Immersion In Aqueous Solution Research Articles

Optically transparent silica film with pH-sensing properties: Influence of chemical immobilization and presence of β-cyclodextrin on protolytic properties of alizarin yellow

A sol-gel synthetic rote was proposed for preparation of optically transparent silica films with covalently bonded azobenzene dye, alizarin yellow. Effect of chemical immobilization on protolytic properties of pH sensor moieties was studied using UV–vis spectroscopy. It was found that indicator dye attached to the silica framework through amide linkage retains the ability to respond on pH change by color transition. The response time of surface azobenzene groups evaluated from the kinetic studies in acidic and neutral medium consists of 10 and 5 min, correspondingly. Acid ionization constants of individual and grafted alizarin yellow were evaluated by spectrophotometric titration in phosphate buffer solutions. It was found that involving of indicator dye carboxylic group in covalent bonding with silica surface leads to the shift of pKa2 value, reflecting the dissociation of phenolic hydroxyl group, from 10.9 to 5.5. Influence of β-cyclodextrin on pH-sensing properties of individual and grafted alizarin yellow was evaluated by spectrophotometric titration in phosphate buffer solutions. Sensor material showed good reversibility, repeatability and long-term stability at immersion in aqueous solutions with pH in the range from 1 to 8.

Natural Wax for Transient Electronics

AbstractEmerging classes of bioresorbable electronic materials serve as the basis for active biomedical implants that are capable of providing sensing, monitoring, stimulating, and other forms of function over an operating period matched to biological processes such as wound healing. These platforms are of interest because subsequent dissolution, enzymatic degradation, and/or bioresorption can eliminate the need for surgical extraction. This report introduces natural wax materials as long‐lived, hydrophobic encapsulation layers for such systems, where biodegradation eventually occurs by chain scission. Studies of wax stability as an encapsulation material demonstrate the ability to retain operation of underlying biodegradable electronic systems for durations between a few days to a few weeks during complete immersion in aqueous solutions in ex‐vivo physiological conditions. Electrically conductive composites result from the addition of tungsten micro/nanoparticles, as a conductive, printable paste with similar lifetimes. Demonstrations of these materials in partially biodegradable wireless light‐emitting diodes and near‐field communication circuits illustrate their use in functional bioresorbable electronic systems. Investigations in animal models reveal no signs of toxicity or other adverse biological responses.

Superabsorbent polymer additives for repeated barrier restoration of damaged powder coatings under wet-dry cycles: A proof-of-concept

Superabsorbent polymers (SAPs) are well known for their ability to absorb and hold high water amounts accompanied by a high volume expansion. In this work we show the benefits of this underlying property of SAPs to induce underwater crack closure with subsequent barrier restoration in damaged protective coatings. For the proof of concept, three layer epoxy-polyester (EP) powder coating systems were developed and applied on carbon steel. In these systems the middle EP layer (also called functional layer) contained crosslinked acrylamide/acrylic acid copolymer SAPs in different amounts ranging from 0 to 40 wt%. The capability of the SAPs to close damages and extend barrier and corrosion protection was evaluated by electrochemical impedance spectroscopy (EIS), NaCl aqueous solution immersion test and optical microscopy. It was found that coatings loaded with a 20 wt% SAP led to the best overall corrosion protection for the studied systems. In order to proof the potential use of this extrinsic healing concept for multiple healing events wet-dry cycles on scratched systems were performed and the corrosion performance was followed by EIS. Although not yet optimal, the results show the potential of the concept for multiple healing events under wet-dry conditions.

Rapid Fabrication of a Crystalline Myristic Acid-Based Superhydrophobic Film with Corrosion Resistance on Magnesium Alloys by the Facile One-Step Immersion Process.

