TiO2/壳聚糖纳米复合涂料制备及其在抗菌纸中的应用

以纳米TiO2、壳聚糖双胍盐酸盐为抗菌剂,加以胶黏剂羧基丁苯胶乳、分散剂六偏磷酸钠、消泡剂叔丁醇,制备了TiO2/壳聚糖纳米复合涂料,利用SEM、FT-IR对涂料的微观形貌和基本结构进行了表征。以表面涂布方式将TiO2/壳聚糖纳米复合涂料施涂于纸张表面,制得涂布抗菌纸,对涂布抗菌纸的微观结构及抗菌性能进行了研究。结果表明,经TiO2/壳聚糖纳米复合涂料涂布后,纸张具备较强的抗菌性能;而且,实验发现,随着涂料体系中壳聚糖组分的不断增加,涂布纸的抗菌性能逐渐提高。当纳米TiO2/壳聚糖的加入比例为1∶1时,双层涂布后的纸张对大肠杆菌和金黄色葡萄球菌的抗菌率分别达到86.55%和92.19%。     

表面改性纳米TiO2粒子杂化PI薄膜的制备与性能研究

采用硅烷偶联剂(γ-巯丙基三乙氧基硅烷)对纳米TiO2粒子进行表面处理,通过原位聚合和流延成膜法制备了不同TiO2含量的PI/TiO2杂化膜,研究了杂化膜的热性能、力学性能,并通过扫描电镜(SEM)和广角X衍射(WAXD)研究了杂化膜的微观形貌结构,同时也对杂化膜的接触角和介电常数(ε)进行了研究分析.结果表明,杂化膜较纯膜的热分解温度(T5％)降低,但平均热分解温度仍然高于520℃,且膜的尺寸稳定性得到了提高,即热膨胀系数( CTE)降低;表面形貌分析表明,1％～5％的表面改性纳米TiO2能较好地分散在PI膜里,杂化膜的介电常数(3.50左右)均高于纯膜的的介电常数(2.91),杂化膜的接触角随着TiO2含量的增加呈现先减少后增加的趋势.     

TiO2/全氟磺酸树脂纳米杂化薄膜的制备

采用溶胶-凝胶法制备了TiO2/全氟磺酸树脂(Perfluorosulfonated Resin,简称PSR)纳米杂化薄膜,并通过透射电镜(TEM)、X射线衍射(XRD)、红外光谱(FT-IR)、紫外可见光谱(UV-vis)及热重分析(TGA)等技术较为全面地测试了杂化薄膜的形貌、晶型、结构、光学及热力学性能.结果表明,TiO2/PSR纳米杂化薄膜表面平整光滑,基本没有裂纹;杂化薄膜在经水热处理后,两相在纳米尺度均匀分散,TiO2粒径约为8～10nm,呈锐钛矿型;同时杂化薄膜具有良好的光学透明性和紫外吸收性能,且随着TiO2含量的增加,全氟磺酸树脂紫外吸收性能有显著提高.     

纳米TiO2表面接枝甲基丙烯酸甲酯的聚合反应

利用表面接枝的方法,在纳米TiO2上接枝偶联剂-γMPS(3-(三甲氧硅基)丙基异丁烯酸)形成"杂化"单体,通过加入引发剂引发甲基丙烯酸甲酯(MMA)在粒子表面发生自由基聚合,形成PMMA/γ-MPS/TiO2纳米复合粒子。通过IR、元素分析、TGA等方法表征了PMMA/-γMPS/TiO2纳米复合粒子的结构,定量研究了TiO2/-γMPS单体接枝率和转化率,PMMA/-γMPS/TiO2纳米复合粒子的接枝率及其相应的影响因素。结果表明:PMMA以化学键的形式连接在纳米TiO2粒子表面并具有较高的接枝率。     

