Hydrophobic interpenetrating polyamide-PDMS membranes for desalination, pesticides removal and enhanced chlorine tolerance.

Hydrophobic membranes for desalination and toxic organic pollutant removal have been fabricated using polyamide - PDMS (polydimethylsiloxane) chemistries in a one-step protocol. The curing of polyamide and PDMS are orthogonal and co-curing both networks imparts hydrophobicity to the thin film composite membranes. The membranes exhibit increased adsorption of pesticides from the feed water along with maintaining excellent salt rejection capability (97% NaCl rejection), thus giving the membranes a multifunctional character. Three toxic pesticides have been used in this study to demonstrate the viability of combining osmosis desalination technology with organic matter adsorption. The membranes also show excellent resistance to fouling by toxic pesticides (85% salt rejection vs 67% for commercial membranes in the presence of pesticides) and significantly improved chlorine tolerance (93.8% salt rejection vs 86.5% for commercial membranes after 20 h of exposure to sodium hypochlorite solution).

"Shape-Coding": Morphology-Based Information System for Polymers and Composites.

Fiber-reinforced composites have become the material of choice for aerospace structures because of their favorable strength-to-weight ratio. Given the increasing amounts of counterfeit composite parts showing up in the complex aerospace supply chain, it is absolutely vital to track a composite part throughout its lifecycle-from production to usage and to disposal. Existing barcoding methods are invasive, affect the structural properties of composites, and/or are vulnerable to tampering. We describe a universal method to store information in fiber-reinforced composites based on solid-state in situ reduction leading to embedded nanoparticles with controlled morphologies. This simple, cost-effective, mild, surfactant-free, and one-step protocol for the fabrication of embedded platinum nanostructures leads to morphology-based barcodes for polymeric composites. We also describe a coding methodology wherein a 1 × 1 cm code can represent 3.4 billion parts to 95 trillion parts, depending on the resolution required along with access to morphology-based chemical encryption systems.

Density Modulation of Embedded Nanoparticles via Spatial, Temporal, and Chemical Control Elements.

Nanoparticle polymer composites have enabled material multifunctionalities that are difficult to obtain otherwise. A simple modification to a commercially available resin system enables a universal methodology to embed nanoparticles in resins via spatial, temporal, thermal, concentration, and chemical control parameters. Changes in nanoparticle density distribution are exploited to demonstrate dynamic optical and electronic properties that can be processed on-demand, without the need for expensive equipment or cleanroom facilities. This strategy provides access to the control of optical (cooperative plasmonic effects), electronic (insulator to a conductor), and chemical parameters (multimetal patterning). Using the same composite resin system, the followings are fabricated: i) diffraction gratings with tuneable diffraction efficiencies (10-78% diffraction efficiencies), ii) organic electrochemical transistors with a low drive voltage, and iii) embedded electrodes in confined spaces for potential diagnostic applications.

First Principle Study of Temperature-Dependent Magnetoresistance and Spin Filtration Effect in WS2 Nanoribbon.

An applicable use of density functional theory (DFT) along with nonequilibrium Green's function (NEGF) is done for exploring the temperature-dependent spin electron transport nature in a ferromagnetic tungsten disulfide (WS2) nanoribbon. To demonstrate the effect of temperature on spin filtration and spin Seebeck effect, we evaluated vital parameters such as spin-polarized current and spin filtration efficiency. Spin filtration efficiency of around ∼95% is obtained in the high-temperature difference range. The high temperature (TL) of the left electrode in comparison to the high temperature (TR) of the right electrode results in higher and lower spin filtration efficiency in parallel magnetization (PM) and antiparallel magnetization (APM), respectively. Transmission spectrum plots at equilibrium are also calculated in PM and APM to justify the temperature-dependent spin transport behavior in the WS2 nanoribbon. Giant thermal magnetoresistance around 1.934 × 103% is achieved. The temperature-dependent negative differential resistance behavior of the current plot has been observed. Huge value of thermal magnetoresistance (MR) and excellent spin filtration obtained for WS2 nanoribbon suggests the potential application of this material in spin caloritronic devices.

Bipolar Analog Memristive Switching of In2O3 Using Al Nanoparticles.

Aluminum nanoparticles (AlNPs) were embedded into a sol-gel synthesized In2O3 thin film by using a combination of thermal evaporation and glancing Angle Deposition technique. Presence of different sizes of aluminum nanoparticles was confirmed from field emission gun scanning electron microscopy. The high-resolution X-ray diffraction confirms the formation of Al2O3 NPs by surface oxidation of aluminum nanoparticles. Embedded Metal-Oxide-Semiconductor like device Al/In2O3/AlNPs/In2O3/p-Si was fabricated, and its memristor behavior was analyzed. The Al/In2O3/AlNPs/In2O3/p-Si device possessed high current conduction and analog resistive switching as compared to Al/In2O3/p-Si device. Significant and consistent memory window up to 150 current (I)-voltage (V) loop was obtained for Al/In2O3/AlNPs/In2O3/p-Si device between ±6 V applied bias. The Al/In2O3/AlNPs/In2O3/p-Si device measured high free carrier concentration, i.e., (Nd)~1.93 × 1020 cm-3 calculated from capacitance (C)-Voltage (V) measurement. The memory was retained in accumulation and depletion regions as obtained from the C-V looping curves.

In situ measurement of temperature dependent picosecond resolved carrier dynamics in near infrared (NIR) sensitive device on action.

