Relative Quantum Yield Measurements of Coumarin Encapsulated in Core-Shell Silica Nanoparticles

Fluorescent silica nanoparticles encapsulating organic fluorophores provide an attractive materials platform for a wide array of applications where high fluorescent brightness is required. We describe a class of fluorescent silica nanoparticles with a core-shell architecture and narrow particle size distribution, having a diameter of less than 20 nm and covalently incorporating a blue-emitting coumarin dye. A quantitative comparison of the scattering-corrected relative quantum yield of the particles to free dye in water yields an enhancement of approximately an order of magnitude. This enhancement of quantum efficiency is consistent with previous work on rhodamine dye-based particles. It provides support for the argument that improved brightness over free dye in aqueous solution is a more general effect of covalent incorporation of fluorescent organic dyes within rigid silica nanoparticle matrices. These results indicate a synthetic route towards highly fluorescent silica nanoparticles that produces excellent probes for imaging, security, and sensing applications.     

Fluorescent monodisperse spherical particles based on mesoporous silica containing rhodamine 6G

Fluorescent monodisperse spherical silica (SiO₂) particles with a regular mesoporous structure containing encapsulated Rhodamine 6G (R6G) dye have been synthesized. The as-synthesized particles have been coated with SiO₂ and SiO₂-CTAB (cetyltrimethylammonium bromide, C₁₆H₃₃N(CH₃)₃Br) shells in order to prevent uncontrolled release of the dye from pores. The kinetics of R6G release from the pores of silica particles has been studied. It has been found that the particles synthesized by adding CTAB and R6G to the reaction mixture, as well as the particles coated with the SiO₂-CTAB shell, are characterized by the maximum duration of dye release from the pores, which is probably associated with the formation of chemical bonds between R6G and CTAB molecules.     

Facile Fabrication of Dendritic Mesoporous SiO2@CdTe@SiO2 Fluorescent Nanoparticles for Bioimaging

A seeded watermelon‐like mesoporous nanostructure (mSiO₂@CdTe@SiO₂, mSQS) composed of a novel dendritic mesoporous silica core, fluorescent CdTe quantum dots (QDs), and a protective solid silica shell is successfully fabricated by loading QDs into dendritic mesoporous silica nanoparticles through electrostatic interaction, and then coating with a solid silica shell by the modified Stöber method. The shell thickness of mSQS can be tuned from 0 to 32 nm as desired by controlling the reaction parameters, including the amount of silica precursor, tetraethyl orthosilicate, that is introduced, the solvent ratio (H₂O:ethanol), and the amount of catalyst (NH₃?H₂O). These fluorescent mSiO₂@QDs@SiO₂ nanoparticles possess excellent stability and thickness‐dependent cytotoxicity, and are successfully applied to bioimaging.     

Synthesis, characterisation and functionalisation of luminescent silica nanoparticles

The synthesis of highly monodispersed, homogeneous and stable luminescent silica nanoparticles, synthesized using a process based on the Stöber method is reported here. These particles have been functionalised with the ruthenium and europium complexes: bis (2,2??-bipyridine)-(5-aminophenanthroline) Ru bis (hexafluorophosphate), abbreviated to (Ru(bpy)₂(phen-5-NH₂)(PF₆)), and tris (dibenzoylmethane)-mono (5-aminophenanthroline) europium(III), abbreviated to (Eu:TDMAP). Both dyes have a free amino group available, facilitating the covalent conjugation of the dyes inside the silica matrix. Due to the covalent bond between the dyes and the silica, no dye leaching or nanoparticle diameter modification was observed. The generic and versatile nature of the synthesis process was demonstrated via the synthesis of both europium and ruthenium-functionalised nanoparticles. Following this, the main emphasis of the study was the characterisation of the luminescence of the ruthenium-functionalised silica nanoparticles, in particular, as a function of surface carboxyl or amino group functionalisation. It was demonstrated that the luminescence of the ruthenium dye is highly affected by the ionic environment at the surface of the nanoparticle, and that these effects can be counteracted by encapsulating the ruthenium-functionalised nanoparticles in a plain 15 nm silica layer. Moreover, the ruthenium-functionalised silica nanoparticles showed high relative brightness compared to the free dye in solution and efficient functionalisation with amino or carboxyl groups. Due to their ease of fabrication and attractive characteristics, the ruthenium-functionalised silica nanoparticles described here have the potential to be highly desirable fluorescent labels, particularly, for biological applications.     

