Resorcinol-formaldehyde Resin Research Articles

Boosting photocatalytic H2O2 production by incorporating extra electron-donor group over resorcinol-formaldehyde resin

Boosting photocatalytic H2O2 production by incorporating extra electron-donor group over resorcinol-formaldehyde resin

Digital Workflow for Rehabilitation of Severely Discolored Teeth Due to Red Staining from Endodontic Material.

The aim of this short communication is to present a technique to rehabilitate severely discolored teeth with computer-aided designed and computer-aided manufactured (CAD-CAM) zirconia crowns. After confirming the absence of periapical lesions and sufficient crown structure, any caries or fractured restorations can be removed and replaced by an interim composite restoration. A shoulder subgingival preparation is performed and scanned with an intraoral scanner to design a CAD-CAM zirconia crown using a monolithic zirconia material. This crown is highly polished using a specific polishing kit, but not glazed. This technique is suggested to be useful in cases of dark discolored teeth due to staining endodontic materials such as resorcinol-formaldehyde resin.

Synergetic Combination of Carbon Xerogels, Graphene Oxide and nano‐ZnO for Aqueous and Organic Supercapacitors

Three‐dimensional carbon xerogels were synthesised via a facile approach that included the use of ZnO nanostructures both as a templating agent and as a catalyst for resorcinol–formaldehyde resin polymerisation simultaneously. Graphene oxide (GO) served as a stabilising agent during the drying and pyrolysis processes, avoiding the collapse of structure and improving the area surface. The method enabled the asobtained materials to possess optimised 3D porous structures for energy‐storage devices, such as wires or spaghetti‐like structures. Also, a high BET surface area was obtained (1661 m2•g−1) without using an additional activating agent. This great surface area improved the specific capacitance compared to materials without GO (358.1 F•g−1 vs 170.4 F•g−1). The carbon‐containing devices derived from resorcinolformaldehyde resin, GO, and Zn oxide showed better performance than the devices without GO. In particular, the sample that contained 2.5% of GO in the synthesis showed a specific capacitance of 166.6 F•g−1 at 0.5 A•g−1 and remained at ∼120 F•g−1 at 5 A•g−1. Also, it showed interesting energy density values at 0.5 A•g−1 (14.8 Wh•kg−1) and a power density of 200.7 W•kg−1. This reveals that the synthesis process made it possible to obtain composite materials with large surface areas without using a supercritical drying process.

Activated Iron-Porous Carbon Nanomaterials as Adsorbents for Methylene Blue and Congo Red.

The adsorption properties of microporous carbon materials modified with iron citrate were investigated. The carbon materials were produced based on resorcinol-formaldehyde resin, treated in a microwave assisted solvothermal reactor, and next carbonized in the tube furnace at a temperature of 700 °C under argon atmosphere. Iron citrate was applied as a modifier, added to the material precursor before the synthesis in the reactor, in the quantity enabling to obtain the nanocomposites with C:Fe mass ratio equal to 10:1. Some samples were additionally activated using potassium oxalate or potassium hydroxide. The phase composition of the produced nanocomposites was determined using the X-ray diffraction method. Scanning and transmission electron microscopy was applied to characterize the changes in samples' morphology resulting from the activation process and/or the introduction of iron into the carbon matrix. The adsorption of nitrogen from gas phase and dyes (methylene blue and congo red) from water solution on the obtained materials was investigated. In the case of methylene blue, the adsorption equilibrium isotherms followed the Langmuir isotherm model. However, in the case of congo red, a linear dependency of adsorption and concentration in a broad equilibrium concentration range was found and well-described using the Henry equation. The most efficient adsorption of methylene blue was noticed for the sample activated with potassium hydroxide and modified with iron citrate, and a maximum adsorption capacity of 696 mg/g was achieved. The highest congo red adsorption was noticed for the non-activated sample modified with iron citrate, and the partition coefficient for this material equaled 171 dm3/g.

