High Extinction Coefficient Research Articles

Synthesis and evaluation of new pyropheophorbide-a derivatives for CAIX-targeted photodynamic therapy

A major challenge of photodynamic cancer therapy is to improve the selectivity of photosensitizers to the target pathological tissue. To overcome this issue, a series of chlorophyll derivatives containing thiadiazole sulfonamide moiety or 4-(2-aminoethyl)benzene sulfonamide moiety were designed and synthesized. These compounds showed intense absorption at 670 nm with high molar extinction coefficients, and strong fluorescence emission around 674 nm. Their singlet oxygen generation ability was also demonstrated to be excellent. They displayed obvious photo-cytotoxic effects to MDA-MB-231 cells in vitro and to tumor-bearing Balb/c nude mice in vivo. The fluorescence images exhibited that N-[2-((5-Sulfamoyl-1,3,4-thiadiazol-2-yl)amino)-2-oxoethyl]pyropheophorbide (AZ-Ppa-2) preferentially accumulated in MDA-MB-231 cell lines overexpressing CAIX (Carbonic anhydrase IX). Molecular Docking simulation revealed that AZ-Ppa-2 could closely bind to the active site residues of CAIX. Sub-organelle localization test indicated that AZ-Ppa-2 primarily localized in the lysosomes. These experiments suggested that AZ-Ppa-2, as a photosensitizer targeting CAIX, possessed an outstanding PDT anti-tumor effect with lasting regression of tumors, and deserved for further study.

Near-infrared absorption and photothermal properties of heptamethine pyrylium dyes with bistriflimide anion

Numerous research endeavors have focused on the near-infrared (NIR) absorption properties and applications of polymethine dyes. Herein, we synthesize two heptamethine pyrylium dyes, TBCY-5 and TBCY-6, containing 5- and 6-membered, respectively, rings in the π-conjugated bridge, thus producing NIR dyes with maximum absorption exceeding 1000 nm. The effect of counter anions on the NIR absorption property was examined by exchanging perchlorate (ClO4) anions with bistriflimide (TFSI) anions. TBCY dyes with TFSI possessed good solubility and a high molar extinction coefficient compared to the dyes with ClO4. TBCY-5 and TBCY-6 showed negative solvatochromism, exhibiting a hypsochromic shift of the NIR absorption in polar solvents. Photothermal experiments revealed that TBCY-5 and TBCY-6 were suitable as efficient photothermal materials.

Tannery Dye Wastewater Treatment in Batch and Once through Continuous Mode by Electro-Oxidation Using MMO Electrode

Treatment of tannery wastewater is challenging because dye concentrations in tannery wastewater are typically lower than any other chemical compound, but their high molar extinction coefficients result in waste streams with heavy coloration even at very low concentrations. In the present work, treatment of Acid Black 210 dye wastewater in batch and once through continuous mode by electro-oxidation through novel Mix Metal Oxide Ti/TiO2-RuO2-IrO2 electrode was explored. The effects of parameters were studied in a laboratory scale to observe the effects on color removal, degradation, and energy consumption efficiency. A response surface methodology with a full factorial BBD model was used for designing and optimizing responses. Multi-response optimization with a desirability function was used to optimize the multiple responses. Optimum conditions for 500 ppm Acid Black 210 dye were achieved at a current intensity of 1.6 A, pH of 6.48, and treatment time of 35 min. The BBD model efficiently interacts between optimizing variables, and its prediction matched the experiment results. At the optimum condition, a once-through continuous setup was run for the flow rates ranging from 5–30 ml min−1. The intermediates formed during the treatment process were analyzed through GC-MS. TOC removal, COD removal, and toxicity bioassay of the sample was also done for disposability analysis.

Photothermal Atomic Force Microscopy Coupled with Infrared Spectroscopy (AFM-IR) Analysis of High Extinction Coefficient Materials: A Case Study with Silica and Silicate Glasses.

Photothermal atomic force microscopy coupled with infrared spectroscopy (AFM-IR) brings significant value as a spatially resolved surface analysis technique for disordered oxide materials such as glasses, but additional development and fundamental understanding of governing principles is needed to interpret AFM-IR spectra, since the existing theory described for organic materials does not work for materials with high extinction coefficients for infrared (IR) absorption. This paper describes theoretical calculation of a transient temperature profile inside the IR-absorbing material considering IR refraction at the interface as well as IR adsorption and heat transfer inside the sample. This calculation explains the differences in peak positions and amplitudes of AFM-IR spectra from those of specular reflectance and extinction coefficient spectra. It also addresses the information depth of the AFM-IR characterization of bulk materials. AFM-IR applied to silica and silicate glass surfaces has demonstrated novel capability of characterizing subsurface structural changes and surface heterogeneity due to mechanical stresses from physical contacts, as well as chemical alterations manifested in surface layers through aqueous corrosion.