TiO_2对PVDF超滤膜结构与性能的影响

实验制备了两种TiO2分散液,并将其填充到聚偏氟乙烯(PVDF)铸膜液中制得PVDF/TiO2杂化膜.考察了分散液填充比率对杂化膜的通量、截留率、接触角等性能的影响,用X射线衍射(XRD)和扫描电镜(SEM)等技术表征杂化膜的微观结构.结果表明,两种TiO2分散液均能不同程度地改善膜的性质,且当分散液的填充比率为10%时,杂化膜的各项性能稳定,表面接触角得到有效改良,对牛血清蛋白(BSA)截留率改变较小,杂化膜纯水通量显著提高,最高水通量可达257.87L/(m2.h).XRD和SEM分析的结果表明,TiO2分散液的加入使其羟基数有不同程度的增加,杂化膜表面更加平滑,亲水性改善.     

壳聚糖/明胶/Y2O3杂化膜的制备、表征和对磷吸附性的研究

用阴离子表面活性剂SDS对Y2O3表面进行改性,并采用溶液共混法制备壳聚糖/明胶/Y2O3杂化膜。采用扫描电子显微镜(SEM)和傅里叶红外光谱仪(FT-IR)对杂化膜的表面形态和基团变化情况等进行表征,并对杂化膜的厚度、断裂强度、断裂伸长率等力学性能以及杂化膜对磷的吸附性能进行测试。结果表明:改性后的Y2O3在杂化膜中分散较均匀;杂化膜中,壳聚糖、明胶、Y2O3颗粒之间存在较强的氢键作用;加入适量的明胶和Y2O3,可以提高杂化膜的断裂强力和断裂伸长率;杂化膜对磷的平衡吸附量可以达到0.42mg/g。     

Al2O3/TiO2/PVDF杂化超滤膜的制备及其性能研究

为提高聚偏氟乙烯(PVDF)超滤膜的亲水性,增强其在水处理中的抗污染能力,用无机纳米二氧化钛(TiO2)、氧化铝(Al2O3)与聚偏氟乙烯共混,采用相转化法制得无机改性有机高分子杂化超滤膜。采用杯式超滤装置考察了无机纳米颗粒的含量对杂化膜水通量的影响;测定了膜的纯水接触角、机械性能、截留效率和膜的孔径及孔径分布;采用扫描电子显微镜对膜表面进行观察。结果表明,纳米颗粒加入量为3%,TiO2与Al2O3的加入比为1∶1时,杂化膜的水通量较有机膜提高了79.5%,但截留率保持不变;杂化膜的机械强度最大增加41.6%;杂化膜的纯水接触角由未改性前的78.68°降至50.54°,亲水性得到明显改善;杂化膜的平均孔径增大,孔径分布更加均匀;纳米颗粒的加入增加了膜表面的孔密度,但没有改变膜断面的微观结构。杂化超滤膜不仅保持了PVDF膜的优良性能,而且增强了其强度、亲水性和抗污染性能。     

季铵化壳聚糖改性ZnO/凹凸棒石纳米复合材料及其抗菌性能

凹凸棒石(APT)一维纳米棒晶在功能载体方面具有广阔的应用前景.本研究在凹凸棒石表面负载ZnO纳米粒子的基础上,采用季铵化壳聚糖进行改性,通过调控复合材料表面电荷进而提升抗菌性能.采用XRD、FESEM、TEM、EDS和BET对ZnO/APT纳米复合材料进行结构表征,采用FTlR和Zeta电位对季铵化壳聚糖改性ZnO/APT纳米复合材料进行改性分析.研究结果表明,ZnO纳米粒子均匀担载在凹凸棒石表面,季铵化壳聚糖成功改性了ZnO/APT复合材料.最小抑菌浓度试验表明,5％季铵化壳聚糖改性ZnO/APT纳米复合材料对金黄色葡萄球菌和大肠埃希菌值分别为0.25 mg/mL和0.5 mg/mL.细胞毒性试验结果表明,在测试浓度范围内,季铵化壳聚糖改性纳米复合材料对HeLa细胞的存活率超过97.3％,具有良好的生物相容性.     

