Facile fabrication of aggregation-induced emission based red fluorescent organic nanoparticles for cell imaging

A cyano-substituted diarylethlene derivative aggregation-induced emission （ALE） dye with two amino end-groups and 4,4＇-（hexafluoroisopropylidene）diphthalic anhydride were facilely incorporated into red fluorescent organic nanoparticles （FONs） via room temperature anhydride ring-opening polymerization under an air atmosphere. These obtained RO-HFDA FONs were characterized by a series of techniques including gel permeation chromatography, Fourier transform infrared spectroscopy, size distribution and zeta potential measurements, UV-Vis absorption spectrum, fluorescent spectroscopy and transmission electron microscopy. Biocompatibility evaluation and cell uptake behavior of RO-HFDA FONs were further investigated to explore their potential biomedical application. We demonstrated that such FONs showed high water dispersibility, stable uniform spherical morphology （150-200 nm）, broad excitation band （350-605 nm）, intense red fluorescence （627 nm） and excellent biocompatibility, making them promising for cell imaging applications.     

Tetraphenylethene End-capped Polyethylenimine Fluorescent Nanoparticles for Cell Imaging

Water soluble tetraphenylethene-based（TPE） aggregation-induced emission fluorescent organic nanoparticles（FONs） were facilely prepared via Schiff base condensation with polyethylenimine（PEI） and subsequent reduction. The obtained TPE-PEI FONs were characterized by a series of techniques including 1H-NMR, 13C-NMR, gel permeation chromatography, UV absorption spectra, fluorescence spectra, Fourier transform infrared spectroscopy, size distribution and zeta potential measurement, and transmission electron microscopy. Biocompatibility evaluation and cell imaging of TPE-PEI FONs were further explored. We demonstrated that such FONs showed intense fluorescence, spherical morphology and excellent biocompatibility, making them very suitable for cell imaging application.     

Stealth Luminescent Organic Nanoparticles Made from Quadrupolar Dyes for Two-Photon Bioimaging: Effect of End-Groups and Core

Molecular-based Fluorescent Organic Nanoparticles (FONs) are versatile light-emitting nano-tools whose properties can be rationally addressed by bottom-up molecular engineering. A challenging property to gain control over is the interaction of the FONs’ surface with biological systems. Indeed, most types of nanoparticles tend to interact with biological membranes. To address this limitation, we recently reported on two-photon (2P) absorbing, red to near infrared (NIR) emitting quadrupolar extended dyes built from a benzothiadiazole core and diphenylamino endgroups that yield spontaneously stealth FONs. In this paper, we expand our understanding of the structure-property relationship between the dye structure and the FONs 2P absorption response, fluorescence and stealthiness by characterizing a dye-related series of FONs. We observe that increasing the strength of the donor end-groups or of the core acceptor in the quadrupolar (D-π-A-π-D) dye structure allows for the tuning of optical properties, notably red-shifting both the emission (from red to NIR) and 2P absorption spectra while inducing a decrease in their fluorescence quantum yield. Thanks to their strong 1P and 2P absorption, all FONs whose median size varies between 11 and 28 nm exhibit giant 1P (10⁶ M⁻¹.cm⁻¹) and 2P (10⁴ GM) brightness values. Interestingly, all FONs were found to be non-toxic, exhibit stealth behaviour, and show vanishing non-specific interactions with cell membranes. We postulate that the strong hydrophobic character and the rigidity of the FONs building blocks are crucial to controlling the stealth nano-bio interface.     

Facile preparation of water dispersible red fluorescent organic nanoparticles and their cell imaging applications

Red fluorescent organic nanoparticles (FONs) based on a cyano-substituted diarylethylene and tetraphenylethene derivative conjugated molecule (R-TPE) were facilely prepared via surfactant modification with lecithin for the first time. The obtained R-TPE-LEC FONs were characterized by a series of techniques including fluorescence and UV spectroscopy, Fourier transform infrared spectroscopy, and transmission electron microscopy. Biocompatibility evaluation and cell uptake behavior of R-TPE-LEC FONs were further investigated to explore their potential biomedical application. We demonstrated that such red FONs exhibit anti-aggregation-caused quenching property, broad excitation wavelength, high water dispersibility, uniform morphology (40–60 nm), and excellent biocompatibility, making them promising for cell imaging application.     

