HRTEM Studies Research Articles

Hydrothermally synthesized carboxylic acid functionalized multiwalled carbon nanotubes grafted MoS2 based hybrid composites: Efficient uranium(VI) scavenging sorbents in columns, fabric and matrix membrane systems

In the present study, pure MoS2 and its composites grafted with multiwalled carbon nanotubes (MoS2-MWCNT: 10–40 mg) and carboxylic acid functionalized multiwalled carbon nanotubes (MoS2-MWCNT-COOH; 10–40 mg) were synthesized using a facile hydrothermal method. MoS2 (MS) and its two composites each containing 40 mg of MWCNT (MS-C4) and MWCNT-COOH (MS-CA4) were subjected to structural, chemical and surface characterization using RAMAN, XPS, FT-IR HRTEM, FESEM, EDX and BET studies. In order to establish their adsorptive behaviour for remediation of U(VI), the systematic batch mode studies were conducted and adsorption data were analysed using different isotherm, kinetic and thermodynamic models. Langmuir maximum adsorption capacity (mg/g) of three MoS2 sorbents for U(VI) follows the order as: MS-CA4 (233.38) > MS-C4 (164.85) > MS (53.77) with thermodynamic parameters describing spontaneous and endothermic nature of adsorption. The electrostatic interactions and monolayer chemisorption via coordinate complex formation are mainly responsible for U(VI) extraction from water. These findings allow to expand the promising application of MS-CA4 in environmental remediation as fillers and packing materials in fabric/PSF mixed membranes and column systems, respectively.

Synthesis of One‐Dimensional Mo2C‐Embedded Carbon Nanofibers with Enhanced Lithium Storage Capacity for Lithium‐Ion Batteries

AbstractMXenes are in the limelight nowadays due to their fascinating structure and outstanding physical and chemical properties. Mo2C, a part of MXenes, has a unique structure where the carbon present in the interstitial voids between the layers of the molybdenum (Mo) atom is very sensitive to even a small addition of electrons. Herein, we have pursued the synthesis of one‐dimensional Mo2C‐embedded carbon nanofibers (Mo2C@CNF) as a potential anode material for lithium‐ion batteries. The Mo2C@CNF is synthesized by simple electrospinning (E‐Spin) technique followed by iodization and thermal treatment at 1000 °C under Argon. The iodization process plays a major role in the formation of Mo2C@CNF, which creates a stronger backbone and high yield of carbon content during the carbonization process. The presence of highly disordered carbon in Mo2C@CNF was demonstrated by FESEM, XRD, RAMAN, and HRTEM studies. The electrochemical performance studies of Mo2C@CNF, carried out using 2032 type coin cell configuration, show an enhanced specific capacity of 1492 mAh g−1 at 0.15 C‐rate during the first discharge. These high‐capacity values obtained due to the synergistic interaction between the embedded Mo2C and carbon nanofibers open up a new avenue to high performance carbide based anodes for energy storage applications.

Chemically Synthesized ZnO Nanostructure: Effect of Polyethylene Glycol (PEG) Surfactants

ZnO nano-particles is synthesized using hydrated zinc chloride (ZnCl2.2H2O) as main raw components. It is calcined at different temperatures (i.e., 200 ⁰C, 400 ºC, 600 ⁰C and 800 ⁰C). Synthesized ZnO is characterized by XRD, SEM/EDS, HRTEM, UV Visible, and Band Gap. XRD result showed pure wurtzite-structure and is crystalline nature. Both XRD results and SAED obtained from pattern HRTEM studies are indicated similar information of the ZnO nanomaterials. Both FESEM and HRTEM techniques are used to observe surface morphology of ZnO nanomaterials. Such analyses are directed to the thermo-chemical reaction of prepared nanostructures. FESEM analysis showed different nano-sized structures of synthesized ZnO. Different nanostructures of ZnO are found in HRTEM images. EDS results of synthesized ZnO is showed to find Zn and oxygen elements. UV Visible and band gap are indicated.

Gold nanoparticles supported on NiO and CuO: The synergistic effect toward enhanced reduction of nitroarenes and A3-coupling reaction

Bimetallic Au/NiO and Au/CuO catalysts have been developed through wet-chemical routes and the role of bimetallic effects on the reduction of nitroarenes and A3-coupling reaction have been investigated. Both bimetallic structures are ideal catalysts for aromatic nitro reduction reaction. However, using Au/NiO in A3-coupling reaction propargylamine products were selectively obtained, while diyne was obtained as the major product using Au/CuO. Both catalysts are more active than NiO and CuO in the mentioned reactions. The new bimetallic catalysts were characterized with different techniques such as XRD, Raman, SEM, HRTEM, SAED, EDX and BET nitrogen adsorption-desorption studies. These catalysts were recovered and reused in the reduction of 4-nitrophenol for about 20 times without losing catalytic activity.