溶胶-凝胶法制备聚醚砜/TiO2杂化膜

采用溶胶-凝胶法制备聚醚砜-二氧化钛杂化膜,用TEM对铸膜液中二氧化钛分散程度进行表征,并用SEM及接触角仪对膜材料的表面及断面形态、膜材料的亲水性能进行表征.结果表明,当TiO2凝胶添加量(质量分数)达到4%时,表面明显分布有大量分布均匀的TiO2纳米粒子,其断面结构则表现为皮层变厚,亚孔层消失,只存在指状大孔结构,表现为水通量随之增大,改善了聚醚砜材料的疏水性,提高了膜的抗污染性.随着二氧化钛纳米粒子浓度的提高,由于纳米粒子的团聚现象导致其在聚合物基上不能分散均匀,当膜受到外力作用时引起膜内部应力集中,使膜力学性能下降.     

TiO2/聚乳酸复合纳米纤维膜的制备及其抗菌性能

采用静电纺丝技术,分别制备了纯聚乳酸(PLA)纳米纤维膜和不同TiO2含量的TiO2/PLA复合纳米纤维膜。利用扫描电子显微镜、傅里叶红外光谱和电子万能试验机分别对复合纳米纤维膜进行了形貌表征、成分分析和力学性能测试,用改良的振荡烧瓶法测试了复合纳米膜的抗菌性能。结果表明:随TiO2含量的增加,纤维直径减小而CV值和表面颗粒尺寸有所增加;复合纳米纤维膜中含有TiO2成分,证明TiO2与聚乳酸能够物理复合;添加适量的TiO2能够提高纳米纤维膜的断裂强度;在光催化条件下,TiO2/PLA复合纳米纤维膜对大肠杆菌和金黄色葡萄球菌表现出良好的抗菌性能,当TiO2含量为1%时,对两种菌的抑菌率分别达到92.9%和92.2%。     

Investigations into the early stages of “in vitro” calcification on chitosan films

This work investigated the mechanisms involved in the “in vitro” calcification of chitosan films. The calcification process on chitosan films is a phenomenon that has not been sufficiently studied, despite its importance in the understanding of many natural processes, such as bone and shell formation. Three different techniques were used in the present investigation: X-ray fluorescence (XRF), atomic force microscopy (AFM) and X-ray diffraction (XRD). Natural and acetylated chitosan films were used as substrates for calcification. The experiments were carried out by immersing chitosan membranes in simulated body fluid (SBF) or in a modified version of SBF, prepared without phosphate ions, during 30 min, 3 or 12 h. Calcium maps obtained by XRF showed that the initial calcium distribution on the chitosan surface was influenced by the acetylation treatment of chitosan films. AFM indicated the distribution pattern of calcium compound deposits at different times, obtained by film surface morphological analysis. The results suggest that the calcification mechanism is nucleation on membranes followed by the crystal growth of calcium compounds. AFM showed that the deposit formation is a function of immersion time: the deposits became more homogeneous and covered the surface more evenly with longer immersion times. XRD showed that the acetylated membranes produced more organized calcium deposits.     

Adsorption of chitosan onto carbonaceous surfaces and its application: atomic force microscopy study

The adsorption of chitosan onto highly ordered pyrolytic graphite(HOPG) surfaces and its applications have been studied by atomic force microscopy (AFM). The results indicated that chitosan topography formed on the HOPG surface significantly depends on the pH conditions and its concentration for the incubation. Under strongly acidic conditions (pH < 3.5) and at a concentration of 1 mg ml?1, chitosan formed into uniform network structures composed of fine chains. When the solution pH was changed from 3.5 to 6.5, chitosan tends to form a thicker film. Under neutral and basic conditions, chitosan changed into spherical nanoparticles, and their sizes were increased with increasing pH. Dendritic structures have been observed when the chitosan concentration was increased up to 5 mg ml?1. In addition, the chitosan topography can also be influenced by ionic strength and the addition of different metal ions. When 0.1 M metal ions Na+, Mg2+, Ca2+ and Cu2+ were added into the chitosan solution at pH 3.0 for the incubation, network structures, branched chains, block structures and dense networks attached with many small particles were observed, respectively. The potential applications of these chitosan structures on HOPG have been explored. Preliminary results characterized by AFM and XPS indicated that the chitosan network formed on the HOPG surface can be used for AFM lithography, selective adsorption of gold nanoparticles and DNA molecules.     

