The Internet of Things (IoT) is a revolutionizing technology which aims to create an ecosystem of connected objects and embedded devices and provide ubiquitous connectivity between trillions of not only smart devices but also simple sensors and actuators. Although recent advancements in miniaturization of devices with higher computational capabilities and ultra-low power communication technologies have enabled the vast deployment of sensors and actuators everywhere, such an evolution calls for fundamental changes in hardware design, software, network architecture, data analytics, data storage, and power sources. A large portion of the IoT devices cannot be powered by batteries only anymore, as they will be installed in hard to reach areas and regular battery replacement and maintenance are infeasible. A viable solution is to scavenge and harvest energy from the environment and then provide enough energy to the devices to perform their operations. This will significantly increase the device life time and eliminate the need for the battery as an energy source. This survey aims at providing a comprehensive study on energy harvesting techniques as alternative and promising solutions to power the IoT devices. We present the main design challenges of the IoT devices in terms of energy and power and provide design considerations for a successful implementation of self-powered the IoT devices. We then specifically focus on piezoelectric energy harvesting as one of the most promising solutions to power the IoT devices and present the main challenges and research directions. We also shed lights on the hybrid energy harvesting for the IoT and security challenges of energy harvesting enabled the IoT systems.

Spinel ferrite MFe₂O₄ (M = Cu, Ca, Mg, Ni, etc.) nanoparticles and their composites are a new promising materialbecause they have shown great interest in the field of sensing, optoelectronics, catalysis, and solar cells due to their unique physical and chemical properties that differ from their bulk structures. Today, lots of CuFe₂O₄ nanomaterials have been synthesized by different methods, such as hydrothermal route and sol-gel combustion methods. Nevertheless, there are hardly any results about photocatalytic activity. For this reason, we tried to increase optical properties by preparing a composite of CuFe₂O₄ nanomaterials with other oxides. In this paper, a CuFe₂O₄@CuO magnetic composite was synthesized via an ultrasound method. The samples prepared were characterized by X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), diffuse reflectance spectrpscopy (DRS), field emission scanning electron microscopy (FESEM) images, vibrating sample magnetometer (VSM), and elemental analysis (energy-dispersive X-ray (EDX)). The catalytic activity of as-synthesized CuFe₂O₄@CuO was evaluated using the degradation of methylene blue. Furthermore, a possible reaction mechanism was discussed. Finally, the catalyst was used for effective degradation of methylene blue (MB) in its solution, which indicated a potential for practical applications in water pollutant removal and environmental remediation.

Research problem: The demand for polymeric materials is increasing day by day, provided that they have excellent virtues to meet desired needs. The best way to obtain high-quality polymeric materials was surface treatment in multiple methods. All the methods that have been used were expensive, multi-stage, harmful to the environment, and other shortages. Therefore, we sought in our paper to invent and develop a surface metallization protocol under green and safe conditions, based on integrating two safe methods for preparing nanomaterials (electrospinning/ultrasound) in one-pot. Aim of this work: The main objective of this work is to answer a question that has been neglected in other papers: how does in-situ metallization affect the crystalline behavior of the semi-crystalline phase of the PAN matrix depending on different amounts of MA NPs and their synergy for the rest of the properties (morphological and structural) is presented, in first degree. In the second degree, an explanation of the synergy mechanism between the mechanical/hydrophilic properties and the modified structural properties of metalized fibers has explained. Results: Here, an unaccustomed and green methodology to metalize the polyacrylonitrile, PAN, surface is reported with the intention of fashioning of a stable fibrous structure and the best specifications. The in-situ metallization process is essentially based on a loading of various amount of silver nanoparticles, as MA NPs “MA NPs”, (1 wt%, 4 wt%, 7 wt% and 10 wt%), which prepared by ultrasound irradiation assisted with a little amount of a reducer system (hydrazine/NaOH), on the PAN surface. The physiochemical characterization of as-synthesized fibrous samples was consisted of two parts: (i) characterization of sample nature (utilizing of XRD and UV-Vis. techniques), (ii) the chemical structure/morphological characterization (utilizing FESEM, TEM and AFM techniques) with performing all relevant measurements. From crystalline and UV-Vis. assessments, the observed shift in the diffraction peaks towards lower angles and slight shifts in the absorption bands of PAN _{(1 0 0)} in the 1AgPAN and 4AgPAN samples, containing smaller-sized nanoparticles, are overt results of an improvement in the crystalline traits of the parent matrix. The FT-IR data revealed the intensification and overlapping of the IR-bands “C= N, C≡ N, N-H, C=O and O-H” without band shifting for fibrous samples with low content of MA NPs (1AgPAN and 4AgPAN samples). The intercalation of the MA NPs between the chains of the molecular matrix and the strong interconnection/hydrogen bonds between both components explain not only the change of the crystalline properties of the crystalline matrix but also the homogeneous distribution and creation of a stable layer of the MA NPs on the 0AgPAN surface, confirmed by the FESEM and TEM images. The results of the study of mechanical properties showed that the loading of small spherical particles onto the polymeric matric, in particular 1AgPAN and 4AgPAN samples, was positively reflected on the improvement of the mechanical performances and the related values, not in the 7AgPAN and 10AgPAN samples. Because the MA NPs have a hydrophobic character, loading them onto the bare polymeric fiber surface made the metalized fibers a stronger hydrophobic than that of hydrophilic character, which is consistent with differences in surface roughness (increasing Ra values). The main focus of this paper was to study the synergy of structural properties with each other. So, the results of the synergistic relationship study showed that the low amount of the MA NPs led to a comprehensive and positive correlation between all structural properties and in turn affected the mechanical properties-hydrophobic/hydrophilic properties. Noting that the fibers of the 1AgPAN and 4AgPAN samples had the best structural stability, compared to the fibers of the 0AgPAN, 7AgPAN and 10AgPAN samples, when they were: decreasing in Z value, increasing fiber diameter/particle size “P.S.”, increasing RCR and C.D. values and decreasing D.D, alteration in values obtained of the mechanical behavior and the increasing of contact angle “CA” values for water “H₂O” droplets and decreasing for ethylene glycol “EG”. As a final result, the changes observed in the aforementioned measurements were reasonably regular and gradual for fibers with low MA NPs content, while the same measurements were significantly deteriorated in the case of fibers with higher MA NPs contents.