The carrier dynamics study of emerging near infrared (NIR) absorbing materials is an essential need to develop device technology toward enhanced NIR light harvesting. In this study, we have documented the design of an indigenously developed time correlated single photoncounting (TCSPC) system working in the NIR (900 nm-1700 nm) spectral region. The system is compatible to study transient photoluminescence of device samples under tunable bias voltages. The liquid nitrogen cooling and electrical heating of the sample chamber provides additional flexibility of temperature dependent study starting from -196 °C to 400 °C. As a model system to study, we have chosen a multilayer InAs/InGaAs/GaAs/AlGaAs dot in the dual well device sample as the thin film quantum dot heterostructures are of huge relevance in various NIR harvesting devices. We have investigated the detail carrier dynamics of the device sample using the transient photoluminescence upon varying temperature (80 K-300 K), varying emission energy and different bias voltages (0 V-15 V). The critical temperature (160 K) and critical bias (12 V) of achieving longest excited state lifetime has been mechanistically explained using various competing photophysical phenomena such as hole diffusion, energy relaxation, etc. The emission wavelength dependent study at below and above critical temperature further provides an insight into the dominance of carrier capture and thermal escape at the two different temperature zones. Along with the detail understanding of the carrier dynamics, the results can be helpful to get an idea of the electrical stability of the device and the operability temperature as well. The reasonable good resolution of the NIR TCSPC system and considerable good results ensure the future application of the same for other devices also.

Investigation of the structural, electronic, and optical properties of Mn-doped CsPbCl3: theory and experiment.

Wide energy gap inorganic halide perovskites have become emerging candidates for potential applications in modern optoelectronics devices. However, to date, these semiconducting compounds have not been explored theoretically to a significant extent. Herein, we performed ab initio computations to explain the structural, electronic and optical behaviour of inorganic CsPbCl3 and Mn-doped CsPbCl3 nanocrystals (NCs). We also synthesized these NCs and further validated our experimental results with density functional theory (DFT) calculations. The results provide insight into the effect of Mn doping on the important properties of CsPbCl3 NCs such as their lattice parameter, electronic band structure, density of states, dielectric constant, absorption coefficient and refractive index. After geometry optimization using the Limited-memory Broyden-Fletcher-Goldfarb-Shanno (LBFGS) algorithm, a reduction in the lattice parameter from 5.605 Å to 5.574 Å was observed after doping Mn in the CsPbCl3 NCs, which is in good agreement with the calculated results from the X-ray diffraction (XRD) pattern (5.610 Å to 5.580 Å) and high-resolution transmission electron microscopy (HRTEM) images (5.603 Å to 5.575 Å). The incorporation of Mn in CsPbCl3 was observed in the electronic band structure in the form of additional states present in the energy gap and an increment in the band gap of the CsPbCl3 NCs. This result is consistent with the photoluminescence (PL) plot, which showed dual color emission in the case of the Mn-doped CsPbCl3, which is attributed to the Mn2+ d-band to d-band transition. The partial density of states (PDOS) of the Mn-doped CsPbCl3 NCs clearly indicates the contribution of the Mn 3d orbitals to the upper valence band and conduction band together with the contribution of the Pb 6p and Cl 3p orbitals. Moreover, a blue-shift phenomenon was observed from the dielectric constant and absorption coefficient spectra, which is due to the incorporation of Mn in CsPbCl3. Also, a significant peak was observed in the absorption coefficient and dielectric constant spectra around 2.08 eV, which is in good agreement with the PL plot. This DFT study with experimental observation provides a way to investigate this type of compound and to tailor its interesting characteristics through doping.

Development and validation of a noncontact spectroscopic device for hemoglobin estimation at point-of-care.

Anemia severely and adversely affects human health and socioeconomic development. Measuring hemoglobin with the minimal involvement of human and financial resources has always been challenging. We describe a translational spectroscopic technique for noncontact hemoglobin measurement at low-resource point-of-care settings in human subjects, independent of their skin color, age, and sex, by measuring the optical spectrum of the blood flowing in the vascular bed of the bulbar conjunctiva. We developed software on the LabVIEW platform for automatic data acquisition and interpretation by nonexperts. The device is calibrated by comparing the differential absorbance of light of wavelength 576 and 600 nm with the clinical hemoglobin level of the subject. Our proposed method is consistent with the results obtained using the current gold standard, the automated hematology analyzer. The proposed noncontact optical device for hemoglobin estimation is highly efficient, inexpensive, feasible, and extremely useful in low-resource point-of-care settings. The device output correlates with the different degrees of anemia with absolute and trending accuracy similar to those of widely used invasive methods. Moreover, the device can instantaneously transmit the generated report to a medical expert through e-mail, text messaging, or mobile apps.

Spin-polarized light-emitting diodes with Mn-doped InAs quantum dot nanomagnets as a spin aligner.

We have fabricated and characterized surface-emitting, spin-polarized light-emitting diodes with a Mn-doped InAs dilute magnetic quantum dot spin-injector and contact region grown by low-temperature molecular beam epitaxy, and an In(0.4)Ga(0.6)As quantum dot active region. Energy-dispersive X-ray and electron energy loss spectroscopies performed on individual dots indicate that the Mn atoms incorporate within the dots themselves. Circularly polarized light is observed up to 160 K with a maximum degree of circular polarization of 5.8% measured at 28 K, indicating high-temperature spin injection and device operation.