A computational and experimental investigation of donor-acceptor BODIPY based near-infrared fluorophore for in vivo imaging.

TD-DFT quantum calculation was performed to predict and/or illustrate the electronic transition, the related absorption and emission maxima of some pyrrole-difluoroboron derivatives with different electron donor-acceptor unit or π-conjugated degree. Upon the calculated results, a new near infrared (NIR) fluorophore (abbreviated as TPBD-BP) was designed and fabricated through linking triphenylamine and pyrrole-difluoroboron units to benzothiadiazole (BTD) backbone. The fluorescence of TPBD-BP in solid state centered at 932 nm, which was 985 nm for TPBD-BP nanoparticles (TPBD-BP dots) encapsulated in PEG-6000. The fluorescence of TPBD-BP in both solid state and dots exhibited off-peak tail emission to NIR-II region (extended to 1300 nm). The TPBD-BP dots showed excellent water solubility, biocompatibility and aggregation induced emission (AIE), which was suitable to be applied in vivo imaging. NIR-II emission signal of TPBD-BP dots can be observed in the reproductive organ of normal nude mice after tail vein injection. This attractive combination of computational and experimental investigation would help to develop new-typed small-molecular NIR fluorophores.

A self-assembled nanohybrid composed of fluorophore-phenylamine nanorods and Ag nanocrystals: energy transfer, wavelength shift of fluorescence and TPEF applications for live-cell imaging.

A fluorophore-phenylamine derivative (L) has been coupled with silver nanocrystals (NCs) to construct an L-Ag nanohybrid. Owing to synergic effects of the L and Ag components, the exciton-plasmon interactions between L and Ag increase the strength of the donor-acceptor interaction within the nanohybrid, a fact that results in an energy-transfer process and further brings about a dramatic redshift of single-photon absorption and fluorescence, and a decreased fluorescence FL lifetime. The coupling effect also leads to enhancement of a series of nonlinear optical properties, including two-photon-excited fluorescence (TPEF), two-photon-absorption (TPA) cross section (δ), two-photon-absorption coefficient (ß), nonlinear refractive index (γ), and third order nonlinear optical susceptibility (χ((3))). The enhanced two-photon fluorescence of the nanohybrid is proven to be potentially useful for two-photon microscopy of live cells, such as HepG2. Moreover, cytotoxicity tests show that the low-micromolar concentrations of the nanohybrid do not cause significant reduction in cell viability over a period of at least 24 h and should be safe for further biological studies.

Multifunctional behavior of a carbazole derivative: Red phosphorescent emission, aggregation-induced long-life exciton and light-emitting diode application.

A D-π-A typed cyanyl-carboxylic derivative (named as CECZA) merely produced prompt fluorescence with lifetime at nanosceond scale in dilute solutions, whose solid-state luminescence exhibited 3.36 µs lifetime with 13.80 % quantum yield (QY, captured at 522 nm for powder at nanometer scale) at 298 K and 43.36 ms lifetime with 30.46 % QY (650 nm, 80 K, tiny crystals). Femtosecond transient absorption, Raman spectroscopy and quantum chemical calculation provided valid clues to reveal its excitonic transition mechanism. The results indicated that the restricted vibration of benzene ring on carbazole group and alkyl chain weakened the vibrational modes of CECZA molecule and strengthened inter-molecular interactions between adjacent molecules at low temperatures, which promoted the persistent phosphorescent emission. Due to strong UV-vis absorption, high quantum efficiency and excellent thermal stability, CECZA can be used as a potential candidate in light-emitting diode (LED) application. Combined with a commercial InGaN blue-emitting chip, CECZA-InGaN emitted daylight white light.

4-(Anthracen-9-yl)-2-phenyl-6-(pyridin-2-yl)pyridine.

In the title compound, C(30)H(20)N(2), the anthracene ring system is approximately planar [maximum deviation = 0.035 (2) Å] and is nearly perpendicular to the central pyridine ring, making a dihedral angle of 75.73 (7)°. The terminal pyridine ring and the phenyl ring are oriented at dihedral angles of 8.11 (10) and 13.22 (10)°, respectively, to the central pyridine ring.

Two quinoline-based two-photon fluorescent probes for imaging of viscosity in subcellular organelles of living HeLa cells.

