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Superparamagnetism has been widely used for many biomedical applications, such as early detection of inflammatory cancer and diabetes, magnetic resonance imaging (MRI), hyperthermia, etc., whereas incorporation of superparamagnetism in stimulus-responsive hydrogels has now gained substantial interest and attention for application in these fields. Recently, pH-responsive superparamagnetic hydrogels showing the potential use in disease diagnosis, biosensors, polymeric drug carriers, and implantable devices, have been developed based on the fact that pH is an important environmental factor in the body and some disease states manifest themselves by a change in the pH value. However, improvement in pH sensitivity of magnetic hydrogels is a dire need for their practical applications. In this study, we report the distinctly high pH sensitivity of new synthesized dual-responsive magnetic hydrogel nanocomposites, which was accomplished by copolymerization (free-radical polymerization) of two pH-sensitive monomers, acrylic acid (AA) and vinylsulfonic acid (VSA) with an optimum ratio, in the presence of presynthesized superparamagnetic iron oxide nanoparticles (Fe 3 O 4 (OH) x ). The monomers contain pH-sensitive functional groups (COO – and SO 3 – for AA and VSA, respectively), and they have also been widely used as biomaterials because of the good biocompatibility. The pH sensitivity of the superparamagnetic hydrogel, poly(acrylic acid- co -vinylsulfonic acid), PAAVSA/Fe 3 O 4 , was investigated by swelling studies at different pH values from pH 7 to 1.4. Distinct pH reversibility of the system was also demonstrated through swelling/deswelling analysis. Thermal stability, chemical configuration, magnetic response, and structural properties of the system have been explored by suitable characterization techniques. Furthermore, the study reveals a pH-responsive significant change in the overall morphology and packing fraction of iron oxide nanoparticles in PAAVSA/Fe 3 O 4 via energy-dispersive X-ray (EDX) elemental mapping with the field emission scanning electron microscopy (FESEM) study (for freeze-dried PAAVSA/Fe 3 O 4 , swelled at different pH values), implying a drastic change in susceptibility and induced saturation magnetization of the system. These important features could be easily utilized for the purpose of diagnosis using magnetic probe and/or impedance analysis techniques.

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Nanoscale ZnO, directly grown on current collector through ALD, shows high electrochemical performance as a binder-free cathode for rechargeable Al-ion batteries (AIBs). Al coin cell fabricated using binder-free ALD grown ZnO cathode (ZnO-ALD-E) manifests an initial discharge capacity of 2563 mAh g -1 , and remains at 245 mAh g -1 at a current rate of 400 mA g -1 after 50 cycles with almost 95% Coulombic efficiency. Distinct and consistent plateaus in discharge/charge curves reveal the Alion insertion/extraction process and electrochemical stability of the battery. The delivered discharge capacity of the battery with ZnO-ALD-E cathode is significantly higher (1000%) than that of batteries fabricated using a conventional ZnO cathode composed of ZnO powder (nanoparticles or bulk) and binder with conductive carbon. Ex-situ XRD and Photoluminescence spectroscopy in different discharge/charge states of Al/ZnO-ALD-E battery reveal the structural information of ZnO-ALD-E, upon Al-ion intercalation/deintercalation. Such remarkable electrochemical performance is attributed to the binder-free, well-defined textured nanostructures of ALD grown ZnO cathode with c-axis orientation along the surface normal, facilitating good electrical contact and enhanced pathways for electron/ion transfer/transport kinetics. First principle based DFT calculations explain the Al-ion intercalation phenomena in the framework of c-axis oriented ZnO. The proposed concept provides a strategy for transitioning to next-generation AIBs with a binder-free cathode.

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Oxidized porous silicon (PS) is a common topographical biocompatible substrate that potentially provides a distinct in vitro environment for better understanding of in vivo behavior. But in the reported studies on oxidized PS, cell-cell and cell-substrate interactions have been detected only by fluorescent labeling. This paper is the first attempt to investigate real-time sensing of these interactions on HaCaT cells by label-free impedance spectroscopy on oxidized PS of two pore diameters (50 and 500 nm). One of the major requirements for successful impedance spectroscopy measurement is to restrict the channeling of electric field lines through the pores. To satisfy this criterion, we have designed the pore depths after analyzing the penetration of the medium by using computational fluid dynamics simulation. A distributed electrical model was also developed for estimating the various cellular attributes by considering a pseudorandom distribution of pores. It is observed from the impedance measurements and from the model that the proliferation rate increases for 50 nm pores but decreases for 500 nm pores compared to that for planar substrates. The rate of decrease in cell substrate separation (h) in the initial stage is more than the rate of increase in cell-cell junction resistance (Rb) corresponding to the initial adhesion phase of cells. It is observed that Rb and h are higher for 50 nm pores than those for planar substrates, corresponding to the fact that substrates more conducive toward cell adhesion encourage cell-cell interactions than direct cell-substrate interactions. Thus, the impedance spectroscopy coupled with the proposed theoretical framework for PS substrates can sense and quantify the cellular interactions.