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.

[1]  Ingo Berndt,et al.  Temperature-sensitive core-shell microgel particles with dense shell. , 2006, Angewandte Chemie.

[2]  K. Suslick,et al.  Water‐Soluble Fluorescent Silver Nanoclusters , 2010, Advanced materials.

[3]  J. Lakowicz.  Principles of fluorescence spectroscopy , 1983 .

[4]  J. K. Thomas,et al.  Fluorescence studies of the conformational changes of poly(methacrylic acid) with pH , 1989 .

[5]  C. Niu,et al.  Fluorescence ratiometric pH sensor prepared from covalently immobilized porphyrin and benzothioxanthene , 2005, Analytical and bioanalytical chemistry.

[6]  Luis M Liz-Marzán,et al.  Au@pNIPAM colloids as molecular traps for surface-enhanced, spectroscopic, ultra-sensitive analysis. , 2009, Angewandte Chemie.

[7]  Kadir Aslan,et al.  Fluorescent core-shell Ag@SiO2 nanocomposites for metal-enhanced fluorescence and single nanoparticle sensing platforms. , 2007, Journal of the American Chemical Society.

[8]  O. Wolfbeis,et al.  Protonation of porphyrins in liquid PVC membranes: Effects of anionic additives and application to pH-sensing , 1997 .

[9]  R. Zhuo,et al.  Preparation of fast responsive, temperature-sensitive poly(N-isopropylacrylamide) hydrogel , 1999 .

[10]  E. Fort,et al.  Surface enhanced fluorescence , 2008 .

[11]  Lidong Li,et al.  Hybrid conjugated polymer-Ag@PNIPAM fluorescent nanoparticles with metal-enhanced fluorescence , 2011 .

[12]  Xinrui Duan,et al.  Cationic conjugated polymers for optical detection of DNA methylation, lesions, and single nucleotide polymorphisms. , 2010, Accounts of chemical research.

[13]  J. Yao,et al.  Silver Nanoparticles Stabilized by Thermoresponsive Microgel Particles: Synthesis and Evidence of an Electron Donor-Acceptor Effect , 2007 .

[14]  Shuiqin Zhou,et al.  Synthesis and Volume Phase Transition of Poly(methacrylic acid-co-N-isopropylacrylamide) Microgel Particles in Water , 1998 .

[15]  K. Geckeler,et al.  Fabrication of Silver Nanoparticles in Hydrogel Networks , 2006 .

[16]  E. Katz,et al.  Specific Biochemical‐to‐Optical Signal Transduction by Responsive Thin Hydrogel Films Loaded with Noble Metal Nanoparticles , 2010, Advanced materials.

[17]  Chi Wu,et al.  Thermodynamically Stable Globule State of a Single Poly(N-isopropylacrylamide) Chain in Water , 1995 .

[18]  R. Aroca,et al.  Surface-enhanced fluorescence with shell-isolated nanoparticles (SHINEF). , 2011, Angewandte Chemie.

[19]  C. D. Geddes,et al.  Editorial: Metal-Enhanced Fluorescence , 2002, Journal of Fluorescence.

[20]  Zhishen Ge,et al.  Fabrication of Thermoresponsive Cross-Linked Poly(N-isopropylacrylamide) Nanocapsules and Silver Nanoparticle-Embedded Hybrid Capsules with Controlled Shell Thickness , 2011 .

[21]  A. Hoffman,et al.  Graft copolymers that exhibit temperature-induced phase transitions over a wide range of pH , 1995, Nature.

[22]  Guo-Li Shen,et al.  Proton "off-on" behaviour of methylpiperazinyl derivative of naphthalimide: a pH sensor based on fluorescence enhancement. , 2004, The Analyst.

[23]  B. Liu,et al.  Conjugated Polyelectrolyte–Metal Nanoparticle Platforms for Optically Amplified DNA Detection , 2010, Advanced materials.

