Highly sensitive determination of 4-nitrophenol with coumarin-based fluorescent molecularly imprinted poly (ionic liquid).

A coumarin-based fluorescent molecularly imprinted poly (ionic liquid) (FL-MIPIL) was prepared using a new coumarin-based alkenyl fluorescent ionic liquid (coumarin-FL-IL) as the functional monomer, IL [V2C4(mim)2][(PF6)2] and ethyleneglycol dimethacrylate as the cross-linkers, and 4-NP as the template molecule. The absolute quantum yields of coumarin-FL-IL and FL-MIPIL were 7.26 % and 30.66 %, respectively. As a result of the electron transfer between coumarin-FL-IL which contains amino groups and 4-NP bearing hydroxyl groups, FL-MIPIL fluorescence was effectively quenched by 4-NP. The prepared FL-MIPIL sensor can rapidly respond to 4-NP within 60 s. The FL-MIPIL sensor had good linear response to 4-NP from 0.001-7.5 µM and low detection limit of 0.5 nM (S/N = 3). The FL-MIPIL sensor exhibited high sensitivity and good selectivity for 4-NP. The outstanding performance of FL-MIPIL could be ascribed to high fluorescence intensity of FL-MIPIL without matrixes and more interactions between FL-MIPIL and 4-NP. The FL-MIPIL sensor has successfully applied to the determination of 4-NP in lake, rain and waste water samples, river sediment, soil and urine samples.

Ultrafine and carboxylated ß-chitin nanofibers prepared from squid pen and its transparent hydrogels.

TEMPO-mediated oxidation has been successfully used to prepare carboxylated chitin nanofibers (ChNFs) with purified chitins originating from the outer shells of crab and shrimp (α-form) or tubeworm (ß-form). However, the method for obtaining carboxylated ChNFs with squid pen chitin (hydrated ß-form) has not been developed yet. It might be due to the existence of the small amount of partial deacetylation (DD ≈ 9%) in the squid pen ß-chitins. Herein, ultrafine (2-4 nm in width and several micrometers in length) and carboxylated ß-ChNFs were fabricated directly from the squid pen with simultaneously removing of protein, CaCO3 and other non-chitin components by one-step oxidation procedure using ammonium persulfate (APS) and followed ultrasonic disintegration under acid conditions. When 45 wt% APS was used to react with squid pen, the carboxylate content of ChNFs reaches 0.802 mmol/g. Therefore, the ß-ChNFs with anionically charged groups (COO-) can be dispersed stably in aqueous solution under basic conditions. Meanwhile, thus-obtained ß-ChNFs aqueous solution even with very low concentration (0.8%) can be transformed to transparent, robust and moldable hydrogels by gas coagulation of acetic acid.

One-pot synthesis of graphene/chitin nanofibers hybrids and their remarkable reinforcement on Poly(vinyl alcohol).

Novel hybrid nanomaterials composed of graphene and chitin nanofibers (ChNFs) were successfully prepared by one-pot ball milling. Under strong shear and collision force of ball milling, graphite was exfoliated to mono-layer or few-layer graphene with the assistance of chitin nanofibers. Unexpectedly, the hybridization of exfoliated graphene and ChNFs was realized simultaneously. Morphology analysis observed that the ChNFs were adsorbed tightly on the surface of graphene, providing for reduced graphene hydrophobicity and enhanced stability of the hybrid dispersion. In addition, the concentration of exfoliated graphene reaches up to 1.5 mg ml-1. Strong interaction between graphene and ChNFs may benefit from the large amounts of carboxylate groups on the surface of ChNFs, which was prepared by TEMPO-mediated oxidation of chitin. As prepared graphene/ChNFs hybrids can remarkably enhance both the tensile strength and toughness of Poly(vinyl alcohol). This study provides a green, simple and large-scale synthesis method for preparing water-dispersible graphene/ChNFs hybrid nanobuilding blocks, which shows great promise potential in various applications requiring biocompatibility, hydrophilicity, electrical conductivity and strong mechanical properties.

Lung function and symptoms among cotton workers and dropouts three years after the start of work.

A longitudinal study of cotton workers was undertaken to assess the presence of work-related medical effects. A cohort of 110 subjects was examined before starting work and one year later. Measurements of pulmonary function were made before and after the work shift. Airway responsiveness was measured using a methacholine challenge test. A questionnaire was used to determine work-related symptoms. The 60 workers who remained after three years experienced an over-shift drop in FEV1 and an increase in airway responsiveness that did not increase after the first year. The data from the dropout group (n = 50) before work and after one year were compared with those for the active workers. The dropout group had a higher prevalence of symptoms of chest tightness and nasal irritation after one year of work. Atopy was not more common in this group. The results suggest that leaving work was related to symptoms of airways inflammation but not to atopy.