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The fluorescence quenching property of graphene oxide (GO) has been newly demonstrated and applied for fluorescence imaging and biosensing. In this work, a new nanostructure was designed for effectively studying the quenching ability of GO. The key element in this design is the fabrication of a layer of rigid and thickness adjustable silica spacer for manipulating the distance between the GO and fluorophores. First, a silica core modified with organic dye molecules was prepared, followed by the formation of a silica shell with a tunable thickness. Afterward, the GO was wrapped around silica nanoparticles based on the electrostatic interaction between the negatively charged GO and positively charged silica. The quenching efficiency of GO to different dye molecules was studied at various spacer thicknesses and varying concentrations of GO. Fluorescence lifetime of fluorophores was measured to determine the quenching mechanism. We found that the quenching efficiency of GO was still around 30% when the distance between dyes and GO was increased to more than 30 nm, which indicated the long-distance quenching ability of GO and confirmed the previous theoretical calculation. The quenching mechanisms were proposed schematically based on our experimental results. We expected that the proposed nanostructure could act as a feasible model for studying GO quenching property and shed light on designing GO-based fluorescence sensing systems. [ABSTRACT FROM AUTHOR]

Hyper-cross-linked polynaphthalene nanoparticles (PNNs) capable of catalyzing the degradation of organic pollutants upon exposure to visible light have been developed. The nascent and metal-free PNNs with a porous structure, high specific surface area, and narrow bandgap are chemically and thermally stable in the catalytic system, which make it promising as a kind of excellent photocatalytic material compared to conventional photocatalysts. The photocatalytic activity of the as-obtained PNNs exhibits remarkable photocatalytic performance for the degradation of rhodamine B (RhB) and methyl blue (MB) under the irradiation of visible light. The easy preparation, high catalytic activity, and recyclability of the PNNs open new opportunities in the visible-light-promoted degradation of organic pollutants. [ABSTRACT FROM AUTHOR]

Water-soluble organic dyes such as fluorescein are widely used, mainly for coloration of, e.g., biological samples and groundwater tracing, and they are not obviously amphiphilic by molecular structure like surfactants. Here, we show that the dyes alone stabilize oil-in-water emulsions. Exemplarily, fluorescein is compared with the classical surfactant sodium dodecyl sulfate (SDS) by means of surface/interfacial tension, concentration of stabilizer and electrolyte, as well as pH. The principle can be extended to further classes of water-soluble dyes, which keep up with or exceed SDS by efficiency. Various organic liquids of different polarities can be employed and be polymerized in the case of styrene as disperse phase. Thus, surfactant free latex solely stabilized by water-soluble dyes is accessible. The emulsions can be destabilized by absorption of the dyes to hydrogels, and their complete removal is easily followed visually. The stabilization mechanisms are different for SDS and the dyes: The latter stabilize droplets not as monomers but by their aggregates as molecular scale Pickering stabilizers, which is a new concept of stabilization. [ABSTRACT FROM AUTHOR]

An Au-Fe2O3@mesoporous SiO2 nanoreactor with a multiyolks/shell structure was synthesized through a multistep method. In this nanoreactor, the spindle Fe2O3 and Au nanoparticles were inside the same mesoporous SiO2 shell as the yolks but in a noncontact manner. The noncontact synergistic effect between Au nanoparticles and the Fe2O3 spindle was studied with a Fenton-like reaction. The catalytic activity of the Au-Fe2O3@mesoporous SiO2 nanoreactor to the Fenton-like reaction for the degradation of organic dyes was dramatically enhanced by the noncontact synergistic effect. [ABSTRACT FROM AUTHOR]

Fluorescent silica nanoparticles (FSNPs) are synthesized through the Stöber method by incorporating silane-modified organic dye molecules. The modified fluorescent organic dye molecule is able to be prepared by allylation and hydrosilylation reactions. The optical properties of as-prepared FSNPs are shown the similar optical properties of PR254A (allylated Pigment Red 254) and have outstanding photostability. The polyvinylpyrrolidone (PVP) is introduced onto the surface of FSNP to enhance the binding affinity of PVP-coated FSNP for latent fingerprints (LFPs) detection. The simple preparation and easy control of surface properties of FSNPs show potential as a fluorescent labeling material for enhanced latent fingerprint detection on hydrophilic and hydrophobic substrates in forensic science for individual identification. [ABSTRACT FROM AUTHOR]