Antibacterial Assessment of Biofabricated Magnesium Oxide Nanoparticles (MgO NPs) using Conocarpus erectus Leaf Extract

Nanobiotechnology is a proficient technology that concers with nano scale materials in several scientific fields such as nanotechnology, chemistry, medicines and biotechnology. A swift and sustainable synthesis of metal oxide nanoparticles by exhausting natural sources is the present-day trend being used instead of lethal biochemical methods. This study prsent the first report for the use of medicinal plant of Conocarpus erectus as an ecofriendly regent in the synthesis of CuO NPs using copper sulphate as a starting material. Conocarpus erectus leaf extract was used as a bioreductor as wll as a capping agent in the manufacturing of MgO NPs. The structure and morphology of prepared MgO NPs were characterized byXRD, UV, FTIR, HRTEM, SEM and EDX analysis. The UV-Vis measurment confimrd the formation of MgO NPs by giving SPR peak at 261 nm. The attendance of various functional groups in Conocarpus erectus leaf extract liable for the development and stabilization of MgO NPs were confirmed by FTIR analysis. XRD measurement confirmed the crystaline f.c.c structure of MgO NPs. HRTEM and SEM studies exhibited the small size, spherical shape and uniformly dispersed magnesium oxide nanoparticles. EDX profile further authorized the elemental composition of the synthesized nanoparticles. The biosynthesized MgO NPs were assessed for the embarrassment of bacteria. Furthermore, plant capped MgO NPs have high inhibition efficiency against S. aureus and E. coli with inhibition zones of 17 mm and 16 mm respectively.

Indium doped CdTe colloidal quantum dots stabilised in aqueous medium for white light emission

Pristine and Indium (In) (1–5 at. %) doped Cadmium Telluride (CdTe:In) quantum dots (QDs) are synthesised through an aqueous colloidal route using 3-Mercaptoproponic acid (3- MPA) as capping agent. The structural and morphological details of these QDs are elucidated from XRD and HRTEM studies. The CdTe:In QDs are obtained by adding InCl3 precursor to reaction mixture. The increase in concentration of InCl3 precursor increases the In doping in CdTe QDs at the same time the particle size of CdTe:In QDs decreases from 3.5 nm to 2.3 nm. The chloride ions from InCl3 precursor control the growth of CdTe:In QDs and 3- MPA as capping agent stabilizes the QDs in aqueous medium. The size reduction of CdTe:In QDs results in blue shifted in absorbance and photoluminescence emission spectra compared to the pristine CdTe QDs with an estimated increase in the band gap from 2.13 to 2.3 eV. A white light emitting nanocomposite phosphour was prepared by mixing the blue emitting 1,4-bis-2-(5-phenyl oxazolyl)-benzene (POPOP) organic fluorophore with green emitting CdTe:In and red emitting CdTe QDs. White light emission was achieved by optimising the concentration of POPOP, In:CdTe and CdTe in the aqueous solution. This POPOP+In:CdTe + CdTe nanocomposite mixture shows the white light emission with CIE coordinates of (0.3321, 0.3391), CCT of 5561 K and a CRI of about 91. Hence, the present study reveals that POPOP + CdTe + CdTe:In (1%) hybrid nanocomposite has potential application in white LED and display technology.

Microwave-assisted facile fabrication of α-Fe2O3/CoFe2O4/Co3O4 ternary nanohybrids with highly enhanced photocatalytic activity

Novel magnetically recyclable α-Fe2O3/CoFe2O4/Co3O4 ternary nanohybrids were fabricated via microwave irradiation assisted co-precipitation as well as co-precipitation together with calcination and well characterized by FESEM, TEM, HRTEM, XRD, Raman, XPS, time resolved PL and UV–vis spectroscopy. FESEM and TEM results confirmed nanoparticles and nanodisc-like morphology of nanostructures in the samples fabricated via simple co-precipitation and microwave assisted co-precipitation, respectively. Raman, XRD, TEM, HRTEM and XPS studies revealed α-Fe2O3, CoFe2O4 and Co3O4 phases confirming the ternary hybrid nature of the prepared nanoparticles and nanodisc samples. α-Fe2O3/CoFe2O4/Co3O4 hybrid nanodiscs exhibited excellent magnetic separability and enhanced photocatalytic efficiency for the decomposition of MB and MG dyes in water. The photocatalytic mechanism demonstrating the dye degradation process and the role of reactive oxygen species responsible of the decolorization of dye investigated via in-situ scavenger trapping experiment were also discussed.

