Oxide Gel Research Articles

3D-printability of aqueous poly(ethylene oxide) gels

Printing technologies combined with a computer-aided design (CAD) have found an increasing number of uses in pharmaceutical applications. In extrusion-based printing, the material is forced through a nozzle to form a three-dimensional (3D) structure pre-designed by CAD. The aim of this study was to evaluate the 3D-printability of biocompatible aqueous poly(ethylene oxide) (PEO) gels and to investigate the effects of three formulation parameters on the 3D printing process. The impact of PEO concentration (gel viscosity), printing head speed and printing plate temperature was investigated at three different levels using a full factorial experimental design. The aqueous PEO gels were printed with a bench-top extrusion-based 3D printing system at an ambient room temperature. The viscosity measurements confirmed that the aqueous PEO gels follow a shear-thinning behaviour suitable for extrusion-based printing. Heating the printing plate allowed the gel to dry faster resulting in more precise printing outcome. With the non-heated plate, the gel formed a dumbbell-shaped grid instead of straight lines. Higher concentration and more viscous PEO gels formed the best structured 3D-printed lattices. In conclusion, the accuracy and precision of extrusion-based 3D printing of aqueous PEO gels is highly dependent on the formulation (PEO concentration) and printing parameters (printing head speed, plate temperature). By optimizing these critical process parameters, PEO may be suitable for printing novel drug delivery systems.

Novel nanostructured iron oxide cryogels for arsenic (As(III)) removal

Novel macroporous iron oxide nanocomposite cryogels were synthesized and assessed as arsenite (As(III)) adsorbents. The two-step synthesis method, by which a porous nanonetwork of iron oxide is firstly formed, allowed a homogeneous dispersion of the iron oxide in the cryogel reaction mixture, regardless of the nature of the co-polymer forming the cryogel structure. The cryogels showed excellent mechanical properties, especially the acrylamide-based cryogel. This gel showed the highest As(III) adsorption capacity, with the maximum value estimated at 118 mg/g using the Langmuir model. The immobilization of the nanostructured iron oxide gel into the cryogel matrix resulted in slower adsorption kinetics, however the cryogels offer the advantage of a stable three-dimensional structure that impedes the release of the iron oxide nanoparticles into the treated effluent. A preliminary toxicity evaluation of the cryogels did not indicate any apparent inhibition of human hepatic cells activity, which together with their mechanical stability and high adsorption capacity for As(III) make them excellent materials for the development of nanoparticle based adsorption devices for drinking water treatment.

Natural Cellulose Derived Nanocomposites as Anodic Materials for Lithium-Ion Batteries.

Bio-inspired synthetic method provides an effective shortcut to fabricate functional nanostructured materials with specific morphologies and designed functionalities. Natural cellulose substances (e. g., commercial laboratory cellulose filter paper) possesses unique three-dimensionally cross-linked porous structures and abundant functional groups for the functional modification on the surfaces. The deposition of metal oxide gel film on the surfaces of the cellulose nanofibers is facilely to be achieved through the surface sol-gel process, resulting in metal oxide replicas of the initial cellulose substance or metal-oxide/carbon nanocomposites. Moreover, the as-deposited metal oxide gel films coated on the cellulose fiber surfaces provide ideal platforms for the further formation of specific functional assemblies, and eventually to the corresponding nanocomposite materials. Based on this methodology, various nanostructured composites were prepared and employed as anodic materials for lithium-ion batteries, including metal-oxides-based (such as SnO2 , TiO2 , MoO3 , Fex Oy , and SiO2 ) and Si-based composites, as summarized in this personal account. Benefiting from the unique hierarchically porous network structures and the synergistic effects among the composite components of the anodic materials, the transfer of electrons/ions is accelerated and the structural stability of the electrode is enhanced, leading to the improved lithium storage performances and promoted cycling stability.

