•TiO2/CuCNFs was prepared in this work.•A novel laccase biosensor based on TiO2/CuCNFs was applied in hydroquinone detection.•The linear range of the prepared biosensor is 1 μM to 89.8 μM.A novel biosensor was prepared on the basis of laccase, Nafion and TiO2 loaded copper and carbon composite nanofibers (TiO2/CuCNFs) obtained through electrospinning, carbonization and solvothermal treatment. The introduction of TiO2 apparently improved the electrocatalysis of the biosensor for the detection of hydroquinone. In addition, cyclic voltammetry analysis of the biosensor showed a pair of well-defined redox peaks, and revealed that the electrochemical behavior of laccase was a surface-controlled process. Chronoamperometry technique was also employed to investigate the biosensor. The results displayed a linear range from 1 μM to 89.8 μM, detection limit of 3.65 μM (S/N = 3), a sensitivity of 24.6 μA/mM, a high selectivity, as well as good repeatability and stability. The biosensor showed great promise in hydroquinone monitoring.

•We report a facile approach to prepare cellulose/TiO2/PANI composite nanofibers that involves P–N heterojunctions.•The response values and sensitivity of cellulose/TiO2/PANI were much higher than those of cellulose/PANI composite nanofibers.•Enhanced sensing was obtained due to the P–N heterojunctions whose depletion layer would be widened when the sensor was exposed to ammonia.We report a facile approach to prepare cellulose/titanium dioxide/polyaniline (cellulose/TiO2/PANI) composite nanofibers that involves P–N heterojunctions at the interface of p-type PANI and n-type TiO2. This work found that the P–N heterojunctions could improve ammonia sensing properties of the prepared nanofibers. Electrospun cellulose acetate nanofibers were deacetylated to prepare regenerated cellulose nanofibers, and then the obtained cellulose nanofibers were immersed into TiO2 sol to adsorb TiO2 nanoparticles onto the surface of them to fabricate cellulose/TiO2 composite nanofibers. In-situ polymerization of aniline was utilized to deposit PANI on the surface of cellulose/TiO2 composite nanofibers. The gas sensing properties of the prepared nanofibers were evaluated by a home-made test system. The cellulose/TiO2/PANI and cellulose/PANI composite nanofibers were exposed to 10, 30, 50, 100, 150, 200 and 250 ppm ammonia vapor at room temperature, respectively. It was found that the response values and sensitivity of cellulose/TiO2/PANI were much higher than those of cellulose/PANI composite nanofibers. Enhanced sensing was obtained by cellulose/TiO2/PANI due to the P–N heterojunctions whose depletion layer would be widened when the composite nanofibers were exposed to ammonia, resulting in their resistance increased dramatically.

•A facile approach to produce AgNPs-CMC/cellulose composite nanofibrous mats has been developed.•Laccase biosensor based on AgNPs-CMC/cellulose composite nanofibrous mats for catechol detection was developed in this work.•The detection limit of the obtained biosensor to catechol is 1.64 μM.•The composite nanofibers could provide a new platform for other redox proteins immobilization.We report a facile approach to synthesize and immobilize silver nanoparticles (AgNPs) onto carboxymethyl cellulose (CMC)-modified electrospun cellulose nanofibers and demonstrate the potential application of as-prepared AgNPs-CMC/cellulose composite nanofibrous mats as effective biosensor substrate materials. Cellulose nanofibers were prepared by the combination of electrospinning with deacetylation. Then, CMC was adsorbed onto cellulose nanofibers to complex silver ions through the chemical binding with the free carboxyl groups of CMC for subsequent reductive formation of AgNPs. The AgNPs-CMC/cellulose nanofibers immobilized with laccase (Lac) by electrostatic interactions were used as biosensor substrate materials for catechol detection. The cyclic voltammetries revealed that the AgNPs-CMC/cellulose nanofibers was beneficial to the immobilization of Lac and facilitated the direct electron transfer between Lac and electrode. Lac/AgNPs-CMC/cellulose/glassy carbon electrode exhibited a detection limit of 1.64 μM (S/N = 3), and a wide linear range from 4.98 μM to 3.65 mM, as well as good repeatability, reproducibility, stability, and selectivity. The CMC/cellulose nanofibrous mats have great potential applications as substrate materials for different biosensors by immobilizing other different functional nanoparticles or enzyme on them.Graphical abstract

A novel phenolic biosensor was prepared on the basis of a composite of polydopamine (PDA)-laccase (Lac)-nickel nanoparticle loaded carbon nanofibers (NiCNFs). First, NiCNFs were fabricated by a combination of electrospinning and a high temperature carbonization technique. Subsequently, the magnetic composite was obtained through one-pot Lac-catalyzed oxidation of dopamine (DA) in an aqueous suspension containing Lac, NiCNFs, and DA. Finally, a magnetic glass carbon electrode (MGCE) was employed to separate and immobilize the composite; the modified electrode was then denoted as PDA-Lac-NiCNFs/MGCE. Fourier transform infrared (FT-IR) spectra and cyclic voltammetry (CV) analyses revealed the NiCNFs had good biocompatibility for Lac immobilization and greatly facilitated the direct electron transfer between Lac and electrode surface. The immobilized Lac showed a pair of stable and well-defined redox peaks, and the electrochemical behavior of Lac was a surface-controlled process in pH 5.5 acetate buffer solution. The PDA-Lac-NiCNFs/MGCE for biosensing of catechol exhibited a sensitivity of 25 μA mM–1 cm–2, a detection limit of 0.69 μM (S/N = 3), and a linear range from 1 μM to 9.1 mM, as well as good selectivity and stability. Meanwhile, this novel biosensor demonstrated its promising application in detecting catechol in real water samples.Keywords: carbon nanofibers; dopamine; electrospinning; laccase; nickel nanoparticle; phenolic biosensor;

ZnO loaded carbon nanofibers (ZnO/CNFs) were successfully fabricated by a combination of electrospinning, carbonization and a hydrothermal process. A novel biosensor was fabricated based on a composite of ZnO/CNFs, laccase (Lac), and Nafion. The addition of ZnO/CNFs apparently facilitated the direct electron transfer (DET) between the active center of Lac and the surface of the glassy carbon electrode (GCE). A pair of stable and well-defined redox peaks was observed on the Nafion–Lac–ZnO/CNF modified GCE. Meanwhile, square wave voltammetry (SWV) was employed to investigate the biosensor, and the sensor showed highly efficient electrocatalysis toward hydroquinone with a sensitivity of 28.50 μA μM−1, a detection limit of 9.50 nM (S/N = 3), a linear range from 5.00 × 10−7 to 2.06 × 10−6 M, as well as good selectivity and stability. Furthermore, this novel biosensor was successfully used in detecting hydroquinone in real water samples.