Food-Grade Quercetin-Loaded Nanoemulsion Ameliorates Effects Associated with Parkinson's Disease and Cancer: Studies Employing a Transgenic C. elegans Model and Human Cancer Cell Lines.

A nanosized food-grade quercetin-loaded nanoemulsion (QNE) system comprising capmul MCM NF (oil) and cremophor RH 40 (surfactant) was developed using a high-speed homogenization technique. The developed QNE was studied for its significant neuroprotective (anti-Parkinsonism) and cytotoxicity (anticancer) effects against Caenorhabditis elegans (C. elegans) strains and human cancer cells, respectively. HR-TEM studies revealed that the QNE was spherical with a mean globule size of ~50 nm. Selected area electron diffraction (SAED) studies results demonstrated that QNE was amorphous. In vivo results show that QNE potentially reduced the α-Syn aggregation, increased mitochondrial and fat content, and improved the lifespan in transgenic C. elegans strain NL5901. QNE significantly downregulated the reactive oxygen species (ROS) levels in wild-type C. elegans strain N2. In vitro results of the MTT assay show that QNE significantly exhibited chemotherapeutic effects in all treated human cancer cells in an order of cytotoxicity: HeLa cells > A549 cells > MIA PaCa-2 cells, based on the IC50 values at 24 h. Conclusively, the QNE showed improved solubility, targetability, and neuroprotective effects against the PD-induced C. elegans model, and also cytotoxicity against human cancer cells and could be potentially used as an anti-Parkinson’s or anticancer agent.

Exploring the Impact of Bioformulated Copper Oxide Nanoparticles on Cytomorphology of Alternaria brassicicola.

Black leaf spot of Brassica species is caused by a foliar pathogen Alternaria brassicicola (A. brassicicola), the noxious killer of mustard, cabbage, and cauliflower crops. The current investigation involved the synthesis of copper oxide nanoparticles (CuO NPs) from potential strain of Trichoderma harzianum (T. harzianum). Characterization of CuO NPs was performed by UV-vis, FTIR, XRD, SEM-EDX, and HR-TEM studies. UV-visible spectra showed an absorption peak at 275nm. FTIR study revealed the presence of N-H bonds which could be due to the presence of enzymes and secondary metabolites released in the filtrate of T. harzianum. SEM and HR-TEM revealed the cube shape CuO NPs formed and average particle size was in the range of 31-45nm. Poisoned food technique was used to check the antifungal efficacy of CuO NPs against A. brassicicola at various concentrations (0.025, 0.050, 0.1, and 0.15mg/mL). In vitro assays carried on potato dextrose agar showed maximum antifungal activity at 0.15mg/mL. The control sample have cylindrical and oblong shape conidia, while transverse septation was 2-4 in untreated population. The lower concentrations of CuO NPs (0.025 and 0.050mg/mL) caused malformed spherical shape conidia with excessive septation, while its higher concentrations (0.1 and 0.15mg/mL) leads to viability loss in fungal culture. Results indicated that a higher concentration of CuO NPs serve as an effective biocidal concentration for the control of phytopathogens.

Antioxidant activity of SeO decorated self-assembled nanotubes of 3,5-bis-trifluromethyl benzylamine derivative of phenylalanine electrochemical activity and its DFT studies

In the current work, selenium oxide (SeO) which functions as an antioxidant in plants is studied and compared with self-assembled nanotubes of 3,5-bis-trifluoromethyl benzylamine derivative of single amino acid phenylalanine nanotubes (BPPNTs) decorated/intercalated SeO nanocomposites. Structural characterizations were done by UV, FT-IR, P-XRD, HR-TEM, Raman, and electrochemical studies. This study is conducted to determine the potential of BPPNTs-SeO composite against the radical formations through in-vitro tests like hydrogen peroxide(H2O2) and 2,2-Diphenyl-1-picrylhydroxyl (DPPH) free radical scavenging assay. The Impacts of covalent fictionalization of BPPNTs-SeO nanocomposites and their geometric and electronic properties are examined by the first-principles calculations. Energy of interaction and the charge distribution of the functionalized BPPNTs with the SeO are used to explain the antioxidant potential of the reported nanocomposite.