An organic dye-modified organolead halide CH3NH3PbBr3 nanoparticle (cubic) is prepared successfully by using a perylenetetracarboxylic diimide (PDI) bearing an -NH3+ headgroup as the capping ligand. The nanopartilces are homogeneous with high crystallinity. The photoluminescence of perovskite is quenched completely by the chemically adsorbed PDI molecules. This efficient fluorescence quenching has confirmed that the PDI molecules are anchored on the surface of CH3NH3PbBr3 nanoparticle. The resulting nanoparticles can be dispersed in organic solvents, and the resulting dispersion remains stable for days. This result provides a general guideline for surface engineering of organolead halide CH3NH3PbBr3 nanoparticles. [ABSTRACT FROM AUTHOR]

The effect of thedonor in an organic dye on the electron lifetimeof dye-sensitized solar cells (DSSCs) employing a cobalt redox electrolytewas investigated. We synthesized organic dyes with donor moietiesof carbazole, coumarin, triphenylamine, and N-phenyl-carbazoleand measured the current–voltage characteristics and electronlifetimes of the DSSCs with these dyes. The cell with the triphenylaminedonor dye produced the highest open circuit voltage and longest electronlifetime. On the other hand, the lowest open circuit voltage and shortestelectron lifetime was obtained with coumarin donor dye, suggestingthat the coumarin attracted the cobalt redox couples to the surfaceof the TiO2layer, thus increasing the concentration ofcobalt complex. On the other hand, the longest electron lifetime withtriphenylamine was attributed to the blocking effect by steric hindranceof the nonplanar structure of the donor. [ABSTRACT FROM AUTHOR]

Understanding the role played by external factors onthe organizationof molecules has the potential to contribute greatly to fundamentalresearch and applications in fields as diverse as nanotechnology,medicine, material chemistry, etc. Countless studies involve the organizationof small organic molecules in environments rich in ionic species,yet their participation in molecular organization is often overlooked.Herein, we critically assess the organization in aqueous solutionof the cationic cyanine dye, thiazole orange, in the presence of differentmonovalent sodium salts. Our findings clearly indicate that not allions are identical with regards to the organization of thiazole orangemolecules and specific ions effects are at play. The conventionalDebye and Hückel model is not sufficient to explain our results,and the participation of ionic species in molecular organization isexplained in terms of the recent theory of water matching affinity.Herein, by choosing the right counterion with the appropriate size,we have shown that it is possible to either induce a simple shiftin the monomer–dimer equilibrium of thiazole orange or to turnon the formation of larger organized structures. [ABSTRACT FROM AUTHOR]

Liquid/liquid interfaces play a crucial role in numerousareasof science. However, direct spectroscopic access to this thin (∼1nm) region is not possible with conventional optical methods. Aftera brief review of the most used techniques to perform interfacialoptical spectroscopy, we will focus on time-resolved surface secondharmonic generation, which allows the measurement of the excited-statedynamics of probe molecules at interfaces. By comparing these dynamicswith those measured in bulk solutions, precious information on theproperties of the interfacial region can be obtained. To illustratethis, several studies performed in our group will be presented. [ABSTRACT FROM AUTHOR]

The surface active derivative of the organic dye Acridine Orange (N-10-dodecyl-acridine orange (DAO)) has been included in mixed Langmuir monolayers with stearic acid (SA). The maximum relative content on DAO for a stable mixed monolayer is a molar ratio of XDAO= 0.5. Brewster angle microscopy (BAM) reveals a high homogeneity at the micrometer level for the mixed monolayer in equimolar proportion (XDAO= 0.5), whereas the appearance of domains occurs for lower content of DAO, i.e., XDAO= 0.2 and 0.1. The aggregation of the DAO headgroup leads to well-defined H-aggregates at the air/water interface for those mixed monolayers with a low content of DAO. However, for the mixed monolayers enriched in DAO, e.g., XDAO= 0.5, the molecular crowding prevents the formation of defined supramolecular structures. Molecular organization and tilting of the DAO headgroup is quantitatively analyzed by in situ UV–visible reflection spectroscopy. The formation of H-aggregates of the DAO headgroup can be reversibly tuned with the applied surface pressure. A molecular mechanism for the conformational rearrangement of the DAO molecule is proposed using RM1 quantum semiempirical calculations. [ABSTRACT FROM AUTHOR]

