Rising environmental concerns and depletion of petro-chemical resources has resulted in an increased interest in biorenewable polymer-based environmentally friendly materials. Among biorenewable polymers, lignin is the second most abundant and fascinating natural polymer next to cellulose. Lignin is one of the three major components found in the cell walls of natural lignocellulosic materials. Lignin is widely available as a major byproduct of a number of industries involved in retrieving the polysaccharide components of plants for industrial applications, such as in paper making, ethanol production from biomass, etc. The impressive properties of lignin, such as its high abundance, low weight, environmentally friendliness and its antioxidant, antimicrobial, and biodegradable nature, along with its CO2 neutrality and reinforcing capability, make it an ideal candidate for the development of novel polymer composite materials. Considerable efforts are now being made to effectively utilize waste lignin as one ...

Progress in Green Polymer Composites from Lignin for Multifunctional Applications: A Review

Unconventional methods in cellulose functionalization

Review: Raw Natural Fiber–Based Polymer Composites

Metallic-based micro and nano-structured materials are incorporated into food contact polymers to enhance mechanical and barrier properties, and to prevent the photodegradation of plastics. Additionally heavy metals are effective antimicrobials in the form of salts, oxides, and colloids, complexes such as silver zeolites, or as elemental nanoparticles. They are incorporated for food preservation purposes and to decontaminate surfaces in industrial environments. Other relevant properties in active food packaging, such as the capability for ethylene oxidation or oxygen scavenging, can be used to extend food shelf-life. Silver based nano-engineered materials are currently the most commonly used in commodities due to their antimicrobial capacity. Copper, zinc and titanium nanostructures are also showing promise in food safety and technology. The antimicrobial properties of zinc oxide at the nanoscale will provide affordable and safe innovative strategies. Copper has been shown to be an efficient sensor for humidity, and titanium oxide has resistance to abrasion and UV-blocking performance. The migration of cations from the polymer matrices is the key point to determine their antimicrobial effectiveness; however, this cation migration may affect legal status of the polymer as a food-contact material.

Metallic-based micro and nanocomposites in food contact materials and active food packaging

An ultrasensitive humidity sensor based on molybdenum-disulfide- (MoS2)-modified tin oxide (SnO2) nanocomposite has been demonstrated in this work. The nanostructural, morphological, and compositional properties of an as-prepared MoS2/SnO2 nanocomposite were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), energy dispersive spectrometry (EDS), nitrogen sorption analysis, and Raman spectroscopy, which confirmed its successful preparation and rationality. The sensing characteristics of the MoS2/SnO2 hybrid film device against relative humidity (RH) were investigated at room temperature. The RH sensing results revealed an unprecedented response, ultrafast response/recovery behaviors, and outstanding repeatability. To our knowledge, the sensor response yielded in this work was tens of times higher than that of the existing humidity sensors. Moreover, the MoS2/SnO2 hybrid nanocomposite film sensor exhibited great enhancement in humidity sensi...

Facile Fabrication of MoS2-Modified SnO2 Hybrid Nanocomposite for Ultrasensitive Humidity Sensing

Novel rare earth (RE-La, Er, Sm) metal doped ZnO photocatalysts for degradation of Congo-Red dye: Synthesis, characterization and kinetic studies.

NiO–SnO 2 ceramic nanofibers have been fabricated by electrospinning technique and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and fluorescence spectra. XRD data revealed that NiO–SnO 2 nanofibers with pure tetragonal rutile structure for SnO 2 and cubic phase corresponding for NiO structure were obtained. The emission characteristics are determined by structural defects and oxygen vacancies and depend on the nickel level in nanofibers. The humidity sensing properties of the nanofibers were tested by electrical measurements by varying the relative humidity from 0 to 100%. The electrical resistivity of samples decreases on the whole humidity range. The electrical investigation under humidity influence showed that NiO–SnO 2 nanofibers can be used as active nanostructures for humidity sensors.

Microstructure, electrical and humidity sensor properties of electrospun NiO–SnO2 nanofibers

Photocatalytic degradation of Rhodamine B dye using ZnO–SnO2 electrospun ceramic nanofibers

A study of the carboxymethylation of wood pulp cellulose and cotton linters cellulose in different organic media, namely, ethanol, acetone, and ethanol-acetone mixtures, is performed. Previously, the ethanol-acetone 1 : 1 (w/w) mixture used as reaction medium was found to give a higher degree of substitution (DS) than the pure solvents separately. In the present work, the kinetic investigation of cellulose carboxymethylation was carried out in ethanol-acetone 3 : 7 (w/w) mixture, as well as in acetone as reaction media, and the same synergistic effect of the solvents mixture was observed. The data suggested a pseudo-first-order kinetic behavior satisfactorily described by the following equation: ln(1.11 − DS) = −kt. The two reaction steps observed are related to the transformations of less ordered regions with higher reaction rate and more ordered regions with smaller reaction rates, respectively. A possible explanation for this behaviour is given, taking into account the different structural changes of cellulose crystallinity and accessibility produced by ethanol-acetone 3 : 7 (w/w) mixture, ethanol, and acetone, as revealed by X-ray diffraction and calorimetry determinations. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67: 481–486, 1998

Carboxymethylcellulose synthesis in organic media containing ethanol and/or acetone

This paper is concerned with the design of the electrospinning process to produce efficient polysulfone fibrous sorbents for oil spill cleanup. To this end, a full factorial experimental design was adopted, and consequently two multiple regression models were developed to predict oil sorption capacities of resulting materials. The optimal electrospinning conditions determined by model-based simulation and desirability function approach were as follows: 25 kV (applied voltage), 15 cm (tip-to-collector distance) and 0.75 mL/h (polymer solution flow-rate). The polysulfone fibrous sorbent produced under the optimal conditions was highly porous (93.89%) and yielded the greatest performances for sorption of dodecane (26.60 g/g) and motor oil (39.06 g/g). The advanced recovery of oily liquids from spent sorbents was achieved by centrifugation (66–71%). In addition, a new polysulfone/NiFe 2 O 4 nanostructured fibrous composite was produced by the electrospinning technique. The sorption performances of the composite were 9.20 g/g and 15.11 g/g for the uptake of dodecane and motor oil, respectively. The advantage of the electrospun composite relied in a facile magnetic separation of the spent sorbent from oil/water system. Sorbent materials were characterized by scanning electron microscopy (SEM), water contact angle measurements, infrared spectra and magnetic measurements.

Niculae Olaru

Papers

Novel rare earth (RE-La, Er, Sm) metal doped ZnO photocatalysts for degradation of Congo-Red dye: Synthesis, characterization and kinetic studies.

Microstructure, electrical and humidity sensor properties of electrospun NiO–SnO2 nanofibers

Photocatalytic degradation of Rhodamine B dye using ZnO–SnO2 electrospun ceramic nanofibers

Carboxymethylcellulose synthesis in organic media containing ethanol and/or acetone

Design and evaluation of electrospun polysulfone fibers and polysulfone/NiFe2O4 nanostructured composite as sorbents for oil spill cleanup