Inorganic/organic hybrid interfacial internal electric field modulated charge separation of resorcinol-formaldehyde resin for boosting photocatalytic H2O2 production

The strategy of inorganic/organic semiconductor material hybridization is of great significance for the development of highly active photocatalysts. Resorcinol-formaldehyde (RF) resin with a special donor-acceptor (D-A) structure shows excellent performance in the photocatalytic production of H2O2. However, the lack of an internal driving force for the separation and transfer of photogenerated electrons and holes in RF resin greatly limits the performance of H2O2 production. Herein, an inorganic/organic hybrid core-shell structure ZnS@RF photocatalyst was prepared by directionally induced coating of RF resin shells of different thicknesses on the surface of monodisperse ZnS nanospheres. Consequently, the photocatalytic H2O2 performance of ZnS@RF with the optimal RF resin shell thickness reaches 367.9 μmol L−1, which is 69 and 2 times that of ZnS and HRF, respectively. Density functional theory (DFT) calculations and related characterization results collectively demonstrate that the excellent photocatalytic H2O2 production performance of ZnS@RF photocatalyst is mainly attributed to the internal electric field (IEF) formed at the hybrid interface of ZnS and RF heterojunction and the optimization of RF shell thickness, which significantly enhances the separation and transfer of photogenerated carriers and modulates the interfacial catalytic reaction kinetics. This work opens up an avenue for designing inorganic/organic hybrid heterojunction photocatalyst materials with excellent photocatalytic activity.

Efficient Preparation and Optimization of Activated Carbon Monoliths from Resorcinol-Formaldehyde Resins for CO2 Capture

Activated carbon monoliths with developed porosity, high surface area and excellent adsorption properties were successfully prepared from resorcinol-formaldehyde resins using a physical activation method. The primary objective of this study was to examine the impact of key parameters, namely hexamethylenetetramine content (0.08–0.2 g), pyrolysis heating rate (5–20 °C/min) and activation time (1–7 h), on the final characteristics of the activated carbon in order to identify the optimal operating conditions to achieve the desired properties. All the cured resin samples were pyrolyzed at 900 °C under a nitrogen atmosphere, while the activation process took place in the presence of CO2. The evaluation of the activated carbon materials was based on the CO2 adsorption capacity and BET surface area, micropore area and total pore volume, which were employed as the criteria for selecting the optimal activated carbon. The synthesized porous carbon monoliths exhibited good properties: high BET surface area (900 m2/g), high CO2 adsorption capacity (5.33 mmol/g at 0 °C and 1 bar, 3.8 mmol/g at 25 °C and 1 bar) and good CO2 selectivity for CO2/N2 and CO2/CH4 mixtures. These results were obtained with a pyrolysis heating rate of 5 °C/min and a 3 h activation period.

State change of Na clusters in hard carbon electrodes and increased capacity for Na-ion batteries achieved by heteroatom doping

Although heteroatom doping is an effective method to improve the capacity of hard carbon (HC) anodes in Na-ion batteries (NIBs), the complicated structure of HC leads to uncertainty when understanding the effects of heteroatom doping on sodium storage. This study shows the effects of phosphorus and sulfur doping to HC on sodium storage using solid-state NMR to improve the capacity of HC prepared by the carbonization of resorcinol formaldehyde (RF) resin at 1100 °C. Heteroatom doping increased the battery capacity of the HC, especially the plateau capacity, but the interlayer distance of the carbon layers in the HC did not expand considerably. 23Na solid-state NMR revealed that heteroatom doping facilitates the formation of quasi-metallic sodium clusters, thereby contributing to the plateau capacity increase. The metallicity of the sodium clusters in heteroatom-doped HC samples was controlled by the amount of doped-phosphorous. XPS and 31P NMR detected various phosphorus sites such as phosphine and phosphine oxide in the carbon structure.

Heterostructure engineering of resorcinol-formaldehyde resins and sulfur-vacancy-containing Zn3In2S6 for high-efficiency photocatalytic H2O2 production