Enhanced magnetic properties of cobalt nanoparticles on FeMn films

Monodisperse cobalt nanoparticles are synthesized by the thermal decomposition of Co₂(CO)₈ in phenyl ether and subsequently deposited on antiferromagnetic (AFM) FeMn films and glass substrates, respectively. Magnetic measurement shows that the as-prepared Co nanoparticles are superparamagnetic and can be transformed into ferromagnetic (FM) through thermal treatment. While keeping monodisperse, the annealed FM Co nanoparticles on AFM FeMn films show a much larger coercivity than the ones on glass substrates due to FM/AFM exchange coupling. Accordingly, we propose a convenient method to enhance magnetic properties of nanoparticles.     

表面沉积铜纳米颗粒的细菌纤维素/壳聚糖交联复合膜的制备及其抗菌性能研究

通过戊二醛交联制备了细菌纤维素/壳聚糖复合材料,并采用磁控溅射技术在交联复合膜表面沉积铜(Cu)纳米颗粒。利用扫描电子显微镜观察纳米纤维膜表面形貌,采用傅里叶红外光谱仪、热重分析仪和X射线衍射仪比较交联复合前后以及镀铜前后复合膜基本化学结构、热稳定性和晶面结构的变化。通过能量色散X射线光谱对壳聚糖和铜在复合膜表面的分布情况进行表征。同时借助抗菌实验探究复合膜对金黄色葡萄球菌和大肠杆菌的抗菌能力。结果表明:壳聚糖与细菌纤维素发生了有效交联,改变了细菌纤维素的基本形貌、化学结构、晶体形态以及热学性能,并且镀铜后交联复合膜的抗菌性能得到了明显的提升(膜与细菌接触20min,对金黄色葡萄球菌和大肠杆菌的抗菌效果均达到了99.999%)。     

Mechanisms of DC conduction in smart PMN–PT/paint nanocomposite films

Understanding conduction mechanisms in dielectric films are critical to their successful applications in devices. DC conduction mechanisms in lead magnesium niobate–lead titanate (0.67Pb (Mg_1/3Nb_2/3)O₃–0.33PbTiO₃)/Paint nanocomposite (PMN–PT/Paint) films are presented and discussed. The conventional cost-effective paint brushing technique was utilized to fabricate PMN–PT/paint nanocomposite films on copper substrate. Atomic force microscopy (AFM) has been recognized as one of the most powerful techniques for the analysis of surface morphologies because it creates 3D images at angstrom and nano scale. It has been exhaustively utilized in the analysis of dispersion of nano-metric components in nanocomposites and polymer blends. Thus, AFM analysis is applied in the present work for the surface morphological and dispersion of nanoparticles investigations in paint-based nanocomposites at different loading of PMN–PT nanoparticles. It is found that the PMN–PT nanoparticles are dispersed uniformly inside the paint matrix. The spatial distribution of PMN–PT in PMN–PT/Paint films is denser with higher PMN–PT content sample. A metal–insulator–metal capacitor was fabricated and the leakage current across was measured with varying voltage and temperature. The governing conduction mechanisms were examined and depicted. The activation energy of nanocomposite films fabricated with 2.5 and 8.98 wt% PMN–PT nanoparticles in the paint mixture are found to be 1.08 and 1.24 eV, respectively. The DC activation energy for former was found to be slightly lower then later and follow the Arrhenius relationship. Thus, showing the conduction was electronic and thermally activated.     