The determination of the orientation and molecular density for several porphyrin dyes adsorbed on planar TiO2surfaces using X-ray reflectometry (XRR) is reported. Adsorption of nanoscale water layers occurred rapidly upon exposure of freshly prepared TiO2surfaces to ambient conditions; however, this was successfully eliminated, resulting in clearly discernible adsorbed dye layers for sensitized surfaces. Adsorbed dye orientations, determined from computations constrained by the measured dye layer thickness, were calculated to have a binding tilt angle of 35°–40°. Combining the XXR data with the orientation models indicates that the porphyrins form densely packed surfaces with an intermolecular spacing of 3–4 Å, consistent with π–π stacking interactions. Changes in the molecular size of probe dyes were reflected in corresponding changes in the measured dye layer thickness, confirming the ability of this technique to resolve small variations in dye layer thickness and consequently adsorption orientation. Application of these results to understanding the behavior of dye-sensitized devices is discussed. [ABSTRACT FROM AUTHOR]

Nanoporous-walled tungsten oxide (WO3) nanotubes (NTs), which had a more positive conduction band edge level compared to that of TiO2, were applied to various organic dyes for dye-sensitized solar cells (DSSCs). The dye-sensitized WO3NTs displayed photosensitization for the organic dyes whose lowest unoccupied molecular orbital (LUMO) level was relatively positive to the conventional TiO2electrode and, thus, not applicable for electron injection to the TiO2electrode. Electron transport time and electron lifetime for the WO3electrode in the DSSCs were investigated. In comparison to the DSSCs based on TiO2, SnO2, and In2O3, the WO3DSSCs displayed the longest lifetime. On the other hand, non-diffusion-like electron transport may be an issue to apply WO3for the DSSCs. [ABSTRACT FROM AUTHOR]

Porous silicon (pSi) surfaces were chemically micropatterned through a combination of photolithography and surface silanization reactions. This patterning technique produces discretely defined regions on a pSi surface functionalized with a specific chemical functionality, and the surrounding surface displays a completely different functionality. The generated chemical patterns were characterized by a combination of IR microscopy and the conjugation of two different fluorescent organic dyes. Finally, the chemically patterned pSi surface was used to direct the attachment of neuronal cells to the surface. This patterning strategy will be useful for the development of high-throughput platforms for investigating cell behavior. [ABSTRACT FROM AUTHOR]

We demonstrate an effective micelle shuttle between water and a hydrophobic ionic liquid and its application in transportation in the biphasic system, using a commercially available and inexpensive Pluronic block copolymer. The poly(ethylene oxide-b-propylene oxide-b-ethylene oxide) (P123) block copolymer self-assembles into micelles in both water and the ionic liquid, 1-butyl-3-methylimidazolium hexafluorophosphate, as characterized by dynamic light scattering. The poly(ethylene oxide) blocks provide the well-solvated corona, whereas the poly(propylene oxide) blocks form the solvophobic core. The micelles can spontaneously transfer between the two phases upon a simple temperature stimulus; the transfer is reversible and repeatable, and 1H NMR analysis indicates quantitative transfer. The micelle nanocarriers are used to transport various cargoes in the biphasic system: fully reversible transport of hydrophobic small organic dyes into and out of water and facile extraction of an ionic liquid-phobic polymer from the ionic liquid. This simple round-trip delivery system may be used in delivery, separations, and extraction in synthesis and biphasic catalysis involving ionic liquids. [ABSTRACT FROM AUTHOR]

The monomer−aggregate equilibrium of four phenothiazine (PN) dyes, containing thionine (TH), methylene blue (MB), new methylene blue (NMB), and 1,9-dimethylmethylene blue (DMB), in the tungsten(VI) oxide (WO3) nanocolloid solution has been investigated by means of UV−vis spectroscopy. Addition of PN dye into the WO3nanocolloid solution brought about significant changes in the absorption spectrum, suggesting the formation of H-type (face-to-face fashion) trimer on the WO3nanocolloid surface. The adsorptivity of PN dyes onto the WO3nanocolloid surface was diminished by the raising the ionic strength, indicating the evidence of the electrostatic interaction between cationic PN dye and negatively charged WO3nanocolloids. The detail analysis of each spectral data provided insight into the effect of molecular structure of PN dyes on the adsorption and aggregation behaviors on the WO3nanocolloid surface. Moreover, in situmeasurement of PN dye aggregation using the centrifugal liquid membrane (CLM) technique revealed that the aggregation of PN dyes on the WO3nanocolloid surface proceeded in a two-step three-stage (monomer → dimer → trimer) formation. The aggregation mechanism of PN dyes on the WO3nanocolloid surface was discussed on the basis of Kasha’s exciton theory. [ABSTRACT FROM AUTHOR]

