Scanning Atomic Force Microscopy Research Articles

Nanomechanical properties of kidney stones, gallstones and oral stones compared with tap water scale by depth sensing indentation

This article focuses on a description of research performed to identify structural and mechanical properties differences between calculi in stones, such as gallstones, kidney stones, dental tartar, and saliva gland sialolite, were analyzed and compared with tap water stone, in order to set interrelations. In this study, biological hard pebble-like structures were analyzed and compared among them using Scanning Electron Microscopy (SEM), X-Ray diffraction (XRD), and Atomic Force Microscopy (AFM). In addition, Nanoindentation was used to obtain values as example in kidney stones the in; stiffness S = 27,827 ± 620 N/nm elastic modulus E = 27.3 ± 4.5 GPa, hardness H = 1.5 ± 0.5 GPa. Samples with the highest amounts of calcium and magnesium oxides were; Tap water stone (39.60%), followed by dental tartar (39.40%), saliva gland sialolite (29.20%), kidney stones (27.70%), and lastly the gallstones (0.30%). Kidney stones showed in particular, whewellite and kaoulinite crystallographic phases, that confers characteristics of greater crystallization with respect to the other stones. Kidney stones positioned in the major hardness stone in human body with 1.5 GPa. In general, samples with the highest amount of calcium oxides, also showed the highest mechanical properties of H and E. Microstructural characteristics and nano-hardness of tap water stone from drinking water where similar to those of dental tartar and saliva gland sialolite, more research still required to associate health concerns and tap water scale derived from drinking water known as hardwater.

Process optimization of broad ion beam milling for preparation of coating cross-sections

The application of Argon ion based broad ion beam milling in the preparation of coating cross-sections is systematically evaluated in this work. In order to reduce and eliminate defects and artefacts from the prepared sectional surface, the substrate side of the sample is found to be best facing the ion beams, and the milling time needs to be optimized to be not too long to introduce scratching of the obtained surface, while not too short to result in particle deposition. Further, the energy of the ion beams is found to have great effect on the etch rate of the sample, thus having a large impact on the process time and quality depending on the materials nature of the samples. It is found that by introducing a second low-energy polishing step after the high-energy milling step, the quality of the cross-section is greatly improved with the measured surface roughness down to the nanometer scale. The capability of broad ion beam milling method to provide smooth cross-sections for the subsequent microscopic investigations by e.g. scanning electron microscopy or atomic force microscopy is important to reveal morphological information of the coating systems with high level of details without distortions due to sample preparation.

The effect of surface roughness on re-passivation and pitting corrosion of super duplex stainless steel UNS S 32760

Stainless steel is used as a battery case material because of its excellent strength and corrosion resistance. Among the stainless steels used in fields requiring superior corrosion resistance, duplex stainless steels, composed of austenite and ferrite, exhibit improved strength and corrosion resistance. In particular, super duplex stainless steel (SDSS), with a pitting resistance equivalent number (PREN) between 40 and 50, offers excellent strength and corrosion resistance, making it suitable for structural components in various applications. However, the actual corrosion resistance of a material is often lower than its theoretical value, which has led to extensive research efforts to enhance practical corrosion resistance. Recent studies reported atomic-scale measurements of corrosion resistance and identified the influence of atomic layers on corrosion. Corrosion properties were studied by Trinh et al. (2020) and Nilsson (1992) [26]; however, they did not examine the re-passivation of the SDSS. SDSS requires re-passivation because of real corrosion. Although structural stainless steels are processed to achieve surface roughness in the micrometer range and undergo passivation, research on this aspect is still lacking. To enhance the performance of SDSS, research on re-passivation before and after pitting is required. Therefore, this study analyzed the effect of surface roughness variation from 100 to 1000 nm on the corrosion resistance and re-passivation with or without pitting of SDSS. The surface conditions corresponding to different roughness levels were analyzed using field emission scanning electron microscopy (FE-SEM) and atomic force microscopy (AFM), while corrosion resistance was evaluated through open circuit potential (OCP) measurements, potentiodynamic polarization tests, and cyclic polarization tests at 0.6 V (before broken passivation layer) and 1.3 V (after broken passivation layer), as well as critical pitting temperature (CPT) tests. Surface roughness reduces the corrosion potential (Ecorr) and increases the corrosion current density (Icorr) for activation polarization. With passivation, as the surface roughness increased, uniform corrosion decreased, resulting in a stronger passive layer. The surface roughness lowered the OCP and increased the corrosion rate, thereby reducing the corrosion resistance. Therefore, when SDSS is used in an environment prone to corrosion, a surface roughness of less than 100 nm exhibits superior corrosion resistance.