In recent years, the many alluring methods to prepare inorganic-organic hybrid nanomaterials have garnered great interest. The in-situ growth phenomenon is the most straightforward way to form these compounds with multiply dimensions. Here in, we demonstrate the in-situ synthesis of noble metal nanoparticles-polyacrylonitrile nanofibers (M NPs-PAN NFs) using an electrospinning route. Synthesis includes two main paths in the presence of dimethyl formamide (DMF). In the first path, the M NPs were prepared from the precursor solution using an in-situ reduction route in the presence of ultrasound irradiation and DMF (as a solvent and weak reducing agent) at 60 °C for nine min. The mechanism of our second path exhibited that the polymer matrix solution (PAN/DMF) acts as an appropriate host solution for the MNPs, due to possessing a high contents of effectiveness groups. These groups not only anchor NM NPs tightly in PAN fibers via dipole-induced dipole interactions but also they stabilize metal nanoparticles by good bonding interaction with their surface atoms. After preparing all nanofibers, TEM images revealed that both M NPs and their related nanofibers have a particular and unique shape without agglomerated particles with different sizes. Field emission scanning electron microscopy (FESEM), x-ray diffraction (XRD), energy-dispersive x-ray spectroscopy (EDS), and Fourier-transform infrared (FT-IR) were also applied to verify the formation of all samples. In this report, we tried to present a preparative synthesis strategy to the preparation of nanofibers.

Sustainable chemistry concepts are illuminating the path for researchers to utilize tree branches in the cellulose synthesis, preparation/, or fabrication processes. This represents a revolutionary solution that links waste management with the transition to a green economy, aiming to reduce harmful carbon emissions resulting from burning and replace them with bio-based materials for important environmental remediation. The central objective of this research was to isolate the cellulose-based structure in nano-size from three sources of shrub and tree stems: bougainvillea, fig, and pine, using an alkaline method followed by bleaching with hydrogen peroxide. The nanocellulose samples (N-Cell.bo., N-Cell.fi., N-Cell.pi.) were physicochemically characterized using XRD, FTIR, and FESEM to confirm the isolation of the cellulose phase and the absence of accompanying impurities. Physicochemical characterization revealed that the nanocellulose samples have diverse morphologies—ranging from extended fibers to folded sheets—and have semi-crystalline structures with appropriate crystalline sizes, and are rich in functional groups of sugar units. The ability of the (N-Cell.bo, N-Cell.fi., N-Cell.pi.) samples to remove aflatoxin B1 and Allura Red Ac was studied in both alkaline (pH 8 and10) and acidic media (pH 4 and 6). The removal study demonstrated very good removal efficiency, depending on the type of pollutant and the medium. A kinetic study of two pollutants at various concentrations (3, 9 and 12 ppm) showed that the removal reactions were attribute to a first-order kinetic model. This study provides a promising future perspective for applying the rich potential of plants in environmental science.