A new cationic modified coumarin derivative, 7-diethylamino-3-(3-(4-(trimethylbenzenaminium iodide) phenyl) acryloyl)-2H-chromen-2-one (1), was synthesized and characterized by 1H NMR and mass spectra. It had a strong intramolecular charge transfer absorption band around 460 nm with large molar extinction coefficients of 3.94 × 104 M-1 cm-1 in DMF and 3.86 × 104 M-1 cm-1 in PBS, respectively. Moreover, a moderate singlet oxygen quantum yield of 0.16 was obtained for 1 in DMF. Using methylene blue (MB) under a 630 nm laser as reference, the in vitro antimicrobial photodynamic therapy (aPDT) activity of 1 against three strains, gram positive bacteria methicillin-resistant staphylococcus aureus (MRSA), negative bacteria acinetobacter baumannii (A. baumannii) and fungus Candida albicans (C. albicans), was carried out by irradiation with a 457 nm laser. It was shown that 1 had no dark toxicity to these bacteria when its concentration was up to 100 μM, while under the 457 nm laser it could kill them effectively with an over 3 log CFU/ml decrease of the bacterial viability with its concentration up to 5 μM. The aPDT capability of 1 against MRSA and A. baumannii was equivalent to that of MB. For C. albicans, 1 exhibited much better aPDT effect than MB.
Background: An increasing prevalence of Candida infections has emerged with the wide use of immune-suppressants and antibiotics. Photodynamic inactivation (PDI) as a new approach to treat localized Candida infections is an emerging and promising field nowadays. This study evaluated the efficacy of photodynamic therapy using two new Cationic benzylidene cyclopentanone photosensitizers(P1 and P2) against strains of clinical fluconazole–resistant Candida albicans.
Methods: Suspensions and biofilms of Candida species were incubated with P1 and P2 concentrations (0.25~50 μM) for 30 min followed by 532nm laser irradiation. For planktonic suspensions, viability of cells was assayed by CFU counting. For biofilms, the metabolic activity was evaluated by XTT. Results: In PDI of a planktonic culture of clinical fluconazole–resistant Candida albicans, P2 showed the higher efficacy. After incubation with 25 μM of P2 for 30 min and irradiation with 532nm laser (36 J cm-2), the viability of C. albicans planktonic cells decreased by 3.84 log10. For biofilm cells, a higher light dose of 75 mW cm-2 was necessary to achieve 97.71% metabolic activity reduction.
Conclusions: The results of this investigation demonstrated that benzylidene cyclopentanone photosensitizer(P2)is an efficient photosensitizer to kill C. albicans. Moreover, single-species biofilms were less susceptible to PDT than their planktonic counterparts.
Based on the intramolecular charge-transfer (ICT) molecule 2-[bis-(4'-diethylamino-biphenyl-4-yl)-methylene]- malononitrile (D7), two novel malononitrile derivatives (C1 and C2) with 2,7- and 3,6-substituted fluorene as conjugated backbones, respectively, were synthesized, which had the same electro-donor and acceptor groups as D7. The effects of the conjugated backbone and substitution site on optical properties of these compounds were investigated. 3,6-substituted fluorene is a better conjugated unit for ICT compared to 2,7 substitution site, whereas it is still weaker than diphenylmethyl unit in D7. However, due to the rigidity of fluorene, C2 possesses much higher fluorescence quantum yield. The results are supported by TD-DFT calculation. This study develops theoretical basis for designing effective optical or electronic materials.