Double Effects of Oxidative Aging on Carbon Nanotube-Asphalt Nanocomposite Interfaces: Enhancement and Deterioration.

Understanding the mechanisms of oxidative aging effects on the carbon nanotube (CNT)-asphalt nanocomposite interface has long been a challenge, as there are two opposing effects: enhancement and deterioration. In this study, a multiscale coupling method is proposed to analyze the dual effect of oxidative aging on the CNT-asphalt nanocomposite. The method is based on density functional theory (DFT) and molecular dynamics (MD) simulations, supported by microscopic interface observation and macroscopic property testing with a focus on the composite interface. The results show that oxidative aging has a resetting effect on benzene ring stacking at the interface and enhances the binding energy of CNT-asphalt. Meanwhile, oxidative aging enhanced the interfacial charge transfer, but no chemical reaction occurred between CNT-aged asphalt. This is also verified by Fourier Transform Infrared Spectroscopy (FTIR). Enhancement and degeneration effects of oxidative aging occur via distinct mechanisms. Oxidative aging enhanced the interfacial shear barrier by approximately 5% and the energy barrier by 44.87%, which increased the high-temperature deformation resistance of the CNT-asphalt nanocomposites. However, molecular oxidation was not responsible for the decline in the fatigue resistance. According to scanning electron microscopy (SEM) and atomic force microscopy (AFM) results, oxidative aging elevates the content of polar molecules, leading to an increase in the solid properties of asphalt and a 39.6% decrease in surface adhesion. This disrupts the three-dimensional network of the CNT and ultimately leads to a reduction in crack resistance. This study clarifies the mechanism underlying the dual effect of oxidative aging and provides fundamental support for understanding asphalt aging behavior and the interfacial behavior of composites.

Comparison of the Eggshell and the Porcine Pericardium Membranes for Guided Tissue Regeneration Applications.

Guided bone regeneration is frequently used to reconstruct the alveolar bone to rehabilitate the mastication using dental implants. The purpose of this article is to research the properties of eggshell membrane (ESM) and its potential application in tissue engineering. The study focuses on the structural, mechanical, and histological characteristics of ESM extracted from Gallus domesticus eggs and to compare them to a commercially available porcine pericardium membrane (Jason® membrane, botiss biomaterials GmbH, Zossen, Germany). Thus, histology was performed on the ESM, and a comparison of the microstructure through scanning electron microscopy and atomic force microscopy (AFM) was conducted. Also, mechanical tensile strength was evaluated. Samples of ESM were prepared and treated with alcohol for fixation and disinfection. Histological analysis revealed that the ESM architecture is constituted out of loose collagen fibers. However, due to the random arrangement of collagen fibers within the membrane, it might not be an effective barrier and occlusive barrier. Comparative analyses were performed between the ESM and the AFM examinations and demonstrated differences in the surface topography and mechanical properties between the two membranes. The ESM exhibited rougher surfaces and weaker mechanical cohesion attributed to its glycoprotein content. The study concludes that while the ESM displays favorable biocompatibility and resorb ability, its non-uniform collagen arrangement limits its suitability as a guided bone regeneration membrane in the current non-crosslinked native form. Crosslinking techniques may enhance its properties for such applications. Further research is needed to explore modifications and processing methods that could leverage the ESM's unique properties for tissue engineering purposes.

