A novel green synthesis of MnO2-Coal composite for rapid removal of silver and lead from wastewater.

The presence of Ag(I) and Pb(II) ions in wastewater poses a significant threat to human health in contemporary times. This study aims to explore the development of a novel and economical adsorbent by grafting MnO2 particles onto low-rank coal, providing an innovative solution for the remediation of water contaminated with silver and lead. The synthesized nanocomposites, referred to as MnO2-Coal, underwent thorough characterization using FTIR, XRD, BET, and SEM to highlight the feasibility of in-situ surface modification of coal with MnO2 nanoparticles. The adsorption of Ag(I) and Pb(II) from their respective aqueous solution onto MnO2-Coal was systematically investigated, with optimization of key parameters such as pH, temperature, initial concentration, contact time, ionic strength, and competing ions. Remarkably adsorption equilibrium was achieved within a 10 min, resulting in impressive removal rates of 80-90 % for both Ag(I) and Pb(II) at pH 6. The experimental data were evaluated using Langmuir, Freundlich, and Temkin isotherm models. The Langmuir isotherm model proved to be more accurate in representing the adsorption of Ag(I) and Pb(II) ions onto MnO2-Coal, exhibiting high regression coefficients (R2 = 0.99) and maximum adsorption capacities of 93.57 and 61.98 mg/g, along with partition coefficients of 4.53 and 71.92 L/g for Ag(I) and Pb(II), respectively, at 293 K. Kinetic assessments employing PFO, PSO, Elovich, and IPD models indicated that the PFO and PSO models were most suitable for adsorption mechanism of Pb(II) and Ag(I) on MnO2-Coal composites, respectively. Moreover, thermodynamic evaluation revealed the spontaneous and endothermic adsorption process for Ag(I), while exothermic behavior for adsorption of Pb(II). Importantly, this approach not only demonstrates cost-effectiveness but also environmental friendliness in treating heavy metal-contamination in water. The research suggests the potential of MnO2-Coal composites as efficient and sustainable adsorbents for water purification applications.

Analog monolayer SWCNTs-based memristive 2D structure for energy-efficient deep learning in spiking neural networks.

Advances in materials science and memory devices work in tandem for the evolution of Artificial Intelligence systems. Energy-efficient computation is the ultimate goal of emerging memristor technology, in which the storage and computation can be done in the same memory crossbar. In this work, an analog memristor device is fabricated utilizing the unique characteristics of single-wall carbon nanotubes (SWCNTs) to act as the switching medium of the device. Via the planar structure, the memristor device exhibits analog switching ability with high state stability. The device's conductance and capacitance can be tuned simultaneously, increasing the device's potential and broadening its applications' horizons. The multi-state storage capability and long-term memory are the key factors that make the device a promising candidate for bio-inspired computing applications. As a demonstrator, the fabricated memristor is deployed in spiking neural networks (SNN) to exploit its analog switching feature for energy-efficient classification operation. Results reveal that the computation-in-memory implementation performs Vector Matrix Multiplication with 95% inference accuracy and few femtojoules per spike energy efficiency. The memristor device presented in this work opens new insights towards utilizing the outstanding features of SWCNTs for efficient analog computation in deep learning systems.

MXene/AgNW composite material for selective and efficient removal of radioactive cesium and iodine from water.

Toxic fission products, such as cesium (137Cs) and iodine (129I) are of great concern because of their long half-lives and high solubility in water. The simultaneous removal of Cs and I using a single adsorbent is an area of increasing interest. In this study, MXene/silver nanowire (AgNW) composite was synthesized through physical mixing and employed for simultaneous removal of iodide (I-) and cesium (Cs+) ions from contaminated water. The MXene/AgNW composite demonstrated excellent adsorption capacities of 84.70 and 26.22 mg/g for I- and Cs+, respectively. The experimental data supported the hypothesis of multilayer adsorption of Cs+ owing to the inter-lamellar structures and the presence of heterogeneous adsorption sites in MXene. The interaction between I- and the AgNW involved chemisorption followed by monolayer adsorption. MXene/AgNW composite material exhibited promising results in the presence of competitive ions under extreme pH conditions. Thus, synthesized composite materials holds promising potential as an adsorbent for the remediation of radioactive liquid waste.

