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Organic pigments are prone to aggregate, resulting in decreasing of their properties. Therefore, pigment dispersants are demanded to have both high adsorption capacity and aggregation inhibiting property for pigment particles. In the present study, the suitability of cellulose nanofibers (CNFs) as a dispersant for quinacridone, a common red–violet organic pigment, was investigated. Quinacridone particles were well adsorbed on the CNFs. Scanning electron microscopy images of the quinacridone–CNF mixtures showed that the quinacridone primary particles were stacked along the cellulose fibers, and the aggregations were inhibited. In addition, the size of the quinacridone particles had an effect on their color. The interactions of quinacridone and cellulose were investigated by Fourier transform infrared (FTIR) and solution-state nuclear magnetic resonance (NMR) spectroscopies. FTIR spectra of the quinacridone–CNF mixtures indicated the intermolecular interactions between quinacridone and cellulose. Because quinacridone and CNFs were insoluble in the NMR solvents, gel-state NMR spectroscopy, which has been used for the whole plant cell wall analysis, was conducted on them. Consequently, whole signals arising from quinacridone and cellulose were enabled to be assigned, and the coupling constant of quinacridone has reported for the first time. The nuclear Overhauser effect spectroscopy (NOESY)-NMR spectrum of the quinacridone–CNF mixture revealed both NH group and aromatic moiety of quinacridone were interacted with glucose unit. The former was considered to be related to hydrogen bonding, and the latter to CH–π interactions. These specific interactions might contribute to achieve the high adsorption capacity of CNFs for quinacridone.

Octacalcium phosphate (OCP), a layered calcium phosphate compound, is an attractive material for new medical combination products, which are hybrid materials consisting of both drugs and biomaterials that have shown excellent therapy scores. OCP is fabricated primarily from soluble calcium salt via an aqueous-mediated hydrolysis process. The coexisting cations are likely to be incorporated into the OCP unit lattice during this process and affect the development of the OCP crystal structure and its thermodynamic stability. However, the key parameters of the coexisting cations, such as the ionic radii and charge number, that affect OCP formation are still unclear. In this study, we focused on the ionic radius of each monovalent ion of alkali metal ions (Li+, Na+, K+, Rb+, and Cs+) for OCP incorporation and formation in a CaHPO4·2H2O (DCPD)-(NH4)2HPO4 system with alkali metal salts. There was little incorporation of Li into the OCP unit lattice at low concentrations, whereas Li was incorporated into the OCP ...

Esterification of wood with maleic anhydride assists its mechanical fibrillation to realize ultrathin lignocellulose nanofibers (LCNFs) with thicknesses of 3 nm. We investigated the effects of the moisture content of raw wood and the esterification reaction time on the properties of the LCNFs. Increasing the moisture content of raw wood decreases both the amount of maleic acid ester and the lignin content in esterified wood. Moisture is required not only for a high degree of esterification but also for the removal of lignin to prepare ultrathin LCNFs suitable for mechanical fibrillation. 2D HSQC-NMR analysis reveals that cellulose, hemicellulose, and lignin are esterified. The maleic acid ester introduced on the LCNF surface tends to be hydrolyzed, resulting in the detachment of the maleic acid ester. Ester hydrolysis, which is facilitated under alkaline and high temperature conditions, converts the LCNF suspension into a gel. Finally, the stability against ultra violet (UV) light irradiation is examined. Since lignin absorbs UV light, the reduction in the viscosity of the LCNF suspension is lower than that of the pure cellulose nanofiber suspension. These results should contribute to the effective utilization of wood, which is the most abundant biomass.

Silica is not only a biocompatible trace element but also an essential element for bone formation and metabolism. Therefore, it is often doped into bioceramics such as calcium phosphate and calcium carbonate for enhancing biomaterial ability. Heretofore, organic silica materials are employed as silica sources, but the residual organic matter is a significant drawback in biomaterial applications. Therefore, in this study, we introduce a one-pot inorganic synthesis method for the formation of silica-doped octacalcium phosphate (OCP) using Na2SiO3 as the silica source. Silica was intercalated into the OCP unit lattice, replacing its hydrous layer structure, and then a layer-by-layer structure of apatite and silica was formed. Furthermore, by immersing the fabricated silica-doped OCP into suitable solutions, both silica-doped hydroxyapatite and carbonate apatite were fabricated through a one-step inorganic processes.

