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This study investigated the effects of different citric acid content on the physico-mechanical and biological durability of rubberwood particleboard. Particleboards with density of 700 kg/m3 were produced with three different citric acid contents, namely 10, 15 and 20 wt%. Particleboards made from 10 wt% urea formaldehyde (UF) resin were served as control for comparison purposes. FTIR analysis was carried out and the formation of ester linkages between -OH on cellulose and carbonyl groups of citric acid was confirmed. The peak intensity increased along with increasing citric content, which indicated that a higher amount of ester linkages were formed at higher citric acid content. Citric acid-bonded particleboard had inferior physical properties (water absorption and thickness swelling) and mechanical properties (internal bonding strength, modulus of rupture and modulus of elasticity) compared to that of the UF-bonded particleboard. However, the performance of particleboard was enhanced with increasing citric acid content. Meanwhile, citric acid-bonded particleboard displayed significantly better fungal and termite resistance than UF-bonded particleboard owing to the acidic nature of citric acid. It can be concluded that citric acid is a suitable green binder for particleboard but some improvement is needed during the particleboard production process.

An electrochemical method was developed for ultrasensitive and selective detection of dopamine in human serum using mesoporous silica thin film modified gold microelectrodes. Vertically aligned mesoporous silica thin films were deposited onto Au microelectrodes by electrochemically assisted self-assembly (EASA). The mesochannels have uniform pore sizes of 2.1 nm in diameter and a negatively charged wall surface. Cyclic voltammetry reveals effective charge permselectivity through the negatively charged mesoporous channels. By using differential pulse voltammetry, the mesoporous silica thin film modified Au microelectrode can be employed for the ultrasensitive detection of dopamine with a detection limit as low as 0.084 μM. In addition, thanks to the electrostatic and steric effects of the silica mesochannels, excellent anti-interference and anti-fouling properties of the electrochemical sensors are demonstrated. [ABSTRACT FROM AUTHOR]

Direct, rapid, and sensitive detection of drugs in complex biological samples is essential for drug abuse control and health risk assessment. In this work, an electrochemical sensor was fabricated based on equipment of vertically-ordered mesoporous silica film (VMSF) on an electrochemically pre-treated three-dimensional graphene electrode (p-3DG), which can achieve direct and sensitive determination of methylthiopyridazine (TR) in urine. Three-dimensional graphene (3DG) with a continuous and interpenetrating graphene network was used as the supporting electrode and simple electrochemical polarization was employed to pre-treat 3DG to improve surface hydrophilicity and electrocatalytic performance. VMSF was easily grown using an electrochemical assisted self-assembly method within 10 s and was stably bound to the p-3DG surface. The nanochannel array on the as-prepared VMSF/p-3DG sensor enriched positively charged TR, leading to significantly improved electrochemical signal. Combined with the high electric activity of p-3DG and the enrichment of nanochannels, VMSF/p-3DG realized sensitive determination of TR ranging from 50 nM to 10 μM with a low detection limit (DL, 30 nM). Owing to the anti-fouling and anti-interference performance of VMSF, the common electroactive molecules including ascorbic acid (AA) and uric acid (UA) did not interfere with the detection. In addition, the detection of TR in buffer and urine exhibited similar sensitivity. Accurate detection of TR in urine was realized. [ABSTRACT FROM AUTHOR]

Herein we report a simple and rapid approach to fabricate a vertically-ordered mesoporous silica–electrochemically reduced graphene oxide nanocomposite film (VMSF/ErGO) on an indium tin oxide (ITO) electrode surface by the electrochemically-assisted self-assembly (EASA) method, which is capable of greatly promoting the electroanalytical performance of rutin compared to the previously reported VMSF modified ITO electrode and, meanwhile, displaying excellent anti-fouling and anti-interference ability in pharmaceutical formulations and human serum. Due to the excellent electrocatalytic activity of ErGO and the synergistic enrichment effects from the π–π interaction of ErGO and the hydrogen bond effect from the VMSF, the present VMSF/ErGO/ITO sensor is able to detect rutin with a wide linear range, a high sensitivity and a low limit of detection. Moreover, the VMSF/ErGO/ITO electrode could retain the high sensing performance with high transmittance upon tailoring the concentration of the modified graphene oxide (GO), which provides a simple approach for modifying transparent ITO electrodes and could be potentially used for optoelectronic devices. [ABSTRACT FROM AUTHOR]