Resorcinol-formaldehyde (RF) resins have garnered significant interest due to their remarkable efficiency in producing photocatalytic H2O2. The combination of RF with inorganic semiconductors to create organic–inorganic heterojunctions represents a promising strategy for enhancing photocatalytic activity. In this work, RF was coated onto Zn3In2S6 nanoflowers with sulfur-vacancy, creating RF/Zn3In2S6 composites with an S-scheme heterostructure. This novel composite exhibited superior photocatalytic activity for H2O2 production in both pure water and seawater, without sacrificial agents. Specifically, the production rate of RF/Zn3In2S6-0.3 in pure water under simulated solar illumination achieved 3174.34 μmol/h/g, marking 8.53 and 4.17 times over RF and Zn3In2S6, respectively. Moreover, its photocatalytic activity in seawater reached an impressive 2290.81 μmol/h/g, 4.93 and 3.12 times greater than that of RF and Zn3In2S6, respectively. The enhanced photocatalytic activity is attributed to the S-scheme charge transfer mechanism, which facilitates efficient charge separation and amplifies redox capabilities. Both experimental and density function theory analyses confirm the S-scheme route in RF/Zn3In2S6-0.3 for photocatalytic H2O2 production. This study not only presents the first account of an organic semiconductor RF being employed in an S-scheme heterojunction interface but also introduces the surface sulfur-vacancy mediated S-scheme heterojunction strategy for photocatalytic H2O2 production, representing a significant advancement in the field.

Sr-doped carbon matrices for use as electrodes in autonomous electrical energy sources

Relevance. The need to create new safe energy sources that can meet the needs of production and medicine where the use of traditional energy sources is impossible or unprofitable. Such sources may include radioisotope power sources, in which energy production is ensured by the natural decay of radionuclides. The most important components of current sources such as supercapacitors are electrode materials, the characteristics of which determine the electrophysical characteristics of radioisotope sources. This work proposes a method for synthesizing a carbon matrix doped with Sr for use as electrodes of radioisotope power sources. Aim. Development, mastery and optimization of a method for synthesizing electrodes of radioisotope power sources based on carbon materials doped with the Sr-90 radioisotope. Objects. Carbon material doped with a radioisotope simulant Sr-90 (Sr stable). Carbon matrices were obtained by carbonizing a resorcinol-formaldehyde resin doped with a stable strontium salt. Methods. Scanning electron microscopy, low-temperature adsorption-desorption of nitrogen, cyclic voltammetry, galvanostatic charge-discharge, impedance microscopy. Results. A carbon matrix doped with a stable strontium isotope was synthesized by the method of semi-carbonization followed by physical activation with carbon dioxide. The structure, porosity and electrochemical characteristics of the material were studied. It was established that physical activation has a positive effect on the development of the specific surface area and mesoporosity of the samples of the synthesized matrix, as a result of which its electrochemical characteristics are improved. The method of physical activation is proposed as the most preferable for the synthesis of a carbon matrix doped with strontium isotopes for use as electrodes of radioisotope power supplies.

Adjustable nanoarchitectonics of N-doping Yolk-Shell carbon spheres via “Pyrolysis-Capture” method for High-Performance supercapacitor

The energy storage capacity of porous carbon materials is closely tied to their surface structure and chemical properties. However, developing an innovative and straightforward approach to synthesize yolk-shell carbon spheres (YCs) remains a great challenge till date. Herein, we prepared a series of porous nitrogen-doped yolk-shell carbon spheres (NYCs) via a “pyrolysis-capture” method. This method involves coating the resorcinol–formaldehyde (RF) resin sphere with a layer of compact silica shell induced by 2-methylimidazole (ME) catalysis to produce a confined nano-space. Based on the confined effect of compact silica shell, volatile gases emitted from the RF resin and ME during pyrolysis can not only diffuse into the pores of the RF resin but can also be captured to form an outer carbon shell. This results in the tunable structures of NYCs materials. As the pyrolysis temperature rises, the shell thickness of NYCs reduces, the pore size expands, the roughness increases, and the N/O content of surface elements is enhanced. Notably, as an electrode material used forsupercapacitors,the optimized NYCs-800 exhibits excellent performance with a capacitance of 301.2F g−1 at the current density of 1 A/g and outstanding cycling life stability of 96.1% after 10,000 cycles. These results signify that controlling the surface structure and chemical properties of NYCs materials is an effective approach for constructing advanced energy storage materials.

