Tauqir A. Sherazi

Equilibrium kinetic and thermodynamic studies of Cr(VI) adsorption onto a novel adsorbent of Eucalyptus camaldulensis waste: Batch and column reactors

Cr(VI) adsorption onto Eucalyptus camaldulensis sawdust (ECS) waste was investigated in batch and column reactors. Various parameters, including the adsorbent dose, pH, initial concentration, particle size, contact time and temperature were optimized. The maximum adsorption capacity (35.58mg g-1, 71.16%) was achieved at pH 2.0. Data fitted well to Freundlich and Halsey’s models (R2=0.992), indicating the multilayer adsorption of Cr(VI). It obeys the pseudo-second order kinetics. Endothermic and non-spontaneous nature of Cr(VI) adsorption was observed with positive values of changes in enthalpy (9.83 kJ mol-1), and Gibbs-free energy (1.52, 1.38, 1.24, 1.10 and 0.97 kJ mol-1), respectively. In this column study, the breakthrough curve time increased from 670 to 1,270min by increasing the bed height from 5 to 15 cm, respectively. Column data was found well fitted to bed depth service time model. Adsorption capacity at 60% breakthrough was 2,443.636mg L-1. The study indicates that ECS waste can be a promising adsorbent for Cr(VI) remediation from industrial effluents.

Binding Strength of Porphyrin−Gold Nanoparticle Hybrids Based on Number and Type of Linker Moieties and a Simple Method To Calculate Inner Filter Effects of Gold Nanoparticles Using Fluorescence Spectroscopy

Gold nanoparticle-porphyrin assemblies were formed by binding functionalized porphyrins to gold nanoparticles (Au-NPs). Spectroscopic properties of hybrids and binding strength of porphyrins to Au-NPs were observed based on number and type of linker moieties using fluorescence spectroscopy. Binding appears to be dependent on number rather than type of linker moieties present on the porphyrin molecules, as tetraaminophenyl porphyrin shows the highest binding among the molecules we studied and causes agglomeration of nanoparticles due to presence of four linker groups. The inner filter effects of Au-NPs are considerably high due to their high extinction coefficient and cause large errors in the evaluation of quenching efficiencies. We have described a very simple method to calculate the inner filter effects of Au-NPs by first loading them with porphyrins and then replacing them with nonfluorescent ligands. The difference in the fluorescence of unbound porphyrins in the presence and absence of Au-NPs describes their inner filter effects.

Fabrication of vertically aligned CNT composite for membrane applications using chemical vapor deposition through in situ polymerization

We report the fabrication of vertically aligned carbon nanotubes (CNT) composite using thermal chemical vapor deposition (CVD). A forest of vertically aligned CNTs was grown using catalytic CVD. Fluorocarbon polymer, films were deposited in the spaces between vertically aligned MWCNTs using thermal CVD apparatus developed in-house. The excessive polymer top layer was etched by exposing the sample to water plasma. Infrared spectroscopy confirmed the attachment of functional groups to CNTs. Alignment of CNTs, deposition of polymer and postetched specimens were analyzed by field emission scanning electron microscope (FESEM). Uniform distribution of monomodel vertically aligned CNTs embedded in the deposited polymer matrix was observed in the micrograph. Observed uniform distribution otherwise is not possible using conventional techniques such as spin coating.

Composite electrolyte with proton conductivity for low-temperature solid oxide fuel cell

In the present work, cost-effective nanocomposite electrolyte (Ba-SDC) oxide is developed for efficient low-temperature solid oxide fuel cells (LTSOFCs). Analysis has shown that dual phase conduction of O−2 (oxygen ions) and H+ (protons) plays a significant role in the development of advanced LTSOFCs. Comparatively high proton ion conductivity (0.19 s/cm) for LTSOFCs was achieved at low temperature (460 °C). In this article, the ionic conduction behaviour of LTSOFCs is explained by carrying out electrochemical impedance spectroscopy measurements. Further, the phase and structure analysis are investigated by X-ray diffraction and scanning electron microscopy techniques. Finally, we achieved an ionic transport number of the composite electrolyte for LTSOFCs as high as 0.95 and energy and power density of 90% and 550 mW/cm2, respectively, after sintering the composite electrolyte at 800 °C for 4 h, which is promising. Our current effort toward the development of an efficient, green, low-temperature solid oxi...

