical conditions of temperature and pressure and the practical capacity is about 10 wt%. Our findings suggest that the Li decorated C2N can be a very promising material for room-temperature hydrogen storage under realistic conditions.</P>

Half metallic g-C₄N₃ on BN layer

Hashmi Arqum,Jicheol Son,Jisang Hong 한국자기학회 2014 한국자기학회 학술연구발표회 논문개요집 Vol.2014 No.5

Transition from half metal to semiconductor in Li doped <i>g</i>-C₄N₃

Hashmi, Arqum,Hu, Tao,Hong, Jisang American Institute of Physics 2014 JOURNAL OF APPLIED PHYSICS - Vol.115 No.12

<P>We have investigated the structural and magnetic properties of Li doped graphitic carbon nitride (g-C4N3) using the van der Waals density functional theory. A free standing g-C4N3 was known to show a half metallic state with buckling geometry, but this feature completely disappears in the presence of Li doping. Besides this structural modification, very interestingly, we have obtained that the Li doped g-C4N3 shows dramatic change in its electronic structure. Both ferromagnetic and nonmagnetic states are almost degenerated in one Li atom doped system. However, the transition from half metallic state to semiconductor is observed with further increase of Li concentration and the calculated energy gap is 1.97 eV. We found that Li impurity plays as a donor element and charge transfer from the Li atom to neighboring N atoms induces a band gap. Overall, we have observed that the electronic and magnetic properties of g-C4N3 are substantially modified by Li doping. (C) 2014 AIP Publishing LLC.</P>

Graphene/phosphorene bilayer: High electron speed, optical property and semiconductor-metal transition with electric field

Hashmi, A.,Farooq, U.,Hong, J. Elsevier 2016 CURRENT APPLIED PHYSICS Vol.16 No.3

<P>We investigated the electric field dependent band structures and optical properties of graphene/phosphorene bilayer. Remarkably, the effective electron Fermi velocity in graphene/phosphorene was comparable to that of pure graphene monolayer. Moreover, this feature was not disrupted even in the presence of a finite external electric field. The electronic band structure changed from a semiconductor to a metallic state with an external electric field strength of 0.5 V/angstrom. In addition, the electric field enhanced the structural stability of a bilayer system because the binding energy was increased approximately 20 -30% as compared with that at zero electric field. We found that the optical anisotropy regarding the electric polarization along armchair and zigzag directions disappeared, but the anisotropic optical properties still survived regarding the electric polarization for in-plane and perpendicular directions. The small effective mass, high speed of electrons, and optical property in graphene/phosphorene bilayer may provide a promising way for graphene based device applications. (C) 2015 Elsevier B.V. All rights reserved.</P>

On-line Observation of Hydrogels during Swelling and LCST-induced changes

Hashmi, Saud,Obiweluozor, Francis,GhavamiNejad, Amin,Vatankhah-Varnoosfaderani, Mohammad,Stadler, Florian J. 한국유변학회 2012 Korea-Australia rheology journal Vol.24 No.3

A new technique for the online observation of rheological data of hydrogels during experiments involving significant volume changes is proposed. In order to accommodate for large volume changes, the gap has to be force controlled and continuously adjusted to the current sample height. Furthermore, the force control also has to ensure the adhesion of the sample to the geometry. For smaller volume changes, it is also possible to employ experiments with constant gap. Due to the volume change, the sample is not clearly defined with respect to the open surfaces in a parallel plate geometry, which leads to too high values, which, however, can be compensated for properly.

Block and Fuzzy Techniques Based Forensic Tool for Detection and Classification of Image Forgery

Hashmi, Mohammad Farukh,Keskar, Avinash G. The Korean Institute of Electrical Engineers 2015 Journal of Electrical Engineering & Technology Vol.10 No.4

In today’s era of advanced technological developments, the threats to the authenticity and integrity of digital images, in a nutshell, the threats to the Image Forensics Research communities have also increased proportionately. This happened as even for the ‘non-expert’ forgers, the availability of image processing tools has become a cakewalk. This image forgery poses a great problem for judicial authorities in any context of trade and commerce. Block matching based image cloning detection system is widely researched over the last 2-3 decades but this was discouraged by higher computational complexity and more time requirement at the algorithm level. Thus, for reducing time need, various dimension reduction techniques have been employed. Since a single technique cannot cope up with all the transformations like addition of noise, blurring, intensity variation, etc. we employ multiple techniques to a single image. In this paper, we have used Fuzzy logic approach for decision making and getting a global response of all the techniques, since their individual outputs depend on various parameters. Experimental results have given enthusiastic elicitations as regards various transformations to the digital image. Hence this paper proposes Fuzzy based cloning detection and classification system. Experimental results have shown that our detection system achieves classification accuracy of 94.12%. Detection accuracy (DAR) while in case of 81×81 sized copied portion the maximum accuracy achieved is 99.17% as regards subjection to transformations like Blurring, Intensity Variation and Gaussian Noise Addition.