Physicochemical characterization of chitin extracted by different treatment sequences from an edible insect.

Chitin present in the shell of edible insects is a potential source of chitin, lipids, and proteins, and it exerts various biological activities. Thus far, only a few studies have focused on the use of chitin as a source of high-protein-diet oligosaccharides. The use of insect chitin for the production of high-protein-diet oligosaccharides can lessen the reliance on diet crops. Moreover, although chitin composition in Tenebrio molitor larva, pupa, and adult has been extensively investigated, chitin extraction from T. molitor larval whole body and exuvium has received poor attention. The present study compared the effectiveness of two techniques for extracting high-protein-diet chitin oligosaccharide from an edible insect (T. molitor). Two different extraction sequences of chitin from the larval stage (molitor stage larvae) and adult stage (molitor stage adult) of edible T. molitor were investigated. Two processing steps were employed: (a) deproteinization (DEP) and (b) demineralization (DEM) treatments. Differences in the order, conditions, and period of their application resulted in two different chitin extraction procedures. The viscosity, degree of polymerization, and crystallinity index of the chitin extracted using the two procedures were measured, and its chemical components (chitin, ash, protein, fat, and moisture contents) were determined. T. molitor adults and larvae treated sequentially with DEM-DEP demonstrated the greatest yield of approximately 14.62 % ± 0.15 and 6.096 % ± 0.10 %, respectively. By contrast, when treated sequentially with DEP-DEM, the recorded yields were 10.96 % ± 0.18 and 5.31 % ± 0.38, respectively. Differences in the degree of deacetylation between both methods were observed. Additionally, Fourier transform infrared spectroscopy and X-ray diffractometry of the extracted chitin along with a commercial sample revealed consistent chain conformation, mean hydrogen bonding, and crystallinity index. In this way, residues produced by farmed edible insects can be recovered and used as a novel source of chitin.

Transition Metal-Catalyzed C-H Functionalization Through Electrocatalysis.

Electrochemically promoted transition metal-catalyzed C-H functionalization has emerged as a promising area of research over the last few decades. However, development in this field is still at an early stage compared to traditional functionalization reactions using chemical-based oxidizing agents. Recent reports have shown increased attention on electrochemically promoted metal-catalyzed C-H functionalization. From the standpoint of sustainability, environmental friendliness, and cost effectiveness, electrochemically promoted oxidation of a metal catalyst offers a mild, efficient, and atom-economical alternative to traditional chemical oxidants. This Review discusses advances in the field of transition metal-electrocatalyzed C-H functionalization over the past decade and describes how the unique features of electricity enable metal-catalyzed C-H functionalization in an economic and sustainable way.

Efficient Tuning of the Opto-Electronic Properties of Sol-Gel-Synthesized Al-Doped Titania Nanoparticles for Perovskite Solar Cells and Functional Textiles.

The efficient electron transport layer (ETL) plays a critical role in the performance of perovskites solar cells (PSCs). Ideally, an unobstructed network with smooth channels for electron flow is required, which is lacking in the pristine TiO2-based ETL. As a potential solution, here we tuned the structure of TiO2 via optimized heteroatom doping of Al. Different concentrations (1, 2, and 3 wt%) of Al were doped in TiO2 and were successfully applied as an ETL in PSC using spin coating. A significant difference in the structural, opto-electronic, chemical, and electrical characteristics was observed in Al-doped TiO2 structures. The opto-electronic properties revealed that Al doping shifted the absorption spectra toward the visible range. Pure titania possesses a bandgap of 3.38 eV; however, after 1, 2, and 3% Al doping, the bandgap was linearly reduced to 3.29, 3.25, and 3.18 eV, respectively. In addition, higher light transmission was observed for Al-doped TiO2, which was due to the scattering effects of the interconnected porous morphology of doped-TiO2. Al-doped titania shows higher thermal stability and a 28% lower weight loss and can be operated at higher temperatures compared to undoped titania (weight loss 30%) due to the formation of stable states after Al doping. In addition, Al-doped TiO2 showed significantly high conductivity, which provides smooth paths for electron transport. Thanks to the effective tuning of band structure and morphology of Al-doped TiO2, a significant improvement in current densities, fill factor, and efficiency was observed in PSCs. The combined effect of better Jsc and FF renders higher efficiencies in Al-doped TiO2, as 1, 2, and 3% Al-doped TiO2 showed 12.5, 14.1, and 13.6% efficiency, respectively. Compared to undoped TiO2 with an efficiency of 10.3%, the optimized 2% Al doping increased the efficiency up to 14.1%. In addition, Al-doped TiO2 also showed improvements in antibacterial effects, required for photoactive textiles.

A Tunable and Wearable Dual-Band Metamaterial Absorber Based on Polyethylene Terephthalate (PET) Substrate for Sensing Applications.

