Facile green synthesis of a novel NiO and its catalytic effect on methylene blue photocatalytic reduction and sodium borohydride hydrolysis.

NiO nanoparticles were synthesized from pine cone extract by green synthesis method, which is a simple, cost-effective, environmentally friendly and sustainable method. The particle size of NiO nanoparticles was determined to be in the range of 10-25 nm by X-diffraction differential and transmission electron microscope analysis, and the bandgap energy of NiO nanoparticles was determined to be 2.66 eV. The catalytic effect of NiO nanoparticles in both microwave-assisted sodium borohydride hydrolysis and photocatalytic reduction of methylene blue was examined and it was determined that they had a high catalytic effect in both applications. It was determined that the hydrogen production rate in sodium borohydride hydrolysis was 1135 mL/g/min. The activation energy of sodium borohydride hydrolysis is 29.69 kJ/mol and 29.59 kJ/mol for the nth-order and Langmuir Hinshelwood kinetic models, respectively. In the photocatalytic reduction of methylene blue with NaBH4, it was determined that the reduction did not occur in the absence of a catalyst, but in the presence of the catalyst, the reduction occurred 98% in 3 min. It was determined that NiO nanoparticles were used five times in the photocatalytic reduction of methylene blue and the reduction efficiency for the fifth time was 93%. It was determined that the photocatalytic reduction of methylene blue was pseudo-first order and the rate constant was 1.63 s-1. It was determined that NiO nanoparticles synthesized by the environmentally friendly green synthesis method can be used as catalysts for two different applications.

NiO nanoparticles were synthesized from pinecone extract in a simple, cost-effective, and green method. The synthesized NiO nanoparticles were characterized using various characterization techniques. NiO nanoparticles have high activity both in the photocatalytic reduction of methylene blue and in the hydrolysis of sodium borohydride, and they are catalysts with high activity in two different applications. Photocatalytic reduction of methylene blue with uncatalyzed NaBH₄ was not achieved and was completed in 3 min in the presence of NiO nanoparticle catalyst. It was determined that the hydrogen production rate in sodium borohydride hydrolysis was 1135 mL/g^/min. NiO nanoparticle catalysts have low activation energy for sodium borohydride hydrolysis.

Catalytic effect of nickel oxide nanoparticles from Lupinus Albus extract on green synthesis and photocatalytic reduction of methylene blue: kinetics and mechanism.

Green synthesis of nanomaterials is advancing due to their ease of synthesis, cheapness, nontoxicity, and renewability. An environmentally friendly biogenic method has been developed for the green synthesis of nickel oxide nanoparticles (NiO NPs) using phytochemical-rich bioextract. They are rich in bioextract phenolics, flavonoids, and berberine. These phytochemicals successfully reduce and stabilize NiNO3 into NiO NPs. In this study, NiO NPs were synthesized by the green synthesis method from Lupinus Albus. Characterization of NiO NPs was carried out by TEM, XRD, SEM, UV, XRF, BET, and EDX analyses. According to XRD analysis, TEM results also support this, where the NiO NPs particle size diameter is 5 nm. It was determined by the Tauc equation that the band energy gap of NiO NPs is 1.69 eV. It was determined that the BET surface area of NiO NPs was 49.6 m2/g. NiO nanoparticles synthesized from Lupinus Albus extract by the green synthesis method were used as catalysts in the photocatalytic reduction of methylene blue with NaBH4. In the photocatalytic reduction of methylene blue with NaBH4, it was determined that there was no color change in 48 h without a catalyst, and in the presence of NiO nanoparticle catalyst, methylene blue was reduced by 97% in 8 min. The kinetics of the photocatalytic reduction of methylene blue with NaBH4 is a pseudo-first-order kinetic model and the kinetic rate constant is determined as 0.66 min-1, indicating that the catalytic effect of NiO NPs is very high at this value. NiO NPs were used five times in the photocatalytic reduction of methylene blue with NaBH4 and it was determined that the reduction of methylene blue was over 90% in each use.

NiO nanoparticles were synthesized from Lupinus Albus extract by green synthesis, which is an easily applied, cost-effective, and environmentally friendly method. The synthesized NiO nanoparticles were characterized using various characterization techniques. NiO nanoparticles have a high catalytic effect in the photocatalytic reduction of methylene blue with NaBH₄. Photocatalytic reduction of methylene blue with uncatalyzed NaBH₄ could not be achieved, and 97% reduction of methylene blue was completed in 8 min in the presence of NiO nanoparticle catalyst.