Developing ordered mesoporous silica-based membranes with highly sensitive detection performance is of great significance for direct electrochemical detection in biological fluids against surface biofouling. Herein, we describe a facile one-step approach for the integration of a vertically-ordered mesoporous silica-nanochannel film (VMSF) with electrochemically reduced graphene oxide (ErGO) by an electrochemically assisted self-assembly (EASA) method. Electrochemical reduction of GO and growth of the VMSF simultaneously occur in a simple one-step process, forming a VMSF/ErGO layer on the glassy carbon electrode (GCE). Arising from the oxygen-containing groups, hydrophobic π-conjugated structure, and the two-dimensional planar structure of ErGO, the VMSF could be stably grown on the GCE surface and it further acted as a protective layer to prevent the internal ErGO electroactive layer from falling off the electrode surface over prolonged use. In comparison with a bare GCE, the present VMSF/ErGO/GCE sensor exhibits an excellent response to doxorubicin with a wide linear range (1 nM−20 μM), a high sensitivity (7.815 μA μM−1) and a low limit of detection (0.77 nM), due to the cooperative signal amplification originating from the electrocatalytic activity and π–π interaction of ErGO and electrostatic preconcentration effect of the VMSF. Furthermore, considering the outstanding anti-fouling and anti-interference ability of the VMSF, direct determination and long-term monitoring of doxorubicin in human whole blood was successfully achieved by the sensor. [ABSTRACT FROM AUTHOR]

Three-dimensional graphene (3DG) with macroporous structure has great potential in the field of electroanalysis owing to a large active area, excellent electron mobility and good mass transfer. However, simple and low-cost preparation of 3DG electrodes with high electrocatalytic ability is still a challenge. Here, a fast and convenient electrochemical polarization method is established to pretreat free-standing 3DG (p-3DG) to offer high electrocatalytic ability. 3DG with monolithic and macroporous structure prepared by chemical vapor deposition (CVD) is applied as the starting electrode. Electrochemical polarization is performed using electrochemical oxidation (anodization) at high potential (+6 V) followed with electrochemical reduction (cathodization) at low potential (−1 V), leading to exposure of edge of graphene and introduction of oxygen-containing groups. The as-prepared p-3DG displays increased hydrophilicity and improved electrocatalytic ability. As a proof of concept, p-3DG was used to selective electrochemical detection of two isomers of benzenediol, hydroquinone (p-BD) and catechol (o-BD). In comparison with initial 3DG, p-3DG exhibits increased reversibility of redox reaction, improved peak current and good potential resolution with high potential separation between p-BD and o-BD. Individual or selective determination of p-BD or o-BD in single substance solution or binary mixed solution is realized. Real analysis of pond water is also achieved. [ABSTRACT FROM AUTHOR]

Vertically ordered mesoporous silica film (VMSF) with uniform mesoporous channels perpendicular to electrode substrate has a wide range of applications in direct electroanalysis of complex samples. However, the detection of nucleic acid bases is difficult to realize at the commonly used VMSF-modified indium tin oxide (VMSF/ITO) electrode due to the high overpotentials of underlying ITO for many small organic molecules. In this work, we demonstrated an electrochemical method for the sensitive detection of guanine (G) by integration of VMSF/ITO and tris(2,2'-bipyridine) ruthenium (II) [Ru(bpy) 3 2+ ] redox mediator. Ru(bpy) 3 2+ electrostatically accumulated by VMSF is able to act as an electron shuttle between G and underlying ITO surface, showing electrocatalytic oxidation of G and enabling the quantitative determination of G with a limit of detection (LOD) of 0.058 μM and a limit of quantitation (LOQ) of 0.2 μM. Electrochemical detection performance for G could be regulated by changing the pH of the supporting electrolyte and the content of Ru(bpy) 3 2+ , achieving a wide dynamic linear range from 0.2 to 10 μM ( R 2 = 0.999), 2 to 100 μM ( R 2 = 0.999), and 10 to 500 μM ( R 2 = 0.998). Furthermore, owing to the good anti-fouling and anti-interference ability of VMSF, this simply sensing strategy can be applied to the direct and rapid detection of G in beer samples, and the detection of ganciclovir (G analog) content in ganciclovir eye drops., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Yang, Zhang, Zhou, Yan and Liu.)