A simple, easy, and rapid process of fabricating superhydrophobic surfaces on magnesium alloy AZ31 by a one-step immersion at room temperature was developed. The myristic acid-modified micro-/nanostructured surfaces showed static water contact angles over 150° and water contact angle hysteresis below 10°, thus illustrating superhydrophobic property. The shortest treatment time for obtaining the superhydrophobic surfaces was 30 s. In addition, we demonstrated for the first time that crystalline solid myristic acid could be formed on a Mg alloy using a suitable molar ratio of Ce ions and myristic acid. The contact angle hysteresis was lowered with an increase in the immersion time. Potentiodynamic polarization curve measurements revealed that the corrosion resistance of AZ31 treated by the immersion process improved considerably by the formation of superhydrophobic surfaces. The chemical durability of the superhydrophobic surfaces fabricated on AZ31 was also examined. The static water contact angle values for the superhydrophobic surfaces after immersion in aqueous solutions at pHs 4, 7, and 10 for 12 h were estimated to be 90 ± 2°, 119 ± 2°, and 138 ± 2°, respectively, demonstrating that their chemical durability in a basic solution was high.

A perovskite-structured aluminium-substituted lithium lanthanum titanate as a potential artificial solid-electrolyte interface for aqueous rechargeable lithium-metal-based batteries

An aluminium-doped lithium lanthanum titanate (A-LLTO) solid electrolyte was prepared using a simple citrate-gel method, and this was followed by a pelletization and the conventional sintering process. When the sintering time was varied at 1350°C for the synthesis of the A-LLTO, the A-LLTO ceramic that was sintered at 1350°C for 6h exhibited the highest ionic conductivity of 3.17×10−4Scm−1 at 25°C. In addition, the stability and durability of the synthesized A-LLTO ceramic was tested through a one-month aqueous-solution immersion for which the pH values were varied between 0 and 14. The stability of the A-LLTO is the highest in the alkaline environment; furthermore, for its use in the aqueous-electrolyte environment, a protected lithium electrode (PLE) structure was made by combining the lithium (Li) metal, a lithium phosphorous oxynitride (LiPON) interlayer, and the A-LLTO, whereby the LiPON interlayer prevented a direct reaction between the Li metal and the A-LLTO. The Li-LiCoO2 and Li-O2 cells comprising the PLE exhibited a superior electrochemical performance when they were used in the alkaline 1M LiNO3-electrolyte environment. After 100 cycles of the charge-discharge at the 1C rate, the aqueous Li-LiCoO2 cells maintained 59.3% of the initial capacity with a coulombic efficiency of 98.3%. In addition, the aqueous Li-O2 cell operated stably for 40 cycles under the limited capacity mode of 0.5mAhcm−2. The outstanding performance of the Li-metal-based cells originates from the A-LLTO solid electrolyte, due to the latter’s high stability, ionic conductivity, and an effective suppression effect regarding the dendritic growth of the Li.

Internal attack by sulphates in cement pastes and mortars dosed with different levels of pyrite

This study aims to investigate cementitious compound behaviour at early stages (up to 168 days), primarily when dosed with different levels of pyrite. To accomplish this, a study was conducted with cement pastes and mortars contaminated by sulphide. For the cement pastes, four contaminant levels were adopted: with one as a reference value (0%), two as cited by the standards, and one value greater than the set standards. In the mortars, two series were studied, one without contamination and the other with use of an aggregate contaminated naturally by pyrite. Pozzolanic cement was used (65% Portland cement CPV + 35% fly ash) and the materials were submerged in curing compounds for 28 days. Subsequently, the samples were subjected to two exposure conditions: 1—a wet-dry cycle and 2—immersion in aqueous solution with aeration. To identify the products formed by pyrite oxidation, and the subsequent by-product-based reactions, and cement hydrates, scanning electron microscopy with elemental analysis was used. For the analysis of the mechanical properties, strength tests were performed to test axial compression and tensile strength in bending. Furthermore, monitoring of the dimensional variation in prisms (2.5 × 2.5 × 28.5) cm3 was performed. In conclusion, we determined that at the exposure times tested, there were signs of sulphide oxidation in the contaminated compounds. It was proven that the higher the degree of pyrite contamination, the higher the relative expansion of the series, which was confirmed by the formation of expansive products identified in the scanning electron microscopy.

