基于PNIPAM/Au纳米复合材料的过氧化氢传感器

将金纳米颗粒(GNPs)组装到PNIPAM凝胶微球表面制备出形貌均匀、性质稳定的PNIPAM/GNPs复合颗粒。利用过氧化氢的还原性将溶液中的AuCl_4~-还原成Au~0,以PNIPAM/GNPs表面吸附的GNPs为种子逐渐沉积,使得GNPs逐渐长大。根据还原过程中过氧化氢浓度与GNPs生长过程中吸收峰强度的变化关系,实现了对过氧化氢的检测,检测线性范围为5×10~(-7)~5×10~(-5)mol·L~(-1)。利用透射电镜、分光光度计及动态光散射仪对PNIPAM/GNPs复合颗粒的形貌、光学性质、粒径变化进行了表征。     

以Au@Ag双金属纳米棒为核的热响应性核壳复合微凝胶的制备及性能表征

本文采用种子沉淀聚合法将交联的聚(N-异丙基丙烯酰胺)(PNIPAM)包覆在单分散性良好的Au@Ag双金属纳米棒(Au@AgNR)表面,制得以Au@AgNR为核、交联PNIPAM为壳层的Au@AgNR@PNIPAM复合微凝胶。用透射电镜观察到复合微凝胶具有规整的核壳结构,动态激光光散射测试结果证实复合微凝胶存在热响应性。当环境温度从20℃升高到50℃,复合微凝胶中Au@AgNR的纵向局域表面等离子体共振波长从695nm红移到719nm,表明复合微凝胶内的Au@AgNRs的LSPR光学性能可利用温度来进行调节。以该复合微凝胶为SERS分析的基底,检测水溶液中痕量的难以吸附在金属粒子表面的1-萘酚(3×10-5M),结果发现复合微凝胶在发生体积相转变时对1-萘酚具有捕捉效应,因此可通过调节测试温度来达到提高待分析物的SERS的信号强度的目的。     

表面覆盖型AuNPs@PNIPAM复合粒子的制备及催化性能

金纳米粒子(AuNPs)表面能高,在水中极易团聚,使其应用受限.本文采用物理共混法,将带有正电荷的温敏聚(N-异丙基丙烯酰胺)(PNIPAM)微凝胶与带负电荷的AuNPs混合,经自组装制备了微凝胶表面覆盖AuNPs的有机-金属复合粒子AuNPs@PNIPAM.该复合粒子不仅具有很好的分散稳定性,而且其粒子的分散液具有温度比色性,在25℃→50℃→25℃的温度变化过程中呈现“红→紫→红”的可逆颜色变化.通过对硝基苯酚(4-NP)的还原反应,研究了复合粒子的催化性能.结果表明,复合粒子具有受温度调控的催化能力,随温度升高催化性能呈现先降后升的趋势.与文献报道的类似材料相比, AuNPs@PNIPAM复合粒子同时具有温度比色性和催化性能.     

单分散CdS纳米晶/PNIPAM复合水凝胶的制备及其温敏荧光特性

采用液体-固体-溶液法(LSS)制备单分散CdS纳米晶;通过自由基聚合制备单分散CdS纳米晶/聚N-异丙基丙烯酰胺(CdS/PNIPAM)复合温敏水凝胶.采用HRTEM、XRD、FTIR、DSC、PL等对CdS纳米晶、CdS/PNIPAM温敏复合凝胶的微观结构与性能进行了表征,变温荧光光谱研究了温度对凝胶荧光性能的影响.结果表明,CdS纳米晶粒径约为2.8 nm,单分散性良好;复合凝胶的荧光发射强度与环境温度存在一定的关联性,且呈可逆性.     

温敏性纤维素/聚N-异丙基丙烯酰胺复合水凝胶的固体核磁共振表征及动力学研究

利用半互穿网络方法将具有温度响应的高分子聚N-异丙基丙烯酰胺(PNIPAM)与天然纤维素复合得到温敏性水凝胶. 通过固体核磁共振的 ¹H, ¹³C CP/MAS(交叉极化/魔角旋转)和QCP(定量交叉极化)等实验手段对复合凝胶的结构进行了定性及定量研究, 并利用固体静态变温核磁共振实验和偶极滤波-自旋扩散实验研究了复合凝胶中PNIPAM分子链段的动力学行为.     