An Unconventional Polymerization Route to Hydrophilic Fluorescent Organic Nanoparticles for Multicolor Cellular Bioimaging

We demonstrated an unconventional polymerization route to synthesize hydrophilic fluorescent organic nanoparticles (FONs) for multicolor cellular bioimaging in this contribution. The route benefits from our unexpected discovery of a rapid polymerization reaction between 1,6‐hexanediol dipropiolate and 2,4,6‐triazide‐1,3,5‐triazine under the catalysis of N,N,N′,N′′,N′′‐pentamethyldiethylenetriamine (PMDETA). Interestingly, the 2,4,6‐triazide‐1,3,5‐triazine and PMDETA system can also induce rapid free radical polymerization at room temperature. The as‐prepared FONs exhibited promising water solubility and stability with an average diameter of 20 nm. The excitation wavelength‐dependent fluorescent properties endow the FONs with blue, yellow, and red fluorescent emission under UV, blue, and green excitation, respectively. The cytotoxicity of FONs was investigated by using a Cell Counting Kit (CCK‐8) assay, which indicated good biocompatiblity. More importantly, the cell uptake experiment verified the FONs were excellent fluorescent nanoprobes for multicolor cellular bioimaging. Therefore, this unconventional route provides a novel fabrication strategy of highly hydrophilic FONs for biomedical applications.     

Fractional occupation numbers and self-interaction correction-scaling methods with the Fermi-Löwdin orbital self-interaction correction approach

We present a new assessment of the Fermi-Löwdin orbital self-interaction correction (FLO-SIC) approach with an emphasis on its performance for predicting energies as a function of fractional occupation numbers (FONs) for various multielectron systems. Our approach is implemented in the massively parallelized NWChem quantum chemistry software package and has been benchmarked on the prediction of total energies, atomization energies, and ionization potentials of small molecules and relatively large aromatic systems. Within our study, we also derive an alternate expression for the FLO-SIC energy gradient expressed in terms of gradients of the Fermi-orbital eigenvalues and revisit how the FLO-SIC methodology can be seen as a constrained unitary transformation of the canonical Kohn–Sham orbitals. Finally, we conclude with calculations of energies as a function of FONs using various SIC-scaling methods to test the limits of the FLO-SIC formalism on a variety of multielectron systems. We find that these relatively simple scaling methods do improve the prediction of total energies of atomic systems as well as enhance the accuracy of energies as a function of FONs for other multielectron chemical species.     

Ultrafast Preparation of AIE‐Active Fluorescent Organic Nanoparticles via a “One‐Pot” Microwave‐Assisted Kabachnik–Fields Reaction

The development of effective strategies for fabrication of fluorescent organic nanoparticles (FONs) with an aggregation‐induced emission (AIE) feature has an important impact on the biomedical applications of these AIE‐active FONs. In the current work, an ultrafast strategy for fabricating AIE‐active FONs is developed through a “one‐pot” microwave‐assisted, catalysts‐free, and solvent‐free Kabachnik–Fields (KF) reaction for the first time. It is demonstrated that such organophosphorous‐containing AIE‐active block polymers can be synthesized within 2 min under air atmosphere through the microwave‐assisted KF reaction. These polymers show amphiphilic properties and can self‐assemble into mPEG‐CHO‐Phe‐NH₂‐DEP FONs, which display high water dispersibility and desirable optical properties. Biological evaluation results suggest that the mPEG‐CHO‐Phe‐NH₂‐DEP FONs exhibit low toxicity and are potential for biological imaging applications. More importantly, many other multifunctional AIE‐active FONs can also be fabricated through the strategy described in this work owing to the universality of KF reaction. Besides, combined with the excellent properties of mPEG‐CHO‐Phe‐NH₂‐DEP FONs, it is believed that such microwave‐assisted KF reaction shall be an effective route for designing various AIE‐active nanomaterials for different biomedical applications.

     

Bright Electrogenerated Chemiluminescence of a Bis‐Donor Quadrupolar Spirofluorene Dye and Its Nanoparticles

A series of symmetric fluorescent dyes built from a spirofluorene core bearing electroactive end groups and having different conjugated linkers were prepared with a view to their use as building blocks for the preparation of electrochemiluminescent (ECL) dyes and nanoparticles. Their electrochemical, spectroelectrochemical, and ECL properties were first investigated in solution, and structure/activity relationships were derived. The electrochemical and ECL properties show drastic variation that could be tuned by means of the nature of the π‐conjugated system, the end groups, and the core. In this series, highly fluorescent dye 1 based on a spirofluorene core and triphenylamine end groups connected via thiophene moieties shows the most promising and intriguing properties. Dye 1 is reversibly oxidized in three well‐separated steps and generates a very intense and large ECL signal. Its ECL efficiency is 4.5 times higher than that of the reference compound [Ru(bpy)₃]²⁺ (bpy=2,2′‐bipyridine). This remarkably high efficiency is due to the very good stability of the higher oxidized states and it makes 1 a very bright organic ECL luminophore. In addition, thanks to its molecular structure, this dye retains fluorescence after nanoprecipitation in water, which leads to fluorescent organic nanoparticles (FONs). The redox behavior of these FONs shows oxidation waves consistent with the initial molecular species. Finally, ECL from FONs made of 1 was recorded in water and strong ECL nanoemitters are thus obtained.     