Engineering durable hydrophobic surfaces on porous alumina ceramics using in-situ formed inorganic-organic hybrid nanoparticles

Hydrophobic surfaces are required for a variety of applications owing to their water repellent and self-cleaning properties. In this work, we present a novel approach to prepare durable hydrophobic surfaces on porous ceramics. A polydimethylsiloxane (PDMS) film was applied to a porous alumina wafer, followed by pyrolysis at 400°C in a non-oxidizing atmosphere (H2:N2=5:95), giving rise to nanoparticles. In these particles, Si, C and O elements formed amorphous networks to which methyl groups that had survived the pyrolysis were bonded. The as-modified porous alumina wafer was hydrophobic with a water contact angle of 136°, which is attributed to the presence of the methyl groups. The hydrophobicity was maintained after immersion in aqueous solutions in a pH range of 2–12 and acetone. The hydrophobicity was also retained after exposure to temperatures as high as 450°C in an oxidative atmosphere (air) and after mechanical abrasion with sandpaper. The hydrophobic porous alumina ceramics developed in the present study are promising for use as membranes in various separation processes.

A facile and novel emulsion for efficient and convenient fabrication of durable superhydrophobic materials

There are significant challenges related to practical applications of superhydrophobic materials due to their limited durability, difficult processing conditions, and complicated synthesis procedures. In this study, a facile and novel emulsion composed of nanopartilcles (i.e. SiO2 or TiO2) and epoxy resin was synthesized to produce superhydrophobic surfaces using spraying, dipping and brushing methods, mimicking ordinary household paints. The obtained superhydrophobic materials had a water contact angle (CA) of ∼152° and a sliding angle (SA) of ∼6° at the room temperature. Interestingly, the emulsion demonstrated a great versatility for application in type of materials and application methods. The hierarchical surface structure fabricated by the emulsion was found to be independent of the substrate type and processing method, resulting in similar water repellent performance among all surfaces obtained. The superhydrophobic surfaces also exhibited excellent durability even after sustaining a series of mechanical damages including finger wiping, tape peeling and sandpaper abrasion. Moreover, they were able to maintain their superhydrophobic performance after immersion in aqueous solutions of pH ranging from 1 to 13 and boiling in water at 100°C. This study shows that the novel emulsion can be used to fabrication of superhydrophobic surfaces using a one-step method that is green, versatile, scalable and independent of operator skill, special equipment, and the type of substrate. It has an excellent promise for real life applications.

Pentiptycene-tbutylpyrene based poly(arylene-ethynylene)s: Highly sensitive and selective TNT sensor in aqueous as well as vapor phase

A series of poly(arylene-ethynylene)s (PAEs) containing pentiptycene and tbutylpyrene or pyrene in the main chain were synthesized. Introduction of pyrene moiety in the pentiptycene polymeric backbone made the polymers extremely sensitive and selective towards TNT in aqueous solution as well as vapour phase as compared to the other interfering nitroaromatic compounds (NACs) like DNT and PA. In solid state, one of the polymer P2 showed superior sensitivity towards TNT vapours with 60.4% and 90% fluorescence loss within respective 10s and 30s of exposure to TNT vapours, which is much higher than most of the reported NACs sensors. Even towards aqueous NACs, the performance of P2 is the best, with 69.8% fluorescence of P2 film getting quenched within 60s of immersion in aqueous solution of TNT (50μM). Fluorescence regain study showed that 94% fluorescence is re-gained after dipping the fluorescence-quenched polymer film in methanol for 20s. The polymers were found to possess high thermal stability (282–585°C) and appreciably high fluorescence quantum yield (0.39–0.65). We also report the sub-nanoscopic free volume and its distribution in the polymers, as quantified by positron annihilation life time spectroscopy (PALS).