Experimental and theoretical evidence for the chemical mechanism in SERRS of rhodamine 6G adsorbed on colloidal silver excited at 1064 nm

The evidence for the existence of a chemical mechanism in surface‐enhanced resonance Raman scattering (SERRS) of rhodamine 6G (R6G) adsorbed on colloidal silver excited at 1064 nm is reported on the basis of experimental and theoretical analyses. A weak absorption peak at around 1060 nm for R6G‐functionalized silver nanoparticles was observed, which is not present in the individual spectra of R6G or silver nanoparticles. Theoretically, the charge difference density reveals that this weak absorption is a metal‐to‐molecule charge transfer excited state. Copyright © 2010 John Wiley & Sons, Ltd.     

FITC Labeled Silica Nanoparticles as Efficient Cell Tags: Uptake and Photostability Study in Endothelial Cells

The use of fluorescent nanomaterials has gained great importance in the field of medical imaging. Many traditional imaging technologies have been reported utilizing dyes in the past. These methods face drawbacks due to non-specific accumulation and photobleaching of dyes. We studied the uptake and internalization of two different sized (30 nm and 100 nm) FITC labeled silica nanoparticles in Human umbilical vein endothelial cell line. These nanomaterials show high biocompatability and are highly photostable inside live cells for increased period of time in comparison to the dye alone. To our knowledge, we report for the first time the use of 30 nm fluorescent silica nanoparticles as efficient endothelial tags along with the well studied 100 nm particles. We also have emphasized the good photostability of these materials in live cells.     

One-step synthesis of dye-incorporated porous silica particles

Fluorescent nanoparticles have a variety of biomedical applications as diagnostics and traceable drug delivery agents. Highly fluorescent porous silica nanoparticles were synthesized in a water/oil phase by a microemulsion method. What is unique about the resulting porous silica nanoparticles is the combination of a single-step, efficient synthesis and the high stability of its fluorescence emission in the resulting materials. The key of the success of this approach is the choice of a lipid dye that functions as a surrogate surfactant in the preparation. The surfactant dye was incorporated at the interface of the inorganic silica matrix and organic environment (pore template), and thus insures the stability of the dye?Csilica hybrid structure. The resulting fluorescent silica materials have a number of properties that make them attractive for biomedical applications: the availability of various color of the resulting nanoparticle from among a broad spectrum of commercially dyes, the controllablity of pore size (diameters of ~5?nm) and particle size (diameters of ~40?nm) by adjusting template monomer concentration and the water/oil ratio, and the stability and durability of particle fluorescence because of the deep insertion of surfactant??s tail into the silica matrix.     

Novel luminescent hybrid materials by covalently anchoring 2-[3-(triethoxysilyl) propyl-1H-Benz [de]isoquinoline-1, 3(2H)-dione to bimodal mesoporous materials

We report on the synthesis of luminescent hybrid mesoporous materials (LHMS) by covalently anchoring 2-[3-(triethoxysilyl) propyl-1H-Benz [de]isoquinoline-1, 3(2H)-dione to bimodal mesoporous materials (BMMs) through postsynthesis methods. The resulting samples were characterized by powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), N₂ adsorption/desorption isotherms, transmission electron microscopy (TEM), ²⁹Si NMR analysis, elemental analysis, and fluorescence measurements. The results revealed that luminescent organic molecules have been successfully introduced into the pore channels of BMMs without disrupting the structure, whereas the ordering degree of BMMs framework decreased after functionalization. The obtained materials (LHMS-10) showed excellent luminous performance, and the emission peak shifted to a lower wavelength in comparison with that of pure luminescent dyes (from 464 to 454 nm) because of the polarity of the silica matrix. And the amount of fluorescence molecule had some influence on the luminescence behavior, which was also investigated and discussed. It can be concluded that the fluorescence properties of the dye molecule can be controlled at will by the loading amount.     