Two viscosity-sensitive two-photon fluorescent probes (QL and QLS) were designed and synthesized, which can be localized in lysosome and mitochondria in living HeLa cells, respectively. As the increases of viscosity from 2.55 to 1150 cP, the fluorescence quantum yield (Φ) of QL and QLS was increased by 28-fold and 37-fold, respectively. At the same time, its effective two-photon absorption cross section (ΦδTPA) was enhanced by 15-fold and 16-fold, respectively. Fluorescence lifetime imaging (FLIM) of living HeLa cells stained with QL and QLS, revealed that lysosomal viscosity ranged from 100.76 to 254.74 cP and mitochondrial viscosity ranged from 92.21 to 286.79 cP. This type of fluorescent probe is helpful in the design and application of materials for monitoring diseases associated with abnormal viscosity.

Structure-directing role of graphene in the synthesis of metal-organic framework nanowire.

Graphene can be decorated with functional groups on either side of its basal plane, giving rise to a bifunctional nanoscale building block that can undergo face-to-face assembly. We demonstrate that benzoic acid-functionalized graphene (BFG) can act as a structure-directing template in influencing the crystal growth of metal-organic framework (MOF). BFG is also incorporated into MOF as framework linker. Because of the high density of carboxylic groups on benzoic acid-functionalized graphene, an unusual MOF nanowire that grows in the [220] direction was synthesized. The diameter of the nanowire correlates closely with the lateral dimensions of the BFG. The intercalation of graphene in MOF imparts new electrical properties such as photoelectric transport in the otherwise insulating MOF. The results point to the possibility of using functionalized graphene to synthesize a wide range of structural motifs in MOF with adjustable metrics and properties.

Synthesis and superior optical-limiting properties of fluorene-thiophene-benzothiadazole polymer-functionalized graphene sheets.

A polymer based on fluorene, thiophene, and benzothiadazole as the donor-spacer-acceptor triad is covalently coupled to reduced graphene oxide (rGO) sheets via diazonium coupling with phenyl bromide, followed by Suzuki coupling. These polymer-graphene hybrids show good solubility in organic solvents, such as chloroform, tetrahydrofuran (THF), toluene, dichlorobenzene, and N,N-dimethylformamide (DMF), and exhibit an excellent optical-limiting effect with a 532-nm laser beam. The optical-limiting threshold energy values (0.93 J cm(-2) for G-polymer 1 and 1.12 J cm(-2) for G-polymer 2) of these G-polymer hybrids are better than that of carbon nanotubes (3.6 J cm(-2)).

A facile strategy to realize a single/double photon excitation-dependent photosensitizer for imaging-guided phototherapy against HeLa cancer cells at separate irradiation channels.

A novel difluoroboron fluorophore with an electron donor-acceptor conjugated structure was synthesized with 26.5% fluorescence quantum yield, 18 035 GM two-photon absorbing cross-section, and undetectable two-photon fluorescence, resulting in 25% 1O2 quantum yield. The unique optical behavior of CNFBBN enabled one-photon fluorescence imaging and two-photon phototherapy against HeLa cancer cells, irradiated at separate wavelengths.

Correction: A facile strategy to realize a single/double photon excitation-dependent photosensitizer for imaging-guided phototherapy against HeLa cancer cells at separate irradiation channels.

Correction for 'A facile strategy to realize a single/double photon excitation-dependent photosensitizer for imaging-guided phototherapy against HeLa cancer cells at separate irradiation channels' by Lin Kong et al., Chem. Commun., 2020, 56, 571-574.

Electrostatically self-assembled polyoxometalates on molecular-dye-functionalized diamond.

We have successfully immobilized phosphotungstic acid (PTA), a polyoxometalate, on the surface of boron-doped diamond (BDD) surface through electrostatic self-assembly of PTA on pyridinium dye-functionalized-BDD. The inorganic/organic bilayer structure on BDD is found to exhibit fast surface-confined reversible electron transfer. The molecular dye-grafted BDD can undergo controllable electrical stripping and regeneration of PTA which can be useful for electronics or sensing applications. Furthermore, we have demonstrated the use of PTA as a molecular switch in which the direction of photocurrent from diamond to methyl viologen is reversed by the surface bound PTA. Robust photocurrent converter based on such molecular system-diamond platform can operate in corrosive medium which is not tolerated by indium tin oxide electrodes.

IR spectroelectrochemical cyclic voltabsorptometry and derivative cyclic voltabsorptometry.