The self-assembly of uniform single-crystalline microrods of organic dye Sudan II (1-(2,4- dimethylphenyl-azo)-2-naphthol) in solution was achieved by reprecipitation with the assistance of amphiphilic block copolymer Pluronic F127. It was found that the formation of F127 micelles was favorable for the production of uniform Sudan II microrods whereas individual F127 molecules favored the formation of Sudan II fibers. The optical absorption and fluorescence emission properties of the uniform microrods were characterized, and the time-dependent spectra of the precipitating solution for microrod formation were measured to monitor the self-assembly process of Sudan II molecules. The Sudan II microrods exhibited intense fluorescence emission, indicating an unusual aggregation-induced emission (AIE) phenomenon for Sudan II. The fluorescent microscopy investigation suggested that the obtained Sudan II microrods exhibited remarkable optical waveguide behavior, which is expected to serve as single rod active optical waveguides that can be used as building blocks for miniaturized photonic devices. Furthermore, novel Sudan II microplates, which exhibited interesting 2D optical waveguide behavior, were readily obtained by reprecipitation of Sudan II from cationic surfactant cetyltrimethylammonium bromide (CTAB) solution. [ABSTRACT FROM AUTHOR]

The use of nanoparticles, either for the delivery of drugs or for imaging contrast agents, or a combination of both (theranostics), is very appealing in biological and biomedical research. The design of high-quality NIR-emitting quantum dots (QDs), with outstanding optical properties in comparison to that of organic dyes, should lead to novel contrast agents with improved performance for optical and multimodal imaging. Moreover, these nanocrystals could also be used for exploring therapeutic applications, such as drug delivery or phototherapy. In this article, we report the coating of commercial ITK705-amino QDs with methoxy-terminated poly(ethylene glycol) (PEG) of different chain lengths. Homogeneous QD solutions that are stable over extended periods of time were prepared. The impact of the particle coating on their in vivo fate after tail IV injection was studied by fluorescence imaging. The speed of the first pass extraction of the coated QDs toward the liver decreased with the PEG length, whereas the hydrodynamic diameter of the particles was increased. [ABSTRACT FROM AUTHOR]

We report the synthesis and unique spectroscopic properties of organic styryl dye nanoparticles. Aqueous-phase ion association between a cationic styryl dye 2-(4-(dimethylamino)styryl)-1-ethylpyridinium (DASPE), possessing both electron donor and acceptor groups in its molecule, and tetraphenylborate (TPB) or tetrakis(4-fluorophenyl)borate (TFPB) anion, in the presence of poly(vinylpyrrolidone), produces the ion-based dye (DASPE) nanoparticles of ∼30−100 nm in diameter. Absorption spectra of the DASPE nanoparticles show a large bathochromic shift in comparison with that of the dye monomer in water. Quantum chemical calculations demonstrate that ion-pair formation brings about a large internal rotation around a single bond in DASPE, and this internal twisting as well as local polarity of the counteranion have a strong influence on the red shift of the optical spectra. Furthermore, nanoparticle formation results in enhanced fluorescence of DASPE: more than a 20-fold enhancement in the fluorescence quantum yield as compared to that of the dye monomer in water, giving a new methodology for the synthesis of fluorescent organic nanoparticles. The observed fluorescence would come from an intramolecular charge-transfer (ICT) excited state stabilized by the matrix of TPB or TFPB, and the enhancement is due to both the high rotational resistance for the single bond in DASPE and the matrix polarity effect that can suppress the nonradiative processes. [ABSTRACT FROM AUTHOR]

Noncharged pyrene molecules were incorporated into multilayer films by first loading pyrene into poly(acrylic acid) (PAA)-stabilized cetyltrimethylammonium bromide (CTAB) micelles (noted as PAA&(Py@CTAB)) and then layer-by-layer (LbL) assembled with poly(diallyldimethylammonium chloride) (PDDA). The stable incorporation of pyrene into multilayer films was confirmed by quartz crystal microbalance (QCM) measurements and UV−vis absorption spectroscopy. The resultant PAA&(Py@CTAB)/PDDA multilayer films show an exponential growth behavior because of the increased surface roughness with increasing number of film deposition cycles. The present study will open a general and cost-effective avenue for the incorporation of noncharged species, such as organic molecules, nanoparticles, and so forth, into LbL-assembled multilayer films by using polyelectrolyte-stabilized surfactant micelles as carriers. [ABSTRACT FROM AUTHOR]