Controllable Electrochemical Liberation of Hydrogen from Sodium Borohydride.

Sodium borohydride (NaBH4 ) has earned recognition as a promising hydrogen carrier, attributed to its exceptional hydrogen storage capacity, boasting a high theoretical storage capacity of 10.8 wt %. Nonetheless, the utilization of traditional pyrolysis and hydrolysis methods still presents a formidable challenge in achieving controlled hydrogen generation especially under ambient conditions. In this work, we report an innovative electrochemical strategy for production H2 by coupling NaBH4 electrooxidation reaction (BOR) at anode in alkaline media with hydrogen evolution reaction (HER) at cathode in acidic media. To implement this, we have developed a bifunctional electrocatalyst denoted as Pd-Mo2 C@CNTs, wherein Pd nanoparticles are grown in situ on Mo2 C embedded within N-doped carbon nanotubes. This electrocatalyst demonstrates exceptional performance in catalyzing both alkaline BOR and acidic HER. We have developed a hybrid acid/alkali cell, utilizing Pd/Mo2 C@CNTs as the anode and cathode electrocatalysts. This configuration showcases remarkable capabilities for self-sustained, precise, and uninterrupted indirect release of H2 stored in NaBH4 , even at high current densities of 100 mA cm-2 with a Faraday efficiency approaching 100 %. Additionally, this electrochemical device exhibits significant promise as a fuel cell, with the ability to deliver a maximum power density of 20 mW cm-2 .

Coronavirus-like Core-Shell-Structured Co@C for Hydrogen Evolution via Hydrolysis of Sodium Borohydride.

Constructing a reliable and robust cobalt-based catalyst for hydrogen evolution via hydrolysis of sodium borohydride is appealing but challenging due to the deactivation caused by the metal leaching and re-oxidization of metallic cobalt. A unique core-shell-structured coronavirus-like Co@C microsphere was prepared via pyrolysis of Co-MOF. This special Co@C had a microporous carbon coating to retain the reduced state of cobalt and resist the metal leaching. Furthermore, several nano-bumps grown discretely on the surface afforded enriched active centers. Applied in the pyrolysis of NaBH4, the Co@C-650, carbonized at 650 °C, exhibited the best activity and reliable recyclability. This comparable performance is ascribed to the increased metallic active sites and robust stability.

The identification of byproducts from the catalytic reduction reaction of 4-nitrophenol to 4-aminophenol: A systematic spectroscopic study.

Acetaminophenol, commonly recognized as paracetamol (considered safer than aspirin) is formed by nitration of phenol (4-nitrophenol (4-NP)) for its conversion to 4-aminophenol (4-AP), followed by the acetylation for the final product. As 4-NP is an intermediate product in acetaminophenol (paracetamol) production from phenol the dynamic analysis of acetylation of amine group is important. This study focuses on the feasibility of spectroscopic studies to monitor the removal of 4-NP using sodium borohydride (NaBH4) probe reaction in the presence of silver, gold, and bimetallic Ag/Au nanoparticles. UV-visible absorbance and fluorescence spectroscopy measurements reveal the formation of 1,4-benzoquinone (BQ), hydroquinone (HQ), and phenol (Ph) as the final products, in addition to the formation of typically reported 4-AP. The intermediates of NaBH4 seem to play a significant role in the formation of BQ, which converts to HQ in the basic medium followed by the formation of phenol in an acidic medium. Complete kinetic analysis with respect to spectroscopic studies of the standard compounds is presented. Similar results were obtained with 4-NP spiked river and seawater samples. The present findings may lead to catalytic benchmarking that can differ from most of the current practices and highlight the importance of adopting a holistic approach towards the fundamental understanding of 4-NP catalytic reduction that must take into account the concentration of NaBH4 and pH interdependencies.

Studies on the Selective Syntheses of Sodium Ditelluride and Dialkyl Ditellurides.