Fluorescent organic nanoparticles of benzofuran-naphthyridine linked molecules: formation and fluorescence enhancement in aqueous media

[structure: see text] Ethynyl-linked benzofuran-naphthyridine compounds show high-yield fluorescence with solvatochromic properties. One of the compounds, ABAN, has successfully formed fluorescent organic nanoparticles (FONs), for which the photophysical properties such as the spectral features and intensity are remarkably different from those at the molecular level (solution) and in bulk material. The results are tentatively rationalized by the FONs inducing coplanarization of the benzofuran-naphthyridine molecule to extend its effective conjugation length and hence increase the oscillator strength.     

A novel approach of preparation and patterning of organic fluorescent nanomaterials

Different fluorescent organic nanoparticles (FONs) from microemulsion were prepared with semi-continuous emulsion copolymerization of methyl methacrylate (MMA) and a polymerizable anionic surfactant. The diameters of particles ranged from 40 to 80 nm. The reactive surfactants were copolymerized with the main monomer. So the desorption of the surfactant from the polymer particles or the migration within the polymer film was impeded and avoided negative influences on the optoelectronic properties of the material. The microemulsion containing FONs was used in an ink-printing process to form different patterns. The photoluminescence properties of the films were investigated. It was expected that the approach of micro-droplet ink-jet printing of FONs would have bright future because no complicated preparation processes were required.     

A new route towards fluorescent organic nanoparticles with red-shifted emission and increased colloidal stability

Suzuki–Miyaura cross-coupling reaction with a new boron reagent has been used to conveniently and efficiently synthetize a dipolar chromophore having an elongated π-conjugated system (i.e., bithiophene based), which displays a red-shifted emission while maintaining fluorescence. Bright orange emitting FONs made from this ‘naked’ dipole have been easily prepared and studied. Very interestingly, these FONs with red-shifted emission combine markedly enhanced colloidal and structural stability in water with giant one- and two-photon brightness. As such, they hold promises as fluorescent probes for bioimaging.     

Recent Advances and Future Prospects of Aggregation‐induced Emission Carbohydrate Polymers

Aggregation‐induced emission (AIE) is an abnormal phenomenon that has sparked great attention for diverse applications in different fields. In particular, the fabrication and biological imaging applications of AIE‐active fluorescent organic nanoparticles (FONs) have become a focus in the emerging and promising fields. A large number of AIE‐active polymeric nanoprobes have recently been fabricated through different strategies. The advances and progress in this direction have also recently been summarized by some groups. However, the fabrication and biomedical applications of AIE‐active FONs based on carbohydrate polymers and AIE‐active dyes are quite rare and limited. In this feature article, the recently reported AIE‐active FONs with different structures and applications based on AIE‐active dyes and carbohydrate polymers are highlighted, and the major current limitations and development tendencies are also discussed.

     

Water-soluble AIE-active Fluorescent Organic Nanoparticles: Design,Preparation and Application for Specific Detection of Cyanide in Water and Food Samples

A dilactosyl-dicyanovinyl-functionalized tetraphenylethene ( TPELC ) was designed, synthesized and used for ratiometric sensing of cyanide. TPELC was comprised of three moieties (tetraphenylethylene, dicyanovinyl group and lactose unit) in one molecule, making TPELC water-soluble and aggregation-induced emission (AIE)-active and selectively reactive to cyanide. Compared with other reported fluorescent probes containing dicyanovinyl group, TPELC is the first AIE luminogen to be assembled as fluorescent organic nanoparticles (FONs) for sensing of cyanide in water without the use of surfactant or the help of organic solvents based on the nucleophilic addition reaction. The detection mechanism was verified by liquid chromatograph mass spectrometry experiments and by protonation of cyanide to reduce the nucleophilicity of cyanide. In addition, TPELC was used for detection of the cyanide content of food samples and test strips were developed to simplify the detection procedure.     

A High‐Throughput Method for Determining the Stability of Pigment Dispersions

Summary: An approach for the high‐throughput preparation and characterisation of aqueous pigment dispersions is described and evaluated. The use of ultrasonication as a rapid technique for dispersing pigments using polymeric dispersants was developed. The results are comparable to those obtained using time‐intensive conventional high‐energy ball mill processing. The quality of the pigment dispersion was evaluated in a high‐throughput fashion using digital image analysis and the results correlated with particle sizes, determined by photo‐correlation spectroscopy.

Cuvettes containing dispersions of varying particle size.     