Facile synthesis of magnetic resorcinol–formaldehyde resin Fe3O4@RF-Au composites for enhanced tetracycline photodegradation with simultaneous H2O2 production

Facile synthesis of magnetic resorcinol–formaldehyde resin Fe3O4@RF-Au composites for enhanced tetracycline photodegradation with simultaneous H2O2 production

Magnetically separable and recyclable ZnFe2O4 nanoparticles as an effective activator in resorcinol-formaldehyde resins-based photocatalysis-self-Fenton system

Non-homogeneous photocatalysis-self-Fenton technology presents an effective strategy for efficient photocatalytic degradation of pollutants, circumventing the issues of extensive contamination of water resources by free iron ions and reducing safety risks and cost issues associated with the generation of hydrogen peroxide (H2O2). In the photocatalysis-self-Fenton reaction, the activation efficiency of H2O2 determines the capacity for photocatalytic degradation and mineralization of pollutants. Consequently, this study adopted ZnFe2O4 (ZFO) as an efficient, magnetically recoverable H2O2 activator, successfully coupling it with resorcinol–formaldehyde (RF) resin to construct a photocatalysis-self-Fenton system, thereby achieving degradation of tetracycline (TC) under visible light. The experimental results revealed that apparent rate constant (kapp) for the RF/ZFO photocatalysis-self-Fenton system is 22.997 times higher than that of the Fenton system and 1.156 times higher than that of the photo-Fenton system. Under visible light, the RF resin can generate H2O2 in situ and is subsequently activated by ZFO, resulting in a highly oxidized hydroxyl radical (OH), attacking contaminants. This study presents new insights into the construction of efficient heterogeneous radiofrequency resin photocatalysis-self-Fenton degradation system and provides new solutions for efficient and environmentally friendly wastewater treatment.

Optimized porous nanostructure of carbon fibers enabling excellent stability of Pt-based catalysts for oxygen reduction reaction

Facile synthesis of highly-dispersed Pt-based electrocatalysts on porous carbon supports with strong durability is extremely desirable for oxygen reduction reaction but remains challenging. The influence of pores in carbon supports on the stability and activity of catalysts is ambiguous and needs to be elucidated. Targeting this aim, herein, we prepared a series of carbon nanofibers with tunable pore diameter and specific surface area using the resorcinol-formaldehyde (RF) resins as a model system. Homogeneous composite precursors composed of RF resins and silica colloids were synthesized by the surfactant-assisted simultaneous polycondensation of RF resins and tetraethylorthosilicate (TEOS). The diameter of the pores induced by removal of silica could be controllable tailored through thermal treatment of the composite under various target temperatures. Pt3Co alloy nanoparticles loaded on the as-synthesized porous carbon nanofibers were prepared by an optimized wet-impregnation method. The experimental results indicated that the carbon nanofibers with pore size distribution focused on ∼1.27 nm and ∼2.34 nm provided the best stability without limiting current density decay, and negative shift of half-wave potential (E1/2) and mass activity (MA) loss of Pt after 20000 potential cycles are relatively mild. Conversely, negative shift of 21 mV, 15 mV and 22 mV in E1/2 and mass activity loss of 51.8%, 30.2% and 33.0% were observed for the Pt3Co nanoparticles supported on MC-60, MC-100 and MC-140 matrices which have pore size distribution focused on ∼2.73 nm, ∼2.73 nm as well as ∼4.66 nm, and ∼4.66 nm, respectively. This work demonstrates the importance of micropores and small mesopores for activity and long-term stability enhancement of carbon supported Pt-based electrocatalysts.

Synthesis of MIL-53(Fe) implanted carbon spheres derived from resorcinol-formaldehyde resins for fast adsorption of antibiotics: Enhanced adsorption and pH adaptability

This article prepared a series of MIL-53(Fe) implanted carbon spheres derived from resorcinol-formaldehyde resins for rapid adsorption of Ciprofloxacin (CIP) using a facile hydrothermal coupling calcination methodology. Results indicated that MIL53(Fe)@RF-800, which was calcined at 800 °C, demonstrated the highest CIP removal efficiency of up to 95% within 60 min in batch adsorption tests. Moreover, MIL53(Fe) @RF-800 could remove over 95.8% of CIP at an amount of 0.2 mg/L, while both Cl− and HCO3− had a negligible impact on the CIP adsorption. It is noteworthy that when there was NO3− or SO42− in the solution, the impact of CIP adsorption displayed an inhibitory trend overall. In addition, MIL53(Fe)@RF-800 exhibited a broad pH range adaptability (over 95% CIP removal efficiency at pH = 3.0–10.5), even under highly acidic (pH < 3.0) or alkaline (pH > 10.5) conditions, the adsorption capacity for CIP was greater than 85%. In conclusion, this study provides novel insights into the development of highly porous MIL-53(Fe)-based adsorbent for rapid and pH-unrestricted adsorption of antibiotics and offers the possibility of practical engineering applications.