Studies on the selective synthetic method for dialkyl ditellurides 1, a representative class of organyl tellurium compounds, were presented. Considering the difficulty in conducting previous harsh reactions and in suppressing the formation of dialkyl tellurides 2 as side products, we optimized reaction conditions for selective syntheses of sodium ditelluride and the corresponding dialkyl ditellurides 1. We reduced tellurium to sodium ditelluride by using NaBH4 and subsequently, treated the obtained sodium ditelluride with alkyl halides (RX) to give the target compounds 1. Consequently, by applying various alkyl halides (RX) we achieved the selective syntheses of dialkyl ditellurides 1 (13 examples with 4 new compounds) in modest to good yields. We also suggested the mechanistic pathways to dialkyl ditellurides 1.

An Efficient Method for Selective Syntheses of Sodium Selenide and Dialkyl Selenides.

The studies on the selective synthesis of dialkyl selenide compounds 1 were presented. Overcoming the complexity and difficulty of selenides (R-Se-R) and/or multiselenides (R-Sen-R; n ≥ 2), we aimed to optimize the reaction condition for the tolerable preparation of sodium selenide (Na2Se) by reducing Se with NaBH4, and then to achieve selective syntheses of dialkyl selenides 1 by subsequently treating the obtained sodium selenide with alkyl halides (RX). Consequently, various dialkyl selenides 1 were efficiently synthesized in good-to-moderate yields. The investigations on reaction pathways and solvent studies were also described.

Fabrication of defective graphene oxide for efficient hydrogen production and enhanced 4-nitro-phenol reduction.

Hydrogen has been considered as one of the most promising alternative energy source to solve the future energy demands due to its high energy capacity and emission-free character. The generation of hydrogen from non-fossil sources is necessary for the sustainable development of human life on this planet. The hydrolysis of sodium borohydride can quickly produce a large amount of hydrogenin situand on-demand in the presence of the catalyst, which can be used as an alternative energy source. So, it is crucial to fabricate the highly efficient, robust, and economical catalyst for the production of hydrogen via hydrolysis of sodium borohydride. Herein, a facile and efficient approach for the synthesis of metal-functionalized reduced graphene oxide for the production of hydrogen at room temperature was used. Moreover, the synthesized catalyst has also been tested in the field of environmental catalysis for the reduction of toxic 4-nitrophenol to valuable 4-aminophenol in the presence of sodium borohydride. The enhanced activity of prepared metal-functionalized reduced graphene oxide is ascribed to a strong affinity between Fe-NXand reduced graphene oxide which facilitates electron transfer as well as synergistic effect. Overall, this work presents a crucial procedure for green chemistry reactions when a carbonaceous material is selected as a catalyst.

Performance of Pd/Sn catalysts supported by chelating resin prestoring reductant for nitrate reduction in actual water.

Catalytic hydrogen reduction has appeared as a promising strategy for chemical denitrification with advantages of high activity and simple operation. However, the risk and low utilization of H2 is the disadvantage of catalytic hydrogen reduction. In recent years, catalytic reduction reactions in the presence of sodium borohydride (NaBH4) have been extensively studied. NaBH4 can be used as an electron source to generate electrons on the surface of the catalyst and can catalyze the reduction of pollutants. But it makes commercialization costly and causes significant environmental pollution if widely use NaBH4. In this study, we prepared supported Pd/Sn bimetallic nanoparticles which could adsorb NaBH4 during the preparation of the Pd/Sn bimetallic catalyst as the prestoring reductant. No additional reducing agent is required during nitrate reduction process. The performance and mechanism for nitrate reduction by using Pd/Sn bimetallic nanoparticles were discussed. Moreover, the catalyst D-Pd1/Sn1 reached a complete nitrate removal in the municipal wastewater treatment plant effluent water within 3 h. The results provide a prospect for denitrification in biological wastewater treatment plants.

Highly efficient remediation of decabromodiphenyl ether-contaminated soil using mechanochemistry in the presence of additive and its mechanism.