An Automated Wireless System for Monitoring Concrete Structures Based on Embedded Electrical Resistivity Sensors: Data Transmission and Effects on Concrete Properties.

Modern infrastructure heavily relies on robust concrete structures, underscoring the critical need for effective monitoring to ensure their safety and durability. This paper addresses this imperative issue by introducing an innovative automated and wireless system for continuous structural monitoring. By employing embedded electrical resistivity sensors coupled with a wireless-based data transmission mechanism, real-time data collection becomes feasible. We provide a general description of the system's architecture and its application in a pilot study covering the effects of the devices on concrete properties and data transmission. The dielectric properties of concrete specimens were investigated under natural and accelerated curing/degradation and the results were used in the final design of the antenna device. Furthermore, a pilot test comprising four reinforced concrete columns was used to investigate the range of data transmission from inside to outside of the concrete, the effects of the hardware device on the compressive strength and concrete distribution in the columns, and the data transmission quality in real time under realistic exposure conditions.

Electric Field-Driven Self-Assembly of Gold Nanoparticle Monolayers on Silicon Substrates.

Nanoparticles (NPs) bridge the gap between bulk materials and their equivalent molecular/atomic counterparts. The physical, optical, and electronic properties of individual NPs alter with the changes in their surrounding environment at the nanoscale. Similarly, the characteristics of thin films of NPs depend on their lateral and volumetric densities. Thus, attaining single monolayers of these NPs would play a vital role in the improved characteristics of semiconductor devices such as nanosensors, field effect transistors, and energy harvesting devices. Developing nanosensors, for instance, requires precise methods to fabricate a monolayer of NPs on selected substrates for sensing and other applications. Herein, we developed a physical fabrication method to form a monolayer of NPs on a planar silicon surface by creating an electric field of intensity 5.71 × 104 V/m between parallel plates of a capacitor, by applying a DC voltage. The physics of monolayer formation caused by an externally applied electric field on the gold NPs (Au-NPs) of size 20 nm in diameter and possesses a zeta potential of -250 to -290 mV, is further analyzed with the help of the finite element simulation. The enhanced electric field, in the order of 108 V/m, around the Au-NPs indicates a high surface charge density on the NPs, which results in a high electric force per unit area that guides them to settle uniformly on the surface of the silicon substrate.

Physical probing of quantum energy levels in a single indium arsenide (InAs) quantum dot.

Indium arsenide (InAs) quantum dots (QDs) grown by molecular beam epitaxy (EBM) on gallium arsenide (GaAs) substrates have exhibited quantized charge-trapping characteristics. An electric charge can be injected in a single QD by a gold-coated AFM nano-probe placed directly on it using a conductive-mode atomic force microscope (C-AFM). The results revealed separate current-voltage (I-V) curves during consecutive measurements, where the turn-on voltages measured at the subsequent voltage sweeps are incrementally lower than that at the initial sweep. We demonstrate that the charge state of the QD can change over a long enough time by measuring the I-V data on the same QD at different time intervals. Discrete energy states (here, five states) have been observed due to the quantized charge leakage from the QD into the surrounding materials. These quantum states with five energy levels have been verified using quantum theory analysis of the quantum-well with the help of a numerical simulation model, which depends on the QD dimensions. The size of the quantum-well in the model is in good agreement with the actual QD size, whose lateral dimension is confirmed using a scanning electron microscope. At the same time, the height is estimated from the atomic force microscope topography.

Application of Cost Effective and Real-Time Resistivity Sensor to Study Early Age Concrete.

Concrete is a widely used construction material, demanding strict quality control to maintain its integrity. The durability and lifespan of concrete structures rely heavily, amongst other factors, on the characteristics of fresh and early age concrete, which are strongly dependent on the curing process. To ensure long-term durability, it is crucial to assess concrete properties throughout construction and verify compliance with design specifications. Currently, electrical resistivity-based sensors are available and used for quality control and monitoring, however, these sensors tend to be costly or only measure at a single location within the concrete cover. This study introduces a printed circuit board (PCB)-based array of electrodes capable of measuring concrete resistivity profiles across the concrete cover, from its fresh state to early age development. In this work, the feasibility of such resistivity PCB-sensors, novel for concrete, is evaluated under laboratory conditions. The sensors exhibit a promising performance in monitoring the efficiency of concrete curing under various conditions. Additionally, they successfully evaluate the effectiveness of internal curing (in our study, promoted by superabsorbent polymers) during the initial stages of hardening. This sensor array provides a valuable tool for monitoring the curing of concrete at early age, and showcases a preliminary solution that could be further developed to ensure long-term performance of concrete infrastructure.