Low damage atomic layer etching technology for gate recessed fabrication

In this work, the damage induced by etching to AlGaN surface employing atomic layer etching (ALE), which use Cl2 plasma and Ar plasma for etching and removal, compared with conventional etching method was investigated. The Hall-effect measurements indicate that a higher two-dimensional electron gas (2DEG) concentration of 1.54 × 1013 cm−2 is achieved and an electron mobility of 1756 cm2/V is obtained on the ALE sample by reducing the bombardment of BCl2+ and BCl + on the surface. Simultaneously, the damage caused by ALE to the etching surface is lower than the conventional etching method according to Raman spectroscopy analyses and atomic force microscopy (AFM) scans. The X-ray photoelectron spectroscopy (XPS) spectrum and Transmission Electron Microscope (TEM) measurements were further carried out to prove that ALE process results in a higher 2DEG concentration due to maintaining stable Al composition and inducing lower damage on the surface.

Preparation and characterization of PSF/SPSF blended ultrafiltration membranes

Purpose This paper aims to improve the permeability and antifouling of polysulfone (PSF) ultrafiltration membranes, the PSF matrix was modified by incorporating sulfonated polysulfone (SPSF). Design/methodology/approach Systematic investigations were conducted on the synergistic effects of a pore-forming agent, coagulation bath temperature and SPSF doping in the casting solution on blended ultrafiltration membranes. The chemical composition of the membranes was analyzed using Fourier transform infrared spectroscopy. The morphology and surface roughness of the membranes were characterized using scanning electron microscopy and atomic force microscopy. The hydrophilicity of the membrane surface was analyzed using a contact angle meter. The permeability and antifouling properties of the blended membranes were also investigated through filtration experiments. Findings The results indicated that the blended ultrafiltration membranes demonstrated an optimal overall performance when PVP-K30 content was 5.0 Wt.%, coagulation bath temperature was 30°C and SPSF content was 2.4 Wt.%. In comparison to a pure PSF ultrafiltration membrane, there was a significant increase in pure water flux (390.7 L·m−2·h−1) by 2.2 times, while bovine serum albumin retention slightly decreased to 93.8%. In addition, the flux recovery rate improved by 2.1 times (71.4%) compared to that of the original PSF ultrafiltration membrane. Practical implications The method provided a simple and practical solution for improving the antifouling and permeability of PSF ultrafiltration membranes. Originality/value SPSF was anticipated to serve as an excellent modification additive for the preparation of ultrafiltration membranes with superior properties.

Evaluation of Optical Window Integrity Under Wall Heat Flux of Scramjet Intake

The structural integrity of sapphire optical windows was numerically and experimentally evaluated under the wall heat flux of the scramjet intake. The considered heating profile was during 60 s, and the heating profile for the numerical and experimental approaches was the same. A numerical study was performed using the finite element method; the numerical results predicted that the maximum temperature of the optical window under the heating condition was about 600 K, the maximum principal stress was less than the strength of the sapphire, and the failure of the optical window would not occur based on the brittle Coulomb–Mohr material failure theory. The heating test was performed using an electrical heater under the heating condition, and the morphology was investigated using scanning electron and atomic force microscopies. The experimental results indicated that no cracks or fractures occurred on the surface of the optical window after the heating test, except for a slight change in the shape and roughness of the microstructure.

Study and characterization of the nanotextured Ga2O3-GaOOH formations synthesized via thermal oxidation of GaAs in ambient air

In this work, we present the characterization of a UV-sensitive material based on Ga2O3-GaOOH, which was obtained through the thermal oxidation of GaAs wafers in ambient air to achieve Ga2O3. The material’s oxidation mechanism was thoroughly examined using structural, compositional, and optical approaches. X-ray diffraction analysis identified the presence of the β-Ga2O3 crystalline phase, with both in-plane and out-of-plane preferred orientations, along with crystalline inclusions attributed to GaOOH. Furthermore, energy-dispersive spectroscopy confirmed the uniform sublimation of Arsenic, as evidenced by elemental mapping, while Fourier-transform infrared spectroscopy suggested the inclusion of −OH bonds. Surface analysis was carried out by field emission scanning electron microscopy and atomic force microscopy, revealing a grain size of approximately 20 nm. Finally, UV-Vis characterization unveiled a bandgap ranging from 2.9 to 3.9 eV, indicative of the material’s potential for UV-sensitive applications. Overall, the results demonstrate the consistency and reliability of the oxidation process, providing valuable insights into the properties of the Ga2O3-GaOOH material for potential technological advancements.

