Ecobiophysical Aspects on Nanosilver Biogenerated from Citrus reticulata

In recent years, a considerable interest was paid to ecological strategies in management of plant diseases and plant growth. Metallic nanoparticles (MNPs) gained considerable interest as alternative to pesticides due to their interesting properties. Green synthesis of MNPs using plant extracts is very advantageous taking into account the fact that plants are easily available and eco-friendly and possess many phytocompounds that help in bioreduction of metal ions. In this research work, we phytosynthesized AgNPs from aqueous extract of Citrus reticulata peels, with high antioxidant, antibacterial, and antifungal potential. These “green” AgNPs were characterized by modern biophysical methods (absorption and FTIR spectroscopy, AFM, and zeta potential measurements). The nanobioimpact of Citrus-based AgNPs on four invasive wetland plants, Cattail (Typha latifolia), Flowering-rush (Butomus umbellatus), Duckweed (Lemna minor), and Water-pepper (Polygonum hydropiper), was studied by absorption spectroscopy, by monitoring the spectral signature of chlorophyll. The invasive plants exhibited different behavior under AgNP stress. Deep insights were obtained from experiments conducted on biomimetic membranes marked with chlorophyll a. Our results pointed out the potential use of Citrus-based AgNPs as alternative in controlling pathogens in aqueous media and in management of aquatic weeds growth

Preparation and Characterization of Some Sol-Gel Modified Silica Coatings Deposited on Polyvinyl Chloride (PVC) Substrates

Transparent and antireflective coatings were prepared by deposition of modified silica materials onto polyvinyl chloride (PVC) substrates. These materials were obtained by the sol-gel route in acidic medium, at room temperature (25 °C), using different alkoxysilanes with various functional groups (methyl, vinyl, octyl or hexadecyl). Physicochemical and microstructural properties of resulted silica materials and of thin coatings were investigated through Fourier Transforms Infrared Spectroscopy (FTIR), UV-Vis spectroscopy, Thermal Gravimetric Analysis (TGA), Dynamic Mechanical Analysis (DMA), Atomic Force Microscopy (AFM) and ellipsometric measurements. Wetting behaviors of the silica coatings were evaluated by measurement of static contact angle against water. FTIR spectra of materials confirmed the high degree of cross-linking that result from the formation of the inorganic backbone through the hydrolysis and polycondensation reactions together with the formation of the organic network. These sol-gel silica coatings showed a reduction in the reflectance (10%) compared with uncoated PVC substrate. AFM reveals that the films are uniform, and adherent to the substrate, but their morphology is strongly influenced by the chemical composition of the coating matrices. These silica coatings can be useful for potential electronic and optical devices

Corrosion Protection of Carbon Steel Using Natural Seaweeds from Seawater

The aim of this work was to investigate the corrosion inhibition effect of natural seaweeds in seawater on carbon steel. The corrosion efficiency of carbon steel in the absence and the presence of natural seaweeds in seawater was evaluated by the gravimetric method at room temperature and calculating the corrosion rate and protection degree. The experimental results showed that the corrosion rate on carbon steel decreased when the seaweeds were used. In addition, the value of protection degree (P) was greater than 60% when seaweeds were used. Natural seaweeds reduce the corrosion rate and can be considered an ecofriendly corrosion inhibitor for carbon steel

Influence of Thin Film Deposition on AFM Cantilever Tips in Adhesion and Young’s Modulus of MEMS Surfaces

Adhesion is a critical factor in microelectromechanical systems (MEMSs) and is influenced by many parameters. In important fields, such as microassembly, an improved understanding of adhesion can result in higher precision. This study examines the influence of deposition of gold and titanium onto the atomic force microscope (AFM) tips in adhesion forces and Young’s modulus, between a few MEMS substrates (silicon, gold, and silver) and the AFM tips. It was found that, except for gold substrate, an AFM tip coated with gold has the highest adhesion force of 42.67 nN for silicon substrates, whereas the titanium-coated AFM tip decreases the force for all the samples. This study suggests that such changes must be taken into account while studying the adhesion force. The final results indicate that utilizing gold substrate with titanium AFM tip led to the lowest adhesion force, which could be useful in adhesion force measurement during microassembly

Nitrates Removal from Simulated Groundwater Using Nano Zerovalent Iron Supported by Polystyrenic Gel