Synthesis of CaO[sbnd]SiO2 compounds and their testing as heterogeneous catalysts for transesterification of sunflower oil

The powder mixtures of calcium oxide (CaO) and silica gel (SiO2) in molar ratios of 1:1, 1.5:1, 2:1 and 3:1 were mechanochemically treated with the addition of water, and were subsequently calcined with a goal of synthesizing CaSiO3, Ca3Si2O7, Ca2SiO4 compounds and CaO/Ca2SiO4 two-phase mixture. The prepared materials were characterized by XRD, FTIR, SEM/EDS, particle size laser diffraction (PSLD), UV–vis diffuse reflectance spectroscopy (DRS), N2 adsorption/desorption isotherms, Hammett indicator for basic strength and volumetric analysis for free CaO content. The catalytic activity of calcium silicates with different Ca/Si ratios was tested in the transesterification of triacylglycerols (sunflower oil) with methanol. Samples obtained with initial composition 2CaO·SiO2 and 3CaO·SiO2 calcined at 700 °C, and 3CaO·SiO2 calcined at 900 °C had high catalytic activity, resulting with triacylglycerols conversion and fatty acids methyl ester formation (FAME or biodiesel) above 96%. The activity of these samples can be attributed to the existence of free CaO defined by CaO/Ca2SiO4 complex mixture. The effect of different amount of catalyst used for transesterification (0.2–2 wt%) was analyzed using the most active catalyst i.e. 3CaO·SiO2 calcined at 700 °C as well as possibility of its reuse for biodiesel synthesis. It was also found that CaSiO3, Ca3Si2O7 and Ca2SiO4, phases did not possess catalytic activity.

Quantification of phosphate ions by diffusive gradients in thin films technique using ferrihydrite as a binding gel and application to marine sediments

A diffusive gradient in thin films (DGT) is a newly developed analytical technique that can isolate and quantify the phosphate ions. A DGT unit comprises two components: the diffusion and binding layers. The diffusion layer comprises polyacrylamide hydrogel, whereas the binding layer from the oxide gel of ferrihydrite is impregnated with polyacrylamide gel. The technique employs a thin film of diffusive hydrogel in contact with a binding phase (ferrihydrite) that can bind phosphate ions. The diffusive and binding gels were characterized via infrared spectroscopy. The main peaks of the diffusive gel were observed at 3336 and 1636 cm−1, whereas those of the binding gel were observed at 3332 and 1638 cm−1. The DGT technique was evaluated as a way to quantify the amount of phosphate ions present in an aqueous KH2PO4 solution. After a contact time of 24 h, ferrihydrite exhibited a high affinity for phosphate, with an uptake efficiency of 98.17%. A linear relationship (R2 = 0.9938) was found to exist between the contact time (3−24 h) and uptake efficiency. Within the 0.2-1.2-mgL−1KH2PO4 concentration range, a linear relationship existed between analyte concentration and the mass of phosphate salt accumulated in the binding gel (R2 = 0.9748). The phosphate ion was eluted from the ferrihydrite hydrogel using 0.25-M H2SO4 over 30 min. The DGT unit was used to measure the phosphate level in six marine sediment samples from Jakarta Bay. The results revealed mass accumulation of P-containing compounds in the 1.009−2.4676-μg range.

A Quasi-Solid-State Solar Rechargeable Battery with Polyethylene Oxide Gel Electrolyte

A quasi-solid-state solar rechargeable battery with poly(ethylene oxide) gel electrolyte as the cathode and an anode electrolyte is proposed in this work. In the fabricated battery, solar energy can be converted and stored as chemical energy under light irradiation, which is further converted to electrical energy in the dark. During this, the working stability of the battery is improved by introducing the gel electrolyte into the battery system.

Fluorescent perylene derivative functionalized titanium oxide gel for sensitive and portable ascorbic acid detection.

An inorganic titanium oxide (TiO) gel sensor was demonstrated for convenient detection of ascorbic acid (AA). It is composed of TiO (PI–TiO) functionalized with a perylene diimide derivative containing carboxylic groups as a new soft dopant material. A traditional solvothermal reaction is adopted to prepare the PI–TiO composite, which exhibits a different spectrum according to the reaction time. The final gel possesses a strong chelating affinity with AA molecules, in which phenol hydroxyl groups are shown to compete with those already present in PI. We further utilize the functionalized gel to prepare a series of films with a simple and portable AA response. A visual colour variation can be recognized by the naked eye, together with obvious fluorescence changes for selective and sensitive AA detection. Finally, the as-prepared gel film displays good stability and reproducibility for real sample responses with satisfying results.