[24]  H. Kawaguchi,et al.  Hybrid microgels with reversibly changeable multiple brilliant color. , 2006, Langmuir : the ACS journal of surfaces and colloids.

[25]  E. Kumacheva,et al.  Polymer microgels: reactors for semiconductor, metal, and magnetic nanoparticles. , 2004, Journal of the American Chemical Society.

[26]  H. Bysell,et al.  Visualizing the interaction between poly-L-lysine and poly(acrylic acid) microgels using microscopy techniques: effect of electrostatics and peptide size. , 2006, Langmuir : the ACS journal of surfaces and colloids.

[27]  O. Wolfbeis,et al.  Nanoparticle-enhanced fluorescence imaging of latent fingerprints reveals drug abuse. , 2009, Angewandte Chemie.

[28]  Claire M. Cobley,et al.  Controlling the synthesis and assembly of silver nanostructures for plasmonic applications. , 2011, Chemical reviews.

[29]  Min Chen,et al.  Fabrication and properties of hollow poly(N‐isopropylacrylamide)‐Ag nanocomposite spheres , 2009 .

[30]  Joseph R Lakowicz,et al.  Distance-dependent metal-enhanced fluorescence from Langmuir-Blodgett monolayers of alkyl-NBD derivatives on silver island films. , 2006, Langmuir : the ACS journal of surfaces and colloids.

[31]  W. Frey,et al.  Environmentally sensitive silver nanoparticles of controlled size synthesized with PNIPAM as a nucleating and capping agent. , 2007, Langmuir : the ACS journal of surfaces and colloids.

[32]  A. Pich,et al.  Preparation of Hybrid Microgels Functionalized by Silver Nanoparticles , 2006 .

[33]  Lidong Li,et al.  Self-assembly of conjugated polymer-Ag@SiO2 hybrid fluorescent nanoparticles for application to cellular imaging. , 2010, Langmuir : the ACS journal of surfaces and colloids.

[34]  M. Antonietti,et al.  NONCLASSICAL SHAPES OF NOBLE-METAL COLLOIDS BY SYNTHESIS IN MICROGEL NANOREACTORS , 1997 .

[35]  S. Dong,et al.  Preparation of DNA-silver nanohybrids in multilayer nanoreactors by in situ electrochemical reduction, characterization, and application. , 2007, Langmuir : the ACS journal of surfaces and colloids.

[36]  P. D. Brown,et al.  Silver Nanoparticle Impregnated Polycarbonate Substrates for Surface Enhanced Raman Spectroscopy , 2008 .

[37]  S. W. Thomas,et al.  Chemical sensors based on amplifying fluorescent conjugated polymers. , 2007, Chemical reviews.

[38]  R. Aroca,et al.  Selective surface-enhanced fluorescence and dye aggregation with layer-by-layer film substrates. , 2007, The Analyst.

[39]  Y. Yanagida,et al.  Stimuli-responsive hydrogel-silver nanoparticles composite for development of localized surface plasmon resonance-based optical biosensor. , 2008, Analytica chimica acta.

[40]  Lidong Li,et al.  Tunable metal-enhanced fluorescence by stimuli-responsive polyelectrolyte interlayer films. , 2011, Macromolecular rapid communications.

[41]  Yan Lu,et al.  Thermosensitive core-shell particles as carriers for ag nanoparticles: modulating the catalytic activity by a phase transition in networks. , 2006, Angewandte Chemie.

[42]  Matthias Karg,et al.  Encapsulation and Growth of Gold Nanoparticles in Thermoresponsive Microgels , 2008 .

[43]  Guillermo C. Bazan,et al.  Homogeneous Fluorescence-Based DNA Detection with Water-Soluble Conjugated Polymers , 2004 .

[44]  Mingwu Shen,et al.  Polyelectrolyte multilayer nanoreactors toward the synthesis of diverse nanostructured materials , 2004 .