Atenolol uptake from pharmaceutical sources onto carbon aerogel prepared by supercritical CO2 drying

Atenolol (ATL) is a popular medication which is widely used to treat hypertension and angina. It is often found in aqueous environments, posing potential risk to human health and ecological well-being. In this study, carbon aerogel was prepared by supercritical CO2 drying of resorcinol–formaldehyde resin subsequently carbonized at 600 °C in an inert atmosphere. This porous material was characterized by SEM, BET, FTIR, and XRD and used for the first time for the removal of ATL from aqueous solutions under varying experimental conditions. Carbon aerogel in the form of microbeads exhibited a relatively high specific surface area of 376.02 m2/g and median pore radius of 9.83 nm. The isotherm models of Langmuir, Freundlich, Temkin, Redlich-Peterson and Brouers-Sotolongo were used to interpret the equilibrium data. Although most of the applied models fitted the data well, the calculated values for maximum sorption capacity (qmax) showed a huge deviation when compared to experimental value of 76.66 mg/g. The pseudo-first and pseudo-second-order kinetic models, Chrastil’s model, and the intraparticle diffusion model were employed for fitting the kinetic data. The rate of the process was rapid with most of the uptake attained in the first 20 min of the contacting. The sorption optimum was achieved at pH pH 9.0 and for sorbent’s dosage of 750 mg/L. Reusability study of the spent aerogel conducted in seven cycles evidenced slight decrease of approximately 1 % in removal efficiency across the cycles indicating that the sorbent maintained its high effectiveness and stability throughout its usage.

Physicochemical and Adsorption Characterization of Char Derived from Resorcinol-Formaldehyde Resin Modified with Metal Oxide/Silica Nanocomposites.

A series of metal- and silica-containing carbon-based nanocomposites were synthesized by pyrolysis of a resorcinol-formaldehyde polymer modified with metal oxide/silica nanocomposites (MxOy/SiO2, where M = Mg, Mn, Ni, Cu and Zn) via the thermal oxidative destruction of metal acetates adsorbed on highly dispersed silica (A380). The concentration of metals was 3.0 mmol/g SiO2. The phase composition and morphological, structural and textural properties of the carbon materials were analyzed by X-ray diffraction, SEM, Raman spectroscopy and low-temperature N2 adsorption. Thermal decomposition under a nitrogen atmosphere and in air was analyzed using TG-FTIR and TG-DTG-DSC techniques to determine the influence of the filler on the decomposition process. The synthesized composites show mesoporous structures with high porosity and narrow pore size distributions. It could be shown that the textural properties and the final composition of the nanocomposites depend on the metal oxide fillers of the precursors. The data obtained show that nickel and copper promote the degree of graphitization and a structural order with the highest porosity and largest specific surface area of the hybrid composites. The good adsorption properties of the obtained materials were shown for the recovery of p-chlorophenol and p-nitrophenol from aqueous solutions.

Seeded Growth of Plasmonic Nanostructures in Deformable Polymer Confinement.

Plasmonic nanostructures exhibit optical properties highly related to their morphologies, enabling diverse applications in various areas such as biosensing, bioimaging, chemical detection, cancer therapy, and solar energy conversion. The expansive uses of these nanostructures necessitate robust and versatile synthesis methods suitable for large-scale production. Here, we introduce our recent efforts in developing a new strategy for controlling the seeded growth of plasmonic metal nanostructures, employing deformable polymer capsules to regulate the growth kinetics and the resulting particle morphology. Employing sol-gel-derived resorcinol-formaldehyde (RF) resin as a typical capsule material, we highlight its advanced features, including mechanical deformability and molecular permeability, that can be manipulated by tuning the capsule thickness and cross-linking degree. These features enable highly controllable confined seeded growth of plasmonic nanostructures. We reveal the significant role of the Ostwald ripening process of the seeds and the capsule structures in determining the morphological evolution of the plasmonic nanostructures. Moreover, we highlight some distinctive plasmonic nanostructures resulting from this unique synthesis strategy and their intriguing functionalities in various potential applications. Our discussion concludes with potential research directions to advance the development of the deformable polymer-confined seeded growth strategy into a general and robust synthesis platform for creating cutting-edge functional plasmonic nanostructures.