Industrial textile wastewater treatment using Neolamarckia cadamba NFC filter paper via cross-flow filtration system

This study investigated the potential use of Neolamarckia cadamba as nanofibrillated cellulose (NFC) filter paper for treating industrial textile wastewater via the cross-flow filtration system. Response surface methodology (RSM) was employed to optimize the system and create a predictive model to evaluate the performance of the NFC filter paper. Experimental results from the central composite design (CCD) showed that a high value of colour removal efficiency of 90.56 % and an optimum value of normalized flux of 0.7397 were achieved at pH 6.5 with 100 % of initial feed concentration of the textile wastewater and 60:40 cellulose dosage ratio of the NFC filter paper. Optimisation and verification experiments were conducted under the optimal conditions determined. The formation of a cake layer in the two stages of the membrane fouling mechanism under the optimum operational condition was revealed using model fitting according to Wiesner and Aptel equations and confirmed via Field emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM) analyses. Water quality in terms of colour, pH, chemical oxygen demand (COD), biochemical oxygen demand (BOD) and turbidity was monitored to determine if the treated wastewater met the discharge limits. The findings of this study demonstrated the potential of using the NFC filter paper for industrial textile wastewater treatment and provided valuable insights for optimising the operating parameters of filter papers.

Investigating biochemical and structural changes of glycated collagen using multimodal multiphoton imaging, Raman spectroscopy, and atomic force microscopy

Advanced glycation end products (AGEs) form extracellular crosslinking with collagenous proteins, which contributes to the development of diabetic complications. In this study, AGEs-related pentosidine (PENT) crosslinks-induced structural and biochemical changes are studied using multimodal multiphoton imaging, Raman spectroscopy and atomic force microscopy (AFM). Decellularized equine pericardium (EP) was glycated with four ribose concentrations ranging between 5 and 200 mM and monitored for up to 30 days. Two-photon excited fluorescence (TPEF) and second harmonic generation (SHG) microscopic imaging probed elastin and collagen fibers, respectively. The glycated EP showed a decrease in the SHG intensities associated with loss of non-centrosymmetry of collagen and an increase of TPEF intensities associated with PENT crosslinks upon glycation. TPEF signals from elastin fibers were unaffected. A three-dimensional reconstruction with SHG + TPEF z-stack images visualized the distribution of collagen and elastin within the EP volume matrix. In addition, Raman spectroscopy (RS) detected changes in collagen-related bands and discriminated glycated from untreated EP. Furthermore, AFM scans showed that the roughness increases and the D-unit structure of fibers remained unchanged during glycation. The PENT crosslinked-induced changes are discussed in the context of previous studies of glutaraldehyde- and genipin-induced crosslinking and collagenase-induced digestion of collagen. We conclude that TPEF, SHG, RS, and AFM are effective, label-free, and non-destructive methods to investigate glycated tissues, differentiate crosslinking processes, and characterize general collagen-associated and disease-related changes, in particular by their RS fingerprints.

(Invited) Predicting Voxel Scale Geometry and Properties in Vat Photopolymerization Via Microscopic and Machine Learning Methods