Facile and rapid synthesis of solar-driven TiO2/g-C3N4 heterostructure photocatalysts for enhanced photocatalytic activity

TiO2 has been successfully coupled with graphitic carbon nitride (g-C3N4) using the thermal deposition method to create an advanced heterojunction photocatalyst. The prepared photocatalysts were studied for photocatalytic hydrogen production and methylene blue dye degradation. The synthesized materials were thoroughly characterized by XRD, XPS, FT-IR, HR-TEM, UV-Vis DRS, and Photoluminescence studies. The results obtained clearly confirm that the photocatalytic efficiency of TiO2 is significantly enhanced after making the nanocomposite with g-C3N4 nanostructures. The hydrogen production rate under simulated sunlight irradiation for a TiO2/g-C3N4 heterojunction photocatalyst has been obtained at approximately 110 μmolg−1h−1. Trapping tests of active species during photocatalysis clearly revealed that O2•‒ played a critical role to enhance the activity. It is significantly proved that the enhancement in the photocatalytic activity is due to the interfacial contact between the TiO2 and g-C3N4, which effectively reduces the electron hole recombination. Eventually, the influence of bandgap energies and their band edge potentials were discussed by proposing a well defined schematic mechanism.

Enhanced photodegradation of methylene blue from aqueous solution using Al-doped ZnS nanoparticles.

The post-transition semiconducting material of pure zinc sulfide (ZnS) and various concentrations of aluminum (Al) (2.5 wt%, 5.0% wt, 7.5 wt%, and 10% calcined at 200 °C) doped ZnS nanoparticles (NPs) were synthesized by sol-gel procedure. The crystal-like nature and phase structure of the product were examined by powder XRD analysis. This analysis shows that the pure ZnS nanoparticle does not form any secondary phase. The functional group of synthesized materials was analyzed by FTIR examination. The energy gap of the materials is calculated using electro-optic analysis and the Kubelka-Munk equation varies from 3.04 nm to 3.63 nm. The photoluminescence studies show the wide emissions (blue to green) for pure ZnS and Al-doped ZnS nanomaterials. The SEM images show the spherical structure and the agglomerated nanostructures. The presence of Zn, S, and Al are confirmed by EDAX spectra. From HR-TEM studies, pure ZnS and Al-doped ZnS nanoparticles exhibit uniform particle sizes. The rate of degradation was observed using MB dye. MB dye has maximum wavelength (λmax) of 664 nm. The dye degradation efficiency was improved as the dye ratio increased. Photocatalytic activities studies show the intensity of photocatalytic activities decreased for the maximum time interval. Doping of Al in ZnS boosts the photocatalytic activity. Hence, Al-doped ZnS appears to be better decomposing MB dye when exposed to visible light.

A HR-TEM study on two generations of magnetite from the Alemao IOCG deposit, Carajás, Brazil: Implication for Fe-Cu mineralization

Multiple generations of magnetite are common in many magmatic-hydrothermal Fe deposits, which can be formed by different mechanisms. This study investigates magnetite from the Alemao IOCG deposit (Brazil) characterized by inclusion-rich cores (Mag-1) and inclusion-poor rims (Mag-2), using electron probe microanalyzer and high-resolution transmission electron microscopy (HRTEM), to understand its formation mechanism and implications for Fe and Cu mineralization. Electron probe microanalysis shows that Mag-1 has Si and Mg contents of 0.28–1.15 wt% and 0.11–0.49 wt%, respectively, higher than Mag-2. Mineral nanoinclusions of minnesotaite, chlorite, quartz, and minor Ti-rich magnetite in the Mag-1 account for the relatively high Si and Mg in the Mag-1, as measured by electron probe microanalysis. The crystal orientation of nanoinclusions relative to the host Mag1 indicates formation by growth entrapment, where they crystallized from boundary layer supersaturated fluids under non-equilibrium conditions.Identification of a reaction front, spatial coupling of parent and product phases at micro- and nano-meter scales support the formation of Alemao Mag2 by coupled dissolution and reprecipitation (CDR). Variations in fluid composition rather than fluctuations in conditions such as temperature and oxygen fugacity are the factors inducing CDR. A conceptual model is proposed for the formation of Alemao magnetite where Fe-rich fluids formed inclusion-rich primary magnetite and CDR reactions modified the texture and chemical composition of primary magnetite to form a core rich, and a rim poor, in nanoinclusions. During CDR, impurities of Si, Ca, Al, Mn, and Mg and nanoinclusions are removed from the primary magnetite and formed product magnetite with higher Fe. The progressive enrichment of Cu from Mag-1 to Mag-2 during CDR indicates that a Cu-rich fluid related to the Cu-Au mineralization is responsible the formation of Cu-rich Mag-2 and chalcopyrite. Therefore, micron- to nano-scale characterization of magnetite with multiple generations can provide important constraints on fluid evolution in ore system.