In this paper, we report the IR (infrared) CVA (cyclic voltabsorptometry) and DCVA (derivative cyclic voltabsorptometry) spectroelectrochemical techniques to elucidate an electrochemical mechanism. First we set potassium ferrocyanide as an example to explain the validity of this method. Then the electrochemical redox of two compounds, 1,4-benzoquinone and 1,4-bis(2-ferrocenylvinyl)benzene, was selected to be examined with this method. 1,4-Benzoquinone exhibits two single-electron waves in the cyclic voltammetric (CV) experiment, whereas two electroactive groups (Fc) are contained in p-(Fc-CH=CH)(2)BZ, but only one redox wave is observed. IR CVA results show that three IR absorption peaks in 1,4-benzoquinone, 1232 cm(-1) (the absorption of final production), 1656 cm(-1) (the absorption of original reactant), and 1510 cm(-1) (the absorption of intermediate), and two IR absorption peaks in 1,4-bis(2-ferrocenylvinyl)benzene, 1620 cm(-1) (the absorption of final oxide production) and 1589 cm(-1) (the absorption of intermediate), can be used to track the electron transfer. On the basis of the IR absorbance at the appropriate monitored wavelength (mentioned above), we can analyze simultaneously the concentration change of the corresponding redox transition during CV scans. Also the combination of the DCVA spectroelectrochemical technique with theory analysis allows reconstructing the current-potential (i-E) curve for each step of electron transfer. The reconstructed i-E curve can help us to understand the electron-transfer process. We believe IR CVA and DCVA spectroelectrochemical techniques can be applicable to the study of a wide range of complex electrochemistry processes.

catena-Poly[[iodidocopper(I)]-µ-4,4',6,6'-tetra-methyl-2,2'-(ethyl-enedithio)dipyrimidine-κN:N'].

In the title coordination polymer, [CuI(C(14)H(18)N(4)S(2))](n), the Cu(I) center is trigonally coordinated by two pyrimidine N-atom donors from two distinct dithio-ether ligands and one iodide anion. The Cu and I atoms are located on a twofold axis, whereas the midpoint of the central C-C bond of the dithio-ether ligand is located on an inversion center. Each organic ligand, acting in a bidentate mode, bridges two Cu(I )ions, resulting in the formation of polymeric zigzag chains. The dihedral angle between the two pyrimidine units bonded to the metal center is 88.01 (2)°. The crystal packing is mainly stabilized by van der Waals forces and π-π stacking inter-actions, with an inter-planar distance between the pyrimidine rings of adjacent chains of 3.638 (3) Å.

In vivo two-photon imaging/excited photothermal therapy strategy of a silver-nanohybrid.

A multi-functional nanohybrid (PyAnOH-Ag) with both a two-photon photothermal therapy (TP-PTT) effect and two-photon excited fluorescence (TPEF) imaging performance has been fabricated based on interfacial coordination interactions. The hybrid possesses a high two-photon absorption cross section (δTPA, 4638 GM) and detectable TPEF signals, which leads to excellent two-photon photothermal conversion. Upon irradiation at 840 nm, the temperature of the PyAnOH-Ag-PBS suspension reaches 42 °C in just 4 min, which results in 80% photothermal toxicity on HepG2 cells. The detectable TPEF signals can be used to monitor the cell ablation procedure. Moreover, PyAnOH-Ag exhibits a good phototherapeutic effect on tumor tissue of H22-modelled mice with almost 100% tumor growth inhibition under 840 nm irradiation for 10 min, which is superior to many reported photothermal agents. This strategy of TPEF guided TP-PTT agents can be potentially applied in a variety of therapeutic agents with monitoring ability.

Chlorido[6-phenyl-4-(p-tol-yl)-2,2'-bipyridyl-κN,N']platinum(II).

The asymmetric unit of the title compound, [Pt(C(23)H(17)N(2))Cl], contains two independent mol-ecules with distinct dihedral angles between the central pyridyl and methylbenzene rings [7.77 (2) and 24.07 (2)°]. Short inter-molecular distances [3.582 (6) and 3.600 (6) Å] between the outer pyridine and the PtNC(3) and PtN(2)C(2) rings, respectively, indicate the existence of π-π inter-actions, which link the mol-ecules into stacks along the a axis. The crystal structure is further stabilized by weak C-H⋯π inter-actions.

A novel flurophore-cyano-carboxylic-Ag microhybrid: Enhanced two photon absorption for two-photon photothermal therapy of HeLa cancer cells by targeting mitochondria.