Convenient and sensitive detection of active analytes in complex matrix is crucial in biological, medical, and environmental analysis. Silica nanochannel array film (SNF) equipped electrochemical sensors have shown excellent anti-fouling performance in direct analysis of complex samples. In this work, we demonstrated an electrochemical sensor with anti-fouling performance for highly sensitive detection of acetaminophen (APAP) based on SNF supported by ß -cyclodextrin-graphene (CDG) nanocomposite modified Au film electrode (AuF). Because of their rich surface hydroxyls and 2D lamellar structure, CDG on AuF can serve as the nanoadhesive for compact binding SNF, which can be grown by electrochemical assisted self-assembly method in a few seconds. Attributable to the electrocatalytic property of graphene and the synergistic enrichment from both CD and SNF nanochannels towards analyte, the SNF/CDG/AuF sensor demonstrates sensitive detection of acetaminophen ranged from 0.2 to 50 μM with an ultralow limit-of-detection of 14 nM. Taking advantage of the anti-fouling ability of SNF, the sensor is able to realize accurate and convenient analysis of APAP in commercially available paracetamol tablets., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Zhou, Ding, Su, Lu, Tang and Xi.)

Three-dimensional graphene (3DG) with macroporous structure has great potential in the field of electroanalysis owing to a large active area, excellent electron mobility and good mass transfer. However, simple and low-cost preparation of 3DG electrodes with high electrocatalytic ability is still a challenge. Here, a fast and convenient electrochemical polarization method is established to pretreat free-standing 3DG (p-3DG) to offer high electrocatalytic ability. 3DG with monolithic and macroporous structure prepared by chemical vapor deposition (CVD) is applied as the starting electrode. Electrochemical polarization is performed using electrochemical oxidation (anodization) at high potential (+6 V) followed with electrochemical reduction (cathodization) at low potential (-1 V), leading to exposure of edge of graphene and introduction of oxygen-containing groups. The as-prepared p-3DG displays increased hydrophilicity and improved electrocatalytic ability. As a proof of concept, p-3DG was used to selective electrochemical detection of two isomers of benzenediol, hydroquinone (p-BD) and catechol (o-BD). In comparison with initial 3DG, p-3DG exhibits increased reversibility of redox reaction, improved peak current and good potential resolution with high potential separation between p-BD and o-BD. Individual or selective determination of p-BD or o-BD in single substance solution or binary mixed solution is realized. Real analysis of pond water is also achieved.

Three-dimensional (3D) electrochemiluminescence (ECL) platform with high sensitivity and good anti-fouling is highly desirable for direct and sensitive analysis of complex samples. Herein, a novel ECL-sensing platform is demonstrated based on the equipment of vertically ordered mesoporous silica-nanochannel films (VMSF) on monolithic and macroporous 3D graphene (3DG). Through electrografting of 3-aminopropyltriethoxysilane (APTES) onto 3DG as molecular glue, VMSF grown by electrochemically assisted self-assembly (EASA) method fully covers 3DG surface and displays high stability. The developed VMSF/APTES/3DG sensor exhibits highly sensitized ECL response of tris(2,2'-bipyridyl) ruthenium (Ru (bpy) 3 2+ ) taking advantages of the unique characteristics of 3DG (high active area and conductivity) and VMSF nanochannels (strong electrostatic enrichment). The VMSF/APTES/3DG sensor is applied to sensitively detect an important environmental pollutant (4-chlorophenol, with limit of detection or LOD of 30.3 nM) in term of its quenching effect (ECL signal-off mode) toward ECL of Ru (bpy) 3 2+ /tri-n-propylamine (TPrA). The VMSF/APTES/3DG sensor can also sensitively detect the most effective antihistamines chlorpheniramine (with LOD of 430 nM) using ECL signal-on mode because it acts as co-reactant to promote the ECL of Ru (bpy) 3 2+ . Combined with the excellent antifouling ability of VMSF, the sensor can also realize the analysis of actual environmental (lake water) and pharmaceutical (pharmacy tablet) samples. The proposed 3D ECL sensor may open new avenues to develop highly sensitive ECL-sensing platform., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 Gong, Tang, Luo, Zhou, Lin, Wang, Yan, Xi and Liu.)