Study of γ-valerolactone production from hydrogenation of levulinic acid over nanostructured Pt-hydrotalcite catalysts at low temperature

Hydrogenation of levulinic acid (LA) to γ-valerolactone (GVL) is an important reaction in biomass upgradation to produce value-added chemicals. In this work, we have successfully prepared well dispersed nanocrystalline Pt-HT catalyst and found that this catalyst is showing excellent performance for the levulinic acid hydrogenation to produce GVL. Pt-HT catalyst showed ∼100% conversion with ∼100% selectivity of GVL at low temperature with external hydrogen in a batch reactor in aqueous medium. Different reaction parameters like hydrogen pressure, temperature, reaction time and loading of Pt were studied in detail. The catalyst was successfully reused up to 7 times without any loss of the catalytic activity. The catalyst was characterized by XRD, SEM, HR-TEM, BET, XPS, TPR, TPD and DFT study. It was observed that the highly dispersed metallic Pt is the active species to achieve the good conversion and selectivity of GVL even at room temperature and the catalyst is showing very high stability and recyclability during hydrogenation, making it very promising truly heterogeneous catalyst for practical γ-valerolactone production via hydrogenation of levulinic acid.

Evolution Of Bi2Te3 Nanoflowers Through Imperfect Orient Attachment Growth

In this work, Bi2Te3 nanoflowers were successfully synthesized through hydrothermal method. The effect of reaction time on crystal growth and the morphological evolution of these nanoflowers were studied in detail. The obtained nanopowders were characterized by employing XRD, FESEM, EDAX, HRTEM, and Raman studies. The XRD results shows that rhombohedral Bi2Te3 is obtained, without any impurities, at a reaction time of 8, 24, and 36 hours. But along with Bi2Te3, elemental Te is obtained at a reaction time of 4 hours. A growth mechanism for the evolution of nanoflowers from primary nanoplates is proposed, based on the experimental results. The HRTEM images shows that an imperfect orient attachment of primary nano plates leads to the twisting and bending of nanoplates, resulting in well-formed nanoflowers. Lattice imperfections, including twinning boundaries, incoherent boundaries, and stacking faults, will reduce thermal conductivity and improve thermoelectric conversion efficiency of the material.

Impact of Green Synthesized Copper Doped Nanostructured Molybdenum Oxide Flakes on Micro Structural, Electrical, and Electrochemical Properties

In the present work, the different weight percentage (0, 2, 4, 6, 8, and 10 wt %) of copper (Cu) incapacitated MoO3 flakes were successfully green synthesized by combustion technique using precursor ammonium heptamolybdate tetrahydrate, fuel Shorea Robusta leaves extract, and copper nitrate trihydrate as dopant. XRD analysis reports that the synthesized Cu doped MoO3 material exhibits orthorhombic configuration with high crystallanity nature and the XRD pattern show a shift in diffractive peak towards lower diffractive angle as the Cu dopant percentage increases. FT-IR analysis shows the presence of stretching bond between molybdenum and oxygen atom (Mo=O) at 993cm-1. From SEM morphological analysis flake like structure was observed. The HRTEM studies shows d-spacing of 0.20 nm for 6 wt% Cu doped MoO3 flakes with irregular shapes. UV-DRS studies reports the bandgap ranges from 3.15 eV to 3.36 eV for different weight percentage Cu doped MoO3 flakes and for 6 wt% Cu doped MoO3 flakes obtained bandgap is less (3.15 eV). EIS studies reveal the impedance ranges from 180 Ω to 300 Ω. The bandgap and impedance results shows good conductivity for 6 wt% Cu doped MoO3 flakes compared to other synthesized weight percentage nanostructured Cu doped MoO3 flakes. The improved bandgap and impedance were observed for 6 wt% Cu doped MoO3. Hence, 6 wt% Cu doped MoO3 can be employed as anode electrode material for LIBs.