Preparation of chitosan films using different neutralizing solutions to improve endothelial cell compatibility

The development of chitosan-based constructs for application in large-size defects or highly vascularized tissues is still a challenging issue. The poor endothelial cell compatibility of chitosan hinders the colonization of vascular endothelial cells in the chitosan-based constructs, and retards the establishment of a functional microvascular network following implantation. The aim of the present study is to prepare chitosan films with different neutralization methods to improve their endothelial cell compatibility. Chitosan salt films were neutralized with either sodium hydroxide (NaOH) aqueous solution, NaOH ethanol solution, or ethanol solution without NaOH. The physicochemical properties and endothelial cell compatibility of the chitosan films were investigated. Results indicated that neutralization with different solutions affected the surface chemistry, swelling ratio, crystalline conformation, nanotopography, and mechanical properties of the chitosan films. The NaOH ethanol solution-neutralized chitosan film (Chi-NaOH/EtOH film) displayed a nanofiber-dominant surface, while the NaOH aqueous solution-neutralized film (Chi-NaOH/H₂O film) and the ethanol solution-neutralized film (Chi-EtOH film) displayed nanoparticle-dominant surfaces. Moreover, the Chi-NaOH/EtOH films exhibited a higher stiffness as compared to the Chi-NaOH/H₂O and Chi-EtOH films. Endothelial cell compatibility of the chitosan films was evaluated with a human microvascular endothelial cell line, HMEC-1. Compared with the Chi-NaOH/H₂O and Chi-EtOH films, HMECs cultured on the Chi-NaOH/EtOH films fully spread and exhibited significantly higher levels of adhesion and proliferation, with retention of the endothelial phenotype and function. Our findings suggest that the surface nanotopography and mechanical properties contribute to determining the endothelial cell compatibility of chitosan films. The nature of the neutralizing solutions can affect the physicochemical properties and endothelial cell compatibility of chitosan films. Therefore, selection of suitable neutralization methods is highly important for the application of chitosan in tissue engineering.     

Effect of surface fluorination of TiO2 particles on photocatalitytic activity of a hybrid multilayer coating obtained by sol-gel method

A multilayer photoactive coating containing surface fluorinated TiO(2) nanoparticles and hybrid matrices by sol gel approach based on renewable chitosan was applied on poly(lactic acid) (PLA) film by a step wise spin-coating method. The upper photoactive layer contains nano-sized functionalized TiO(2) particles dispersed in a siloxane based matrix. For the purpose of improving TiO(2) dispersion at the air interface coating surface, TiO(2) nanoparticles were modified by silane coupling agent 1H,1H,2H,2H-perfluorooctyltriethoxysilane (FTS) with fluoro-organic side chains. An additional hybrid material consisting of chitosan (CS) cross-linked with 3-glycidyloxypropyl trimethoxy silane (GOTMS) was applied as interlayer between the PLA substrate and the upper photoactive coating to increase the adhesion and reciprocal affinity. The multilayer TiO(2)/CS-GOTMS coatings on PLA films showed a thickness of ~4-6 μm and resulted highly transparent. Their structure was exhaustively characterized by SEM, optical microscope, UV-vis spectroscopy and contact angle measurements. The photocatalytic activity of the multilayer coatings were investigated using methyl orange (MeO) as a target pollutant; the results showed that PLA films coated with surface fluorinated particles exhibit higher activity than films with neat particles, because of a better dispersion of TiO(2) particles. The mechanical properties of PLA and films coated with fluorinated particles, irradiated by UV light were also investigated; the results showed that the degradation of PLA substrate was markedly suppressed because of the UV adsorptive action of the multilayer coating.     

