Self-Luminous Wood Coatings with Carbon Dots/TiO2 Grafted Afterglow SrAl2O4: Eu, Dy Core-Shell Phosphors for Long-Lasting Formaldehyde Removal.

Long-term relief of indoor volatile pollution has become a competitive issue worldwide in both visible and dark environments. A novel self-luminous wood coating with carbon dots (CDs)/titanium dioxide (TiO2) nanomaterial coated SrAl2O4: Eu2+, Dy3+ (CDs/TiO2@SAO) composite was prepared for the long-term degradation of formaldehyde through a simple sol-gel method. The microstructure, chemical composition, ultraviolet-visible (UV-vis) spectra, and long-lasting fluorescence of the CDs/TiO2@SAO photocatalyst were analyzed to illustrate the mechanism for degrading formaldehyde. The obtained CDs with a particle size of ~2-7 nm have a good graphite structure and presented good absorption in visible light. In addition, owing to the synergistic effect of the CDs/TiO2 nanomaterial coating layer and the long-afterglow luminescence of the SAO phosphor, the CDs/TiO2@SAO composite can absorb a part of the visible light for photocatalytic degradation and store luminous energy efficiently at daytime so as to give out visible luminescence continuously for a few hours in the darkness. Furthermore, the functional wood coatings with CDs/TiO2@SAO composite presented continuous and efficient photocatalytic activity in the presence and absence of light exposure. The current research could provide a new strategy for designing an efficient photocatalyst for degrading formaldehyde pollution in the daytime with a visible light supply and in an indoor dark environment without an external light source.

Flexible and Freestanding MoS2 Nanosheet/Carbon Nanotube/Cellulose Nanofibril Hybrid Aerogel Film for High-Performance All-Solid-State Supercapacitors.

Flexible supercapacitors assembled with two-dimensional materials have become a research hotspot in recent years. Here, we have prepared two-dimensional nanomaterial MoS2 and SWCNT, CNF aerogel composite electrode, and its flexible all-solid-state supercapacitor. SWCNT can inhibit the accumulation of MoS2 nanosheets and enhance the conductivity of the composite electrode. CNF can improve the dispersion uniformity of MoS2 and SWCNT, and endow the composite electrode with a high specific surface area (328.86 m2 g-1) and excellent flexibility. MoS2-SWCNT/CNF supercapacitor has a good rectangular CV curve and symmetrical triangular GCD curve. The CV curve of the MoSCF3 supercapacitor with the highest MoS2-SWCNT content remains rectangular even at the scanning rate of 2000 mV s-1. Its voltage window can reach 1.5 V. MoS2-SWCNT/CNF supercapacitor has a specific capacity of 605.32 mF cm-2 (scanning rate of 2 mV s-1) and 30.34 F g-1 (0.01 A g-1), an area specific energy of 35.61 mWh cm-2 (area specific power of 0.03 mW cm-2), and extremely high cycle stability (91.01% specific capacity retention rate after 10 000 cycles) and good flexibility. The fine nanocomposite structure gives MoS2-SWCNT/CNF supercapacitor impressive electrochemical performance and excellent flexibility, which can be used in the field of portable electronic devices and flexible devices.

Combined stabilizers prepared from cellulose nanocrystals and styrene-maleic anhydride to microencapsulate phase change materials.

Cellulose nanocrystals (CNCs) combined with styrene-maleic anhydride (SMA) as stabilizers were used to stabilize paraffin droplets for fabricating paraffin/melamine-urea-formaldehyde (MUF) microcapsules. Effects of mixed emulsifier of CNCs and SMA on the morphologies, chemical structures, and properties of paraffin/MUF microcapsules were characterized by Field emission scanning electron microscopy (FE-SEM), Fourier-transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), thermogravimetric analyzer (TGA), differential scanning calorimetry (DSC), and paraffin leakage rate test. The results showed that using CNCs alone as emulsifier did not work in manufacturing paraffin/MUF microcapsules, but mixed emulsifier of CNCs and SMA was suitable. When CNCs and SMA each account for 50 % of the mixed stabilizer, the phase change latent heat values of melting and crystallization of MicroC5S5 were about 123.6 J/g and 118.4 J/g, respectively. This demonstrates that CNCs can be mixed with SMA to stabilize paraffin droplets in situ polymerization and reduce the need for surfactants.

Nanocellulose supported hierarchical structured polyaniline/nanocarbon nanocomposite electrode via layer-by-layer assembly for green flexible supercapacitors.