Investigation on Lithium Isotope Fractionation with Diffusion, Electrochemical Migration, and Electrochemical Isotope Effect in PEO-PC Based Gel Electrolyte

Lithium isotope fractionation, based on the difference of the diffusion coefficients, migration mobility, as well as the electrochemical isotope effect, can be achieved in the appropriate solvents. The Propylene Carbonate-Polyethylene Oxide gel electrolyte was utilized to separate Li isotopes by eliminating the fluid flow mixing and part of the solvation shell around Li ions. A higher Li isotope fractionation (△7Li = −4.53‰) was achieved with the effects of both diffusion and electrochemical migration in a long 10-cm cell test. Also, a short 2-cm cell gel electrolyte short duration test yielded a very high separation factor of 1.033, which is a very promising separation factor for Li isotope separation. Similarly, the electrochemical intercalation test into the graphite plate electrode associated with the diffusion and migration assisted separation shows a separation factor of 1.033. Influence of the electrochemical cell length was studied with an electrochemical model, and results show that an appropriate cell length needs to be determined by considering both the separation time and the separation factor.

Design and optimization of kollicoat ® IR based mucoadhesive buccal film for co-delivery of rizatriptan benzoate and propranolol hydrochloride

This work aimed to develop a mucoadhesive buccal film for potential co-delivery of rizatriptan benzoate (RB) and propranolol hydrochloride (PRH). Kollicoat ® IR, polyethylene oxide (PEO), hydroxypropyl methylcellulose (HPMC K4M), glycerol, stevia, and Aloe vera gel powder (AVgel powder) were used to prepare film by solvent casting method. In order to characterize and optimize formulations, Design-Expert software with central composite design (CCD) was used. The selected independent variables were concentrations of Kollicoat ® IR, PEO, glycerol, and AVgel powder. Five selected dependent variables were in vitro disintegration time, folding endurance, swelling ratio, and in vitro drugs release. Film with 50 mg PRH, 25 mg RB, 5 mg stevia, 63 mg HPMC K4M, 100 mg Kollicoat ® IR, 66.33 mg PEO, 0.22 ml glycerol, and 0.8 mg AVgel powder was selected as optimized formulation. The optimized film was characterized by scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC) to evaluate morphology, chemical structure, and physical properties of the film. The mechanical properties of optimized film were measured by Santam instrument. Ex vivo permeation were studied by Franz diffusion cell, while rat buccal mucosa was used as a model membrane. The optimized film with incorporation of AVgel powder as a natural permeation enhancer could transport 73.22% of PRH and 96.11% of RB over 100 min through rat buccal mucosa and showed no buccal mucosal damage after histopathological evaluation. Overall, the optimized film could be a potential candidate for the effective treatment of migraine.

The choice of embedding media affects image quality, tissue R2*, and susceptibility behaviors in post‐mortem brain MR microscopy at 7.0T

The quality and precision of post-mortem MRI microscopy may vary depending on the embedding medium used. To investigate this, our study evaluated the impact of 5 widely used media on: (1) image quality, (2) contrast of high spatial resolution gradient-echo (T1 and T2 * -weighted) MR images, (3) effective transverse relaxation rate (R2 * ), and (4) quantitative susceptibility measurements (QSM) of post-mortem brain specimens. Five formaldehyde-fixed brain slices were scanned using 7.0T MRI in: (1) formaldehyde solution (formalin), (2) phosphate-buffered saline (PBS), (3) deuterium oxide (D2 O), (4) perfluoropolyether (Galden), and (5) agarose gel. SNR and contrast-to-noise ratii (SNR/CNR) were calculated for cortex/white matter (WM) and basal ganglia/WM regions. In addition, median R2 * and QSM values were extracted from caudate nucleus, putamen, globus pallidus, WM, and cortical regions. PBS, Galden, and agarose returned higher SNR/CNR compared to formalin and D2 O. Formalin fixation, and its use as embedding medium for scanning, increased tissue R2 * . Imaging with agarose, D2 O, and Galden returned lower R2 * values than PBS (and formalin). No major QSM offsets were observed, although spatial variance was increased (with respect to R2 * behaviors) for formalin and agarose. Embedding media affect gradient-echo image quality, R2 * , and QSM in differing ways. In this study, PBS embedding was identified as the most stable experimental setup, although by a small margin. Agarose and Galden were preferred to formalin or D2 O embedding. Formalin significantly increased R2 * causing noisier data and increased QSM variance.