Mechanochemistry has been proved to be an effective method to remediation of organic-contaminated sites. However, the high ball-to-powder mass ratio (CR) limits the large-scale application of mechanochemistry. In this study, co-milling additives were introduced to enhance the mechanochemical degradation of decabromodiphenyl ether (BDE209)-contaminated soil under the condition of low CR. Based on additive screening experiments, sodium borohydride was selected as the ideal additive to assist the mechanochemical degradation of BDE209, and the resulting removal efficiency was approximately 100% with 2 h of ball milling at a rotational speed of 550 rpm. The main degradation intermediates and degradation pathway of BDE209 were identified using gas chromatography-tandem mass spectrometry. It was proposed that the degradation of BDE209 by sodium borohydride-assisted mechanochemistry was a concurrent process of stepwise and multistage debromination. Meanwhile, the meta-bromine atom in BDE209 was more susceptible to debromination than those at the para and ortho positions. The evolution of the concentration of Br- was monitored by ion chromatography, which revealed that reduction and oxidation both occurred in the removal of BDE209. This paper provides a new perspective for reducing the CR in the mechanochemical remediation of BDE209-contaminated soil.

Simultaneous Determination of Human Serum Albumin and Low-Molecular-Weight Thiols after Derivatization with Monobromobimane.

Biothiols are extremely powerful antioxidants that protect cells against the effects of oxidative stress. They are also considered relevant disease biomarkers, specifically risk factors for cardiovascular disease. In this paper, a new procedure for the simultaneous determination of human serum albumin and low-molecular-weight thiols in plasma is described. The method is based on the pre-column derivatization of analytes with a thiol-specific fluorescence labeling reagent, monobromobimane, followed by separation and quantification through reversed-phase high-performance liquid chromatography with fluorescence detection (excitation, 378 nm; emission, 492 nm). Prior to the derivatization step, the oxidized thiols are converted to their reduced forms by reductive cleavage with sodium borohydride. Linearity in the detector response for total thiols was observed in the following ranges: 1.76-30.0 mg mL-1 for human serum albumin, 0.29-5.0 nmol mL-1 for α-lipoic acid, 1.16-35 nmol mL-1 for glutathione, 9.83-450.0 nmol mL-1 for cysteine, 0.55-40.0 nmol mL-1 for homocysteine, 0.34-50.0 nmol mL-1 for N-acetyl-L-cysteine, and 1.45-45.0 nmol mL-1 for cysteinylglycine. Recovery values of 85.16-119.48% were recorded for all the analytes. The developed method is sensitive, repeatable, and linear within the expected ranges of total thiols. The devised procedure can be applied to plasma samples to monitor biochemical processes in various pathophysiological states.

Performance and potential mechanism of Cr(VI) reduction and subsequent Cr(III) precipitation using sodium borohydride driven by oxalate.

The method of treating high concentrations of Cr(VI) alone by NaBH4 has proved feasible, but the effects of the coexistence of Cr(VI) and organic compounds have not been evaluated. The objective of this study was to explore the potential mechanism by which oxalate affects the reduction of high concentrations of Cr(VI) treated by sodium borohydride (NaBH4) and the subsequent precipitation of Cr(III). The results show that Cr(VI) reduction could be gradually promoted by oxalate (1.0-10 mM). Compared with the control solution, the reduction of Cr(VI) in a 10 mM oxalate solution could be increased from 56.6% to 99.1%. Particularly, the promotion of Cr(VI) reduction attributed to the enhancement of OH- production from NaBH4 hydrolysis due to the increasing concentration of C2O42- species, forming conjugated acid-base pairs in the form HC2O4--C2O42-, which provided an effective buffer. In 0.10-0.40 mM oxalate-Cr(VI)-NaBH4 systems, the resulting Cr(III) could precipitate at different levels within 20 h, and showed settlement rates in the range of 8.8% and 95.8%, but no precipitate was found in 1.0-10 mM oxalate-Cr-NaBH4 systems. This is related to whether there was a sufficient oxalate dosage, which could be complexed with Cr (III) at a molar ratio of 1:1. The precipitates were analysed by means of electron spin resonance (ESR), atomic force microscopy (AFM), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR), indicating that Cr (III) could support oxalate coprecipitation. The results of the present study reveal the influence of oxalate on Cr(VI) reduction and subsequent Cr (III) precipitation, which are of great significance to the application of NaBH4 in the treatment of industrial wastewater containing Cr(VI)-oxalate.

Destabilization of NaBH4 by Transition Metal Fluorides.