In this study, a novel two-photon photothermal therapy (TP-PTT) agent based on an organic-metal microhybrid with surface Plasmon resonance (SPR) enhanced two-photon absorption (TPA) characteristic was designed and synthesized using a fluorescent cyano-carboxylic derivative 2-cyano-3-(9-ethyl-9H-carbazol-3-yl) -acrylic acid (abbreviated as CECZA) and silver nanoparticles through self-assembly process induced by the interfacial coordination interactions between the O/N atom of CECZA and Ag+ion at the surface of Ag nanoparticles. The coordination interactions caused electron transfer from the Ag nanoparticles to CECZA molecules at the excited state, resulting in a decreased fluorescence quantum yield. The interfacial coordination interactions also enhanced the nonlinear optical properties, including 13 times increase in the TPA cross-section (δ). The decreased fluorescence quantum yield and increased two photon absorption caused by the SPR effect led excellent two-photon photothermal conversion, which was beneficial for the TP-PTT effect on HeLa cancer cells.

Coordination coupling enhanced two-photon absorption of a ZnS-based microhybrid for two-photon microscopy imaging in HepG2.

Coordination coupling induced self-assembly of ZnS microparticles was performed with the help of a π-conjugated sulphur-terminal Zn(ii) complex ZnS2L (L = N-hexyl-3-{2-[4-2,2':6',2''-terpyridin-4'-yl-phenyl]ethenyl}-carbazole). The interactions between ZnS and ZnS2L components at the interface, which were analyzed by far-IR and XPS, resulted in a tunable single-photon excited fluorescence and an enhanced nonlinear optical response, including a two-photon absorption cross section and a two-photon excited fluorescence. Such an enhancement in nonlinear optical properties was triggered by the coordination coupling effect between terminal S atoms of ZnS2L and naked Zn2+ ions at the surface of ZnS particles. Thus, the novel hybrid system displayed a unique two-photon excited fluorescence to facilitate promising two-photon microscopy imaging of HepG2 cells upon NIR light illumination at 840 nm. The hybrid shows a stronger ability to enter the cells than free ZnS2L.

Sensitive determination of anionic surfactants in water with trans-4-[4'-(N-methyl-N-hydroxylethylamino)-cinnamyl-N-9-(4'-(2,2':6',2''-terpyridine))-phenylmethylene]pyridine bromide by the light-absorption ratio variation approach.

The light-absorption ratio variation approach was described and applied to the determination of anionic surfactants (AS) in water with a novel chromophore, trans 4-[4'-(N-methyl-N-hydroxylethylamino)-cinnamyl-N-9-(4'-(2,2':6',2''-terpyridine))-phenylmethylene]pyridine bromide (BTMHCTPP). The complexations between BTMHCTPP and sodium dodecyl sulfate (SDS) and sodium dodecylbenzenesulfonate (SDBS) at pH 3.85 were characterized by the break point approach. Results have shown that both 1BTMHCTPP:1SDS and 1BTMHCTPP:1SDBS complexes were formed, and that deltaA(r) (deltaA(r) = light-absorption ratio variation) is linear for the range of AS between 0.05 and 1.00 mg/L. The limits of detection (3sigma) are 0.045 mg/L for SDS and 0.040 mg/L for SDBS. The complexation is selective in the presence of EDTA, and it has been applied to the analysis of water samples with satisfactory results.

[Synthesis, characterization and properties of N,N-dimethylferrocenylmethylhexadecylammonium bromide].

N,N-dimethylferrocenylmethylhexadecylammonium bromide (FC16AB) was synthesized and characterized by the spectra of UV-Visible, FTIR 1H NMR, ESMS, etc. Surface tensions of different concentrations of FC16AB water solution were measured, which shows that FC16AB has good surface activity. The surface pressure-area (pi-A) curves and differentiated pi-A curves of FC16AB on water, Cl-, and SO(4)2- subphases were studied. The results indicate that FC16AB molecules can form the most stable monolayer on the subphase containing Cl-.

[Synthesis and monolayer behaviors of 4-methyl-5-hydroxy-ethyl isothiazole stearic ester].

4-methyl-5-hydroxy-ethyl isothiazole stearic ester (HISE) was synthesized and characterized by FTIR spectroscopy, 1H NMR and MS. The monolayer-forming ability of HISE was studied in subphases with different pH values using isotherms of surface pressure-area per molecule (pi-A). It was observed that the collapse pressure and the film-forming ability of the monolayers of HISE increased gradually as pH values ascended. Research of differentiated pi-A curves (d pi(/dA-A) indicated that there were one or two phase change points during the compressing process, and the incompressibility and the stability of HISE monolayers on alkalescent subphases were better than on acid subphases.