纳米金-PNIPAM类智能凝胶*

聚N-异丙基丙烯酰胺（PNIPAM）类智能凝胶与纳米金（AuNPs）组成的复合材料兼具了金的光学性质和PNIPAM的温敏特性,受到国内外专家学者的普遍关注。本文介绍了该复合物的制备方法,主要包括直接分散法、聚合物基底原位合成法、AuNPs原位合成法、模板法等,并对各自特点进行了说明。此外,文中还对PNIPAM类智能凝胶与AuNPs组成的复合材料的各种应用进行了综述,简要分析了目前存在的问题并展望了今后该材料研究方向。     

温敏性纤维素/聚Ν-异丙基丙烯酰胺复合水凝胶的固体核磁共振表征及动力学研究

利用半互穿网络方法将具有温度响应的高分子聚N-异丙基丙烯酰胺( PNIPAM)与天然纤维素复合得到温敏性水凝胶。通过固体核磁共振的1 H,13 C CP/MAS(交叉极化/魔角旋转)和QCP(定量交叉极化)等实验手段对复合凝胶的结构进行了定性及定量研究,并利用固体静态变温核磁共振实验和偶极滤波-自旋扩散实验研究了复合凝胶中PNIPAM分子链段的动力学行为。     

丝胶基半互穿温敏凝胶的合成及其溶胀行为的研究

采用半互穿网络技术, 将具有生物相容性的丝胶蛋白(silk sericin)作为第二网络进入聚(N-异丙基丙烯酰胺)(PNIPAM)水凝胶网络中, 在水溶液中制备得到具有半互穿网络结构的丝胶基温敏水凝胶(SS/PNIPAM semi-IPNs). 采用称重法研究了产物的(消)溶胀、温度敏感性、最大溶胀度及脉冲响应行为; 利用扫描电镜(SEM), 差示扫描量热仪(DSC)和动态热机械分析仪(DMA)分别考察了产物的内部形态、热相转变行为和其储能模量随温度的变化. 结果表明: 具有较高亲水性的丝胶蛋白的引入增大了semi-IPNs水凝胶的内部孔径, 导致SS/PNIPAM半互穿水凝胶的溶胀度增加, 并且其储能模量随温度变化更明显. 相比于纯PNIPAM水凝胶, 半互穿水凝胶的消溶胀速率和低临界溶解温度(LCST)变化不大.     

墨鱼骨有机质与纳米金复合膜光学传感器的构建及其应用

利用纳米金种法制备墨鱼骨有机质纳米金复合膜(CDMS/AuNPs),构建一种有机质复合纳米材料的光学传感器。采用扫描电镜(SEM)和紫外-可见吸收光谱对复合膜的结构和光学性质进行表征。根据金纳米颗粒(AuNPs)的局域表面等离子体共振(LSPR)效应,利用亚硝酸盐还原氯金酸诱导纳米金种生长,进而应用于亚硝酸盐的检测。在优化实验条件下,CDMS/AuNPs传感器的吸光度与亚硝酸盐的浓度在2.5×10-6～5.0×10-5mol/L范围内呈良好的线性关系(R=0.9950),检出限为8.0×10-7 mol/L(S/N=3)。     

温敏性荧光纳米材料的合成

合成了以荧光材料罗丹明B/SiO2为核,交联聚N-异丙基丙烯酰胺(PNIPAM)为壳的具有核/壳结构的纳米颗粒。用氢氟酸除去二氧化硅模板核后,形成了核壳结构的温敏荧光微球。28～36℃范围内的温敏性实验表明,该粒子的低临界溶解温度(LCST)为33℃,具有温敏性,用SEM、TEM、XRD、FT-IR等手段对温敏荧光微球的组成和结构进行了表征和分析,探讨了磁性温敏纳米颗粒的制备机理。     

Assembly of Preformed Gold Nanoparticles onto Thermoresponsive Poly(N‐isopropylacrylamide)‐Based Microgels on the Basis of Au‐thiol Chemistry

The assembly of preformed gold nanoparticles (AuNPs ) onto the thermoresponsive poly(N ‐isopropylacrylamide) (PNIPAM )‐based microgels was achieved on the basis of the driving force of Au‐thiol chemistry. The loading amount of AuNPs can be controlled by varying the ratio of AuNPs relative to PNIPAM ‐based microgels. The as‐prepared PNIPAM /Au hybrid microgels showed well‐defined reversible swelling/deswelling transition in response to temperature, which can be employed to tune the plasmonic property of hybrid microgels. As the temperature was increased, the position of localized surface plasmon resonance (LSPR ) band red‐shifted to some extent mainly due to the increase in the local refractive index around AuNPs .     