Additive manufacturing (AM) promises disruption of traditional manufacturing supply chains, democratizing and distributing manufacturing, enhancing flexibility and enabling previously impossible geometries and customization. Applications range from aerospace to regenerative medicine, leveraging the numerous benefits of the technology. Within polymer AM, vat photopolymerization, enabled by advances in high-resolution display technologies (e.g. liquid crystal display - LCD, digital light processing - DLP) to locally cure liquid resin into solid polymer, prints millions of voxels per layer simultaneously in a few seconds or less. Typically, these layers are combined step-wise until a 3-dimensional part is formed. Fundamental understanding and control of the printing process with geometrically and mechanically precise voxels requires characterization of parts at voxel and sub-voxel length scales. Despite the precise, high-resolution light engines, resultant parts exhibit defects such as over/under-polymerization, 3-dimensional anisotropy, weakened layer interfaces and more. In this presentation, we examine the formation of these defects starting from individual voxels and simple patterns, but extending to complex voxel-voxel interactions. We discuss novel, multiscale measurement tools such as atomic force microscopy and laser scanning confocal microscopy that elucidate the small-scale printing process in both space and time. The novel characterizations are used to develop new models of the printing process and enable precise geometric and mechanical control of the individual voxels. Finally, we introduce the use of neural network models and big-data to predict the output of arbitrary photomasks.

Thermal induced deflection in atomic force microscopy cantilevers: analysis & solution

Atomic force microscopy (AFM) cantilevers are commonly made from two material layers: a reflective coating and structural substrate. Although effective, this can result in thermally induced cantilever deflection due to ambient and local temperature changes. While this has been previously documented, key aspects of this common phenomenon have been overlooked. This work explores the impact of thermally induced cantilever deflection when in- and out-of-contact, including the topographic scan artefacts produced. Scanning thermal microscopy probes were employed to provide direct cantilever temperature measurement from Peltier and microheater sources, whilst permitting cantilever deflection to be simultaneously monitored. Optical lever-based measurements of thermal deflection in the AFM were found to vary by up to 250% depending on the reflected laser spot location on the cantilever. This highlights AFM’s inherent inability to correctly measure and account for thermal induced cantilever deflection in its feedback system. This is particularly problematic when scanning a tip in-contact with the surface, when probe behaviour is closer mechanically to that of a bridge than a cantilever regarding thermal bending. In this case, measurements of cantilever deflection and inferred surface topography contained significant artefacts and varied from negative to positive for different optical lever laser locations on the cantilevers. These topographic errors were measured to be up to 600 nm for a small temperature change of 2 K. However, all cantilevers measured showed a point of consistent, complete thermal deflection insensitivity 55% to 60% along their lengths. Positioning the reflected laser at this location, AFM scans exhibited improvements of up-to 97% in thermal topographic artefacts relative to other laser positions.

Simply controlling the surface structure of graphene oxide films using multiple drop-casting

Aqueous graphene oxide inks are promising to fabricate a large-area thin film which can be utilized in various applications such as sensors and energy storage and conversion. In this work, we experimentally demonstrate a facile way to controllably fabricate wrinkled structures on the surface of graphene oxide films by using a drop-casting method. Simple drop-casting of the graphene oxide ink enabled to fabricate randomly distributed wrinkles uniformly over the entire film deposited after water was totally evaporated. Deposition mechanism after a single drop-casting was clearly demonstrated, which involves graphene oxide flake transport, aggregation/deposition at the pinned contact edge of a sessile droplet during water solvent evaporation and also buckled deformation(wrinkle formation) of the deposited graphene oxide thin film due to compressive stress by the receding water droplet contact line. Multiple drop-casting on the initially formed wrinkled structures of the graphene oxide film allowed the wrinkles to grow in their width and height linearly by increasing the number of drop-casting, which resulted in the increase of the size polydispersity and area density of wrinkles. The wrinkle growth mechanism during multiple drop-casting was explained in the perspective of collision and accumulation of graphene oxide flakes dispersed within additional dropped droplet on the initially formed wrinkles during water evaporation and droplet contact line recession, which was supported by high-resolution imaging of the films using scanning electron microscopy (SEM) and atomic force microscopy (AFM). This work suggests that the behavior of the graphene oxide flakes dispersed within a sessile droplet can affect surface structures of deposited thin films, and it can be foundational to extend the simple multiple drop-casting strategy to controlled fabrication of various 2D nanomaterial thin films with wrinkled structures by appropriately controlling ink solution and evaporation conditions, which can be used in a variety of functional applications.