In situ formation of copper nanoparticles in a p(NIPAM-VAA-AAm) terpolymer microgel that retains the swelling behavior of microgels

Abstract Copper nanoparticles (CuNPs) are formed inside a microgel assembly by an in situ reduction method, confirmed by changes observed in the absorption spectra of CuNPs at different pH values. The presence of CuNPs has been also confirmed by X-ray diffraction (XRD) studies. The terpolymer microgel p(N-isopropylacrylamide-vinyl acetic acid-acrylamide) (p[NIPAM-VAA-AAm]), which is reported for the first time, was synthesized by free radical emulsion polymerization of a temperature-sensitive NIPAM monomer, pH sensitive VAA monomer and a hydrophilic AAm monomer. The effect of temperature below and above the pKa of VAA and the effect of pH at 20°C in the absence and presence of CuNPs on the hydrodynamic radius of microgel was studied. Size of microgel particles is a function of temperature due to the presence of NIPAM, and a function of pH due to the presence of VAA. The presence of CuNPs has little or no effect on the size of microgels by varying pH, which allows these gels to retain their properties with added benefits of CuNPs for possible drug delivery applications.

Ciprofloxacin: from infection therapy to molecular imaging

Diagnosis of deep-seated bacterial infection remains a serious medical challenge. The situation is becoming more severe with the increasing prevalence of bacteria that are resistant to multiple antibiotic classes. Early efforts to develop imaging agents for infection, such as technetium-99m (99mTc) labeled leukocytes, were encouraging, but they failed to differentiate between bacterial infection and sterile inflammation. Other diagnostic techniques, such as ultrasonography, magnetic resonance imaging, and computed tomography, also fail to distinguish between bacterial infection and sterile inflammation. In an attempt to bypass these problems, the potent, broad-spectrum antibiotic ciprofloxacin was labeled with 99mTc to image bacterial infection. Initial results were encouraging, but excitement declined when controversial results were reported. Subsequent radiolabeling of ciprofloxacin with 99mTc using tricarbonyl and nitrido core, fluorine and rhenium couldn’t produce robust infection imaging agent and remained in discussion. The issue of developing a robust probe can be approached by reviewing the broad-spectrum activity of ciprofloxacin, labeling strategies, potential for imaging infection, and structure–activity (specificity) relationships. In this review we discuss ways to accelerate efforts to improve the specificity of ciprofloxacin-based imaging.

Bioinspired superhydrophilic-hydrophobic integrated surface with conical pattern-shape for self-driven fog collection

It is well recognized by the scientific community that the fog can be deposited and transported on asymmetric surfaces, thus numerous efforts have been made to create such surfaces. However, it is still challenging to design a surface capable of fast deposition and rapid transportation simultaneously. Herein, inspired by the asymmetric structure of cactus spines and the cooperative hydrophilic/hydrophobic regions of desert beetles, a superhydrophilic-hydrophobic integrated conical stainless steel needle (SHCSN) is fabricated by a facile method. This integrated needle surface combines the merits of the fast deposition of fog on hydrophobic region and then rapid transportation on superhydrophilic surface. The droplet average transportation velocity on SHCSN is greater than other types of surfaces because of large Laplace pressure and self-driven phenomenon at its superhydrophilic-hydrophobic boundary. The best fog harvest efficiency was realized by optimizing the length of the hydrophobic region using theoretical modeling and experimental exploration, whereas the robust superhydrophilic needle surface induced the increase of collection time. This SHCSN was realized to be more efficient in fog collection than uniform superhydrophilic, uniform hydrophobic/superhydrophobic needle surfaces.

Technetium-99m radiolabeling and biological study of epirubicin for in vivo imaging of multi-drug resistant Staphylococcus aureus infection via single-photon emission computed tomography

The development of functional imaging is a promising strategy for diagnosis and treatment of infectious and cancerous diseases. In this study, epirubicin was developed as a [99mTc]‐labeled radiopharmaceutical for the imaging of multi‐drug‐resistant Staphylococcus aureus infections. The labeling was carried out using sodium pertechnetate (Na99mTcO4; ~370 MBq). The other parameters such as amount of ligand, reducing agent (SnCl2.2H2O), and pH were optimized. The highest labeling yield ≥96.98% was achieved when 0.3 mg epirubicin, 13 μg SnCl2.2H2O, and ~370 MBq Na99mTcO4 were incubated at pH 7 for 15 min in the presence of ascorbic acid at room temperature. Radiochemical purity, stability, charge, and glomerular filtration rate were studied to evaluate the biological compatibility for in vivo administration. Biodistribution investigations showed radiotracer uptake (13.89 ± 1.56% ID/gm organ) by liver and 7.79 ± 0.38% ID/gm organ by kidneys at 30 min post‐injection which promisingly wash out at 24 hr post‐injection. Scintigraphy study showed selective uptake in S. aureus‐infected tissues in contrast to turpentine oil‐induced inflamed tissues. Target‐to‐non‐target ratio (6.7 ± 0.05) was calculated at 1 hr post‐injection using SPECT gamma camera. The results of this study reveal that the [99mTc]‐epirubicin can be a choice of imaging and monitoring the treatment process of multi‐drug resistant S. aureus bacterial infections.