A Novel Organic Conversion Coating based on N-Benzoyl-N-Phenylhydroxylamine Chemistry for the Corrosion Protection of AA2024-T3

This work demonstrates a novel organic conversion coating treatment on an AA2024-T3 substrate. The process is based on simple immersion in aqueous solutions containing an organic molecule, N-Benzoyl-N-phenylhydroxylamine (BPHA), after a hydrothermal oxide has been formed on the alloy surface. Potentiodynamic polarization results indicate that BPHA conversion coating outperforms coatings formed in the same concentration of other corrosion inhibitors, including NaVO3, Na2SiO3, CeCl3, and benzotriazole. BPHA coating also displays strong and persistent corrosion inhibition under ASTM B117 salt spray exposure conditions and static immersion testing. The cross-section of BPHA-coated substrate is prepared by focus ion beam-scanning (FIB), and analyzed by high angle annular dark field (HAADF) scanning transmission electron microscopy (STEM) coupled with energy dispersive spectroscopy (EDS), which show a thick surface film with a three-layer structure. Raman spectroscopy and XPS are used to examine the surface chemistry of BPHA-coated samples, both of which suggest the formation of a BPHA surface film, possibly stabilized by the keto-to-iminol conversion that made the BPHA molecule strongly nucleophilic. The formation of BPHA-metal oxide complex seems to be closely related to the excellent corrosion resistance of BPHA coating.

The Influence of Chloride Ion Concentration on Passivity Breakdown in Magnesium

An empirically derived dependence of an apparent breakdown potential (Eb) of magnesium (Mg) on chloride ion concentration is reported. In situations where spontaneous breakdown in the absence of external polarization is observed, leading to the subsequent propagation of localized corrosion, Eb can be determined by following time-dependent changes in free corrosion potential (Ecorr). Breakdown of temporary passivity is marked by a clear inflection in the time-dependent value of Ecorr, characterized by a sharp decrease in potential from a maximum value where Ecorr = Eb. Characterization of localized corrosion behavior by in situ scanning vibrating electrode studies, prior to and following the point of breakdown, is used to explain the observed Ecorr vs. time characteristics. Examples of typical behavior upon immersion in aqueous solutions containing different chloride ion concentrations ([Cl−]) are given for commercially pure Mg and an AZ31 alloy. For high purity Mg, which remains passive at pH 11 at all ch...

Atmospheric Pressure Non-Equilibrium Plasma as a Green Tool to Crosslink Gelatin Nanofibers.

Electrospun gelatin nanofibers attract great interest as a natural biomaterial for cartilage and tendon repair despite their high solubility in aqueous solution, which makes them also difficult to crosslink by means of chemical agents. In this work, we explore the efficiency of non-equilibrium atmospheric pressure plasma in stabilizing gelatin nanofibers. We demonstrate that plasma represents an innovative, easy and environmentally friendly approach to successfully crosslink gelatin electrospun mats directly in the solid state. Plasma treated gelatin mats display increased structural stability and excellent retention of fibrous morphology after immersion in aqueous solution. This method can be successfully applied to induce crosslinking both in pure gelatin and genipin-containing gelatin electrospun nanofibers, the latter requiring an even shorter plasma exposure time. A complete characterization of the crosslinked nanofibres, including mechanical properties, morphological observations, stability in physiological solution and structural modifications, has been carried out in order to get insights on the occurring reactions triggered by plasma.

Fabrication of CdSe nanocrystals using porous anodic alumina and their optical properties