Synthesis and characterization of kesterite Cu2ZnSn(SxSe1-x)4 thin films with low-cost for efficient solar cells

In this study, we conducted an investigation on the Cu2ZnSnS4 (CZTS) kësterite compound, which is considered an attractive material for its favorable absorption properties, making it a suitable semiconductor for photovoltaic applications. However, its market potential is limited by its low efficiency of 12.6%, primarily caused by the presence of secondary phases that act as recombination centers. Theoretically, the efficiency limit for CZTS ranges from 31% to 33%.To enhance the photovoltaic performance of CZTS, we employed a doping strategy by incorporating selenium (Se) into the Cu2ZnSn(SxSe1-x)4 film, where the sulfur-to-selenium ratio (S/Se) was optimized within the range of 0< x <1. The CZTS films were deposited onto FTO substrates using the spray pyrolysis technique, which is a simple and cost-effective method. The characterization of these films involved X-ray diffraction (XRD) and UV–visible spectroscopy analysis. Additionally, the morphology and topography of the CZTSSe layers were examined using scanning electron microscopy (SEM) and atomic force microscopy (AFM), respectively. Transmission electron microscopy (TEM) was also employed.The results obtained in this study indicate that CZTSSe films exhibit band gap values ranging from 1.54 eV to 1.68 eV and grain compactness, with larger agglomerated grains on the film surface when the S/Se ratio is approximately 0.5 or lower. Moreover, the resistivity measurements revealed significant variations when sulfur and selenium were combined, suggesting the influence of their composition on the electrical properties of the CZTS films.

Non-Invasive Intranasal Delivery of pApoE2: Effect of Multiple Dosing on the ApoE2 Expression in Mice Brain.

Chitosan-based polymeric micelles are promising non-viral nanocarriers for safe and targeted gene delivery. Multi-functionalized chitosan polymeric micelles were prepared by grafting fatty acid, cell-penetrating peptide, and mannose on the chitosan backbone. The polymeric micelles were subjected to surface morphology and surface topography using scanning electron microscopy and atomic force microscopy, respectively. The hemotoxic profile of the prepared polymeric micelles was established against erythrocytes and was found to be <5% hemotoxic up to the concentration of 600 µg/mL. In vitro ApoE2 expression in primary astrocytes and neurons was analyzed. Multi-functionalized polymeric micelles produced greater (p < 0.05) transfection in astrocytes and neurons in comparison to mono-functionalized micelles. Intranasal administration of polymeric micelles/pApoE2 polyplex led to significantly higher (p < 0.05) in vivo pApoE2 expression than chitosan and unfunctionalized polymeric micelles-treated mice groups. The outcomes of this study predict that the developed multi-functionalized polymeric micelles could be an effective and safe gene delivery platform to the brain through the intranasal route.

Structural properties of aqueous grown polydopamine thin films determined by neutron reflectometry

In this work, neutron reflectometry (NR) studies of the bio-mimetic polymer, polydopamine (PDA), deposited from differing initial concentrations of precursor material dopamine hydrochloride for a range of polymerization times, is reported. PDA can form a complex and highly versatile polymer film, with many structure studies having been performed previously, but a comprehensive structural determination of PDA by NR is lacking in the literature. It was found that simple box models were incapable of fully explaining the observed data, necessitating the use of a composite model consisting of the weighted average of both the 1 and 2 box models to fully capture the heterogeneous nature of the PDA film structure. Confocal laser scanning microscopy (CLSM) and atomic force microscopy (AFM) were performed to capture the surface structure and relative mechanical difference between the separate domains of the PDA. The CLSM results provide evidence that the PDA domains are larger than the coherent scattering length of a neutron used in these measurements, 10μm, supporting the need for a composite model. The AFM measurements show complex structure below the coherence length provide physical justification for the two box model. It was determined that film structure and quality are both heavily impacted by the initial concentration of dopamine hydrochloride and the polymerization time, giving confidence to the highly customizable nature of PDA as an adhesion promoting interface treatment in composite systems, such as plastic bonded explosives (PBX).

Substance P-Derived Extracellular-Matrix-Mimicking Peptide Hydrogel as a Cytocompatible Biomaterial Platform.

