Jiyan Liu

The Preparation of Graphene Reinforced Poly(vinyl alcohol) Antibacterial Nanocomposite Thin Film

Methylated melamine grafted polyvinyl benzylchloride (mm-g-PvBCl) was prepared which was used as additive in poly(vinyl alcohol) (PVA) and graphene nanosheets (GNs) were used to reinforce the mechanical strength. Using casting method, antimicrobial nanocomposite films were prepared with the polymeric biocide loading lever of 1u2009wt%, 5u2009wt%, and 10u2009wt%. Thermogravimetric analysis (TGA) characterization revealed the 2.0u2009wt% of graphene content in resultant nanocomposites films. XRD showed that the resultant GNs 2 theta was changed from 16.6 degree to 23.3 degree. Using Japanese Industry Standard test methods, the antimicrobial efficiency for the loading lever of 1u2009wt%, 5u2009wt%, and 10u2009wt% was 92.0%, 95.8%, and 97.1%, respectively, against gram negative bacteria E. coli and 92.3%, 99.6%, and 99.7%, respectively, against the gram positive S. aureus. These results indicate the prepared nanocomposite films are the promising materials for the food and drink package applications.

Do the cations in clay and the polymer matrix affect quantum dot fluorescent properties

This paper studied the effects of cations and polymer matrix on the fluorescent properties of quantum dots (QDs). The results indicated that temperature has a greater impact on fluorescence intensity than clay cations (mainly K(+) and Na(+) ). Combined fluorescence lifetime and steady-state spectrometer tests showed that QD lifetimes all decreased when the cation concentration was increased, but the quantum yields were steady at various cation concentrations of 0, 0.05, 0.5 and 1u2009M. Poly(ethylene oxide) (PEO), poly(vinyl alcohol) (PVA) and diepoxy resin were used to study the effects of polymers on QD lifetime and quantum yield. The results showed that the lifetime for QDs 550u2009nm in PEO and PVA was 17.33 and 17.12u2009ns, respectively; for the epoxy resin, the lifetime was 0.74u2009ns, a sharp decrease from 24.47u2009ns. The quantum yield for QDs 550u2009nm changed from 34.22% to 7.45% and 7.81% in PEO and PVA, respectively; for the epoxy resin the quantum yield was 2.25%. QDs 580u2009nm and 620u2009nm showed the same results as QDs 550u2009nm. This study provides useful information on the design, synthesis and application of QDs-polymer luminescent materials. Copyright

Preparation of carbon quantum dots based high photostability luminescent membranes

Urethane acrylate (UA) was used to prepare carbon quantum dots (C-dots) luminescent membranes and the resultants were examined with FT-IR, mechanical strength, scanning electron microscope (SEM) and quantum yields (QYs). FT-IR results showed the polyurethane acrylate (PUA) prepolymer -Cxa0=xa0C-vibration at 1101xa0cm-1 disappeared but there was strong vibration at1687cm-1 which was contributed from the-Cxa0=xa0O groups in cross-linking PUA. Mechanical strength results showed that the different quantity of C-dots loadings and UV-curing time affect the strength. SEM observations on the cross-sections of the membranes are uniform and have no structural defects, which prove that the C-dots are compatible with the water-soluble PUA resin. The C-dot loading was increased from 0 to 1xa0g, the maximum tensile stress was nearly 2.67xa0MPa, but the tensile strain was decreased from 23.4% to 15.1% and 7.2% respectively. QYs results showed that the C-dots in the membrane were stable after 120xa0h continuous irradiation. Therefore, the C-dots photoluminescent film is the promising material for the flexible devices in the future applications.

Quantum yield and lifetime data analysis for the UV curable quantum dot nanocomposites

The quantum yield (QY) and lifetime are the important parameters for the photoluminescent materials. The data here report the changes of the QY and lifetime for the quantum dot (QD) nanocomposite after the UV curing of the urethane acrylate prepolymer. The data were collected based on the water soluble CdTe QDs and urethane acrylate prepolymer. Colloidal QDs were in various concentration from 0.5×10−3 molL−1 to 10×10−3 molL−1, and 1% (wt%) 1173 was the photoinitiator. The QY before the curing was 56.3%, 57.8% and 58.6% for the QDs 510 nm, 540 nm and 620 nm, respectively. The QY after the curing was changed to 8.9%, 9.6% and 13.4% for the QDs 510 nm, 540 nm and 620 nm, respectively. Lifetime data showed that the lifetime was changed from 23.71 ns, 24.55 ns, 23.52 ns to 1.29 ns, 2.74 ns, 2.45 ns for the QDs 510 nm, 540 nm and 620 nm, respectively.

The Degradation Mechanisms Study of the Organoclay by Using the NitrogenAbsorption/Desorption and X-ray Diffraction

Surfactants modified organoclays are known to undergo degradation during the melt process. In this work nitrogen absorption/desorption and X-ray diffraction were applied to study the mechanic of the degradation by employing the thermal treated commercial organoclay 93A. The 93A powder samples were heated in the Muffle furnace for 2 minutes at temperature ranged from 200 Celsius from 600 Celsius (200°C, 250°C, 300°C, 350°C and 600°C). The N2 absorption/desorption results showed the BET surface area is 10.402 m2/g, 9.455 m2/g, 14.169 m2/g, 8.860 m2/g and 9.198 m2/g respectively. The XRD results showed the d-space [001] 2θ=3.8 for all the samples (200°C -350°C) which did not change compared with the original 93A while the 600°C this unique reflection disappeared. The results indicate that the silicate clay skeletons thermal resistant ability can protect the surfactant molecules from degradation in the test temperature range low 350°C and the surfactant (which intercalated in the galleries) at the edge part of the galleries is first to degrade. High heating temperature can accelerates the vapour of the surfactants in the degradation process.