Pyridyl anchored indolium dyes for the p-type dye sensitized solar cell

Three new thiophenyl bridged triarylamine-donor based dyes with pyridyl anchoring groups and indolium acceptors have been synthesized and studied as sensitizers for the p-type dye-sensitized solar cell (p-DSSC). Compared to known dicyano and pyridinium dyes with the same triarylamine cores, these new sensitizers have broadened and red-shifted UV–vis absorption spectra, with high extinction coefficients and absorption extending beyond 700 nm. TD-DFT calculations on the indolium family indicate that these dyes combine strong donor acceptor communication, with a high degree of charge separation in the excited state – an ideal combination for sensitizer dyes. The phenylpyridyl anchored bis-indolium gives the highest power conversion efficiency (0.097%) through a short circuit photocurrent (JSC) of 3.04 mA cm−2, open circuit voltage (VOC) of 97 mV and fill factor of 36%. This exceeds the performance of the P1 reference dye in this study, and represents the best performance so far for a cationic, pyridine anchored p-DSSC dye.

Effective PDT/PTT dual-modal phototherapeutic killing of bacteria by using poly(N-phenylglycine) nanoparticles.

This study investigated, for the first time, the antimicrobial properties of polyethylene glycol-functionalized poly(N-phenylglycine) nanoparticles (PNPG-PEG NPs). PNPG-PEG NPs exhibit high extinction coefficient in the near-infrared (NIR) region; they can convert light energy into heat energy with high thermal transformation efficiency. Additionally, they can generate cytotoxic reactive oxygen species (ROS) upon light irradiation. Also, PNPG-PEG NPs are not cytotoxic. All these properties make them appropriate for combined dual-modal photothermal and photodynamic therapies. The antibacterial activity of PNPG-PEG NPs was assessed using Escherichia coli (Gram-negative) and Staphylococcus aureus (Gram-positive) pathogenic strains. The results revealed that NIR light (810nm) irradiation for 10min could kill effectively the planktonic bacteria and destroy Escherichia coli and Staphylococcus aureus biofilms. The results demonstrated that PNPG-PEG NPs represent a very effective nanoplatform for killing of pathogenic bacteria.

Recent Progress of Cyanine Fluorophores for NIR-II Sensing and Imaging.

The cyanine fluorophores, a kind of classic organic fluorophores, are famous for their high extinction coefficient, simple synthetic route, and relatively long absorption and emission wavelengths. Moreover, the excellent biocompatibility and low toxicity in biological samples make cyanine fluorophores show excellent application value in the biomedical field, especially in Near-Infrared II (NIR-II) sensing and imaging. In this review, we briefly outline the history, characteristics, and current state of development of cyanine fluorophores. In particular, we described the application of cyanine fluorophores in NIR-II sensing and imaging. We hope this review can help researchers grab the latest information in the fast-growing field of cyanine fluorophores for NIR-II sensing and imaging.

A Chromic and Near‐Infrared Emissive Mechanophore Serving as a Versatile Force Meter in Micelle–Hydrogel Composites

AbstractMechanofluorochromic polymers, which can indicate damage or excessive stress in highly polarized environments with a clearly perceptible optical signal, are potentially useful in a variety of exciting applications. However, most reported fluorochromic mechanophores exhibit poor color contrast and fluorescence penetration, or are irreversible in polarized phase after mechanical activation. Here, this challenge is tackled by designing and engineering a novel near‐infrared (NIR) emissive, rhodanmin derived mechanophore (Rh‐Co) in a kind of hydrogel composites. The ring‐opened Rh‐Co is unique in high molar extinction coefficient and bright NIR emission with such optical transition under force directly corresponding to covalent bond scission and reversibly switchable in an aqueous environment. The hydrogel composites thus can sensitively change their color from yellow to green and emit highly penetrated NIR fluorescence when different types of forces (tension, compression, and friction force) are applied, highlighting the potential applications of Rh‐Co in biocompatible environments as a “force meter.”