Resolving Optical and Catalytic Activities in Thermoresponsive Nanoparticles by Permanent Ligation with Temperature‐Sensitive Polymers

Thermoresponsive nanoparticles (NPs) represent an important hybrid material comprising functional NPs with temperature‐sensitive polymer ligands. Strikingly, significant discrepancies in optical and catalytic properties of thermoresponsive noble‐metal NPs have been reported, and have yet to be unraveled. Reported herein is the crafting of Au NPs, intimately and permanently ligated by thermoresponsive poly(N‐isopropylacrylamide) (PNIPAM), in situ using a starlike block copolymer nanoreactor as model system to resolve the paradox noted above. As temperature rises, plasmonic absorption of PNIPAM‐capped Au NPs red‐shifts with increased intensity in the absence of free linear PNIPAM, whereas a greater red‐shift with decreased intensity occurs in the presence of deliberately introduced linear PNIPAM. Remarkably, the absence or addition of free linear PNIPAM also accounts for non‐monotonic or switchable on/off catalytic performance, respectively, of PNIPAM‐capped Au NPs.     

Thermoresponsive core-shell microgels with silica nanoparticle cores: size, structure, and volume phase transition of the polymer shell

Core-shell microgels made of the thermoresponsive polymer poly(N-isopropylacrylamide) (PNIPAM) and silica nanoparticles as inorganic cores were investigated by dynamic light scattering (DLS) and small angle neutron scattering (SANS). In order to study the response of the particles upon changes of temperature, experiments were done in a temperature interval close to the volume phase transition temperature of the PNIPAM shell. While DLS probes the hydrodynamic dimensions of the particles, determining their centre of mass diffusion, SANS provides the correlation length xi of the PNIPAM network. Additionally, the composite particles were characterised by electron microscopy as well as atomic force microscopy to reveal the core-shell structure and at the same time the approximate dimensions and the shape of the microgels.     

Preparation of thermoresponsive core–shell polymeric microspheres and hollow PNIPAM microgels

A reliable and efficient route for preparing thermoresponsive hollow microgels based on cross-linked poly(N-isopropyl acrylamide) (PNIPAM) was developed. Firstly, monodisperse thermoresponsive core–shell microspheres composed of a P(styrene (St)-co-NIPAM) core and a cross-linked PNIPAM shell were prepared by seeded emulsion polymerization using P(St-co-NIPAM) particles as seeds. The size of the P(St-co-NIPAM) core can be conveniently tuned by different dosages of sodium dodecyl sulfate. The thickness of the cross-linked PNIPAM shell can be controlled by varying the dosage of NIPAM in the preparation of PNIAPM shell. Then, hollow PNIPAM microgels were obtained by simply dissolving the P(St-co-NIPAM) core with tetrahydrofuran. The core–shell microspheres and the hollow microgels were characterized by transmission electron microscopy, dynamic light scattering, atomic force microscopy, and Fourier-transform infrared spectroscopy.     

Use of thermally annealed multilayer gold nanoparticle films in combination analysis of localized surface plasmon resonance sensing and MALDI mass spectrometry

A self-assembled film of gold nanoparticles (AuNPs) with a raspberry-like morphology was prepared on a glass plate by the layer-by-layer thermal annealing of multilayer films of AuNPs. It was possible to control the morphology of the obtained films of AuNPs by changing the annealing temperature, duration of annealing, and number of layers. On investigating the plasmonic properties of these films, we found that AuNP films with a raspberry-like morphology yielded the highest refractive index unit, which is a critical parameter in localized surface plasmon resonance (LSPR) sensing, as compared to other types of AuNP films. Self-assembled AuNP films with a raspberry-like morphology were subsequently functionalized with 11-mercaptoundecanoic acid (MUA) to enable the binding of lysozyme to the MUA-modified Au surface. The superior limit of detection for the LSPR sensing of lysozyme in a buffer solution was found to be in the picomolar range (～10(-12) M). The high sensitivity observed in the region was attributed to the raspberry-like morphology, where the AuNPs were packed closely together, and the electromagnetic field confinement was most intense (i.e., at hot spots). The MUA-modified, self-assembled AuNP films with a raspberry-like morphology were finally used in the combination analysis of LSPR sensing and matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) for the selective detection and identification of lysozyme in human serum.     

Thermoresponsive polymer-stabilized silver nanoparticles

Silver nanoparticles (Ag NPs) stabilized by a thermoresponsive polymer, poly(N-isopropylacrylamide) (PNIPAM), have been synthesized by the reduction of silver ions with NaBH(4) in aqueous solutions. The obtained Ag NPs are very stable at room temperature due to the extended coil conformation of the PNIPAM chain at temperatures below its volume phase transition temperature ( approximately 32 degrees C). At higher temperatures (such as 45 degrees C) above the phase transition of PNIPAM, only minute aggregation between Ag NPs was observed, showing that the collapsed PNIPAM chains still retain the ability to stabilize Ag NPs. The PNIPAM-stabilized Ag NPs were then characterized as a function of the thermal phase transition of PNIPAM by UV-vis spectroscopy, dynamic light scattering, transmission electron microscopy, and cyclic voltammeter. Consistent results were obtained showing that the phase transition of PNIPAM has some effect on the optical properties of Ag NPs. Switchable electrochemical response of the PNIPAM-stabilized Ag NPs triggered by temperature change was observed.     