Nanostructured thin layers of vanadium oxides doped with cobalt,prepared by pulsed laser ablation: chemistry,local atomic structure,morphology and magnetism

Cobalt-doped vanadium oxide thin layers prepared by pulsed laser ablation are investigated from the following points of view: (1) the chemical states by X-ray photoelectron spectroscopy (XPS), (2) the local atomic order by X-ray absorption fine structure at both vanadium and cobalt K-edges, (3) the morphology of the films by atomic force microscopy (AFM) and (4) the magnetic properties by magneto-optical Kerr effect (MOKE). The chemical composition of the host matrix was found to be close to VO₂ at the sample surface, with V₂O₃ in the bulk. Co ions are found near the surface in high ionisation states Co⁴⁺ (for the samples synthesised in a high vacuum condition, denoted by VO1), or with Co^{(4? δ )+} (for the samples synthesised in an oxygen atmosphere, denoted by VO2), whereas in the bulk, Co^1.5+ is obtained for VO1 and Co²⁺ is obtained for VO2. The AFM revealed nanoparticles with sizes 10–25?nm for VO1 samples, whereas a few bigger nanoparticles are observed for VO2 samples. The VO1 samples presented high coercitive fields with a relatively low saturation magnetisation at room temperature, superposed with a superparamagnetic component attributed to the observed nanoparticles, whereas the VO2 samples presented double-loop hysteresis curves, indicating the co-existence of two kinds of magnetic moieties with antiparallel coupling at zero applied field. The proposed two magnetic phases are Co-doped V₂O₃ and VO₂.     

Surface modification of titanium substrates with silver nanoparticles embedded sulfhydrylated chitosan/gelatin polyelectrolyte multilayer films for antibacterial application

To develop Ti implants with potent antibacterial activity, a novel “sandwich-type” structure of sulfhydrylated chitosan (Chi-SH)/gelatin (Gel) polyelectrolyte multilayer films embedding silver (Ag) nanoparticles was coated onto titanium substrate using a spin-assisted layer-by-layer assembly technique. Ag ions would be enriched in the polyelectrolyte multilayer films via the specific interactions between Ag ions and –HS groups in Chi-HS, thus leading to the formation of Ag nanoparticles in situ by photo-catalytic reaction (ultraviolet irradiation). Contact angle measurement and field emission scanning electron microscopy equipped with energy dispersive X-ray spectroscopy were employed to monitor the construction of Ag-containing multilayer on titanium surface, respectively. The functional multilayered films on titanium substrate [Ti/PEI/(Gel/Chi-SH/Ag) _n /Gel] could efficiently inhibit the growth and activity of Bacillus subtitles and Escherichia coli onto titanium surface. Moreover, studies in vitro confirmed that Ti substrates coating with functional multilayer films remained the biological functions of osteoblasts, which was reflected by cell morphology, cell viability and ALP activity measurements. This study provides a simple, versatile and generalized methodology to design functional titanium implants with good cyto-compatibility and antibacterial activity for potential clinical applications.     

Development and in vitro evaluation of surface modified poly(lactide-co-glycolide) nanoparticles with chitosan-4-thiobutylamidine

The objective of this study was to develop a nanoparticulate drug delivery system based on the surface modification of poly(lactide-co-glycolide) (PLGA) nanoparticles with a thiolated chitosan. PLGA nanoparticles were prepared by the emulsification-solvent evaporation method. Immobilization of chitosan to the surface of PLGA nanoparticles via amide bonds was mediated by a carbodiimide. Thiol groups were covalently bound to the chitosan surface of particles by reaction with 2-iminothiolane. Obtained nanoparticles were characterized in vitro regarding size, zeta potential, thiol group content, stability at different pH values, mucoadhesion, and drug release. Results demonstrated that the surface modification of PLGA nanoparticles with thiolated chitosan (chitosan-TBA) leads to nanoparticles of a mean diameter of 889.5 ± 72 nm and positive zeta potential of + 24.74 mV. The modified nanoparticles contained 7.32 ± 0.24 μmol thiol groups per gram nanoparticles. The size of nanoparticles was strongly influenced by the pH of the surrounding medium, being 925.0 ± 76.3 nm at pH 2 and 577.8 ± 66.7 nm at pH 7.4. Thiolated nanoparticles showed a 3.3-fold prolonged residence time on the mucosa and an unchanged release profile in comparison to unmodified PLGA nanoparticles. These data suggest that surface modified chitosan-TBA conjugate PLGA nanoparticles have the potential to be used as mucoadhesive drug delivery system.