The 3D fabrication of bio-compatible materials under an aqueous environment is a fundamental requirement for tissue
engineering. In this work, a series of polyethylene glycol- (PEG-), carboxylate anionic group- or pyridyl cationic groupfunctionalized
benzylidene cyclopentanone photo-initiators (B2, B3, X2, X3, Y1 and P1) were synthesized. Their
water-solubility, photophysical properties and cytotoxicity were investigated. Using eosin as reference, their initiation
efficiencies in water-soluble photoactive formulation (SR610 with 20% of DI water) excited by one- or two-photon were
studied. The results showed that there were no significant differences on partial linear photophysical properties of these
initiators, such as [see manuscript] and [see manuscript], but differences on their (see manuscript), Φ, and σmax are clear. In addition, their cytotoxicity
is different. Two PEG-functionalized initiators (B3 and X3) with two PEG groups on one side of benzylidene
cyclopentanone cores have obvious toxicity, while other four intiators are safety to HepG2 cells at the concentration of
20 μM. Moreover, the water-solubility of X2 and X3 (containing two longer PEG) were much better than those of other
four initiators. Using these initiators, 3D micro-structures fabricated by two-photon polymerization of water-soluble
acrylate all could be achieved. In addition, their threshold energies were all lower than 0.5 mW. However, the stiffness of
3D micro-structures was affected by the water-solubility of these photo-initiators. Those structures built by formulations
containing X2 and X3 would collapse easily. Conversely, other structures could sustain very well. This work proves that
B2,Y1,and P1 have extensive application prospects in 3D fabrication for tissue engineering.
A series of amphiphilic benzylidene cycloalkanes ketone photosensitizers C1-C4 with or without folate receptor-targeted
agent were designed and synthesized. Their photophysical properties and in vitro photodynamic therapy (PDT) effects
were studied. The results showed that all compounds exhibited appropriate lipid-water partition coefficients and high
reactive oxygen yields. The introduction of the folate receptor-targeted agent had no obvious influence on the basic
photophysical & photochemical properties of C2 and C4 compared to those of their corresponding prototype compounds
(C1 and C3). In vitro studies were carried out using MCF-7 cells (FR+), Hela cells (FR+) and A549 cells (FR-), which
represented different levels of folate receptor (FR) expression. All of C1-C4 showed low dark toxicity and superior PDT
effects compared with the clinical drug PSD-007 (a mixture of porphyrins). What’s more, folate receptor-targeted
photosensitizers (C2 and C4) achieved higher accumulation and more excellent PDT effects in MCF-7 cells (FR+) and
Hela cells (FR+) than photosensitizers (C1 and C3) without folate receptor-targeted agent and PSD-007. The photocytotoxicity
of these photosensitizers showed no obvious differences in A549 cells (FR-).
A series of benzylidene cyclopentanone photosensitizers modified by polyethylene glycol, carboxylate anionic or pyridyl
cationic groups with gradient lipid-water partition coefficients were reported. Detailed characterization and systematic
studies of these photosensitizers, including their linear and nonlinear photophysical properties, in vitro photodynamic
therapy (PDT) and two-photon excited PDT (2PE–PDT) activities were conducted and compared with a clinical drug
PSD-007 (a mixture of porphyrins). Three of them exhibited appropriate lipid-water partition coefficients, high reactive
oxygen yields, large two-photon absorption cross-section and low dark toxicity under therapy dosage, could be absorbed
efficiently by liver hepatocellular HepG2 cells and presented strong PDT and 2PE-PDT activity by in vitro cell
experiments. Furthermore, in vivo tumor experiments were carried out on BALB/c mouse models using B3 as the
photosensitizer. The results showed that the tumor growth could be effectively suppressed by B3 under 2PE-PDT. This
work demonstrated the feasibility of using a simple molecular structure to construct high efficient photosensitizers for
2PE-PDT.
We report the properties of two series of polyethylene glycol-functionalized bis(arylidene)cycloalkanone photosensitizers
designed for two-photon excited photodynamic therapy (PDT) with the aim to reveal the effect of the size of central ring
on the two-photon excited PDT efficiency. These photosensitizers are the derivatives of bis(arylidene) cyclopentanone
(B2, B3) and bis(arylidene) cyclobutanone (Q1-Q4). The bis(arylidene) cyclopentanone type photosensitizers were
found to have larger two-photon absorption cross sections than the bis(arylidene) cyclopentanone ones with the same
substituents. The singlet oxygen yields of the bis(arylidene) cyclobutanone derivatives are higher than the data of
bis(arylidene) cyclopentanone derivatives. All the studied photosensitizers showed no obvious toxicity under dark
situation. One- and two-photon excited PDT activities were successfully demonstrated by in vitro cell experiments.