In order to improve the suitability of NaBH4 as a clean fuel, its decomposition temperature needs to be decreased to below 535 °C, while its hydrogen release must be as high as possible. In this work, the influence of a collection of first and second period transition metal fluorides on the destabilization of NaBH4 is studied on samples produced by ball milling NaBH4 with 2 mol% of a metal fluoride additive. The effects obtained by increasing additive amount and changing oxidation state are also evaluated for NbF5, CeF3, and CeF4. The as-milled products are characterized by in-house power X-ray diffraction, while the hydrogen release and decomposition are monitored by temperature programmed desorption with residual gas analysis, differential scanning calorimetry, and thermogravimetry. The screening of samples containing 2 mol% of additive shows that distinctive groups of transition metal fluorides affect the ball milling process differently depending on their enthalpy of formation, melting point, or their ability to react at the temperatures achieved during ball milling. This leads to the formation of NaBF4 in the case of TiF4, MnF3, VF4, CdF2, NbF5, AgF, and CeF3 and the presence of the metal in CrF3, CuF2, and AgF. There is no linear correlation between the position of the transition metal in the periodic table and the observed behavior. The thermal behavior of the products after milling is given by the remaining NaBH4, fluoride, and the formation of intermediate metastable compounds. A noticeable decrease of the decomposition temperature is seen for the majority of the products, with the exceptions of the samples containing YF3, AgF, and CeF3. The largest decrease of the decomposition temperature is observed for NbF5. When comparing increasing amounts of the same additive, the largest decrease of the decomposition temperature is observed for 10 mol% of NbF5. Higher amounts of additive result in the loss of the NaBH4 thermal signal and ultimately the loss of the crystalline borohydride. When comparing additives with the same transition metal and different oxidation states, the most efficient additive is found to be the one with a higher oxidation state. Furthermore, among all the samples studied, higher oxidation state metal fluorides are found to be the most destabilizing agents for NaBH4. Overall, the present study shows that there is no single parameter affecting the destabilization of NaBH4 by transition metal fluorides. Instead, parameters such as the transition metal electronegativity and oxidation state or the enthalpy of formation of the fluoride and its melting point are competing to influence the destabilization. In particular, it is found that the combination of a high metal oxidation state and a low fluoride melting point will enhance destabilization. This is observed for MnF3, NbF5, NiF2, and CuF2, which lead to high gas releases from the decomposition of NaBH4 at the lowest decomposition temperatures.

Spectral Characteristics of Autofluorescence in Renal Tissue and Methods for Reducing Fluorescence Background in Confocal Laser Scanning Microscopy.

Significant autofluorescence (AF) of renal tissue is one of the major causes restricting the use of immunofluorescent staining. This study aimed at controlling renal tissue AF and testing an effective method for optimizing specific signals. In the present study, we observed emergence of strong AF in all renal cells under different fluorescent channels. Significant concentration-dependent reduction in AF of kidney tissue was observed with the use of sodium borohydride (NaBH4) and Sudan black B (SBB) alone (p < 0.05). Under maximum effective concentration, semi-quantitative analysis revealed that inhibitory effect of SBB on AF was superior to that of NaBH4 (P < 0.01). When the two chemicals were combined, we observed that background can be reduced, and specific staining can be optimized at optimum concentration. Intensity of renal tissue was examined by confocal λ scanning, which showed that peaks were located at the range of approximately 480 - 590 nm and similar to those of flavin and lipofuscin. These results indicated that combined use of NaBH4 and SBB, when targeted at different sources of AF in renal tissue, is the most effective means of reducing background and preserving specificity of fluorescent labels. In addition, this method does not interfere with various steps of immunofluorescence experiments.

The Chemical Properties of Hydrogen Atoms Adsorbed on M0 -Nanoparticles Suspended in Aqueous Solutions: The Case of Ag0 -NPs and Au0 -NPs Reduced by BD4.

The nature of H-atoms adsorbed on M0 -nanoparticles is of major importance in many catalyzed reduction processes. Using isotope labeling, we determined that hydrogen evolution from transient {(M0 -NP)-Hn }n- proceeds mainly via the Heyrovsky mechanism when n is large (i.e., the hydrogens behave as hydrides) but mainly via the Tafel mechanism when n is small (i.e., the hydrogens behave as atoms). Additionally, the relative contributions of the two mechanisms differ considerably for M=Au and Ag. The results are analogous to those recently reported for the M0 -NP-catalyzed de-halogenation processes.

Cobalt Carbonate Hydroxide Nanowire Array on Ti Mesh: An Efficient and Robust 3D Catalyst for On-Demand Hydrogen Generation from Alkaline NaBH4 Solution.