Chicken skin based Milli Watt range biocompatible triboelectric nanogenerator for biomechanical energy harvesting.

This work reports a high-performance, low-cost, biocompatible triboelectric nanogenerator (TENG) using chicken skin (CS). The device is suitable to power wearable devices, which is critical to adapt electronics in monitoring, predicting, and treating people. It also supports sustainability by providing a cost-effective way to reduce the poultry industry's waste. It has been shown here that CS-derived biowaste is an effective means of generating tribopositive material for TENGs. The CS contains amino acid functional groups based on (Glycine, Proline, and Hydroxyproline), which are essential to demonstrate the electron-donating ability of collagen. The skin was cut into 3 × 3 cm2 and used as the raw material for fabricating the TENG device with a stacking sequence of Al/Kapton/spacing/CS/Al. The chicken skin-based TENG (CS-TENG) is characterized at different frequencies (4-14 HZ) using a damping system. The CS-TENG produces an open-circuit voltage of 123 V, short-circuit current of 20 µA and 0.2 mW/cm2 of a power density at 20 MΩ. The biocompatible CS-TENG presents ultra-robust and stable endurance performance with more than 52,000 cycles. The CS-TENG is impressively capable of scavenging energy to light up to 55 commercial light-emitting diodes (LEDs), a calculator, and to measure the physiological motions of the human body. CS-TENG is a step toward sustainable, battery-less devices or augmented energy sources, especially when using traditional power sources, such as in wearable devices, remote locations, or mobile applications is not practical or cost-effective.

Synthesis of Graphene Oxide from Sugarcane Dry Leaves by Two-Stage Pyrolysis.

Natural or synthetic graphite as precursors for the preparation of graphene oxide (GO) have constraints due to their limited availability, high reaction temperature for processing of synthetic graphite and higher generation cost. The use of oxidants, long reaction duration, the generation of toxic gases and residues of inorganic salts, the degree of hazard and low yield are some of the disadvantages of the oxidative-exfoliation methods. Under these circumstances, biomass waste usage as a precursor is a viable alternative. The conversion of biomass into GO by the pyrolysis method is ecofriendly with diverse applications, which partially overcomes the waste disposal problem encountered by the existing methods. In this study, graphene oxide (GO) is prepared from dry leaves of sugarcane plant through a two-step pyrolysis method using ferric (III) citrate as a catalyst, followed by treatment with conc. H2SO4. The synthesized GO is analyzed by UV-Vis., FTIR, XRD, SEM, TEM, EDS and Raman spectroscopy. The synthesized GO has many oxygen-containing functional groups (-OH, C-OH, COOH, C-O). It shows a sheet-like structure with a crystalline size of 10.08 nm. The GO has a graphitic structure due to the Raman shift of G (1339 cm-1) and D (1591 cm-1) bands. The prepared GO has multilayers due to the ratio of 0.92 between ID and IG. The weight ratios between carbon and oxygen are examined by SEM-EDS and TEM-EDS and found to be 3.35 and 38.11. This study reveals that the conversion of sugarcane dry leaves into the high-value-added material GO becomes realistic and feasible and thus reduces the production cost of GO.

Development of low-cost bacterial cellulose-pomegranate peel extract-based antibacterial composite for potential biomedical applications.