Owing to the capability of destructing the cancerous cells under two-photon irradiation, bis(arylidene)cycloalkanone
based photosensitizers with proper substituents can be good candidates for two-photon excited PDT applications in the
future.
A number of optical limiting effects of organic compounds related to two-photon absorption (TPA) processes have
been reported recent years. Actually, very large TPA cross-sections (σ) above thousands GM are obtained. However,
the anti-damage property of organic compounds is still a problem, which limits their application on high power
lasers. Thus, to increase the anti-damage property of organic compounds is important. Dicyanomethylene (DCM) is
a strong electron acceptor. Some reported DCM derivatives show good stability and nonlinear optical activity. In
this work, we investigate the optical limiting and anti-damage properties of two novel DCM derivatives in different
solvents by nonlinear transmission method using femtosecond 1064 nm laser as excitation source. The results show
that solvents have distinct effects on both damage threshold and TPA capability of compounds, indicating the
solvent selection is very important. Moreover, an interesting phenomenon is observed that a linear absorption
appears after damage threshold for both compounds in all solvents, which is supposed due to TPA induced excited
absorption. More detailed discussions are presented.
Dark diffusion transient in a blue-green sensitized holographic photopolymer was investigated based on a previously published theoretical model of monomer diffusion. Diffusion time constant of monomers was obtained by fitting the experimental data to the theoretical model. According to the results of diffusion time constant, experiments were designed and conducted to investigate the evolution of grating efficiency with non-continuous holographic exposure. The experimental result indicated that the saturated diffraction efficiency of a non-continuously exposed grating is about 1.25 times of that of continuously exposed one under the same recording condition.
The results of three independently strategies for the optimizations of electro-optic organic chromophores is
presented. The first strategy to enhance the nonlinear optical response, applied at the molecular level, is the
extension of the conjugation path in a ionic chromophore. The second strategy, applied at the supramolecular
level, is the bottom-up nano-engineering of an inclusion complex of the ionic chromophore in an amylose helix.
The third strategy, also applied a the molecular level, is to use a modulated conjugation path between donor and
acceptor in order to localize eigenfunctions on different parts of the molecule. The first hyperpolarizability of
the different series of compounds has been experimentally determined by frequency-resolved femtosecond hyper-Rayleigh scattering. The effects of the three different enhancement strategies are analyzed and interepreted in
terms of the quantum limits.
The effects of a complex hybrid conjugation path in linear molecules as an strategy to optimize the intrinsic first
hyperpolarizability is investigated. A series of 7 novel chromophores with different hybrid conjugation paths were
synthesized and characterized. Hyper-Rayleigh scattering experiments confirm that complex hybrid conjugation
paths, including benzene, thiophene and/or thiazole rings in combination with azo- and/or ethenyl-linkages,
between a dihydroxyethylamino donor group and different acceptor groups, results in an enhanced intrinsic
hyperpolarizability that exceed the apparent limit for two of the chromophores.
Sum rules have been shown to impose a fundamental limit on the of nonlinear-optical susceptibility. All of the measured values of the hyperpolarizability and second hyperpolarizability over the last 25+ years, be it on- or off-resonance, fall a factor of 103/2 below these limits. Not only is this result scientifically puzzling on a fundamental level; but, has implications on the kinds of practical devices that can be made. In this work, we discuss molecular engineering techniques that aim to break this bottleneck.
We present the results of the combination of two independently valid optimization strategies for the first hyperpolarizability of ionic organic chromophores. The first strategy to enhance the nonlinear optical response, at the molecular level, is the extension of the conjugation path in the chromophore itself. The second strategy, at the supramolecular level, is the bottom-up nano-engineering of an inclusion complex of the chromophore in an amylose helix by self-assembly. We have studied a series of five (dimethylamino)stilbazolium-type chromophores with increasing conjugation length between the (dimethylamino)phenyl donor ring and the pyridinium acceptor ring in combination with four amylose helices of different molecular weights. The first hyperpolarizability of the self-assembled inclusion complexes has been experimentally determined by frequency-resolved femtosecond hyper-Rayleigh scattering at 800 and 1300 nm. These values are compared with experimental values for the free chromophores in solution and with theoretical values. Where experimental values for the hyperpolarizability in solution were lower than theoretically predicted, an enhancement upon inclusion was observed - with the longest chromophore in the best amylose helix showing an enhancement by one order of magnitude. Molecular modelling of the inclusion of the chromophore suggests that the coplanarity of the two rings is more important than all-trans configuration in the conjugation path. The degree of enhancement, however, is not enough to breach the apparent limit of the first hyperpolarizability which is about an order of magnitude below the fundamental limit calculated by Kuzyk. This analysis confirms the determining role of the arrangement of the excited-state energy levels on the nonlinear response.