Study of the structure, roughness and optical properties of HfO2 coatings deposited on microscopic glass substrates

In this work, we deposited HfO2 films on microscopic glasses by direct current (DC) magnetron sputtering for different deposition times, namely 120 min and 180 min. The phase composition of the coatings was assessed by X-ray diffraction (XRD). The surface roughness, the optical constants, the refractive index n, the extinction coefficient k and the thickness of the prepared HfO2 coatings were estimated by ellipsometric measurements. The XRD results pointed to the presence of a polycrystalline monoclinic phase. A slight difference was found in the surface roughness of the two HfO2 films, which was 5.1 nm and 5.7 nm, respectively, for the deposition times of 120 minutes and 180 minutes. The optical constants n and k were determined at the wavelength of 630 nm by using the Cauchy model. The results showed almost the same value of the refractive index for both films (1.88 and 1.89), but a higher extinction coefficient (0.01) for the film grown for 180 minutes, compared to a value of 0.007 for the one deposited for 120 minutes. The films thickness was 410 nm and 780 nm for deposition times of 120 minutes and 180 minutes, respectively. The deposited HfO2 films were transparent, with the longer deposition time corresponding to an improved reflection (57%), compared to the 28% reflection for the film deposited for 120 minutes.

Bifunctional free radical photoinitiator based on syringaldehyde

AbstractSyringaldehyde, a natural compound, was chosen to design a novel acylphosphine oxide (S1). Maximum absorption at 337 nm with very high molar extinction coefficient (above 13,000 M−1 cm−1) was detected for S1. As a type I photoinitiator, S1 could initiate the photopolymerization of TMPTA and ca. 50% of the double bond conversion (DC) could be obtained upon irradiation of LED@385 nm or LED@420 nm for 300 s. As coinitiator in type II system, S1 could cooperate with DETX and exhibit higher performance (ca. 60% of DC) than typical pair of DETX and EDAB. Density functional theory (DFT) is used to study the characteristics of excited state and transition manners of S1 after light absorption. Orbital distributions of singlet and triplet electron clouds, transition energy levels, and oscillator strength are also predicted. Results suggest that after intersystem crossing (ISC) and internal conversion (IC), free radicals formed through α‐cleavage (Norrish Type I reaction) or breakage of O‐H bond in S1. All results indicate that S1 could act as a bifunctional photoinitiator. Based on the above results, the roles of S1 during photoinitiation are also proposed.

Bifacial dye-sensitized solar cells utilizing green-colored NIR sensitive unsymmetrical squaraine dye

Dye-sensitized solar cells (DSSCs) with the capability of photon harvesting from both front and rear sides, consisting of newly developed NIR dye (SQ-140), iodine-based redox electrolyte, and transparent counter electrode with high bifaciality factor (BFF) and good cumulated photoconversion efficiency (PCE), are successfully fabricated and characterized. The use of transparent TiO2-based photoanode leads to improved BFF as compared to its opaque TiO2 counterparts: from 74% to 86% under similar experimental conditions and device parameters. The high molar extinction coefficient of the NIR dye SQ-140, needing a thinner TiO2 layer, was found to be advantageous to maintaining the high BFF even in thicker TiO2 films without serious compromise in the PCE. The lower efficiency of the bifacial DSSC under rear illumination was attributed to the hampered optical penetration as well as absorption of light by the intense colored iodine-based redox electrolyte.

Aggregation Turns BODIPY Fluorophores into Photosensitizers: Reversibly Switching Intersystem Crossing On and Off for Smart Photodynamic Therapy

Aggregation Turns BODIPY Fluorophores into Photosensitizers: Reversibly Switching Intersystem Crossing On and Off for Smart Photodynamic Therapy

A water-soluble thiophene-croconaine dye with a high molar extinction coefficient for NIR fluorescence imaging-guided synergistic photothermal/photodynamic therapy of cancer.

Phototherapeutic agents with near-infrared (NIR) fluorescence, strong reactive oxygen species generation and photothermal conversion capabilities are highly desirable for use in cancer therapy. Herein, a water-soluble NIR croconaine dye (TCR) with a thiophene-croconaine rigid core and two symmetric alkyl chains was designed and synthesized. TCR exhibits intense NIR absorption and fluorescence that peaked at 780 and 815 nm, respectively, with a high molar extinction coefficient of 1.19 × 105 M-1 cm-1. Moreover, TCR has a high photothermal conversion efficiency of 77% and is capable of generating hydroxyl radicals (OH˙) under 735 nm laser irradiation. Based on these outstanding properties, TCR has proven its application in NIR fluorescence imaging-guided synergistic photothermal/photodynamic therapy of cancer.

Robust singlet fission process in strong absorption π-expanded diketopyrrolopyrroles.