This study was aimed to develop low-cost bacterial cellulose (BC)-based antibacterial composite with pomegranate (Punica granatum L.) peel extract (PGPE) for potential biomedical applications. BC was cost-effectively produced by utilizing food wastes, and PGPE was ex situ impregnated into its hydrogel. Field-emission scanning electron microscopic (FE-SEM) observation showed a nanofibrous and microporous morphology of pristine BC and confirmed the development of BC-PGPE composite. Fourier transform infrared (FTIR) spectroscopy indicated the chemical interaction of PGPE with BC nanofibers. BC-PGPE composite held 97 % water of its dry weight and retained it for more than 48 h. The BC-PGPE composite exhibited better reswelling capabilities than pristine BC after three consecutive re-wetting cycles. The antibacterial activity of the BC-PGPE composite was determined via minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), disc diffusion, and plate count methods. The PGPE extract showed good antimicrobial activity against Staphylococcus aureus (Gram-positive) and Escherichia coli (Gram-negative), both in the form of extract and composite with BC, with relatively better activity against the former. The BC-PGPE composite produced a 17 mm zone of inhibition against S. aureus, while no inhibition zone was formed against E. coli. Furthermore, BC-PGPE composite caused a 100 % and 50 % reduction in the growth of S. aureus and E. coli, respectively. The findings of this study indicate that BC-PGPE composite could be a promising antibacterial wound dressing material.

Memristive Switching and Density-Functional Theory Calculations in Double Nitride Insulating Layers.

In this paper, we demonstrate a device using a Ni/SiN/BN/p+-Si structure with improved performance in terms of a good ON/OFF ratio, excellent stability, and low power consumption when compared with single-layer Ni/SiN/p+-Si and Ni/BN/p+-Si devices. Its switching mechanism can be explained by trapping and de-trapping via nitride-related vacancies. We also reveal how higher nonlinearity and rectification ratio in a bilayer device is beneficial for enlarging the read margin in a cross-point array structure. In addition, we conduct a theoretical investigation for the interface charge accumulation/depletion in the SiN/BN layers that are responsible for defect creation at the interface and how this accounts for the improved switching characteristics.

A Healthcare Paradigm for Deriving Knowledge Using Online Consumers' Feedback.

Home healthcare agencies (HHCAs) provide clinical care and rehabilitation services to patients in their own homes. The organization's rules regulate several connected practitioners, doctors, and licensed skilled nurses. Frequently, it monitors a physician or licensed nurse for the facilities and keeps track of the health histories of all clients. HHCAs' quality of care is evaluated using Medicare's star ratings for in-home healthcare agencies. The advent of technology has extensively evolved our living style. Online businesses' ratings and reviews are the best representatives of organizations' trust, services, quality, and ethics. Using data mining techniques to analyze HHCAs' data can help to develop an effective framework for evaluating the finest home healthcare facilities. As a result, we developed an automated predictive framework for obtaining knowledge from patients' feedback using a combination of statistical and machine learning techniques. HHCAs' data contain twelve performance characteristics that we are the first to analyze and depict. After adequate pattern recognition, we applied binary and multi-class approaches on similar data with variations in the target class. Four prominent machine learning models were considered: SVM, Decision Tree, Random Forest, and Deep Neural Networks. In the binary class, the Deep Neural Network model presented promising performance with an accuracy of 97.37%. However, in the case of multiple class, the random forest model showed a significant outcome with an accuracy of 91.87%. Additionally, variable significance is derived from investigating each attribute's importance in predictive model building. The implications of this study can support various stakeholders, including public agencies, quality measurement, healthcare inspectors, and HHCAs, to boost their performance. Thus, the proposed framework is not only useful for putting valuable insights into action, but it can also help with decision-making.

Formation and crystallization of TiO2 nanostructures on various surfaces.

A comparative study of the synthesis of TiO2 nanorods on fluorine-doped tin oxide (FTO) glass, Si, SiO2, Si/Ta, Si/TiN, Si/TiN/Ti and Si/HFO2 substrates by hydrothermal reaction is presented. Detailed analysis on the growth of TiO2 on pre-annealed Si/TiN/Ti and HfO2 (HFO) surfaces is also given. For Si/TiN/Ti, a pre-annealing procedure led to the transformation of Ti to a TiO2 layer which acts as a seed for aligned growth of TiO2 nanorods. In contrast, Si/HFO does not provide a nucleation site for the formation of aligned nanorods. Various samples were prepared by varying the synthesis conditions, i.e. pre- and post-annealing temperatures and hydrothermal reaction time to figure out the optimum conditions which lead to unidirectional and highly aligned nanorods. X-ray diffraction, scanning electron microscopy, ultraviolet-visible spectroscopy and Raman spectroscopy were used to study structural, morphological and optical properties of synthesized samples. It is found that TiO2 nanorods exhibit a rutile phase on the Si/Ti/TiN and Si/HFO substrates, but highly oriented vertical growth of nanorods has been observed only on pre-annealed Si/TiN/Ti substrates. On the other hand, TiO2 nanorods form dandelion-like structures on Si/HFO substrates. Growth of vertically oriented TiO2 nanorods on Si/TiN/Ti is attributed to the TiO2 seed layer which forms after the process of pre-annealing of substrates at a suitable temperature. Variation in hydrothermal reaction time and post-annealing temperature brings further improvement in crystallinity and morphology of nanorods. This work shows that the pre-annealed Si/TiN/Ti substrate is the optimal choice to achieve vertically oriented, highly aligned TiO2 nanorods.