Colloidal crystals with three-dimensional periodicities in the refractive index have a photonic band gap (PBG) in which electromagnetic waves are forbidden. We present a method to fabricate stacked colloidal crystals containing a two-dimensional defect as a middle layer by combining vertical deposition method with Langmuir-Blodgett (LB) technique. The defect layer introduces an impurity mode within the optical stop band, which is observed as a defect peak (pass band) in the optical density spectrum. The dependence of the position of the impurity mode on the size of the defect layer is investigated. It is found that the defect behaved as a donor impurity, as it originates from the bottom of the conduction band. We also study the effect of the sphere size of the surrounding colloidal crystal on the position of defect model through changing the sphere size of the surrounding colloidal crystal with a fixed sphere size of the defect layer.
Electronic structural modifications of previously reported highly conjugated (polypyridyl)metal-(porphinato)zinc(II) NLO chromophores have been carried out. A primary focus of these modifications probed the role played by the porphyrin macrocycle in effecting large molecular hyperpolarizabilities; specifically, its meso-aryl substituents were replaced with electron withdrawing perfluoroalkyl groups. In doing so, we are effectively lowering HOMO and LUMO of the porphyrin fragment by 0.35eV while retaining the extensive mixing of B, Q, and CT states, and enforcing head-to-tail transition dipole alignment of the component metal-polypyridyl and porphyrin based chromophoric building blocks; this enables supermolecular structures with singly degenerate excited states polarized along the long donor-to-acceptor (D-to-A) charge transfer axis. This work will be placed in the context of ongoing electrooptic experiments and efforts aimed at fabricating new materials from these supermolecular chromophoric species.
The syntheses and electrooptic properties of a family of nonlinear optical chromophores are described. Typically, these species feature an ethyne-elaborated, highly polarizable porphyrinic component, and metal polypyridyl complexes that serve as integral donor and acceptor elements. The frequency dependence of the dynamic hyperpolarizability of a wide-range of these chromophores, that vary widely with respect to their electronic structure, was determined from hyper-Rayleigh light scattering (HRS) measurements carried out at fundamental incident irradiation wavelengths (λinc) of 830, 1064, and 1300 nm. These data show that: (i) Coupled oscillator photophysics and metal-mediated cross-coupling can be exploited to elaborate high βλ supermolecules that exhibit significant excited-state electronic communication between their respective pigment building blocks; (ii) High-stability metal polypyridyl compounds constitute an attractive alternative to electron releasing dialkyl- and diarylamino groups, the most commonly used donor moieties in a wide-range of established NLO dyes, and long-recognized to be the moiety that often limits the thermal stability of such compounds; (iii) This design strategy clearly enables ready elaboration of extraordinarily large βλ chromophores at telecommunication-relevant wavelengths; and (iv) Multiple charge-transfer (CT) transitions within a single chromophore can be designed to have transition dipole moments of the same or opposite sign; because the sign of the resonance enhancement factor is frequency dependent, appropriate engineering of the relative contributions of these CT states at a given wavelength provides a new means to regulate the magnitude of dynamic hyperpolarizabilities.
A novel crosslinkable polyurethane is used as the core layer of the electro-optic (E-O) modulator. The refractive index and dispersion of this material have been detected by analyzing the F-P oscillation in transmission spectra. Calculated results from the effective index method are given to design the Mach-Zehnder and straight 5-layer ridge waveguide device (including the metal electrodes). With light at 1.31 micrometers being fiber coupled into waveguide, the mode properties of these devices have been demonstrated in a micron control system. The guided mode is accordant with the theoretical analysis.
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