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Thakur S.,Himachal Pradesh University | Rai R.,Himachal Pradesh University | Sharma S.,Ferroelectric Research Laboratory | Tiwari A.,Linkoping University | Tiwari A.,Tekidag AB
Advanced Materials Letters | Year: 2016

Polycrystalline samples of (K0.45Na0.45Li0.1NbO3)1-x-(Ba0.96La0.04Ti0.815Mn0.0025 Nb0.0025Zr0.18 O3)x ceramics (where x = 0.1, 0.3, 0.5, 0.7 and 0.9) were prepared by using a high temperature solid state reaction technique. The XRD patterns of the BLTMNZ doped KNLN at room temperature with x = 0.7 have pure pervoskite phase with tetragonal structure at room temperature and have maximum value of dielectric constant at x = 0.9. Detailed studies of dielectric and impedance properties of the materials in a wide range of frequency (100Hz-1MHz) and temperatures (30 - 500 °C) showed that properties are strongly temperature and frequency dependent. The plots of Z" and M" versus frequency at various temperatures show peaks in the higher temperature range (> 300 °C). The compounds show dielectric relaxation, which is found to be of non-Debye type and the relaxation frequency shifted to higher side with increase in temperature. The Nyquist plot and conductivity studies showed the NTCR character of samples. Copyright © 2016 VBRI Press.

Parlak O.,Linkoping University | Turner A.P.F.,Linkoping University | Tiwari A.,Linkoping University | Tiwari A.,Tekidag AB
Journal of Materials Chemistry B | Year: 2015

Switchable interfaces can deliver functionally reversible reactivity with their corresponding analytes, which allows one to positively respond to the activity of biological elements, including enzymes and other biomolecules, through an encoded stimulus. We have realized this by the design of stimuli-responsive graphene interfaces for the pH-encoded operation of bioelectronics. Herein, we have demonstrated stimuli-responsive graphene interfaces for the pH-encoded operation of bioelectronics. The resulting switchable interfaces are capable of the highly specific, on-demand operation of biosensors, which has significant potential in a wide range of analytical applications. © The Royal Society of Chemistry 2015.

Sharma D.,Durban University of Technology | Ashaduzzaman M.,Linkoping University | Golabi M.,Linkoping University | Shriwastav A.,Indian Institute of Technology Kanpur | And 3 more authors.
ACS Applied Materials and Interfaces | Year: 2015

Molecular imprinting generates robust, efficient, and highly mesoporous surfaces for biointeractions. Mechanistic interfacial interaction between the surface of core substrate and protein corona is crucial to understand the substantial microbial toxic responses at a nanoscale. In this study, we have focused on the mechanistic interactions between synthesized saponin imprinted zinc oxide nanohoneycombs (SIZnO NHs), average size 80-125 nm, surface area 20.27 m2/g, average pore density 0.23 pore/nm and number-average pore size 3.74 nm and proteins corona of bacteria. The produced SIZnO NHs as potential antifungal and antibacterial agents have been studied on Sclerotium rolfsii (S. rolfsii), Pythium debarynum (P. debarynum) and Escherichia coli (E. coli), Staphylococcus aureus (S. aureus), respectively. SIZnO NHs exhibited the highest antibacterial (∼50%) and antifungal (∼40%) activity against Gram-negative bacteria (E. coli) and fungus (P. debarynum), respectively at concentration of 0.1 mol. Scanning electron spectroscopy (SEM) observation showed that the ZnO NHs ruptured the cell wall of bacteria and internalized into the cell. The molecular docking studies were carried out using binding proteins present in the gram negative bacteria (lipopolysaccharide and lipocalin Blc) and gram positive bacteria (Staphylococcal Protein A, SpA). It was envisaged that the proteins present in the bacterial cell wall were found to interact and adsorb on the surface of SIZnO NHs thereby blocking the active sites of the proteins used for cell wall synthesis. The binding affinity and interaction energies were higher in the case of binding proteins present in gram negative bacteria as compared to that of gram positive bacteria. In addition, a kinetic mathematical model (KMM) was developed in MATLAB to predict the internalization in the bacterial cellular uptake of the ZnO NHs for better understanding of their controlled toxicity. The results obtained from KMM exhibited a good agreement with the experimental data. Exploration of mechanistic interactions, as well as the formation of bioconjugate of proteins and ZnO NHs would play a key role to interpret more complex biological systems in nature. © 2015 American Chemical Society.

Mishra S.,Linkoping University | Mishra S.,University of the Free State | Ashaduzzaman M.,Linkoping University | Ashaduzzaman M.,Dhaka University of Engineering and Technology | And 7 more authors.
Biosensors and Bioelectronics | Year: 2016

Graphene interfaces with multi-stimuli responsiveness are of particular interest due to their diverse super-thin interfacial behaviour, which could be well suited to operating complex physiological systems in a single miniaturised domain. In general, smart graphene interfaces switch bioelectrodes from the hydrophobic to hydrophilic state, or vice versa, upon triggering. In the present work, a stimuli encoded zipper-like graphene oxide (GrO)/polymer interface was fabricated with in situ poly(N-isopropylacrylamide-co-diethylaminoethylmethylacrylate), i.e., poly(NIPAAm-co-DEAEMA) directed hierarchical self-assembly of GrO and glucose oxidase (GOx). The designed interface exhibited reversible on/off-switching of bio-electrocatalysis on changing the pH between 5 and 8, via phase transition from super hydrophilic to hydrophobic. The study further indicated that the zipper-like interfacial bioelectrochemical properties could be tuned over a modest change of temperature (i.e., 20-40. °C). The resulting auto-switchable interface has implications for the design of novel on/off-switchable biodevices with 'in-built' self-control. © 2016 Elsevier B.V.

Kumari P.,Shoolini University of Biotechnology and Management Sciences | Rai R.,Shoolini University of Biotechnology and Management Sciences | Sharma S.,Ferroelectric Research Laboratory | Shandilya M.,Shoolini University of Biotechnology and Management Sciences | And 2 more authors.
Advanced Materials Letters | Year: 2015

Lead based piezoelectric perovskite materials are well known for their excellent piezoelectric properties, which are extensively used in industrial applications. Though, considering the toxicity of lead and its compounds, there is a general awareness for the development of environmental friendly lead-free materials as evidenced from the legislation passed by the European Union in this effect. The different class of materials is now being considered as potentially attractive alternatives to lead zirconate titanate (PZT) based perovskites for various applications. In this review, we review the progresses made on lead-free piezoelectric materials emphasizing on their synthesis, structure-property correlation, etc. Advancement of the various piezo systems such as bismuth sodium titanate, alkali niobates etc. and non-perovskites for example bismuth layer-structured ferroelectrics has been deliberated. It is found that some lead-free compositions show stable piezoelectric responses though they are not as high as the PZT system. This subject is of current interest to the ceramic researchers worldwide as evidenced from the large number of research publications and has motivated us to come out with a critical over view the field. This article would drive to the researchers to advance the piezoelectric properties of the non-lead based perovskite compounds to achieve materials at par with the PZT system. © 2015 VBRI Press.

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