Advanced wireless communication technology claims miniaturized, reconfigurable, highly efficient, and flexible meta-devices for various applications, including conformal implementation, flexible antennas, wearable sensors, etc. Therefore, bearing these challenges in mind, a dual-band flexible metamaterial absorber (MMA) with frequency-reconfigurable characteristics is developed in this research. The geometry of the proposed MMA comprises a square patch surrounded by a square ring, which is mounted over a copper-backed flexible dielectric substrate. The top surface of the MMA is made of silver nanoparticle ink and a middle polyethylene terephthalate (PET) substrate backed by a copper groundsheet. The proposed MMA shows an absorption rate of above 99% at 24 and 35 GHz. In addition, the absorption features are also studied for different oblique incident angles, and it is found that the proposed MMA remains stable for θ = 10-50°. The frequency tunability characteristics are achieved by stimulating the capacitance of the varactor diode, which connects the inner patch with the outer ring. To justify the robustness and conformability of the presented MMA, the absorption features are also studied by bending the MMA over different radii of an arbitrary cylinder. Moreover, a multiple-reflection interference model is developed to justify the simulated and calculated absorption of the proposed MMA. It is found that the simulated and calculated results are in close agreement with each other. This kind of MMA could be useful for dual-band sensing and filtering operations.

One-step preparation of RGO/Fe3O4-FeVO4 nanocomposites as highly effective photocatalysts under natural sunlight illumination.

The study used a one-step hydrothermal method to prepare Fe3O4-FeVO4 and xRGO/Fe3O4-FeVO4 nanocomposites. XRD, TEM, EDS, XPS, DRS, and PL techniques were used to examine the structurally and morphologically properties of the prepared samples. The XRD results appeared that the Fe3O4-FeVO4 has a triclinic crystal structure. Under hydrothermal treatment, (GO) was effectively reduced to (RGO) as illustrated by XRD and XPS results. UV-Vis analysis revealed that the addition of RGO enhanced the absorption in the visible region and narrowed the band gap energy. The photoactivities of the prepared samples were evaluated by degrading methylene blue (MB), phenol and brilliant green under sunlight illumination. As indicated by all the nanocomposites, photocatalytic activity was higher than the pure Fe3O4-FeVO4 photocatalyst, and the highest photodegradation efficiency of MB and phenol was shown by the 10%RGO/Fe3O4-FeVO4. In addition, the study examined the mineralization (TOC), photodegradation process, and photocatalytic reaction kinetics of MB and phenol.

Design and synthesis of a combined meso-adsorbent/chemo-sensor for extraction and detection of silver ions.

We synthesized a new pH-dependent meso-captor/sensor for the visual monitoring and selective sequestering of Ag(I) ions from wastewater. The SBA-16 microspheres were successfully synthesized via a direct hydrothermal treatment through surfactant-assisted cooperative self-assembly. The meso-captor/sensor was designed via the direct immobilization of the chromogenic Acid Blue 90 (AB90) chelate into cubical large, open mesoporous SBA-16 carriers and investigate of its ability to detect and retain silver ions from aqueous solutions. Results show that the synthesized SBA-16 microspheres were retained after modification and the AB90 functional groups were immobilized hierarchically inside the mesopore channels. This was evidenced by the N2 adsorption, X-ray Photoelectron Spectroscopy (XPS), Fourier Transform Infrared (FTIR), Scanning Electron Microscope (SEM), High-Resolution Transmission Electron Microscope (HR-TEM), and elemental analyses. Batch adsorption experiments were carried out and the effects of various parameters on Ag(I) ions removal and detection were determined. The optimum adsorption/detection of Ag(I) ions were recorded at a pH of 6.2 within 30 min with color change from a brilliant blue to a pale blue-gray. The spectral response for [SBA-16@AB90 â†’ Ag(I)] complex showed a maximum reflectance at λmax = 385 nm within 2.5 min response time (tR); the LOD was close to 3.87 µg/L while the LOQ approached 12.83 µg/L, this was attributed to the concentration range at which a linear signal has been observed against Ag(I) analyte concentration (i.e., 5 to 1000 µg/L) at pH 6.2 with standard deviation (SD) of 0.077 (RSD% = 9.5 at n = 8).

Ultrafast Photoinduced Electron Transfer in a π-Conjugated Oligomer/Porphyrin Complex.

Controlling charge transfer (CT), charge separation (CS), and charge recombination (CR) at the donor-acceptor interface is extremely important to optimize the conversion efficiency in solar cell devices. In general, ultrafast CT and slow CR are desirable for optimal device performance. In this Letter, the ultrafast excited-state CT between platinum oligomer (DPP-Pt(acac)) as a new electron donor and porphyrin as an electron acceptor is monitored for the first time using femtosecond (fs) transient absorption (TA) spectroscopy with broad-band capability and 120 fs temporal resolution. Turning the CT on/off has been shown to be possible either by switching from an organometallic oligomer to a metal-free oligomer or by controlling the charge density on the nitrogen atom of the porphyrin meso unit. Our time-resolved data show that the CT and CS between DPP-Pt(acac) and cationic porphyrin are ultrafast (approximately 1.5 ps), and the CR is slow (ns time scale), as inferred from the formation and the decay of the cationic and anionic species. We also found that the metallic center in the DPP-Pt(acac) oligomer and the positive charge on the porphyrin are the keys to switching on/off the ultrafast CT process.