Tannic Acid Aqueous Solution Research Articles

A Drop-By-Drop Self-Assembled All-Natural Hydrogel as a Desensitizer for Rapid and Enduring Management of Dentin Hypersensitivity.

Dentin hypersensitivity (DH) is a prevalent dental condition arising from the exposure of dentin tubules (DTs), leading to discomfort upon external stimuli. However, achieving swift and profound occlusion of these exposed DTs for immediate and enduring relief remains challenging due to the intricate dentin structure and oral environment. Herein, a pioneering and facile drop-by-drop strategy involving an in situ generated natural supramolecular hydrogel formed by self-assembling silk fibroin (SF) and tannic acid (TA) within the narrow DT space is proposed. When SF and TA aqueous solutions are applied successively to exposed dentin, they penetrate deeply within DTs and coassemble into compact gels, robustly adhering to DT walls. This yields a rapid and compact occlusion effect with an unprecedented depth exceeding 250µm, maintaining stable occlusion efficacy even under rigorous in vitro and in vivo erosion and friction conditions for no less than 21 days. Furthermore, the biocompatibility and effective occlusion properties are verified through cell studies in simulated oral settings and an in vivo rabbit model. This study, for the first time, demonstrates the translational potential of hydrogel-based desensitizers in treating DH with prompt action, superior occlusion depth and enduring treatment benefits, holding promise as clinical-friendly restorative solutions for delicate-structured biosystems.

A Polyvinyl Alcohol-Tannic Acid Gel with Exceptional Mechanical Properties and Ultraviolet Resistance.

Design and preparation of gels with excellent mechanical properties has garnered wide interest at present. In this paper, preparation of polyvinyl alcohol (PVA)-tannic acid (TA) gels with exceptional properties is documented. The crystallization zone and hydrogen bonding acted as physical crosslinkages fabricated by a combination of freeze-thaw treatment and a tannic acid compound. The effect of tannic acid on mechanical properties of prepared PVA-TA gels was investigated and analyzed. When the mass fraction of PVA was 20.0 wt% and soaking time was 12 h in tannic acid aqueous solution, tensile strength and the elongation at break of PVA-TA gel reached 5.97 MPa and 1450%, respectively. This PVA-TA gel was far superior to a pure 20.0 wt% PVA hydrogel treated only with the freeze-thaw process, as well as most previously reported PVA-TA gels. The toughness of a PVA-TA gel is about 14 times that of a pure PVA gel. In addition, transparent PVA-TA gels can effectively prevent ultraviolet-light-induced degradation. This study provides a novel strategy and reference for design and preparation of high-performance gels that are promising for practical application.

Double-Cross-Linked Networks Based on Methacryloyl Mucin.

Mucin is a glycoprotein with proven potential in the biomaterials field, but its use is still underexploited for such applications. The present work aims to produce a synthesis of methacryloyl mucin single-network (SN) hydrogels and their double-cross-linked-network (DCN) counterparts. Following the synthesis of the mucin methacryloyl derivative, various SN hydrogels are prepared through the photopolymerization of methacrylate bonds, using reaction media with different pH values. The SN hydrogels are converted into DCN systems via supplementary cross-linking in tannic acid aqueous solution. The chemical modification of mucin is described, and the obtained product is characterized; the structural modification of mucin is assessed through FTIR spectroscopy, and the circular dichroism and the isoelectric point of methacryloyl mucin is evaluated. The affinity for aqueous media of both SN and DCN hydrogels is estimated, and the mechanical properties of the systems are assessed, both at macroscale through uniaxial compression and rheology tests and also at microscale through nanoindentation tests.