In this work, for the first time, a cobalt carbonate hydroxide (Co(CO3 )0.5 (OH)⋅0.11 H2 O) nanowire array on Ti mesh (CHNA/Ti) was applied to drive the dehydrogenation of alkaline NaBH4 solution for on-demand hydrogen production. Compared with other nanostructured Co-based catalyst systems, CHNA/Ti can be activated more quickly and separated easily from fuel solutions. This self-supported cobalt salt nanowire array catalyst works as an efficient and robust 3D catalyst for the hydrolysis reaction of NaBH4 with a hydrogen generation rate of 4000 mL min-1 gCo-1 and a low apparent activation energy of 39.78 kJ mol-1 and offers an attractive system for on-demand hydrogen generation.

Micromotor-based energy generation.

A micromotor-based strategy for energy generation, utilizing the conversion of liquid-phase hydrogen to usable hydrogen gas (H2), is described. The new motion-based H2-generation concept relies on the movement of Pt-black/Ti Janus microparticle motors in a solution of sodium borohydride (NaBH4) fuel. This is the first report of using NaBH4 for powering micromotors. The autonomous motion of these catalytic micromotors, as well as their bubble generation, leads to enhanced mixing and transport of NaBH4 towards the Pt-black catalytic surface (compared to static microparticles or films), and hence to a substantially faster rate of H2 production. The practical utility of these micromotors is illustrated by powering a hydrogen-oxygen fuel cell car by an on-board motion-based hydrogen and oxygen generation. The new micromotor approach paves the way for the development of efficient on-site energy generation for powering external devices or meeting growing demands on the energy grid.

Selective C-Methylenation of N-Unsubstituted Indoles Using CO2 Under NaBH4/I2 System.

The selective C-methylenation of N-unsubstituted indoles using CO2 as the C1 source to access diindolylmethane (DIM) and its derivatives is described. This reaction provides a novel method for four-electron reductive functionalization of CO2 with N-unsubstituted indoles via formation of C-CH2-C bonds, and a new access to molecular structures.

A facile synthesis of 2-(4-((4-chlorophenyl)(hydroxy)methyl) phenoxy)-2-methylpropanoic acid: Metabolite of anti-hyperlipidemic drug Fenofibrate.

Synthesis and characterization of drug metabolites has emerged as an important area of research in consideration to the significant contribution of studies on metabolites in drug research. The present work comprises synthesis of 2-(4-((4-chlorophenyl)(hydroxy)methyl) phenoxy)-2-methylpropanoic acid, a metabolite of anti-hyperlipidemic drug fenofibrate. The desired compound was prepared by two different synthetic routes. The ketone group of fenofibric acid was reduced using sodium borohydride in one route whereas the hydrolysis of isopropyl ester of the reduced fenofibrate was achieved by the mild alkaline hydrolysis in the other path. Both the ways of synthesis furnished the desired compound in excellent yield and purity. The new synthetic congener was characterized by spectroscopic methods.

The Removal of Formaldehyde from Urea Formaldehyde Adhesive by Sodium Borohydride Treatment and Its Application in Plywood.

The global production of plywood is constantly increasing as its application in the furniture and interior decoration industry becomes more widespread. An urgent issue is how to decrease the formaldehyde released from plywood, considering its carcinogenic effect on humans and harm to the environment. Reducing the free formaldehyde content of the urea formaldehyde (UF) adhesives used in the preparation process is considered an effective method. Therefore, it is necessary to identify a new type of formaldehyde scavengers. Here, the strongly reducing substance sodium borohydride was used to reduce and degrade the free formaldehyde in UF adhesives, and its effects on the properties of the UF adhesive and plywood were studied. When 0.7% sodium borohydride was added to the UF adhesive with a molar ratio of formaldehyde to urea of 1.4:1, the free formaldehyde content of the UF resin decreased to 0.21%, which is 53% lower than that of the untreated control. Moreover, the formaldehyde released from the plywood was reduced to 0.81 mg/L, ~45% lower than that from the group. The bonding strength of the treated samples could reach ~1.1 MPa, which was only reduced by ~4% compared to that of the control. This study of removing formaldehyde from UF adhesive by reduction could provide a new approach for suppressing formaldehyde release from the final products.