Controlling the stability and adhesion performance of cold-setting phenol–resorcinol–formaldehyde resin adhesives through methanol addition

Phenol–resorcinol–formaldehyde (PRF) resin adhesives are commonly used in the manufacture of laminated timber products, and they are cold-set at room temperature rather than hot-pressed to generate a three-dimensional polymer structure in the products. However, their excellent reactivity often leads to poor storage stability and a short pot life. This study examines the influence of methanol addition on the stability and adhesion performance of PRF resins. These resins were synthesized by various levels of methanol addition (5 %, 10 %, and 15 %), and their structures were investigated using Fourier-transform infrared (FTIR) and nuclear magnetic resonance (NMR) spectroscopies. Furthermore, differential scanning calorimetry (DSC) was used to analyze their thermal behavior, and their cure kinetics were analyzed with two isoconversional analyses: Kissinger–Akahira–Sunose (KAS) and Vyazovkin (VYZ) method. The adhesion performances of PRF resins were evaluated for glue-laminated timber (GLT). The results demonstrated that the viscosity and solids content of PRF resins decreased while their gelation time increased as the methanol addition level increased. Methanol addition has also improved the resin stability over time. The chemical structure of PRF resins did not change considerably with an increase in the methanol level. However, methanol interaction with formalin in a hardener presumably hindered the reactivity of PRF resins. This was supported with an increase in the apparent activation energy of the curing process of PRF resins as the methanol level increased. In addition, decreasing the methanol levels from 15 % to 5 % enhanced the adhesion performance of GLT bonded with PRF resins. The results indicated that adding methanol to PRF resins improved its stability while simultaneously weakened its performance. However, 5 % methanol level is recommended for PRF resins.

Resorcinol/formaldehyde resin-derived carbon conductive network for superior fluorinated graphite based lithium primary batteries

The high energy density of fluorinated graphite (CFx) based lithium primary battery has aroused tremendous attention. However, the nonconductive CFx always induces high interface impedance and low power density. Herein, the carbon conductive network is generated by thermal treatment of resorcinol/formaldehyde (RF) resin on CFx and RF resin spheres (RF RSs), a conductive carbon layer coats on CFx surface, the electrical conductivity of CFx is improved. The oxygen functional groups in incomplete carbonized RF RSs also dedicate to the electrochemical performance of CFx. When different mass ratios of CFx/RF RSs are employed, the cathodes exhibit improved rate performance and voltage plateaus, and the initial voltage delays observed in CFx are significantly reduced. Notably, CFx/RF RSs−13 cathode delivers an impressive discharge capacity of 843.8 mAh g−1 with a voltage plateau of 2.68 V at 10 mA g−1. This leads to the maximum energy density of 2174.9 Wh kg−1 and a peak power density of 18600 W kg−1. Additionally, CFx/RF RSs−13 cathode demonstrates commendable electrochemical stability across a wide temperature spectrum (−20–70 °C). Given these superior electrochemical attributes, the CFx/RF RSs combination holds significant promise for deployment in high-power devices and for standard operations under extreme temperature conditions.

Engineering Magnetic Nanoclusters for Highly Efficient Heating in Radio-Frequency Nanowarming.

Effective thawing of cryopreserved samples requires rapid and uniform heating. This is achievable through nanowarming, an approach that heats magnetic nanoparticles by using alternating magnetic fields. Here we demonstrate the synthesis and surface modification of magnetic nanoclusters for efficient nanowarming. Magnetite (Fe3O4) nanoclusters with an optimal diameter of 58 nm exhibit a high specific absorption rate of 1499 W/g Fe under an alternating magnetic field at 43 kA/m and 413 kHz, more than twice that of commercial iron oxide cores used in prior nanowarming studies. Surface modification with a permeable resorcinol-formaldehyde resin (RFR) polymer layer significantly enhances their colloidal stability in complex cryoprotective solutions, while maintaining their excellent heating capacity. The Fe3O4@RFR nanoparticles achieved a high average heating rate of 175 °C/min in cryopreserved samples at a concentration of 10 mg Fe/mL and were successfully applied in nanowarming porcine iliac arteries, highlighting their potential for enhancing the efficacy of cryopreservation.