Advanced remediation of pyrene contaminated soil by double dielectric barrier discharge (DDBD) plasma and subsequent composting process.

Due to increasing industrialization, soils are increasingly contaminated by polycyclic aromatics such as pyrene and need gentle treatment to keep the soil functioning. This study applied a double dielectric barrier discharge (DDBD) plasma reactor and composting reactor to remediate pyrene-contaminated soil. The effect of peak-to-peak applied voltages on the remediation efficiency of pyrene was investigated. The experimental results illustrate that pyrene remediation efficiency increased from 43% to 85% when the peak-to-peak applied voltage was increased from 28.0 to 35.8 kV. When using the combined method of DDBD and composting, 90-99% of pyrene could be removed, while a reduction of 76.5% was achieved using only composting, indicating the superiority of the combined system. Moreover, the authors could demonstrate that DDBD plasma treatment improves humification in the post-composting process as humic acid (HA) concentrations increased to 7.7 mg/g with an applied voltage of 35.8 kV; when composting was used as the sole treatment method, only 3.4 mg/g HA were produced. The microbial activity in the DDBD plasma-treated soil peaked on the 5th day and had a 2nd rise afterwards. The authors demonstrate that the combined technology of DDBD plasma and composting is a promising method for soil remediation with persistent organic pollutants. This treatment approach improves pollutant degradation efficiency and facilitates further humification, potentially restoring the function of contaminated soil. This approach could be considered a cost-effective and green strategy for soil remediation with persistent organic pollutants.

Root Cultures, a Boon for the Production of Valuable Compounds: A Comparative Review.

Medicinal plants are an inevitable source of pharmaceutical drugs and most of the world population depends on these plants for health benefits. The increasing global demand for bioactive compounds from medicinal plants has posed a great threat to their existence due to overexploitation. Adventitious root and hairy root culture systems are an alternative approach to the conventional method for mass production of valuable compounds from medicinal plants owing to their rapid growth, biosynthetic and genetic stability. The main purpose of this review is to investigate the recent scientific research published worldwide on the application of adventitious and hairy root cultures to produce valuable compounds from medicinal plants. Furthermore, a comparison of adventitious root vs. hairy root cultures to produce valuable compounds has also been discussed. Various aspects such as medium composition, carbon source, pH, amount of macronutrients, optimization strategy, scale-up cultures, and use of biotic abiotic and nano-elicitors at various concentrations are the topic of discussion in this review. Several studies on adventitious and hairy root cultures of Polygonum multiflorum¸ Withania somnifera¸ Echinacea purpurea and Ajuga bracteosa have been discussed in detail which highlights the importance of elicitation strategies and bioreactor system, presenting commercial applications.

Tuning the Surface Wettability of Cyclic Olefin Copolymer by Plasma Treatment and Graphene Oxide Deposition and Reduction.