光学分子成像技术观察纳流芯片对DNA分子的研究

λ-DNA与荧光染料YOYO-1结合,利用荧光显微技术对DNA分子在毛细现象作用下进入宽40 nm、深60 nm的纳米沟道内,并在其内部被拉伸以及沿沟道移动的情形进行了观察.讨论了DNA分子在沟道内的运动情况.结合光学分子成像技术与该尺寸范围的纳流芯片,将有助于研究生物分子的动力学和静力学性质.     

Preparation of SERS active Ag nanoparticles encapsulated by phospholipids

A cost‐effective way of fabricating lipid‐coated surface‐enhanced Raman spectroscopy (SERS) substrate having reproducible high SERS activity was proposed. Ag nanoparticle embedded in 1,2‐dioleoyl‐sn‐glycero‐3‐phosphocholine (DOPC) and 1,2‐dioleoyl‐3‐trimethylammonium‐propane (DOTAP) membranes was produced by direct deposition of a 5‐nm‐thick layer of Ag onto the solid‐supported phospholipid membrane, and subsequent dissolution of the Ag nanoparticle‐embedded membrane in iso‐octane allowed easy one‐pot fabrication of DOPC‐ or DOTAP‐coated Ag nanoparticles. In particular, DOTAP produced nearly monodisperse lipid‐encapsulated Ag nanoparticles (9 nm in diameter) exhibiting reproducible high SERS activity (detecting up to 10 nM of rhodamine 6G and 0.5 μM of glutathione). In addition, the process was modified to incorporate variety of Raman active molecules (rhodamine 6G, malachite green, 4‐aminothiopheonol, 4‐mercaptopyridine) into the particle‐encapsulating lipid bilayer. The DOTAP/Raman dye‐coated Ag nanoparticles also generated high SERS activity to enable potential application of the DOTAP/Raman dye‐coated Ag nanoparticles feasible in different areas. Copyright © 2014 John Wiley & Sons, Ltd.     

Permeability of R6G across Cx43 hemichannels through a novel combination of patch clamp and surface enhanced Raman spectroscopy

We have measured the permeability of rhodamine-6G across Cx43 hemichannels reconstituted on a pipette tip. Cx43 hemichannels were overexpressed in Sf9 cells, and affinity-purified. The hemichannels were reconstituted in a lipid bilayer on a pipette tip by the tip-dip method. R6G in the pipette permeated across the channels into the bath. The permeability of R6G was quantified by measuring R6G concentration in the bath after several hours by surface enhanced Raman spectroscopy (SERS) with 100 nm silver colloid particles. The ratio of the permeability of dye to salt, as extracted by this combined electrical-SERS technique, is compatible with similar ratios for other dyes across whole gap junction channels. The results for the permeability ratio were further compared to fluorescence measurements. The novel combination of patch and SERS techniques can be extended to quantifying the transport of biologically significant non-fluorescent molecules, such as cAMP and IP3, across 1 nm sized pores, such as the gap junction channel.     

Photoluminescent core-shell particles of organic dye in silica

Using a single silica precursor, Rhodamine 6G organic dye molecules have been entrapped in silica particles resulting into core-shell particles of ∼500 nm diameter. Energy dispersive X-ray analysis, X-ray photoelectron spectroscopy and transmission electron microscopy analysis reveals that dye molecules are trapped inside the silica particles. Photoluminescence investigations show that highly luminescent and photostable core-shell particles are formed. Such core-shell particles can be easily suspended in water and would be useful for a variety of applications. However, there is a blue shift in the photoluminescence wavelength in case of core-shell particles compared to bare dye powder sample.     