In this paper, Porous anodic alumina (PAA) template with highly ordered nanopores structure was synthesized on aluminum foils by two step anodization process. PAA template has hexagonal pores with average size between 30 and 180nm. L-cysteine (L-Cys) functionalized cadmium selenide nanocrystals (CdSe NCs) were successfully embedded inside PAA layers by simple immersion in aqueous solution. The effect of pore diameter enlargement on the microstructure of CdSe NCs/PAA films was systematically studied by FE-SEM, XRD, EDX, Raman, UV–VIS absorbance and PL analysis. FE-SEM microscopy was used to investigate the surface morphology of PAA templates before and after CdSe NCs deposition. XRD investigation demonstrates that CdSe NCs into PAA templates were cubic in nature with zinc-blende structure. Raman measurements exhibit the characteristic modes of CdSe on the PAA layers as well as the films crystallinity as function of widening pores diameter. Optical properties of deposited CdSe NCs on PAA templates have been investigated using optical absorption and PL techniques. Photoluminescence spectroscopy has been used to determine the bandgap energy and the average size of CdSe NCs deposited on PAA layer. This method involves fitting the experimental spectra, using a model based on quantum confinement of electrons in CdSe nanocrystals having spherical and cylindrical forms (Quantum Dots (QDs) and Quantum Wires (QWs)). This model allows correlation between the PL spectra and the microstructure of the CdSe/PAA. Both photoluminescence and optical absorption show that the PL peak energy and the optical absorption edge of CdSe NCs/PAA exhibit similar behavior with changes in nanostructure size. The spectral behaviors of optical absorption and PL are consistent with a quantum confinement model throughout the sizes and shapes of the CdSe nanocrystals of the luminescent films. The effective bandgap energies determined from the PL peaks position are in good agreement with those estimated from the optical absorbance spectra.Investigations have shown that optical properties of CdSe/PAA nanostructure were influenced by the pores sizes of PAA. It was observed an increase in CdSe NCs size from 2.22 to 2.56nm when the average pores diameter of PAA increases from 30 to 180nm. This finding indicates an enhancement in PL intensity and a red-shift in PL emission peaks from 2.35 to 2.14eV. By applying the quantum confinement model, we demonstrated that the redshift of PL peak is attributed to the change of CdSe NCs size with the pores diameter and that their spectral behaviors are related to the shape and the size distribution of the nanoparticles.

Colorimetric detection, quantification and extraction of Fe(III) in water by acrylic polymers with pendant Kojic acid motifs

We synthesized a solid sensory material for the extraction, detection and quantification of iron(III) in aqueous media. The material is a film-shaped colorless polymer membrane that exhibits gel behavior. The Fe(III) extraction and sensing characteristics are imparted by a new monomer derived from a natural product (i.e., Kojic acid), which exhibits chelating properties toward Fe(III). The sorption of Fe(III) on the membrane in water has been thoroughly characterized, including the sorption kinetics, sorption isotherms and profiles as a function of the pH. Fe(III) sorption followed pseudo first-order kinetics and required approximately 30min to reach equilibrium. The maximum sorption capacity was approximately 0.04mmol/g, and the sorption isotherms are well modeled by the Langmuir equation. The complexes that were found in the solid phase are in good agreement with those previously identified in the aqueous phase. Moreover, the sorption is highly specific (i.e., a recognition process) and results from the formation of a colored complex (iron(III)-Kojic acid derivative moieties). Therefore, the colorless sensory membrane turns red upon immersion in aqueous solutions containing Fe(III). The color output allows for both the qualitative visual determination of the Fe(III) concentration as well as also titration of Fe(III) using a) a UV/vis technique (limit of detection of 3.6×10−5M; dynamic range of five decades, lower concentration=1.65×10−6M) and b) a computer vision-based analytical chemistry approach via color definition of the sensory membrane (RGB parameters) obtained from an image recorded with a handy device (e.g., a smartphone) (limit of detection of 2.0×10−5M).

Morphological, Structural and Optical Properties of Mg Doped ZnO Nanostructured Growth by Aqueous Solution Method

Mg doped Zinc oxide nanorods films were successfully deposited on glass substrate prepared by aqueous solution-immersion method. The influence of annealing temperature on the nanorod films were studied at different annealing temperatures 0°C, 250°C and 500°C respectively. FESEM showed the morphology of the films with hexagonal nanorods growth. XRD results indicated the crystalline structure of ZnO doped Mg nanorods films where the peak intensity of ZnO was decreased as annealing temperature increases. Photoluminescence (PL) measurement at room temperature showed the increasing of intensity peak for visible spectra with increasing of annealing temperature.