Silver nanostructures prepared via novel green approach as an effective platform for biological and environmental applications

Silver nanoparticles play a significant role in biomedical sciences due to their unique properties allowing for their use as an effective sensing and remediation platform Herein, the green synthesis of silver nanostructures (Ag NSs), prepared via aqueous extract of waste Brassica oleracea leaves in the presence of silver nitrate solution (10-4 M), is reported. The Ag NSs are fully characterized and their efficacy with respect to 4-nitrophenol reduction, glucose sensing, and microbes is determined. Visually, the color of silver nitrate containing solution altered from colorless to yellowish, then reddish grey, confirming the formation of Ag NSs. HRTEM and SEAD studies revealed the Ag NSs to have different morphologies (triangular, rod-shaped, hexagonal, etc., within a size range of 20–40 nm) with face-centered cubic (fcc) crystal structure. The Ag NSs possess high efficacy for nitrophenol reduction (<11 min and degradation efficiency of 98.2%), glucose sensing (LOD: 5.83 µM), and antimicrobial activity (E. coli and B. subtilis with clearance zones of 18.3 and 14 mm, respectively). Thus, the current study alludes towards the development of a cost-effective, sustainable, and efficient three-in-one platform for biomedical and environmental applications.

Metal/metal oxide-decorated covalent organic frameworks as electrocatalysts for electrocarboxylation and water splitting

A o-tolidine based triazine (TTP) covalent organic framework was prepared, and successful formation of the porous polymer network was confirmed by solid state 13C and 15N CP-MAS NMR spectra, XRD, and other morphological techniques. The synthesized TTP was decorated with transition metal/metal oxide nanoparticles (Cu, Ni, and Cu–Ni). The presence of CuO and NiO nanoparticles on the TTP matrix were confirmed by Raman spectroscopy and the PXRD analysis and different morphologies with modest changes in particle size and porosity were confirmed by FE-SEM and HR-TEM studies. As evidenced by onset potential and current density, the Cu-TTP sample exhibited excellent electrocatalytic activity for the electrochemical carboxylation of propylene oxide in the presence of CO2 and HER, whereas the Ni-TTP sample displayed excellent OER activity. The presence of pyridinic, pyrrolic, and quaternary nitrogen was attributed to the excellent catalytic activity of Cu-TTP for electrocarboxylation and HER activity, whereas secondary amine bonds and a combination of mechanisms were responsible for the increased OER activity of Ni-TTP the sample, as evidenced by XPS.

Influence of Amidation on the Release Profiles of Insulin Drug from Chitosan-Based Matrices

The present study deals with the comparative analysis of insulin drug release from pure chitosan (CS) and its crosslinked amide derivatives. The objective of this study was to investigate the influence of fatty acid derivatives on the release profiles of insulin drug from CS-based matrices. In order to form cross-linked CS-based amide derivatives, the CS biopolymer was reacted with four different fatty acids with varying amount of unsaturation, including stearic acid (SA), oleic acid (OA), linoleic acid (LA), and linolenic acid (LLA), and then subjected to cross-linking. Following this, the pure CS and cross-linked CS amide derivatives were loaded with insulin drug and were characterized thoroughly by making use of various instrumental techniques such as FTIR, UV–Vis, TGA, HRTEM, DLS, PDI, and zeta potential studies. In addition, the insulin release profiles were studied and compared between pure CS and CS amides at two different pHs, 7.4 and 1.2. Finally, the insulin drug release data was investigated with five different pharmacokinetic models (zero, first, Higuchi, Kersmeyer–Peppas, and Hixson models). From the analysis, the cross-linked CS amides was found to be superior to pure CS, and within the amide derivatives, the one with a high amount of unsaturation, LLA-derived CS biopolymer, was shown to be better for the release of insulin drug by means of the diffusion and dissolution pathways.

Radiation damage during HRTEM studies in pure Al and Al alloys

Abstract During transmission electron microscopy (TEM) investigations of Al alloys, defects caused by the electron irradiation can occur. Since the image contrast of these irradiation defects is similar to that of early stages of precipitates, care is needed to avoid confusion. In the present paper the formation and the coarsening of radiation damage defects were studied by in situ TEM in both, pure Al and Al alloys. High-resolution (HR)TEM images show on an atomic level that the radiation defects are extrinsic Frank loops (some converted into unfaulted prismatic loops); they are distributed homogeneously within the TEM foil but inhomogeneously on the four {111} planes. Applying HRTEM imaging conditions, the minimum electron energy causing defects is found to be as low as 110 keV using a [110] beam direction. The results for pure Al are very similar to those of the Al alloys. Therefore, during HRTEM studies (using accelerating voltages &gt; 100 kV) the formation of radiation defects seems inevitable; they can be distinguished from the early stages of precipitates if they lie on different planes.