Magnetic nanocomposite spinel and FeCo core-shell and mesoporous systems

The fabrication of condensed silica and mesoporous silica coated spinel CoFe₂O₄ and FeCo alloy magnetic nanocomposites are reported. The encapsulation of well-defined 5 nm thick uniform silica layer on CoFe₂O₄ magnetic nanoparticles was performed. The formation of mesopores in the shell was a consequence of removal of organic group of the precursor through annealing. The NiO nanoparticles were loaded into the mesoporous silica. The mesoporous silica shells leads to a larger coercivity than that of pure CoFe₂O₄ magnetic nanoparticles due to the decrease of interparticle interactions and magneto-elastic anisotropy. In addition, the FeCo nanoparticles were coated by condensed and mesoporous silica. The condensed silica can protect the reactive FeCo alloy from oxidation up to 300 °C. However, saturation magnetization of FeCo nanoparticles coated by silica after 400 °C annealing is dramatically decreased due to the oxidation of the FeCo core. The mesoporous silica coated magnetic nanostructure loaded with NiO as a final product could be used in the field of biomedical applications.     

Protein adsorption drastically reduces surface‐enhanced Raman signal of dye molecules

There is an increasing interest in developing surface enhancement Raman spectroscopy methods for intracellular biomolecule and for in vitro protein detection that involve dye or protein–dye conjugates. In this work, we have demonstrated that protein adsorption on silver nanoparticle (AgNP) can significantly attenuate the surface‐enhanced Raman spectroscopy (SERS) signal of dye molecules in both protein/dye mixtures and protein/dye conjugates. SERS spectra of 12 protein/dye mixtures were acquired using 4 proteins [bovine serum albumin (BSA), lysozyme, trypsin, and concanavalin A] and three dyes [Rhodamine 6G, adenine, and fluorescein isothiocyanate (FITC)]. Besides the protein/dye mixtures, spectra were also obtained for the free dyes and four FITC‐conjugated proteins. While no SERS signal was observed in protein/FITC mixtures or conjugates, a significantly reduced SERS intensity (up to 3 orders of magnitude) was observed for both R6G and adenine in their respective protein mixtures. Quantitative estimation of the number of dye molecules absorbed onto AgNP implied that the degree of R6G SERS signal reduction in the R6G/BSA sample is 2 to 3 orders of magnitude higher than what could be accounted for by the difference in the amount of the absorbed dyes. This finding has significant implications for both intracellular SERS analyses and in vitro protein detection using SERS tagging strategies that rely on Raman dyes as reporter molecules. Copyright © 2009 John Wiley & Sons, Ltd.     

Tunable Aminooxy‐Functionalized Monolayer‐Protected Gold Clusters for Nonpolar and Aqueous Oximation Reactions

Aminooxy (–ONH₂) groups are well known for their chemoselective reactions with carbonyl compounds, specifically aldehydes and ketones. The versatility of aminooxy chemistry has proven to be an attractive feature that continues to stimulate new applications. This work describes application of aminooxy click chemistry on the surface of gold nanoparticles. A trifunctional amine‐containing aminooxy alkane thiol ligand for use in the functionalization of gold monolayer‐protected clusters (Au MPCs) is presented. Diethanolamine is readily transformed into an organic‐soluble aminooxy thiol ( AOT ) ligand using a short synthetic path. The synthesized AOT ligand is coated on ≤2‐nm‐diameter hexanethiolate‐(C₆S)‐capped Au MPCs using a ligand‐exchange protocol to afford organic‐soluble AOT /C₆S (1:1 ratio) Au mixed monolayer‐protected clusters (MMPCs). The synthesis of these Au(C₆S)( AOT ) MMPCs and representative oximation reactions with various types of aldehyde‐containing molecules is described, highlighting the ease and versatility of the chemistry and how amine protonation can be used to switch solubility characteristics.     