Selective altering of surface wettability in microfluidic channels provides a suitable platform for a large range of processes, such as the phase separation of multiphase systems, synthesis of reaction controlled, nanoliter sized droplet reactors, and catalyst impregnation. Herein we study the feasibility to tune the wettability of a flexible cyclic olefin copolymer (COC). Two methods were considered for enhancing the surface hydrophilicity. The first is argon/oxygen plasma treatment, where the effect of treatment duration on water contact angle and COC surface morphology and chemistry were investigated, and the second is coating COC with GO dispersions of different concentrations. For enhancing the hydrophobicity of GO-coated COC surfaces, three reduction methods were considered: chemical reduction by Hydroiodic acid (HI), thermal reduction, and photo reduction by exposure of GO-coated COC to UV light. The results show that as the GO concentration and plasma treatment duration increased, a significant decrease in contact angle was observed, which confirmed the ability to enhance the wettability of the COC surface. The increase in hydrophilicity during plasma treatment was associated with the increase in surface roughness on the treated surfaces, while the increase during GO coating was associated with introducing oxygen-containing groups on the GO-coated COC surfaces. The results also show that the different reduction methods considered can increase the contact angle and improve the hydrophobicity of a GO-coated COC surface. It was found that the significant improvement in hydrophobicity was related to the reduction of oxygen-containing groups on the GO-coated COC modified surface.

Single wall carbon nanotube based optical rectenna.

We present an optical rectenna by engineering a rectifying diode at the interface between a metal probe of an atomic force microscope (AFM) and a single wall carbon nanotube (SWCNT) that acts as a nano-antenna. Individual SWCNT electrical and optical characteristics have been investigated using a conductive AFM nano-probe in contact with two device structures, one with a SWCNT placed on a CuO/Cu substrate and the other one with a SWCNT on a SiO2/Si substrate. The I-V measurements performed for both designs have exhibited an explicit rectification behavior and the sensitivity of carbon nanotube (CNT)-based rectenna to light. The measured output current at a set voltage value demonstrates the significant effect of the light irradiation on the current signal generated between the Au nano-probe and CNT interface. This effect is more prominent in the case of the CuO/Cu substrate. Detailed analysis of the system, including the energy band diagram, materials characterization and finite element simulation, is included to explain the experimental observations. This work will pave the way for more investigations and potential applications of CNTs as nano-rectennas in optical communication and energy harvesting systems.

Nanojunction Material Effect on the Photoelectric Response of Single-Wall Carbon Nanotube Rectennas.

To optimize the performance of carbon nanotube (CNT)-based rectennas, we have studied the effect of metal work function on the photodetection characteristics. Two materials of conducting nanoprobes, namely, gold (Au) and platinum (Pt), have been used to form a rectifying diode at the interface with the CNT. The electrical and optical characteristics of single-wall carbon nanotubes (SWCNTs) dispersed on top of a SiO2/Si substrate have been investigated using a conductive mode atomic force microscope (C-AFM). The I-V measurements performed for both diodes have exhibited an explicit rectification behavior with high sensitivity of a CNT-based rectenna to light. It has been observed that the lower work function metal (Au) leads to a higher on/off current ratio than the high work function metal (Pt). These experimental observations will be explained using the material characterization of the complete system along with representative energy-band diagrams.

Author Correction: Photodetection Characteristics of Gold Coated AFM Tips and n-Silicon Substrate nano-Schottky Interfaces.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Synaptic Characteristics of Amorphous Boron Nitride-Based Memristors on a Highly Doped Silicon Substrate for Neuromorphic Engineering.

In this study, the resistive switching and synaptic properties of a complementary metal-oxide semiconductor-compatible Ti/a-BN/Si device are investigated for neuromorphic systems. A gradual change in resistance is observed in a positive SET operation in which Ti diffusion is involved in the conducting path. This operation is extremely suitable for synaptic devices in hardware-based neuromorphic systems. The isosurface charge density plots and experimental results confirm that boron vacancies can help generate a conducting path, whereas the conducting path generated by a Ti cation from interdiffusion forms is limited. A negative SET operation causes a considerable decrease in the formation energy of only boron vacancies, thereby increasing the conductivity in the low-resistance state, which may be related to RESET failure and poor endurance. The pulse transient characteristics, potentiation and depression characteristics, and good retention property of eight multilevel cells also indicate that the positive SET operation is more suitable for a synaptic device owing to the gradual modulation of conductance. Moreover, pattern recognition accuracy is examined by considering the conductance values of the measured data in the Ti/a-BN/Si device as the synaptic part of a neural network. The linear and symmetric synaptic weight update in a positive SET operation with an incremental voltage pulse scheme ensures higher pattern recognition accuracy.