Superparamagnetic iron oxide nanoparticles (SPIONs, ~11-nm cores) were PEGylated without anchoring groups and studied as efficient MRI T 2 contrast agents (CAs). The ether group of PEG is efficiently and directly linked to the positively charged surface of SPIONs, and mediated through a dipole-cation covalent interaction. Anchor-free PEG-SPIONs exhibit a spin-spin relaxivity of 123 ± 6 mM−1s−1, which is higher than those of PEG-SPIONs anchored with intermediate biomolecules, iron oxide nanoworms, or Feridex. They do not induce a toxic response for Fe concentrations below 2.5 mM, as tested on four different cell lines with and without an external magnetic field. Magnetic resonance phantom imaging studies show that anchor-free PEG-SPIONs produce a significant contrast in the range of 0.1–0.4 [Fe] mM. Our findings reveal that the PEG molecules attached to the cores immobilize water molecules in large regions of ~85 nm, which would lead to blood half-life of a few tens of minutes. This piece of research represents a step forward in the development of next-generation CAs for nascent-stage cancer detection. Contrast-probed anchor-free PEGylated iron oxide contrast agent

We report our studies on the responsivity of sulfur-doped diamond films to ultraviolet radiation using two types of device configurations: the planar configuration with electrodes directly on the diamond surface, and the electron field emission configuration with a bias electrode suspended above the diamond surface. Diamond films of different grain sizes were employed: microcrystalline diamond, sub-microcrystalline diamond, and nanocrystalline diamond. The responsivity values of diamond films in the field emission configuration reached ∼10 mA/W at around 220 nm, which is ∼40% higher than that of the planar configuration. These responsivity values of diamond films are comparable to those of commercially available photodiodes in the wavelength range of 210–300 nm, but with the advantage of being solar blind. The responsivity data were correlated with the bandgap structure of sulfur-doped diamond.

Candle wax was used as a precursor for the production of a diamond-nanotube composite in a single step. The composite films were fabricated by sulfur-assisted hot-filament chemical vapor deposition technique. The morphology of the composite films was analyzed by scanning electron microscopy and transmission electron microscopy. Raman spectra of the films show characteristic diamond band at 1,332 cm⁻¹, D-band around 1,342 cm⁻¹, and graphitic G-band around 1,582 cm⁻¹. The electron energy-loss spectroscopy recorded at the carbon K-edge region shows signature features of diamond and carbon nanotube in the fabricated material. The ability to synthesize diamond-nanotube composites at relatively low temperatures by a single-step process opens up new possibilities for the fabrication of nanoelectronic devices.

Conventional T1- or T2-weighted single mode contrast-enhanced magnetic resonance imaging (MRI) may produce false results. Thereby, there is a need to develop dual contrast agents, T1- and T2-weighted, for more accurate MRI imaging. The dual contrast agents should possess high magnetic resonance (MR) relaxivities, targeted tumor linking, and minimum recognition by the immune system. We have developed nitrodopamine-PEG grafted single core truncated cubic iron oxide nanoparticles (ND-PEG-tNCIOs) capable of producing marked dual contrasts in MRI with enhanced longitudinal and transverse relaxivities of 32±1.29 and 791±38.39 mM-1s-1, respectively. Furthermore, the ND-PEG-tNCIOs show excellent colloidal stability in physiological buffers, and higher cellular internalization in cancerous cells than in phagocytic cells, indicating the immune evasive capability of the nanoparticles. These findings indicate that tNCIOs are strong candidates for dual contrast MRI imaging, which is vital for non-invasive real-time detection of nascent cancer cells in vivo and for monitoring stem cells transplants.

We demonstrate the hybrid fabrication process of a graphene integrated highly transparent resistive random-access memory (TRRAM) device. The indium tin oxide (ITO)/Al₂O₃/graphene nonvolatile memory device possesses a high transmittance of >82% in the visible region (370-700 nm) and exhibits stable and non-symmetrical bipolar switching characteristics with considerably low set and reset voltages (<±1 V). The vertical two-terminal device shows an excellent resistive switching behavior with a high on-off ratio of ∼5 × 10³. We also fabricated a ITO/Al₂O₃/Pt device and studied its switching characteristics for comparison and a better understanding of the ITO/Al₂O₃/graphene device characteristics. The conduction mechanisms in high and low resistance states were analyzed, and the observed polarity dependent resistive switching is explained based on electro-migration of oxygen ions.

We report unipolar resistive switching suitable for nonvolatile memory applications in polycrystalline BiFeO₃ thin films in planar electrode configuration with non-overlapping Set and Reset voltages, On/Off resistance ratio of ∼10⁴ and good data retention (verified for up to 3,000 s). We have also observed photovoltaic response in both high and low resistance states, where the photocurrent density was about three orders of magnitude higher in the low resistance state as compared to the high resistance state at an illumination power density of ∼100 mW/cm². Resistive switching mechanisms in both resistance states of the planar device can be explained by using the conduction filament (thermo-chemical) model.