Self-assembled short peptide-based hydrogel platforms have become widely applicable biomedical therapeutic maneuvers for their soft, tunable architecture, which can influence cellular behavior and morphology to an inordinate extent. In this work, a short supramolecular hydrogelator peptide, substance P, has been designed and synthesized from the C terminus conserved "FFGLM" section of a biologically abundant neuropeptide by using a fusion approach. In addition, to incorporate a good hydrophobic-hydrophilic balance, the truncated pentapeptide segment was further C-terminally modified by the incorporation of an integrin-binding "RGD" motif. Thanks to its N-terminal Fmoc group, this octapeptide ensemble "FFGLMRGD" undergoes rapid self-assembly to give rise to an injectable, pH-responsive, hydrogel-based self-supporting platform that exhibited good cytocompatibility with the cultured mammalian cells under both 2D and 3D culture conditions without exerting any potent cytotoxic effect in a Live/Dead experiment. A rheological experiment demonstrated its hydrogel-like mechanical properties, including thixotropicity. The atomic force microscopy and field emission scanning electron microscopy images of the fabricated hydrogel show a tangled fibrous surface topography owing to the presence of the N-terminal Fmoc-FF residue. Furthermore, an in-vitro scratch assay performed on fibroblast cell lines confirmed the wound-ameliorating potency of this designed hydrogel; this substantiates its future therapeutic prospects.

Sustainable removal of phenol from wastewater using a biopolymer hydrogel adsorbent comprising crosslinked chitosan and κ-carrageenan

A biopolymer-based adsorbent comprising chitosan (CS) and κ-carrageenan (κ-Carr) was synthesised and evaluated to treat phenolic-contaminated water. The developed CS/κ-Carr hydrogel demonstrated excellent performance with a phenol adsorption uptake of 80 %. The morphologies of CS/κ-Carr hydrogels with different ratios of CS to κ-Carr ranging from 1:2 to 7:3 were characterised using scanning electron microscopy and atomic force microscopy; their chemical structures were investigated by spectral analyses using Fourier-transform infrared spectroscopy, thermogravimetric analysis, and differential scanning calorimetry; their adsorption characteristics were determined using tests for swelling, chemical stability, hygroscopic moisture content, and hydrophilicity. Finally, a batch-type evaluation method demonstrated adsorption performance at 25 °C and pH 6.9. Adsorption isotherms and kinetic data were successfully obtained using the Freundlich and pseudo-second-order models, respectively. The results indicate that one-pot synthesis of an insoluble CS/κ-Carr hydrogel adsorbent exhibits considerable potential for the removal of phenol from aqueous solutions, providing an environmentally friendly technology enhancing the phenol adsorption performance of CS.

In-depth opto-electrical analysis of Ni:CdS film towards the performance as Ag/Ni:CdS/FTO Schottky diode

Nickel doped cadmium sulfide (Ni:CdS) thin films are deposited onto glass and FTO substrate using spray pyrolysis technique. The effect of annealing temperature on the thin films and its morphological, microstructural, optical dispersion, linear-nonlinear and electrical, properties are extensively investigated by using various techniques such as field emission scanning electron microscope (FESEM) and atomic force microscopy (AFM), X-ray diffraction (XRD) and ultraviolet visible (UV-VIS) diffuse reflectance spectroscopy. Morphological studies revealed that doped thin films surface is almost homogeneous and well-covered. Peaks associated with Ni, Cd and S elements are present in EDS analysis, which confirm the composition of the films. The energy band calculation using the Tauc plot from the recorded absorption spectra reveals the decrement in the energy gap from 3.75 eV to 3.61 eV and the refractive index is in the range of 2.57–2.62. The effect of annealing temperature on complex dielectric constant are also analyzed. Moreover, the dispersion of refractive index is calculated in terms of Wemple-DiDomenico approach. Third order susceptibility and nonlinear refractive index are calculated of Ni:CdS films. The designed Ag/Ni:CdS/FTO Schottky diode is tested under illumination conditions, and the empirical diode parameters, viz. ideality factor, barrier height, series resistance etc. are influenced by annealing temperature.