The development of a hierarchical structured multicomponent nanocomposite electrode is a promising strategy for utilizing the high efficiency of an electroactive material and improving the electrochemical performance. We propose cellulose nanofibril (CNF) aerogels with a nanoscale fiber-entangled network as the skeleton (via layer-by-layer (LbL) assembly) of electroactive materials polyaniline (PANi), carboxylic multiwalled carbon nanotubes (CMWCNTs), and graphene oxide (GO) to obtain structurally ordered polymer-inorganic hybrid nanocomposite electrodes for high-capacity flexible supercapacitors. The uniformly distributed multilayer nanoarchitecture, interconnected network, and hydrophilicity of the electrode provide a high specific surface area, excellent ion diffusion channels, and large effective contact area, thereby improving the electrochemical performance of the supercapacitor electrode. The specific capacitance of the CNF-[PANi/CMWCNT]10 (CPC10) and CNF-[PANi/RGO]10 (CPR10) electrodes reaches 965.80 and 780.64 F g-1 in 1 M aqueous H2SO4 electrolyte, respectively; the corresponding values in PVA/H3PO4 electrolyte are 1.59 and 1.46 F cm-2. In addition, the assembled symmetric supercapacitors show good energy densities of 147.23 and 112.32 mW h cm-2, as well as excellent durability and flexibility. Our approach offers a simple and effective method for fabricating an ideal well-structured nanocomposite electrode for green and flexible energy storage devices via LbL assembly.

A facile method for fabricating robust cellulose nanocrystal/SiO2 superhydrophobic coatings.

A large number of superhydrophobic coatings are prepared using individual particles (especially SiO2) to build rough surfaces. However, those surface structures collapse very easily, resulting in poor mechanical strength of the coating. To overcome this problem, cellulose nanocrystals (CNCs) are used as a framework material to prepare a necklace-like CNC/SiO2 nanostructure (referred to as CNC/SiO2 rod) via in-situ growth of SiO2 as building blocks of superhydrophobic coatings. The CNC/SiO2 superhydrophobic coatings could be prepared by spraying or smearing the CNC/SiO2 rods onto substrates treated with a commercial spray adhesive. The reason for selecting CNC is its high strength and appropriate size, which results in the formation of a firm grass-like surface microstructure when it is partially installed within the adhesive. The resulting coatings have ultra-high mechanical robustness under very harsh conditions and can resist abrasion by 240 grit sandpaper for 50 cycles (1000 cm) under a load of 100 g. They also perform well under finger-wipe, knife-scratch, water-drip, ultraviolet radiation, and acidic and alkaline conditions as well as have self-cleaning and oil-water separation ability. Given the simplicity of the proposed method and the excellent performance, these coatings should find wide use in a range of applications.

Dual-emitting film with cellulose nanocrystal-assisted carbon dots grafted SrAl2O4, Eu2+, Dy3+ phosphors for temperature sensing.

In this study, we synthesized a novel dual-emitting fluorescent phosphor from cellulose nanocrystal (CNC)-assisted carbon dots (CDs)-grafted SrAl2O4, Eu2+, Dy3+ (SAO) through a facile core-shell process. The CNC-CDs-coated SAO presents excellent scattered dual-emission and improved water resistance without destruction of the SrAl2O4 crystals. The phosphors were then reacted with coupling amino-silane and assembled with nanofibrillated cellulose skeletons to create flexible isotropic films. The obtained phosphors and hybrid films were characterized via electron microscopy, photoluminescence analysis, and X-ray photoelectron spectroscopy. The results demonstrate that the optical signals of phosphors can be controlled by CDs content. The assembled cellulose films exhibit strong temperature responses, high light-induced scattering, and good flexibility. The luminescent emission of films is highly sensitive to surrounding temperature variation (243-383 K) and good linearity behavior was obtained for such a sensitive sensor. Such flexible nanofibrillated cellulose films are excellent candidates for temperature sensor devices in industrial applications.

Fabrication Flexible and Luminescent Nanofibrillated Cellulose Films with Modified SrAl2O4: Eu, Dy Phosphors via Nanoscale Silica and Aminosilane.

Flexible 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO)-oxidized nanofibrillated cellulose (ONFC) films with long afterglow luminescence containing modified SrAl2O4: Eu2+, Dy3+ (SAOED) phosphors were fabricated by a template method. Tetraethyl orthosilicate (TEOS) and (3-aminopropyl) trimethoxy-silane (APTMS) were employed cooperatively to improve the water resistance and compatibility of the SAOED particles in the ONFC suspension. The structure and morphology after modification evidenced the formation of a superior SiO2 layer and coarse amino-compounds on the surface of the phosphors. Homogeneous dispersions containing ONFC and the modified phosphors were prepared and the interface of composite films containing the amino-modified particles showed a more closely packed structure and had less voids at the interface between the cellulose and luminescent particles than that of silica-modified phosphors. The emission spectra for luminescent films showed a slight blue shift (3.2 nm) at around 512 nm. Such flexible films with good luminescence, thermal resistance, and mechanical properties can find applications in fields like luminous flexible equipment, night indication, and portable logo or labels.

Highly flexible cross-linked cellulose nanofibril sponge-like aerogels with improved mechanical property and enhanced flame retardancy.