The main objectives of this present paper were to indicate the immobilization of nano zerovalent iron (nZVI) onto a polymeric material (Purolite A400) and the synthesis of the polymeric material (A400-nZVI) through sodium borohydride (NaBH4) reduction. The obtained polymeric material (A400-nZVI) was used for the nitrate ions removal from a simulated groundwater at different conditions. The polymeric materials, without and with nano zerovalent iron (A400 and A400-nZVI), were characterized trough the FTIR, SEM-EDAX, XRD, and TGA analysis. The analysis confirmed the presence of nano zerovalent iron (nZVI) onto the polymeric material (A400). The adsorption capacity of A400-nZVI, used as polymeric adsorbent, was evaluated by kinetic and thermodynamic studies. The obtained experimental results indicated that the nitrate ions reduction was fitted well by models: pseudo-second-order kinetic and Freundlich isotherm. According to the kinetic model results, a reaction mechanism could exist in the stage of reactions. The higher value of removal nitrate (>80%) was obtained under acidic condition. The results indicated that the obtained polymeric material (A400-nZVI) can be considered as a potential polymeric adsorbent for different pollutants from groundwater and wastewater

Theoretical and Experimental Analysis of Surface Roughness and Adhesion Forces of MEMS Surfaces Using a Novel Method for Making a Compound Sputtering Target

Achieving a compound thin film with uniform thickness and high purity has always been a challenge in the applications concerning micro electro mechanical systems (MEMS). Controlling the adhesion force in micro/nanoscale is also critical. In the present study, a novel method for making a sputtering compound target is proposed for coating Ag–Au thin films with thicknesses of 120 and 500 nm on silicon substrates. The surface topography and adhesion forces of the samples were obtained using atomic force microscope (AFM). Rabinovich and Rumpf models were utilized to measure the adhesion force and compare the results with the obtained experimental values. It was found that the layer with a thickness of 500 nm has a lower adhesion force than the one with 120 nm thickness. The results further indicated that due to surface asperity radius, the adhesion achieved from the Rabinovich model was closer to the experimental values. This novel method for making a compound sputtering target has led to a lower adhesion force which can be useful for coating microgripper surfaces

Influence of Organic-Modified Inorganic Matrices on the Optical Properties of Palygorskite–Curcumin-Type Hybrid Materials

Clays are very important from an economic and application point of view, as they are suitable hosts for organic compounds. In order to diversify the fields of application, they are structurally modified by physical or chemical methods with cationic species, and/or different bifunctional compounds, such as organosilanes. In this study, palygorskite was modified with (3-Aminopropyl) triethoxysilane, which was subsequently modified at the amino group by grafting an acetate residue. By using this strategy, two types of host hybrid materials were obtained on which curcumin derivatives were deposited. The composites obtained were structurally characterized and their photophysical properties were investigated in relation to the structure of the host matrices and interactions with curcumin-type visiting species. The hybrid composites have different colors (orange, yellow, pink), depending on the polarity of the inorganic matrices modulated by different organic groups grafted at the surface. Fluorescence emission in the visible range is characterized by the presence of two emission maxima, one belonging to the chromophore and the other influenced by the physical interactions between auxochromes and host matrices. These hybrid materials, compared to other composite structures, are obtained by a simple adsorption process. They are temperature stable in aggressive environments (acid/base) and render the fluorescent properties of dyes redundant, with improved luminescent performance compared to them

Colored Coating Materials with Spectrally Selective Reflectance for Woodland Camouflage Textile Fabrics

The camouflage effect aims to reproduce natural or artificial surroundings in terms of color, [...

Investigation of Hybrid Films Based on Fluorinated Silica Materials Prepared by Sol–Gel Processing

In this research, fluorinated silica materials were prepared through sol–gel processing with tetraethylorthosilicate (TEOS), triethoxymethylsilane (MTES), and trimethoxyhexadecylsilane (HDTMES), using a fluorinated solution (FS) under acidic medium. The fluorinated solution (FS) was obtained by diluting the perfluorooctanoic acid (PFOA) in 2-propanol. These fluorinated sol–gel silica materials were placed on the glass surfaces in order to achieve the antireflective and hydrophobic fluorinated hybrid films. The structure and surface properties of the final samples were investigated by Fourier transform infrared spectroscopy (FTIR), ultraviolet/visible spectroscopy, thermogravimetric analysis (TGA), atomic force microscopy (AFM), and contact angle (CA) determinations. FTIR spectra demonstrated the presence of a silica network modified with alkyl and fluoroalkyl groups. Thermal analysis showed that the fluorinated sol–gel silica materials prepared with HDTMES have a good thermostability in comparison with other samples. Ultraviolet/visible spectra indicated that the fluorinated hybrid films present a reflectance of ~9.5%, measured at 550 nm. The water contact angle analysis found that the wettability of fluorinated hybrid films was changed from hydrophilic (64°) to hydrophobic (~104°). These hybrid films based on fluorinated sol–gel silica materials can be useful in various electronics and optics fields