Revision surgery in carpal tunnel syndrome: a retrospective study comparing the Canaletto® device alone versus a combination of Canaletto® and Dynavisc® gel

The aim of our study was to demonstrate the benefits of combining the Canaletto® implant with carboxymethylcellulose/polyethylene oxide gel in the surgical treatment of carpal tunnel syndrome (CTS) recurrences.Our case series included 39 patients (40 hands, one bilateral case) who underwent revision surgery for recurrent CTS (28 cases) or resistant CTS (12 cases). The mean age of the patients was 56 years. The Canaletto® only was implanted in the first 21 cases (group I). In the following 19 cases (group II), Dynavisc® gel was added to the protocol and applied around the median nerve when the Canaletto® was implanted.At 12 months’ follow-up (group I) and 11 months’ follow-up (group II), the pre-versus post-operative difference between the average values of the DN4 neuropathic Pain Score was 0.55/10 in group I and 2.25/10 in group II; the Pain Score was 2.23/10 (in group I) and 2.52/10 (in group II); the Quick DASH Score was 18.98/100 (group I) and 19.06/100 (in group II); the hand grip strength was 19.55% (group I) and 28.53% (group II); the sensory nerve conduction velocity was 8.67 m/s (group I) and 10.27 m/s (group II); the distal motor latency was 1.05 m/s (group I) and 1.75 m/s (group II). Nine patients recovered from hypoesthesia in both groups, 5 patients regained satisfactory trophism of the thenar muscles in group I and 3 patients in group II. No improvement whatsoever was noted in 2 patients in group II, despite the electromyogram being normal. One patient from group II suffered an infection that required revision surgery to remove the Canaletto®; this led to a moderate improvement.Our results show that when resistant or recurrent CTS is diagnosed, the combined treatment of an anti-adhesion gel such as Dynavics® around the median nerve with the Canaletto® implant after performing secondary neurolysis leads to satisfactory post-operative outcomes. Compared to other techniques described in the current literature, our technique is less invasive, quicker and associated with minimal morbidity of the surgical site.

Hierarchical Porous Fluorinated Graphene Oxide@Metal-Organic Gel Composite: Label-Free Electrochemical Aptasensor for Selective Detection of Thrombin.

Current research effort aims at developing and designing new sensing platform architectures for effectively assaying biological targets that are significantly important for human healthcare and medical diagnosis. Here, we proposed a novel nanostructured sensor based on the combination of fluorinated graphene oxide and iron-based metal-organic gel (FGO@Fe-MOG). The unique properties including hierarchical porosity along with excellent electron transfer behavior make it an ideal candidate for electrochemical sensing of thrombin with superior detection limits compared to other (electrochemical, fluorescence, and colorimetric) strategies. Specifically, thrombin-binding aptamer was immobilized onto FGO@Fe-MOG through strong electrostatic interaction without any special modification or labeling, and the electrochemical impedance spectroscopy was used as the analyzing tool. The introduced aptasensor revealed high selectivity and reproducibility toward thrombin with the detection limit of 58 pM. The effectiveness, reliability, and real applicability of the proposed FGO@Fe-MOG nanohybrid were also confirmed by the determination of thrombin in a complex biological matrix represented by human serum. Taking into account the superior detection limit, high selectivity, reproducibility, and precision, the developed scalable and label-free aptasensor meets the essential requirements for clinical diagnosis of thrombin.

Dynamic assembly of liquid crystalline graphene oxide gel fibers for ion transport.

Colloidal dispersions with liquid crystallinity hold great promise for fabricating their superstructures. As an example, when graphene oxide (GO) sheets are assembled in the liquid crystalline state, they can turn into ordered macroscopic forms of GO such as fibers via the wet spinning process. Here, we report that by reinforcing intersheet interactions, GO liquid crystals (LCs) turn into mechanically robust hydrogels that can be readily drawn into highly aligned fibrillar structures. GO hydrogel fibers with highly aligned sheets (orientation factor, f = 0.71) exhibit more than twice the ionic conductivity compared to those with partially aligned structures (f = 0.01). The hierarchically interconnected two-dimensional nanochannels within these neatly aligned GOLC hydrogel fibers may facilitate controlled transport of charge carriers and could be potentially explored as cables for interconnecting biosystems and/or human-made devices.

