Spectroscopic study of the modification of cellulose with polyethylenimines

Wearable, Machine Washable, Breathable Polyethylenimine/Sodium Alginate Layer-by-Layer-Coated Cotton-Based Multifunctional Triboelectric Nanogenerators

Cotton-based textiles are ubiquitous in daily life and are prime candidates for application in wearable triboelectric nanogenerators. However, pristine cotton is vulnerable to bacterial attack, lacks antioxidant and ultraviolet (UV)-protective abilities, and shows lower triboelectric charge generation against tribonegative materials because it is present in the neutral region of the triboelectric series. To overcome such drawbacks, herein, a facile layer-by-layer method is proposed, involving the deposition of alternate layers of polyethylenimine (PEI) and sodium alginate (SA) on cotton. Such modified fabric remains breathable and flexible, retains its comfort properties, and simultaneously shows multifunctionalities and improved triboelectric output, which are retained even after 50 home laundering cycles. Also, the modified fabric becomes more tribopositive than nylon, silk, and wool. A triboelectric nanogenerator consisting of modified cotton and polyester fabric is proposed that shows a maximum power density of 338 mW/m2. An open-circuit voltage of ∼97.3 V and a short-circuit current of ∼4.59 μA are obtained under 20 N force and 1 Hz tapping frequency. Further, the modified cotton exhibits excellent antibacterial, antioxidant, and UV-protective properties because of the incorporation of PEI, and its moisture management properties are retained due to the presence of sodium alginate in the layer. This study provides a simple yet effective approach to obtaining durable multifunctionalities and improved triboelectric performance in cotton substrates.

Preparation and characterization of high-strength and water resistant lignocelluloses based composites bonded by branched polyethylenimine (PEI)

High-strength and water resistant lignocelluloses based composites (LC) were fabricated using branched polyethylenimine (PEI) as the main bonding agent combined with glutaraldehyde cross-linking reaction and grinding pre-treatment. Physical and mechanical properties of different composites prepared were measured and investigated. It is evident that PEI was efficient in endowing LC with high strength and excellent water resistance. The obtained physical and mechanical properties of LC were complied with the requirement of the Chinese national standard for medium-density fiberboard (MDF). Most notably, the glutaraldehyde cross-linking and grinding pre-treatment could further improve these properties. When 5% PEI and 2.5% glutaraldehyde were incorporated, together with 2-hour grinding treatment, the LC prepared exhibited the optimum modulus of rupture (MOR) 58.1 MPa, modulus of elasticity (MOE) 5077 MPa, internal bonding strength (IB) 2.14 MPa, and thickness swell (TS) 30.2%. The excellent properties obtained could be attributed to the cross-linking effect and Schiff's base addition reaction among lignocelluloses, PEI and glutaraldehyde, which were confirmed by the Fourier transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS) analysis. The high-strength LC prepared in this study is expected to be used as load-bearing material in structural application.

Monolithic cellulose supported metal nanoparticles as green flow reactor with high catalytic efficiency

A highly effective, stable and reusable flow microreactor was developed by utilizing the environmentally sustainable porous monolithic cellulose based on a facile temperature induced phase separation (TIPS) method. The obtained microreator could be applied to efficiently and continuously catalysing the reduction reaction of 4-nitrophenol (an important reaction in water treatment) without any post-treatment or regeneration of catalysts. Moreover, the monolith overcame the brittleness of the crystalline cellulose and showed a good mechanical resilience, suggesting a great potential for the practical application in severe environment. Compared with previous reported Pd supported catalytic systems, this microreactor exhibited extremely high catalytic efficiency (turnover frequency, TOF = 4660 h^-1, almost 4 times higher than that of cellulose nanocrystals supported catalyst) and long-term stability. This work provided a new strategy to construct highly effective and reusable metal NPs involved catalytic system by utilizing biodegradable cellulose materials.

Preparation and characterization of keratin-based biocomposite hydrogels prepared by electron beam irradiation

The biocompatible and highly porous keratin-based hydrogels were prepared using electron beam irradiation (EBI). The conditions for keratin-based hydrogel formation were investigated depending on several conditions, including the presence of poly(vinyl alcohol) (PVA), concentration of keratin solution, EBI dose, and poly(ethylene imine) (PEI) additives. The pure keratin (human hair and wool) aqueous solution was not gelled by EBI, while the aqueous keratin solutions blended with PVA were gelled at an EBI dose of more than 90 kGy. Furthermore, in the presence of PEI, the aqueous keratin solution blended with PVA could be gelled at a considerably lower EBI dose, even at 10 kGy. This finding suggests that the PEI additives significantly influence the rate of gelation and that PEIs function as an accelerator during gelation. The resulting keratin-based hydrogels were characterized using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), gel fraction, degree of swelling, gel strength, and kinetics of swelling analyses.

Continuous growth and improved PL property of ZnO nanoarrays with assistance of polyethylenimine

Recent studies show that polyethylenimine (PEI) benefits the hydrothermal growth of ZnO nanorod arrays due to its effect on chelating Zn(2+) ions and selectively absorbing on the crystal facets. In the present work, PEI is found to play more complex roles during the growth. The observation on the solution color and the UV-VIS and FTIR spectra demonstrate a Mannich reaction between HCHO and -NH2 groups of PEI during the hydrothermal procedure. -N=CH2 groups produced by the Mannich reaction contribute to the color change. The HMT decomposition is the controlling step for the whole growth and the decomposition rate depends on the hydrothermal temperature and the PEI addition amount. Increasing the PEI amount elevates the hydrothermal temperature to 130 °C and as a result the crystal quality is improved. A stepping heating process is designed to grow ultralong ZnO nanorod arrays by optimizing the solution composition. The rod length reaches to about 13 μm by one growth circle. The mechanisms associated with PEI addition provide a novel route for synthesizing metal oxide nanomaterials, particularly those requiring the higher hydrothermal temperature.