Processing of ZrO2 scaffolds coated by glass–ceramic derived from 45S5 bioglass

Three dimensional, highly porous, ZrO2 scaffolds coated by glass–ceramic derived from 45S5 bioglass were fabricated. The surface reactivity of 45S5 in aqueous solution was investigated as a function of the immersion time. The influence of the solid loading on the rheological behavior of 45S5 aqueous slips with ammonium polyacrylate (NH4PA) was studied; besides the effect of poly(vinyl)alcohol (PVA) on the relative viscosity was determined. The structure and microstructure of uncoated and coated ZrO2 scaffolds were characterized. The high ionic exchange capability of 45S5 was demonstrated by the pH rise, the significant weight loss and the amorphous calcium phosphate nucleation, upon its immersion in aqueous solution. The addition of PVA did not affect the dispersion properties of the 45S5 powder, which were basically controlled by its negative surface charge. 30wt% 45S5 slips with 4wt% PVA exhibited a yield stress and an adequate viscosity in the low shear rate range, to produce a bioglass coating into the ZrO2 scaffold. The glass-ceramic coating was distributed along the strut surfaces, forming a thin film without altering the porosity and the strut thickness of the original ZrO2 scaffold structure.

Biological thiols-triggered hydrogen sulfide releasing microfibers for tissue engineering applications

By electrospinning of polycaprolactone (PCL) solutions containing N-(benzoylthio)benzamide (NSHD1), a H2S donor, fibrous scaffolds with hydrogen sulfide (H2S) releasing capability (H2S-fibers) are fabricated. The resultant microfibers are capable of releasing H2S upon immersion in aqueous solution containing biological thiols under physiological conditions. The H2S release peaks of H2S-fibers appeared at 2–4h, while the peak of donor alone showed at 45min. H2S release half-lives of H2S-fibers were 10–20 times longer than that of donor alone. Furthermore, H2S-fibers can protect cells from H2O2 induced oxidative damage by significantly decreasing the production of intracellular reactive oxygen species (ROS). Finally, we investigated the H2S-fibers application as a wound dressing in vitro. Given that H2S has a broad range of physiological functions, H2S-fibers hold great potential for various biomedical applications. Statement of significanceHydrogen sulfide, as a gaseous messenger, plays a crucial role in many physiological and pathological conditions. Recent studies about functions of H2S suggests H2S-based therapy could be promising therapeutic strategy for many diseases, such as cardiovascular disease, arthritis, and inflammatory bowel disease. Although many H2S donors have been developed and applied for biomedical studies, most of H2S donors have the shortage that the H2S release is either too fast or uncontrollable, which poorly mimic the biological generation of H2S. By simply combining electrospinning technique with our designed biological thiols activated H2S donor, NSHD1, we fabricated H2S releasing microfibers (H2S-fibers). This H2S-fibers significantly prolonged the releasing time compared to H2S donor alone. By adjusting the electrospinning parameters, tunable releasing profiles can be achieved. Moreover, the H2S fibers can protect cardiac myoblasts H9c2 and fibroblast NIH 3T3 from oxidative damage and support their proliferation as cellular scaffolds. To our knowledge, this is the first report of electrospun fibers with H2S releasing capacity. We anticipate this H2S-releasing scaffold will have great potential for biomedical applications.

3D plotting of growth factor loaded calcium phosphate cement scaffolds

Additive manufacturing allows to widely control the geometrical features of implants. Recently, we described the fabrication of calcium phosphate cement (CPC) scaffolds by 3D plotting of a storable CPC paste based on water-immiscible carrier liquid. Plotting and hardening is conducted under mild conditions allowing the (precise and local) integration of biological components. In this study, we have developed a procedure for efficient loading of growth factors in the CPC scaffolds during plotting and demonstrated the feasibility of this approach. Bovine serum albumin (BSA) or vascular endothelial growth factor (VEGF), used as model proteins, were encapsulated in chitosan/dextran sulphate microparticles which could be easily mixed into the CPC paste in freeze-dried state. In order to prevent leaching of the proteins during cement setting, usually carried out by immersion in aqueous solutions, the plotted scaffolds were aged in water-saturated atmosphere (humidity). Setting in humidity avoided early loss of loaded proteins but provided sufficient amount of water to allow cement setting, as indicated by XRD analysis and mechanical testing in comparison to scaffolds set in water. Moreover, humidity-set scaffolds were characterised by altered, even improved properties: no swelling or crack formation was observed and accordingly, surface topography, total porosity and compressive modulus of the humidity-set scaffolds differed from those of the water-set counterparts. Direct cultivation of mesenchymal stem cells on the humidity-set scaffolds over 21days revealed their cytocompatibility. Maintenance of the bioactivity of VEGF during the fabrication procedure was proven in indirect and direct culture experiments with endothelial cells. Statement of SignificanceAdditive manufacturing techniques allow the fabrication of implants with defined architecture (inner pore structure and outer shape). Especially printing technologies conducted under mild conditions allow additionally the (spatially controlled) integration of biological components such as drugs or growth factors. That enables the generation of individualized implants which can better meet the requirements of a patient and of tissue engineering constructs. To our knowledge, simultaneous printing of biological components was up to now only described for hydrogel/biopolymer-based materials which suffer from poor mechanical properties. In contrast, we have developed a procedure (based on 3D plotting of a calcium phosphate cement paste) for the fabrication of designed and growth factor loaded calcium-phosphate-based scaffolds applicable for bone regeneration.