Sugar determination via the homogeneous reduction of Au salts: A novel optical measurement

A novel optical assay for sugar determination based on the catalytic and biocatalytic growth of gold nanoparticles (AuNPs) is presented. The reaction of carbohydrates with these Au salts in alkaline media generates AuNPs at room temperature (RT) without the need for Au seeds in the solution or fibrous mesh. The optical properties of the resulting AuNPs relates to the total reducing sugar content of the samples analyzed. The development of such inexpensive optical assay was evaluated qualitatively and quantitatively on food beverages and honey samples. Its application can be of help to control the glucose content of the diet or easily extended in a host of industrial, biomedical and clinical fields.     

Thermoresponsive Polymer Brush Modulation on the Direction of Motion of Phoretically Driven Janus Micromotors

We report a thermoresponsive poly(N‐isopropylacrylamide) (PNIPAM) brush functionalized Janus Au–Pt bimetallic micromotor capable of modulating the direction of motion with the change of the ambient temperature. The PNIPAM@Au–Pt micromotor moved along the Au–Pt direction with a speed of 8.5 μm s^?1 in 1.5 % H₂O₂ at 25 °C (below the lower critical solution temperature (LCST) of PNIPAM), whereas it changed the direction of motion (i.e., along the Pt–Au direction) and the speed decreased to 2.3 μm s^?1 at 35 °C (above LCST). Below LCST, PNIPAM brushes grafted on the Au side were hydrophilic and swelled, which permitted the electron transfer and proton diffusion on the Au side, and thus the motion is regarded as a self‐electrophoretic mechanism. However, PNIPAM brushes above LCST became hydrophobic and collapsed, and thus the driving mechanism switched to the self‐diffusiophoresis like that of Pt‐modified Janus silica motors. These motors could reversibly change the direction of motion with the transition of the hydrophobic and hydrophilic states of the grafted PNIPAM brushes. Such a thermoresponsive polymer brush functionalization method provides a new strategy for engineering the kinematic behavior of phoretically driven micro/nanomotors.     

Doubly thermoresponsive brush‐linear‐linear ABC triblock copolymer nanoparticles prepared through dispersion RAFT polymerization

Doubly thermoresponsive ABC brush‐linear‐linear triblock copolymer nanoparticles of poly[poly(ethylene glycol) methyl ether vinylphenyl]‐block‐poly(N‐isopropylacrylamide)‐block‐polystyrene [P(mPEGV)‐b‐PNIPAM‐b‐PS] containing two thermoresponsive blocks of poly[poly(ethylene glycol) methyl ether vinylphenyl] [P(mPEGV)] and poly(N‐isopropylacrylamide) (PNIPAM) are prepared by macro‐RAFT agent mediated dispersion polymerization. The P(mPEGV)‐b‐PNIPAM‐b‐PS nanoparticles exhibit two separate lower critical solution temperatures or phase‐transition temperatures (PTTs) corresponding to the linear PNIPAM block and the brush P(mPEGV) block in water. Upon temperature increasing above the first and then the second PTT, the hydrodynamic diameter (D_h) of the triblock copolymer nanoparticles undergoes an initial shrinkage at the first PTT and the subsequent shrinkage at the second PTT. The effect of the chain length of the PNIPAM block on the thermoresponsive behavior of the triblock copolymer nanoparticles is investigated. It is found that, the longer chains of the thermoresponsive PNIPAM block, the greater contribution on the transmittance change of the aqueous dispersion of the triblock copolymer nanoparticles. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 2266–2278     

Control of metal-enhanced fluorescence with pH- and thermoresponsive hybrid microgels

In this paper, we report on the Ag nanoparticle-containing hybrid poly(N-isopropylacrylamide-co-acrylic acid) (PNIPAM-co-PAA) microgels with pH- and thermoresponsive metal-enhanced fluorescence (MEF). The hybrid microgels were prepared by in situ reducing Ag salts to Ag nanoparticles in the PNIPAM-co-PAA microgels. According to the interaction distance-dependent nature of MEF effects, we can realize a controllable MEF effect by adjusting the average interaction distance between fluorophores and Ag nanoparticles due to the good stimuli-responsive swelling-shrinking behavior of the hybrid microgels. The results show that MEF effect can be well tuned in the pH region 2-12 as well as the temperature region of 20-50 °C. By this method, an enhanced fluorescence detection can possibly be manipulated by adjusting external stimuli such as pH and temperature.