He I ultraviolet photoelectron spectroscopy of benzene and pyridine in supersonic molecular beams using photoelectron imaging

We performed He I ultraviolet photoelectron spectroscopy (UPS) of jet-cooled aromatic molecules using a newly developed photoelectron imaging (PEI) spectrometer. The PEI spectrometer can measure photoelectron spectra and photoelectron angular distributions at a considerably higher efficiency than a conventional spectrometer that uses a hemispherical energy analyzer. One technical problem with PEI is its relatively high susceptibility to background electrons generated by scattered He I radiation. To reduce this problem, we designed a new electrostatic lens that intercepts background photoelectrons emitted from the repeller plate toward the imaging detector. An energy resolution (ΔE/E) of 0.735% at E = 5.461 eV is demonstrated with He I radiation. The energy resolution is limited by the size of the ionization region. Trajectory calculations indicate that the system is capable of achieving an energy resolution of 0.04% with a laser if the imaging resolution is not limited. Experimental results are presented for jet-cooled benzene and pyridine, and they are compared with results in the literature.     

Heterogeneous exchange reactions of unstable simple systems

The analysis of less than 10⁻⁹ g of the isotope²⁰⁴Pb in lunar samples was carried out by an (n, 2n) activation using high energy (>8. 8 MeV) neutrons. A procedure of using the neutrons produced by bombardment of a specially designed Be sample holder with deuterons in a cyclotron was developed and compared to irradiation carried out in the core of a nuclear reactor, Radiochemical separations and X ray-γ ray coincidence counting techniques are necessary to achieve the required sensitivity. Although the flux of neutrons of sufficient energy from the cyclotron procedure is somewhat lower can be obtained in the best reactor irradiations, the high radioactivity due to other elements produced by the (n, γ) reactions in the reactor is eliminated. Radiochemical procedures for the analysis of Bi, Tl, Zn in the same samples are also described.     

Linear scaling local correlation approach for solving the coupled cluster equations of large systems

A linear scaling local correlation approach is proposed for approximately solving the coupled cluster doubles (CCD) equations of large systems in a basis of orthogonal localized molecular orbitals (LMOs). By restricting double excitations from spatially close occupied LMOs into their associated virtual LMOs, the number of significant excitation amplitudes scales only linearly with molecular size in large molecules. Significant amplitudes are obtained to a very good approximation by solving the CCD equations of various subsystems, each of which is made up of a cluster associated with the orbital indices of a subset of significant amplitudes and the local environmental domain of the cluster. The combined effect of these two approximations leads to a linear scaling algorithm for large systems. By using typical thresholds, which are designed to target an energy accuracy, our numerical calculations for a wide range of molecules using the 6-31G or 6-31G* basis set demonstrate that the present local correlation approach recovers more than 98.5% of the conventional CCD correlation energy.     

Synthesis of organic nanoparticles of naphthalene-thiourea-thiadiazole-linked molecule as highly selective fluorescent and colorimetric sensor for Ag(I)

A novel fluorescent and colorimetric sensor was synthesized by a reprecipitation to probe Ag⁺ ions in water on naphthalene-thiourea-thiadiazole (NTTA) molecular nanocrystals. The fluorescent organic nanoparticles (FONs) allowed a highly sensitive determination of free Ag⁺ ions in aqueous media. The possible mechanism was discussed.     

A high transmission hemispherical energy analyzer for ion spectrometry

A hemispherical energy analyzer was constructed by using a novel approach to control the fringing electrostatic field. It provides several properties useful in ion spectrometers: namely, rather simple fabrication and compact size, high transmission efficiency at moderate resolution, and the capability to adjust resolution by changing the intersphere potentials. A computer program was developed to evaluate ion trajectories through the hemispherical analyzer. Data obtained from the trajectories were used to predict the characteristics of the analyzer. Experiments performed to determine the kinetic energy dependence of the absolute transmission and the resolution functions are in accord with theoretical calculations.     

The effect of hydrothermal growth temperature on preparation and photoelectrochemical performance of ZnO nanorod array films

Highly oriented ZnO nanorod arrays with controlled diameter and length, narrow size distribution and high orientation consistency have been successfully prepared on ITO substrates at different growth temperatures by using a simple hydrothermal method. XRD results indicate that the nanorods are high-quality single crystals growing along [001] direction with a high consistent orientation perpendicular to the substrate. SEM images show that the nanorods have average diameters of about 30-70 nm by changing growth temperature. The thin films consisting of ZnO nanorods with controlled orientation onto ITO substrates allow a more efficient transport and collection of photogenerated electrons through a designed path. For a sandwich-type cell, the relatively high overall solar energy conversion efficiency reaches about 2.4% when the growth temperature is at 95 °C.