Preparation and Performance of Radiata-Pine-Derived Polyvinyl Alcohol/Carbon Quantum Dots Fluorescent Films

Abstract

In this study, the low-cost processing residue of Radiata pine (Pinus radiata D. Don) was used as the lone carbon source for synthesis of CQDs (Carbon quantum dots) with a QY (The quantum yield of the CQDs) of 1.60%. The CQDs were obtained by the hydrothermal method, and +a PVA-based biofilm was prepared by the fluidized drying method. The effects of CQDs and CNF (cellulose nanofibers) content on the morphology, optical, mechanical, water-resistance, and wettability properties of the PVA/CQDs and PVA/CNF/CQDs films are discussed. The results revealed that, when the excitation wavelength was increased from 340 to 390 nm, the emission peak became slightly red-shifted, which was induced by the condensation between CQDs and PVA. The PVA composite films showed an increase in fluorescence intensity with the addition of the CNF and CQDs to polymers. The chemical structure of prepared films was determined by the FTIR spectroscopy, and no new chemical bonds were formed. In addition, the UV transmittance was inversely proportional to the change of CQDs content, which indicated that CQDs improved the UV barrier properties of the films. Furthermore, embedding CQDs Nano-materials and CNF into the PVA matrix improved the mechanical behavior of the Nano-composite. Tensile modulus and strength at break increased significantly with increasing the concentration of CQDs Nano-materials inside the Nano-composite, which was due to the increased in the density of crosslinking behavior. With the increase of CQDs content (>1 mL), the water absorption and surface contact angle of the prepared films decreased gradually, and the water-resistance and surface wettability of the films were improved. Therefore, PVA/CNF/CQDs bio-nanocomposite films could be used to prepare anti-counterfeiting, high-transparency, and ultraviolet-resistant composites, which have potential applications in ecological packaging materials. IntroductionPolyvinyl alcohol (PVA) is a kind of semi-crystalline polymer with a linear structure and strong hydrogen bonds intermolecular. It has been widely used in papermaking [1], textiles [2], coatings [3], adhesives [4], packaging [5], and biomedicine [6] because of its toughness [7], adhesiveness [8], biocompatibility [9], swelling behavior [10], lack of toxicity [11], and sufficient thermal stability; it is also odorless and tasteless. However, PVA is highly hydrophilic and water-soluble [12], and its light transmittance is not suitable for light-barrier packaging [13]. In order to expand the application of PVA, much attention has been paid to fabricating functional PVA composites. The existence of hydrogen-bonding groups in PVA structure and the ability to form hydrogen bonds makes PVA suitable for mixing with other materials to improve its functional properties [14,15]. In previous studies, the prepared silica in situ enhanced PVA/chitosan biodegradation films [16], PVA/tea polyphenol composite films [17], PVA reinforced with cellulose nanocrystals or cellulose nanofibers (CNF) [18], and CNF/PVA-borax hybrid foams [19] had...

Smart, Tunable CQDs with Antioxidant Properties for Biomedical Applications—Ecofriendly Synthesis and Characterization

“…The quantum dots prepared using hydrochloric acid appear to be the of a polydispersive nature and have the highest range of size, which is from 2 nm to 11 nm. It has been reported that the CQDs' size affects its luminescence behavior [1][2][3]. Thus, it can be assumed that the right choice of the carbonizing agent enables the preparation of nanodots with desired properties using the hydrothermal method, which is known to be challenging.…”

“…Fluorescence spectra of the raw carbon dots (a: Dot-1; d: Dot-2; g: Dot-3; j: Dot-4) are typical for these quantum nanomaterials [2,4,6,8,37,38,43,44]. There is an obvious emission dependence on the visible excitation wavelength, which is typical for quantum nanobojects below 10 nm in size due to the surface defects, conjugated π-domains, as well as crystalline structure disturbance [1][2][3]. One may observe that the choice of the carbonizing agent has a significant impact on the PL properties, which proves different PL intensity of the unmodified CQDs.…”

“…Recent decades have shown that nanomaterials constitute a powerful tool in numerous industrial branches [1]. A promising tool are quantum dots (QDs) which can be described as objects of the size below 10 nm with unique properties [1][2][3][4].…”

“…Recent decades have shown that nanomaterials constitute a powerful tool in numerous industrial branches [1]. A promising tool are quantum dots (QDs) which can be described as objects of the size below 10 nm with unique properties [1][2][3][4]. Since their development, they have been successfully used in optoelectronics [1], food packaging [5], metals detection [6][7][8], bioimaging [9][10][11][12][13][14], photocatalysis [15,16], sensing [17][18][19][20][21][22][23], cell labelling [24], or fluorescent inks and others [25,26].…”

“…In 2004, a new type of carbon-based materials was accidentally obtained during nanotube purification [29]. Until then, numerous types of carbon quantum dots (CQDs) have been obtained with various possible applications due to their very attractive properties, such as luminesce, good water solubility, high photostability, resistance to photobleaching or photoblinking, possibility, chemical inertness and, finally, lack of toxicity and biocompability [1][2][3]. Furthermore, CQDs' region of photoluminescence is very broad, starting in the ultraviolet and ending in the near-infrared.…”