Cellulose nanofibril (CNF) aerogel is highly flammable and its mechanical strength is very soft, which is unfavourable due to safety concerns and impractical when used as the thermal insulation material. In this work, we used N-methylol dimethylphosphonopropionamide (MDPA) and 1,2,3,4-butanetetracarboxylic acid (BTCA) as co-additives and then prepared lightweight flame resistant CNF sponge-like aerogels via an eco-friendly freeze-drying and post cross-linking method. The CNF/BTCA/MDPA aerogel exhibited a better flame retardant performance, outstanding self-extinguishing behaviour and significantly increased char residue (by as much as 268%) compared with the neat CNF aerogel. Meanwhile, the resilience of the aerogel samples improved significantly as the flexibility decreased slightly. Furthermore, the aerogel samples still exhibited excellent thermal insulating properties with thermal conductivity as low as 0.03258W/(m k). The combination of these characteristics makes the CNF-based aerogel a promising insulation candidate for thermal protective equipment (e.g., fire-protection clothing or advanced spacesuit elements) in the future.

Layer-by-layer assembled polyaniline/carbon nanomaterial-coated cellulosic aerogel electrodes for high-capacitance supercapacitor applications.

Traditional layer-by-layer (LbL) assembled electrodes are mostly multilayer composites formed on two-dimensional membrane materials. In this case, the electroactive material cannot enter the interior of the substrate. With porous aerogels as the substrate, the LbL assembly of the electroactive material into the three-dimensional aerogel skeleton can be realised, greatly improving the utilisation and the electrochemical performance of the electroactive material. To create a promising aerogel electrode for high-performance energy storage devices, we herein report an aerogel based on wood pulp fibre (WPF) and cellulose nanocrystals (CNC), for use as a porous substrate for LbL assembly of nanostructural polyaniline (PANI) and graphene oxide (GO) or carboxylic multi-walled carbon nanotubes (CMCNT). Owing to the uniformly distributed multilayer nanoarchitecture, interpenetrating channels, and hydrophilic character of the cellulosic aerogel substrate, the produced electrodes of (PANI/CMCNT)10 and (PANI/CMCNT)10 both display high specific capacitances, favourable capacitance retention, good cycling stabilities, and structural flexibility. In the three-electrode test, their gravimetric specific capacitances are as high as 716.62 and 636.63 F g-1, respectively. In addition, the assembled symmetric supercapacitors show good areal specific capacitances (1.95 and 1.49 F cm-2) in addition to high areal specific energies (168.64 and 113.57 mW h cm-2, respectively). These results demonstrate that the integration of the LbL-assembled electroactive materials and porous cellulosic aerogel substrate can be a promising strategy to design high-efficiency green energy storage devices.

Nanocellulose/polypyrrole aerogel electrodes with higher conductivity via adding vapor grown nano-carbon fibers as conducting networks for supercapacitor application.

Nanocellulose-based conductive materials have been widely used as supercapacitor electrodes. Herein, electrode materials with higher conductivity were prepared by in situ polymerization of polypyrrole (PPy) on cellulose nanofibrils (CNF) and vapor grown carbon fiber (VGCF) hybrid aerogels. With increase in VGCF content, the conductivities of CNF/VGCF aerogel films and CNF/VGCF/PPy aerogel films increased. The CNF/VGCF2/PPy aerogel films exhibited a maximum value of 11.25 S cm-1, which is beneficial for electron transfer and to reduce interior resistance. In addition, the capacitance of the electrode materials was improved because of synergistic effects between the double-layer capacitance of VGCF and pseudocapacitance of PPy in the CNF/VGCF/PPy aerogels. Therefore, the CNF/VGCF/PPy aerogel electrode showed capacitances of 8.61 F cm-2 at 1 mV s-1 (specific area capacitance) and 678.66 F g-1 at 1.875 mA cm-2 (specific gravimetric capacitance) and retained 91.38% of its initial capacitance after 2000 cycles. Furthermore, an all-solid-state supercapacitor fabricated by the above electrode materials exhibited maximum energy and power densities of 15.08 W h Kg-1, respectively. These electrochemical properties provide great potential for supercapacitors or other electronic devices with good electrochemical properties.

Facile Preparation of a Robust and Durable Superhydrophobic Coating Using Biodegradable Lignin-Coated Cellulose Nanocrystal Particles.

It is a challenge for a superhydrophobic coating to overcome the poor robustness and the rough surface structure that is usually built using inorganic particles that are difficult to degrade. In this study, a robust superhydrophobic coating is facilely prepared by using commercial biodegradable lignin-coated cellulose nanocrystal (L-CNC) particles after hydrophobic modification to build rough surface structures, and by choosing two different adhesives (double-sided tape and quick-setting epoxy) to support adhesion between the L-CNC particles and the substrates. In addition to excellent self-cleaning and water repellence properties, the resulting coatings show outstanding mechanical strength and durability against sandpaper abrasion, finger-wipe, knife-scratch, water jet, UV radiation, high temperature, and acidic and alkali solutions, possessing a wide application prospect.