Room‐temperature self-healable and stretchable waterborne polyurethane film fabricated via multiple hydrogen bonds

A simple strategy is reported for preparing self-healable cationic waterborne polyurethane (WPU/TAx), in which cross-links are formed via hydrogen bonds between tannic acid (TA) and the rigid domains of linear WPU. The cut could be able to completely heal in air condition at room temperature in one week without any external stimulation. The healing time can be largely reduced to 3 h when the cut sample are treated at 50 °C. The rigid domain’s containing multiple types of H-bonds classified as ordered H-bonds and disordered bonds is the main reason for the self-healing property, which is supported by Infrared spectrum. These H-bonds are also responsible for greatly improved mechanical properties of WPU. The maximum tensile strength and elastic modulus of WPU/TA5.1 are twice and 2.5 times that of pure WPU respectively, up to 32 MPa and 2.44 MPa. The combination of enhanced mechanical properties and self-healing in moderate conditions is achieved by just simply mixing WPU dispersion and tannic acid aqueous solution.

Optimized Dyeing Process for Enhancing the Functionalities of Spent Coffee Dyed Wool Fabrics Using a Facile Extraction Process.

Spent coffee grounds are the byproduct of coffee brewing and are generally discarded as waste. However, spent coffee has high levels of organic compounds that have multiple biological effects, including antibacterial and antioxidant activities. In this light, spent coffee grounds were tested for fabric dyeing to both functionalize as well as color the fabrics. The dyeing solution was prepared by extracting spent coffee grounds collected from a local coffee house by using a manual espresso machine. The spent coffee extract was applied to wool fabrics using a laboratory infrared dyeing machine. After the dyeing process was completed, the fabrics were mordanted with a tannic acid aqueous solution. To optimize the dyeing conditions, the times and temperatures during the process were varied, and the functionalities and other properties including color and strength of the wool fabrics dyed with the spent coffee extract were investigated. The wool fabrics dyed with the spent coffee extract were significantly colored, and the color withstands the effect of washing and light exposure. Moreover, the dyeing process with the spent coffee extract and the mordanting process with tannic acid gave the wool fabrics antibacterial and antioxidant properties.

Synthesis of titania coated magnetic activated carbon for effective photodegradation of tannic acid in aqueous solution

Titania coated magnetic activated carbon (TMAC) was synthesized by a combined pre-adsorption and impregnation method. The physicochemical properties of prepared samples were characterized by means of X-ray diffraction (XRD), nitrogen adsorption/desorption measurement, fourier-infrared spectroscopy (FT-IR) and vibrating sample magnetometer. The pre-adsorbing ethanol was proven to be an effective way to inhibit magnetic species and silica gel to fill the micropores of activated carbon (AC), thus giving rise to a high specific surface area up to 909 m2 g−1 for obtained TMAC. The tannic acid aqueous solution was used as a pollution model to evaluate the photocatalytic activity of the TMAC sample under ultraviolet (UV) illumination. The result indicates that the as-synthesized TMAC exhibits high photocatalytic activity and cycle stability for degrading tannic acid. Furthermore, this magnetic photocatalyst could be easily separated from aqueous solution by using an external magnet field, which endows it with a potential for industrial application.

Functional fabric treatment using tannic acid and extract from purple-fleshed sweet potato

Purple-fleshed sweet potato (PSP) has a reddish purple color with high amounts of anthocyanins and phenolic acids, both of which have various health-promoting effects. The acylated anthocyanins present in PSP are more heat-resistant than the nonacylated types found in other plants. Therefore, PSP extract was considered as a natural pigment and functional agent for textile dyeing and/or finishing processes. Here, wool and cotton fabrics are pretreated by a tannic acid aqueous solution to increase their dyeability and then dyed by PSP extract. The dyed fabrics are then investigated by various analysis techniques. The results revealed that wool and cotton fabrics can be dyed bluish red through the pretreatment and dyeing process. The wool and cotton fabrics also showed antibacterial and antioxidant characteristics.