Fluorescence Spectral Properties of Rhodamine 6G at the Silica/Water Interface

In this work, total internal reflection synchronous fluorescence spectroscopy (TIRSF) is applied successfully to investigate rhodamine 6G (R6G) at the silica/water interface. In comparison with the bulk spectra, 5 nm red shift is observed in the interface spectra, which is mainly due to the limitation of freedom of rotational movement of R6G molecules at the interface. The increase of R6G concentration induces the self-quenching of adsorbate at the interface. The dependence of interfacial fluorescence on the acidity and ionic strength was studied. Both the acidity and ionic strength affect the adsorptive behaviors of R6G at the silica/water interface.     

Semiconducting Polymer Nanoparticles as Fluorescent Probes for Biological Imaging and Sensing

In recent years, semiconducting polymer nanoparticles have emerged as a new class of extraordinarily bright fluorescent probes. These polymer nanoparticles, which are primarily composed of π‐conjugated polymers, exhibit a variety of outstanding features, including exceptional fluorescence brightness, fast radiative rate, good photostability, facile surface functionalization, and low cytotoxicity. These advantageous characteristics make polymer nanoparticles highly promising for applications in biological imaging and sensing. This progress report highlights recent advances in the synthesis, characterization, and applications as bio‐labels or sensors of these highly emissive organic nanoparticles.     

丹酰氯SiO2纳米发光标记物的制备

通过合成丹酰氯的荧光单体硅酯前驱物,采用油包水的反相微乳液法,以丹酰氯的荧光单体硅酯前驱物为核材料,成功地制备了丹酰氯的荧光纳米颗粒,克服了传统方法制备核壳荧光纳米颗粒中存在的荧光染料泄漏问题.通过透射电子显微镜表征该纳米粒子呈球形,大小均匀,直径为40nm左右.所制得纳米颗粒荧光性质稳定,受外界环境的影响小,且潜在生物亲和性,是一种新型的荧光标记物.     

近红外染料Yb(P4)(CoP) 掺杂 PS/SiO2复合纳米荧光标记物的制备及其性能

利用苯乙烯与3-甲基丙烯酰氧基丙基三甲氧基硅烷(KH570)化学反应合成共聚前驱物, 再采用凝胶-溶胶法,与四乙氧基硅烷在一定的条件下共同水解与缩合,合成了近红外染料 合镱(Ⅲ)掺杂的聚苯乙烯/二氧化硅复合纳米粒子。这种制备染料掺杂复合纳米粒子的方法既克服了传统物理包埋方法染料容易泄漏的问题,又不受到化学键合方法对近红外染料分子性质的限制。用扫描电子显微镜表征该复合纳米粒子呈球形,大小均匀,直径约100 nm。所制得的纳米粒子荧光性质稳定,受外界环境的影响小,具潜在生物亲和性,是一种新型的近红外荧光标记物。     

Amphifunctional Mesoporous Silica Nanoparticles with “Molecular Gates” for Controlled Drug Uptake and Release

It is demonstrated that the uptake and release of hydrophobic drugs/dyes by mesoporous silica nanoparticles (MSN) is critically dependent on the functional groups present on their outer surfaces. For this, amphifunctional MSNs are synthesized, possessing hydrophobic pores and hydrophilic functional groups on the outer surface. Further, the outer surface is modified with a different chain length of molecules, e.g., propargyl alcohol, triethylene glycol, and PEG (2000) via azide–alkyne click chemistry. The effect of these different surface functional groups on uptake of drug/dye is demonstrated with Nile red, proflavine (free base form), and rhodamine 6G. The uptake of these molecules is found to be inversely proportional to the bulkiness of surface functionality. To counter this effect, an alternate method of loading is proposed and demonstrated. Finally, the effect of these different functional groups on the release of loaded drug proflavine is studied, which supports the hypothesis that bulkier outer surface groups also hinder the release of drugs loaded in the porous MSN.