Hierarchical porous reduced graphene oxide decorated with molybdenum disulfide for high-performance supercapacitors

Two-dimensional materials are relevant for supercapacitor applications due to their excellent electrical, thermal, and physical properties. In this study, one-pot solvothermal method with l-cysteine mixed in ethylene glycol is utilized to prepare S/N co-doped reduced graphene oxide, which is decorated with molybdenum disulfide. Furthermore, these two-dimensional sheets are found to form three-dimensional hydrogel architectures. Field emission scanning electron microscopy and high-resolution transmission electron microscopy show this compound gel with hierarchical porous structure. The specific surface area of this compound gel is estimated to 151.41 m2 g−1, which is larger than that of S/N co-doped reduced graphene oxide gel (28.98 m2 g−1). This composite is used to fabricate binder-free electrodes. The electrochemical tests reveal high specific capacitance of the electrodes reaching up 400.10 F g−1 at a current density of 1 A g−1. The symmetric supercapacitors assembled by two similar S/N co-doped reduced graphene oxide/molybdenum disulfide electrodes deliver specific capacitance as high as 95.10 F g−1 at a current density of 1 A g−1 with capacitance retention of 91.32% after 5000 cycles. These results demonstrate that S/N co-doped reduced graphene oxide/molybdenum disulfide composite with hierarchical porous structure is promising binder-free material for high-performance supercapacitors.

Electrochemical sensor for detection of cancer cell based on folic acid and octadecylamine-functionalized graphene aerogel microspheres

Early diagnosis of cancers is critical for prevention of metastasis and early treatment. The study reports an electrochemical sensor for detection of cancer cell based on folic acid (FA) and octadecylamine (OA)-functionalized graphene aerogel microspheres (FA-GAM-OA). Citric acid was mixed with FA and OA and heated at 180 °C for 4 h to form FA and OA-functionalized graphene oxide. The graphene oxide was employed as solid particle surfactant for stabilizing toluene-in-water emulsion. The graphene oxide sheets in the emulsion were self-assembled into graphene oxide gel microspheres on the water/toluene interfaces. Followed by free drying and reduction in H2 at 400 °C for 5 h. The resulted FA-GAM-OA shows a sphere-like structure with an average diameter of 1.2 µm, the rich of open-pores and folic acid groups. Small particle size and good hydrophilicity make FA-GAM-OA can be dispersed in water for sensor preparation. The small size of graphene sheets and their self-assembly avoid a serious agglomeration of graphene sheets. The FA-GAM-OA offers a large surface area (1723.6 m2 g−1) and high electronic conductivity (2978.2 S m−1). The covalent linkage and ordered alignment of folic acid groups at FA-GAM-OA surface achieve to specific cancer cell capture with high capture efficiency. The electrochemical sensor based on FA-GAM-OA exhibits extremely good analytical performances in detection of liver cancer cells with a linear range of 5–105 cell mL−1 giving a low detection limit of 5 cells mL−1 (S/N = 3). The method was successfully applied to electrochemical detection of liver cancer cells in whole blood.

Tailored Network Formation in Graphene Oxide Gels.

Graphene oxide (GO)-based gels are attractive because of their ability to retain individual nanosheet properties in a three-dimensional (3D) bulk material. The final morphology and properties of these 3D gel networks depend strongly on the type and density of cross-links, and these gels can be dried and annealed to form aerogels with both high conductivity (560 S/m) and high surface area (1700 m2/g). The results show that both ammonia content and the parent nanosheet morphology (crumpled vs flat) have a strong influence on the cross-linked structure and composition; notably, nitrogen is found in the gels, suggesting that ammonia actively participates in the reaction rather than as a mere catalyst. The GO nanosheet morphology may be altered using spray-drying to obtain crumpled GO (cGO) nanosheets and form cGO gels; this allows for an additional handle in the creation of GO-based gels with tunable density, electrical conductivity, and surface area.