Electrochemically Dissolved Aluminum Coagulants for the Removal of Natural Organic Matter from Synthetic and Real Industrial Wastewaters

In this work, the effects of some experimental parameters (supporting electrolyte, current density, and initial pH) on the anodic dissolution of aluminum and on the electrocoagulation of tannic acid aqueous solutions as well as real industrial wastewaters containing tannic acid were investigated. Experimental results indicated that both chemical and electrochemical dissolution play an important role in the formation of hydroxo-aluminum species. The chemical dissolution of aluminum is strongly influenced by the solution pH. Corrosion studies have demonstrated that the presence of chloride ions in water accelerates dissolution of aluminum by pitting corrosion while phosphate ions inhibit the corrosion of aluminum by formation of a thick passive layer of aluminum hydroxide/phosphate on the aluminum surface. The results obtained can be used to better understand the mechanism of the electrocoagulation process due to the importance of the anode surface electrodissolution in the treatment process. Electrocoagula...

Removal of Natural Organic Matter from Wastewater by Electrocoagulation Using Aluminum Electrodes

Electrocoagulation is a promising alternative to the conventional chemical coagulation in water treatment systems. In electrocoagulation, coagulants are generated in situ by anodic dissolution of sacrificial electrodes, usually aluminum or iron electrodes. Anodic dissolution of the sacrificial anodes leads to the formation of hydrolysis products (hydroxo-metal species) that involve the destabilization of suspended, emulsified or dissolved pollutants and/or the formation of insoluble particles that adsorb and enmesh the pollutants. Furthermore, the formation of hydrogen bubbles as a result of water reduction at the cathode surface promotes the flocculation process by the soft turbulence in the system and produces a soft mix. The electrogenerated gaseous bubbles help the destabilized particles to colloid and generate larger particles which facilitate separation of the flocculated pollutants by carrying the particles to the top of the solution where they can be more easily removed by electroflotation. Electrochemical coagulation was successfully applied for turbidity, heavy metals, dyes and phenols removals from synthetic and real wastewaters and for breaking oil/water emulsions at both laboratory scale and pilot plant scale. In this work, effects of some experimental parameters (supporting electrolyte, current density, and initial pH) on anodic dissolution of aluminum and on electrocoagulation of tannic acid aqueous solutions as well as real industrial wastewaters containing tannic acid were investigated. Experimental results indicated that both chemical and electrochemical dissolution play an important role in the formation of hydroxo-aluminum species. The chemical dissolution of aluminum is strongly influenced by the solution pH. Electrocoagulation using aluminum electrodes achieved high removal efficiency of chemical oxygen demand from aqueous solutions containing tannic acid. The primary mechanism for removing tannic acid from water by electrocoagulation using Al electrodes involves the adsorption of tannic acid molecules on the aluminum hydroxide surface. Also, results of the treatment of real wastewater obtained from pulp and paper industry with initial COD concentration of 1450 mg/L have shown that more than 60 % of COD can be removed by electrocoagulation using Al electrodes under optimized experimental conditions. The specific energy required for the electrochemical process with Al electrodes was estimated to range from 1 to 2 kWh m-3.

Green, effective chemical route for the synthesis of silver nanoplates in tannic acid aqueous solution

Silver nanoplates, with average size tunable from 50 to 500 nm, have been synthesized via a simple room-temperature tannic acid (TA) solution-phase chemical reduction method. The synthesis was a seedless process in which tannic acid was used as a reducing as well as a capping agent, and did not need any other surfactant or capping agent to direct the anisotropic growth of the silver nanoparticles. The morphology of silver nanoplates has been confirmed by transmission electron microscopy, the growth process of nanoplates has been studied by UV/vis spectroscopy. Control experiments have been explored for a more thorough understanding of the growth mechanism. It was found that both the concentrations of TA and the pH of solution were the key elements to control the morphology silver nanoplates. The optical in-plane dipole plasmon resonance bands of these silver plates could be tuned from 520 to 1100 nm.