The acetylation behavior of xylan and cellulose in kraft pulp (KP) was investigated. Heteronuclear single quantum coherence-nuclear magnetic resonance (HSQC-NMR) spectroscopy was used to identify the positions at which the hydroxyl groups of polysaccharides were acetylated. X-ray diffraction analysis was used to determine the acetylation of cellulose in the crystal region. It was found that only xylan was obviously acetylated in the initial stages of the reaction. In the next stage of the acetylation, however, both the xylan and surface of the cellulose crystals reacted. Then, acetylation of the inner crystal region of the cellulose started before the completion of the xylan modification. To improve the reactivity of xylan in KP, the effect of drying or the dehydration of never-dried KP prior to acetylation was also investigated. The use of supercritical CO2 (scCO2) drying produced a KP with a higher specific surface area. This caused the xylan to exhibit a higher reactivity than that resulting from freeze drying and vacuum drying after solvent exchange. Furthermore, never-dry dehydration pretreatment produced xylan with the highest reactivity. This suggests that the cellulose–cellulose and/or cellulose–hemicellulose adhesion in the cell wall that arises as a result of drying reduces the reactivity of the xylan.

The influences of two structural modifications on the photocurrent generation performance of the Langmuir–Blodgett (LB) film of the 6-O-phthalocyaninyl cellulose derivative were investigated. These structural modifications were the substituent groups at the O-2 and O-3 positions, and the central metal of the phthalocyanine moiety. Specifically, 6-O-Zn/phthalocyaninyl- (8a) and Pd/phthalocyaninyl (8b) -2,3-di-O-myristoylcelluloses were prepared instead of 6-O-Zn/phthalocyaninyl-2,3-di-O-myristylcellulose (2). The LB monolayer film of compound 8a on an indium thin oxide electrode showed higher photocurrent generation performance than that of compound 2. This suggested that myristoyl groups (C-14 acyl groups) were more beneficial to photocurrent generation than myristyl groups (C-14 alkyl groups), as the substituent at the O-2 and O-3 positions. The LB monolayer film of compound 8b showed photocurrent generation from 500 to 700 nm, although a blue-shift in the Q-band maximum was observed. The photocurrent generation performance of compound 8b was significantly higher than that of compound 8a. This indicated that Pd was more beneficial to photocurrent generation than Zn. The film of compound 8b prepared by the horizontal lifting method showed better photocurrent generation performance than that prepared by the vertical dipping method. Consequently, compound 8b is a complementary material to the porphyrin-appended cellulose derivative (1) for photocurrent generation system.

Quinacridone, a red pigment, is prone to aggregation, which results in undesirable color changes. Cellulose nanofibers (NFs) have been reported to adsorb quinacridone and suppress its aggregation. In this study, we investigated the potential of chitin and chitosan NFs which possess acetoamide and amino groups, as a quinacridone dispersant. Chitosan NFs, obtained by fibrillation using high-pressure homogenizer, adsorbed more quinacridone than cellulose NFs. SEM observations showed that chitosan NFs inhibited the aggregation of quinacridone, but chitin NFs did not. NMR analysis suggested the hydrogen bonding between chitosan NFs and quinacridone induced by the amino groups. The results indicated that the amino groups more facilitated the intermolecular interactions between NFs and quinacridone than the hydroxyl groups whereas the acetamide groups hindered them. Color measurements showed that the redness of quinacridone improved when cellulose or chitosan NFs were added. Chitosan NFs were found to be a novel candidate for quinacridone dispersants.

6-O-[Acetylacetonato-bis(2,2′-bipyridine)ruthenium(II)]-2,3-di-O-myristyl cellulose (3) was prepared from 2,3-di-O-myristyl cellulose (1) by two reaction steps in 37.7 % total yield. The LB monolayer film of compound 3 was successfully deposited onto an indium tin oxide electrode by a vertical dipping method and showed photocurrent generation performance in the range of 400–600 nm. Compound 3 was expected as a complementary material of porphyrin-bound cellulose derivative for biomaterial-based solar cells.

A regio-selectively squaraine (SQ)-bounded cellulose derivative ( 4 ) with a degree of substitution of SQ (DS SQ ) of 0.55 was prepared from 6- O -(4-methoxytrityl) cellulose ( 1 ) by three reaction steps in 77% total yield. Lauryl SQ carboxylate ( 8 ) was also prepared as a reference sample. The photostability of SQ moieties of compound 4 in CHCl 3 was not improved when compared with SQ-COOH ( 7 ), but that of SQ moiety of compound 8 was improved unexpectedly. The Langmuir–Blodgett monolayer films 4B and 8B on an indium tin oxide (ITO) electrode were successfully prepared from compounds 4 and 8 by a vertical dipping method, respectively. The films 4B and 8B showed photocurrent generation performances in the region of 550–680 nm. The quantum yield at 650 nm of film 4B was higher than that of film 8B . These results showed that the cellulose backbone of compound 4 acts as an effective scaffold for the good photocurrent generation performances and that compound 4 was a promising complementary material of the porphyrin-bounded cellulose derivatives (for photocurrent generation at 400–420 nm) for effective utilization of solar light, as well as the phthalocyanine-bounded cellulose derivatives (for photocurrent generation at 650–720 nm).