Origin of the thermal plasticity property of zirconium oxide gels for use in direct thermal nanoimprinting

Some types of oxide gels derived from solutions exhibit a thermal plasticity property. In our previous report, the thermal plasticity property was utilized to produce oxide patterns and thin film transistors. However, it was not clear why some oxide gels exhibited a thermal plasticity property. In this report, we prepared not only a plastic ZrO2 gel but also a non-plastic ZrO2 gel, and investigated the structural and thermal properties of these gels to clarify why some gels exhibit a thermal plasticity property. We identified a clustered structure in ZrO2 gels, with a Zr-O-Zr core coordinated by organic ligands. This structure was strongly related to the thermal plasticity property. The thermal plasticity property of ZrO2 gel resulted from desorption and oxidization of the extra ligands by heating. We determined that the plastically deformed gels were consisted of clusters, and that the behaviour of ligands was a trigger in making a gel plastically deformed.

The Effect of Incorporation of Multi-Walled Carbon Nanotube into Poly(Ethylene Oxide) Gel Electrolyte on the Photovoltaic Performance of Dye-Sensitized Solar Cell

ABSTRACTGel polymer electrolytes (GPEs) consist of poly(ethylene oxide) (PEO), sodium iodide (NaI) and different amount of multi-walled carbon nanotubes (MWCNT) were prepared. The conductivity study revealed that the highest ionic conductivity of GPE was 7.02 × 10−3 S cm−1. The structural and complexation between the materials are authenticated via X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy. Under the exposure of AM 1.5, the fabricated DSSCs exhibited the highest photoenergy conversion efficiency of 7.23% with a short circuit current density (JSC) of 18.64 mA cm−2, open circuit voltage (VOC) of 0.590 mV and fill factor (FF) of 65.7%.

A new record of silica-rich coating on carbonate substrates in southeast-central Iran: Constraints on geochemical signatures

There exist few data on the geochemical signatures and occurrence of silica-rich coatings developed on siliceous carbonate substrates. The rock coatings in the Maran-e-Galu area in southeast-central Iran are composed of four layers; a lower thick layer (1 mm) of silica, a lower thin film of Fe-Mn oxide, an upper thick (1 mm) silica-rich layer, and an upper thin film of Fe-Mn oxide. Energy dispersive X-ray spectrometer (EDS), X-ray diffraction and bulk coating geochemistry data obtained by XRF and ICP-MS highlight that the 1–3 mm thick silica-rich coatings occur as a silica glaze of opal composition on the siliceous carbonate substrate. The coatings were probably formed by the interaction of rainfall, water vapor or dew with silicate and carbonate-rich detrital atmospheric dust, releasing H4SiO4with a pH of 5–10 in this semiarid-arid desert environment. This led to the formation of silica gels as well as minor Fe-Mn oxide gels by evaporation and supersaturation, and finally changed to the black brown silica glaze probably at ambient temperatures of >40 °C Major and minor element signatures are consistent with the known silica glazes, displaying enrichment in Ba, Sr, P, and LREEs with little to no Eu and Ce anomalies and a weak Tm anomaly. However, the very low content of aluminum oxide is well correlated with the known classified silica glaze of genetic type 1, reflecting the absence of detrital clay minerals. The low Fe and Mn contents in bulk coatings (3.6 and 10 magnitudes lower than crustal abundance, respectively) and lack of biochemical processes in the atmospheric dust highlight the semiarid-arid climate setting. We thereby conclude that a new variant of silica glaze of 1–3 mm thickness could form on siliceous carbonate substrates under an alkaline pH in semiarid-arid regions.

Three-Dimensional Printing of Polyaniline/Reduced Graphene Oxide Composite for High-Performance Planar Supercapacitor.

We apply direct ink writing for the three-dimensional (3D) printing of polyaniline/reduced graphene oxide (PANI/RGO) composites with PANI/graphene oxide (PANI/GO) gel as printable inks. The PANI/GO gel inks for 3D printing are prepared via self-assembly of PANI and GO in a blend solvent of N-methyl-2-pyrrolidinone and water, and offer both shaping capability, self-sustainability, and electrical conductivity after reduction of GO. PANI/RGO interdigital electrodes are fabricated with 3D printing, and based on these electrodes, a planar solid-state supercapacitor is constructed, which exhibits high performance with an areal specific capacitance of 1329 mF cm-2. The approach developed in this work provides a simple, economic, and effective way to fabricate PANI-based 3D architectures, which leads to promising application in future energy and electric devices at micro-nano scale.