Preparation of mesopore-rich carbons using attapulgite as templates and furfuryl alcohol as carbon source through a vapor deposition polymerization method

Mesoporous carbons with specific surface areas in the range of 409–937 m 2 g −1, mesopore volumes in the range of 0.55–2.26 cm 3 g −1 and mesopore volume fraction higher than 86% are prepared by using crude attapulgite, calcined attapulgite and HCl-treated attapulgite as inorganic templates and furfuryl alcohol as the carbon source through a vapor deposition polymerization (VDP) method at 130 °C. The influences of VDP time, the calcination temperature and HCl concentration on the pore structure of the resultant carbons are investigated. The results indicate that the optimized VDP time, the calcination temperature and the HCl concentration are 6 h, 800 °C and 5 M, respectively, and the corresponding carbons have the maximum surface areas and mesopore volumes. Adsorption of tannic acid on the mesoporous carbons in tannic acid aqueous solution with an initial concentration of 200 mg l −1 at 20 °C reveals that the equilibrium adsorption capacities ( q e) are in the range of 111–464 mg g −1. The mesoporous carbon prepared from attapulgite calcined at 800 °C (C– T 800-6) exhibits the highest specific surface area (937 m 2 g −1), the largest mesopore volume (2.26 cm 3 g −1) and the highest q e (464 mg g −1) among all the resultant carbons.

Reactivity of Tannic Acid with Common Corrosion Products and Its Influence on the Hydrolysis of Iron in Alkaline Solutions

To ascertain the role of tannic acid in the anticorrosive protection of steels, the reaction between 5% tannic acid aqueous solutions with lepidocrocite, goethite, superparamagnetic goethite, akaganeite, poorly crystalline maghemite, magnetite and hematite was studied using color changes, infrared and Mossbauer spectroscopy. After three months of interaction with lepidocrocite, the formation of an iron tannate complex was detected by its dark blue color and confirmed by infrared and Mossbauer analysis. Evidence for the chemical transformation was obtained for goethite in nanoparticles and poorly crystalline maghemite after reaction for six months. The other iron compounds do not transform to another oxide or phase upon treatment with the tannic acid solution. These results showed that lepidocrocite is the most reactive phase and that the size and degree of crystallinity have strong influence on the formation of the tannate complexes. The precipitation of iron phases from alkaline solutions of iron (II) sulfate heptahydrate containing different amount of tannic acid and potassium nitrate as oxidative agent was also studied. Mossbauer and infrared results show that in the absence of tannic acid some common rust components are obtained (viz. goethite, superparamagnetic goethite, maghemite and non-stoichiometric magnetite). The presence of 0.1% tannic acid in a low alkalinity solution results in the precipitation of iron oxyhydroxides and some iron tannates. Concentrations of 1% tannic acid are required for the formation of the tannates complexes as main reaction product.

Preparation and Antibacterial Activity of Silk Fibroin Fiber Containing Metal Complexes.

The preparation and the antibacterial activity of silk fibroin fibers containing metal complexes of Cu2+, Zn2+, Ni2+, Fe2+, and Ag+ were studied. The metalation was carried out in aqueous solutions of metal ions at low pH and in the solution of metal-ammine complexes at high pH using untreated silk fibroin fiber and fibers treated with a tannic acid aqueous solution. In solution of metal ions at low pH, unstable metal complexes were formed on the fiber without tannic acid, and exhibited no antibacterial activity owing to the low content of metal ions. From the metal-ammine complex solutions, very stable complexes were formed on the fiber but exhibited no activity owing to the high stability of biuret type complexes formed. On the other hand, metal complexes of Cu2+, Fe2+, Ag+ with tannic acid were formed on the fiber treated with tannic acid even at low pH. But the fixation of the complexes onto the fiber was not enough. Only Ag(I)-tannic acid complex on the fiber exhibited the antibacterial activity even in the low content. The sufficient metalation of the fiber containing tannic acid were under-gone in solutions of metal-ammine complexes of Cu2+, Zn2+, and Ni2+. These complexes on the fiber formed with tannic acid as ligands without peptide-nitrogen, and exhibited the strong antibacterial activity. Metalated silk fibroin fibers obtained from the metal-tannic acid complexes were effective, as one of the functional fibers, for the anti-bacterial fibers.