Neurobehavioral impairments caused by developmental imidacloprid exposure in zebrafish

BackgroundNeonicotinoid insecticides are becoming more widely applied as organophosphate (OP) insecticides are decreasing in use. Because of their relative specificity to insect nicotinic receptors, they are thought to have reduced risk of neurotoxicity in vertebrates. However, there is scant published literature concerning the neurobehavioral effects of developmental exposure of vertebrates to neonicotinoids. MethodsUsing zebrafish, we investigated the neurobehavioral effects of developmental exposure to imidacloprid, a prototypic neonicotinoid pesticide. Nicotine was also administered for comparison. Zebrafish were exposed via immersion in aqueous solutions containing 45μM or 60μM of imidacloprid or nicotine (or vehicle control) from 4h to 5d post fertilization. The functional effects of developmental exposure to both imidacloprid and nicotine were assessed in larvae using an activity assay and during adolescence and adulthood using a battery of neurobehavioral assays, including assessment of sensorimotor response and habituation in a tactile startle test, novel tank swimming, and shoaling behavior. ResultsIn larvae, developmental imidacloprid exposure at both doses significantly decreased swimming activity. The 5D strains of zebrafish were more sensitive to both nicotine and imidacloprid than the AB* strain. In adolescent and adult fish, developmental exposure to imidacloprid significantly decreased novel tank exploration and increased sensorimotor response to startle stimuli. While nicotine did not affect novel tank swimming, it increased sensorimotor response to startle stimuli at the low dose. No effects of either compound were found on shoaling behavior or habituation to a startling stimulus. DiscussionEarly developmental exposure to imidacloprid has both early-life and persisting effects on neurobehavioral function in zebrafish. Its developmental neurotoxicity should be further investigated.

Effect of air-annealing on the morphological, microstructural and optical properties of CdSe NCs grown into porous anodic alumina template

In this work, cadmium selenide nanocrystals (CdSe NCs) were embedded into porous anodic alumina (PAA) template by simple immersion in aqueous solution containing l-cysteine (Cys) functionalized CdSe NCs and water. The prepared samples were heat treated at different temperatures between 150 and 300°C during 30min under air. The effect of thermal treatment under air on the CdSe NCs/PAA has been shown from morphological, microstructural and optical studies. Several characterization techniques such as scanning electron microscopy (SEM), atomic force microscopy (AFM), and X-ray diffraction (XRD) spectroscopy were used to investigate the surface morphology and microstructural properties of CdSe nanoparticles on the PAA template as function of air-annealing temperature. XRD study shows the transformation phase of deposited CdSe nanoparticles on the PAA template from cubic structure to hexagonal structure at 300°C. The morphology of CdSe nanorods array which are into the PAA surface were exhibited by AFM scan. Optical properties of CdSe NCs into PAA have been studied at different air-annealing temperatures using optical absorption and photoluminescence (PL) spectroscopy. The results showed that the crystal quality was significantly improved with the annealing temperature increase, bringing about an enhancement in PL and a decrease in optical band gap from 2.44 to 2.2eV exhibiting a red shift.