Activator-free zinc aluminate (ZA) nanophosphor was synthesized through a sol-gel combustion route, which can be used both as a blue-emitting phosphor material and a white-emitting phosphor material, depending on the annealing temperature during synthesis. The material also has the potential to be used in optical thermometry. These fascinating color-tunable emission characteristics can be linked with the various defect centers present inside the matrix and their changes upon thermal annealing. Various defect centers, such as anionic vacancy, cationic vacancy, antisite defect, etc., create different electronic states inside the band gap, which are responsible for the multicolor emission. The color components are isolated from the complex emission spectra using time-resolved emission spectroscopy (TRES) study. Interestingly, the lifetime values of the various defect centers were found to change significantly from milliseconds to microseconds upon thermal annealing, which makes the phosphors more diverse (i.e., either long-persistent blue-emitting phosphors or short-persistent white-emitting phosphors). Fourier transform infrared (FTIR) and diffuse reflectance spectroscopy (DRS) confirmed the presence of antisite defect centers such as Al or Zn in the matrix. X-ray absorption fine structure (EXAFS) study showed that the spinel structure was more disordered in nature for low-temperature-annealed compounds. Electron paramagnetic resonance (EPR) and positron annihilation lifetime spectroscopy (PALS) studies were also carried out in order to characterize various anionic and cationic vacancies and their clusters present in the compounds. Antisite defect centers such as Al or Zn, which act as an electron or hole trap, were found to be responsible for the diverse lifetime behavior. To gain insight about the electronic states inside the band gap, density functional theory (DFT)-based calculations were performed for both pure and various vacancy-introduced spinel structures. Finally, based on the theoretical and experimental results, for the first time, a detailed investigation of various defect-induced emission behavior in ZA is presented, which also explains the mechanism of color tunability and dynamic lifetimes.

The interpretation of low‐resistivity anomalies in the lithospheric mantle of several cratonic regions has invoked hydrogen, or connected networks of graphite with iron‐rich silicates, and/or metal sulfides. Electrical laboratory measurements are a powerful approach for exploring these alternatives. We report electrical measurements of two xenoliths (pyroxenite and dunite) from Tanzania; two metal sulfides (FeS and Fe‐S‐Ni); and several mixtures of metal sulfides (3.4–18.2 vol.%) with xenolith. A multi‐anvil press was employed to maintain a 2 GPa pressure and temperatures up to 1,627 K. The addition of 3.4 vol.% FeS to the pyroxenite or dunite matrix has little effect on bulk resistivity, particularly for T > 800 K. However, the resistivity drops dramatically–by factors of up to 1,000, depending on temperature–upon addition of 6.5 vol.% FeS in the dunite. Addition of 18.2% FeS causes a further decrease of the same magnitude relative to the 6.5% sample. Scanning electron microscope images do not reveal the formation of a connected FeS network as part of the decreased resistivity. Possible explanations for the apparently conflicting results include connections of the sulfide that are not imaged in the back‐scattered images, either because of limited resolution, or perhaps the inherent limitations of the 2‐D perspective. The complete data set (xenoliths, metal sulfides, and mixtures) was modeled with a modified version of Archie's law, and we find satisfactory agreement over a truncated temperature range. We conclude that the low‐resistivity anomalies in Tanzania, Kaapvaal, and Gawler cratons can be explained by the presence of a few vol.% of solid sulfide.

High energy density, flexible supercapacitors typically use various carbon allotropes and 2-dimensional metals as the electrode material. As an alternative, here we report, fully printed, bendable and high-capacity micro-supercapacitors (MSCs)...

The development of a novel, molecularly imprinted polymer (MIP), based on polyaniline nanofibers (PANInfs) for the electrochemical detection of aldicarb (Ald), is reported. PANInfs are synthesized by the simple interfacial polymerization method with and without the presence of Ald. A part of the PANInfs containing Ald (MIP‐Ald) is dispersed in deionized (DI) water and sonicated to remove Ald and obtain MIP. The MIP, bare PANInfs (non‐imprinted polymer or [NIP]), and the nonsonicated polymer (MIP‐Ald) are separately drop cast onto hydrolyzed indium tin oxide (ITO)‐coated glass. All these three types of electrodes are characterized by Fourier transform infrared spectroscopy, Raman spectroscopy, scanning electron microscopy, and cyclic voltammetry (CV) techniques to understand their structure, morphology, and successful synthesis of the desired compounds. The electrochemical detection of Ald is conducted using differential pulse voltammetry (DPV). This MIP‐based sensor is able to detect Ald in the range of 50–80 nM with a limit of detection 500 pM L−1, having a sensitivity of 6.83 ± 0.09 μA nM−1 cm−2, making it an ideal candidate for Ald detection. This method is adapted to synthesize MIPs of other pesticides by which the cost and the detection time is reduced considerably.

Abstract-Dynamic changes can present significant challenges for visually impaired travelers to safely and independently navigate urban environments. To address these challenges, we are developing the NavPal suite of technology tools [1]. NavPal includes a dynamic guidance tool [2] in the form of a smartphone app that can provide real-time instructions based on available map information to guide navigation in indoor environments. In this paper we enhance our past work by introducing a framework for blind travelers to add map/navigation information to the tool, and to invite trusted sources to do the same. The user input is realized through audio breadcrumb annotations that could be useful for future trips. The trusted sources mechanism provides invited trusted individuals or organizations an interface to contribute real-time information about the surrounding environment. We demonstrate the feasibility of our solution through a prototype Android smartphone-based outdoor navigation aid for blind travelers. An initial usability study with visually impaired adults informed the design and implementation of this prototype.