Singlet fission (SF) has drawn tremendous attention as a multiexciton generation process that could mitigate the thermal loss and boost the efficiency of solar energy conversion. Although a SF-based solar cell with an EQE above 100% has already been fabricated successfully, the practical efficiency of the corresponding devices is plagued by the limited scope of SF materials. Therefore, it is of great importance to design and develop new SF-capable compounds aiming at practical device application. In the current contribution, via a π-expanded strategy, we presented a new series of robust SF chromophores based on polycyclic DPP derivatives, Ex-DPPs. Compared to conventional DPP molecules, Ex-DPPs feature strong absorption with a fivefold extinction coefficient, good molecular rigidity to effectively restrain non-radiative deactivation, and an expanded π-skeleton which endow them with well-suited intermolecular packing geometries for achieving efficient SF process. These results not only provide a new type of high-efficiency SF chromophore but also address some basic guidelines for the design of potential SF materials targeting practical light harvesting applications.

Distinguishing cancer cells from normal cells with an organelle-targeted fluorescent marker.

In this paper we report a hemicyanine dye that is used to distinguish cancer cells from normal cells with its ability to target different organelles. Probe 1, a red emission hemicyanine functional dye, was connected to oxazolo[4,5-b]pyridine and diethylaminobenzene with a double bond. The maximum absorption peaks of probe 1 were located in the 509-552 nm range in organic solvents. Meanwhile, the probe possessed a high molar extinction coefficient (5.50 × 104 M-1 cm-1 in DMSO) with high photostability. The maximum emission wavelength of the probe ranged from 572 nm to 644 nm, and it also had a large Stokes shift (126 nm in DMSO). In particular, the probe showed weak fluorescence in water (Φ = 0.016), whereas it displayed strong fluorescence at 595 nm in β-cyclodextrin (β-CD) solution (Φ = 0.13). In addition, cell colocalization experiments showed that probe 1 (3 μM) was located in the endoplasmic reticulum in cancer cells, while it could target lysosomes in normal cells. What's more, further cell imaging experiments demonstrated that the average fluorescence intensity of probe 1 (0.3 μM) in cancer cells increased with the addition of β-CD, but it did not occur in normal cells. The study provides a convenient way to distinguish cancer cells from normal ones, which has potential for application in the early detection of cancer.

Natural flavylium-inspired far-red to NIR-II dyes and their applications as fluorescent probes for biomedical sensing.

Fluorescent probes that emit in the far-red (600-700 nm), first near-infrared (NIR-I, 700-900 nm), and second NIR (NIR-II, 900-1700 nm) regions possess unique advantages, including low photodamage and deep penetration into biological samples. Notably, NIR-II optical imaging can achieve tissue penetration as deep as 5-20 mm, which is critical for biomedical sensing and clinical applications. Much research has focused on developing far-red to NIR-II dyes to meet the needs of modern biomedicine. Flavylium compounds are natural colorants found in many flowers and fruits. Flavylium-inspired dyes are ideal platforms for constructing fluorescent probes because of their far-red to NIR emissions, high quantum yields, high molar extinction coefficients, and good water solubilities. The synthetic and structural diversities of flavylium dyes also enable NIR-II probe development, which markedly advance the field of NIR-II in vivo imaging. In the last decade, there have been huge developments in flavylium-inspired dyes and their applications as far-red to NIR fluorescent probes for biomedical applications. In this review, we highlight the optical properties of representative flavylium dyes, design strategies, sensing mechanisms, and applications as fluorescent probes for detecting and visualizing important biomedical species and events. This review will prompt further research not only on flavylium dyes, but also into all far-red to NIR fluorophores and fluorescent probes. Moreover, this interest will hopefully spillover into applications related to complex biological systems and clinical treatments, ranging in focus from the sub-organelle to whole-animal levels.

Microstructure and Optical Properties Study of Nd-doped BiFeO3 (Ba1-xNdxFeO3) Films on Quartz Substrate

Bismuth ferrite oxide (BFO), due to its remarkable properties, has become one of the most attractive multiferroic materials to be extensively studied. BFO doped with various materials, including Neodymium (Nd), could improve its properties that apply to numerous electronic devices. However, the studies related to the properties of Nd-doped BFO (Ba1-xNdxFeO3) thin films on a quartz substrate, especially the optical properties, are relatively scarce. This study aimed to investigate the microstructure and optical properties of the Nd-doped BFO (BNFO) as the variation of the Nd concentrations. The BNFO thin films with Nd concentrations of 0.05 (BNFO5); 0.1 (BNFO10); and 0.2 (BNFO20) have been deposited on the quartz substrates via the sol-gel method and using spin coating. The films were annealed at 600 °C for 1.5 h. The XRD result of the BNFO films revealed a single phase of BFO with a cubic structure. The lattice constants and volume cells of the films declined with more Nd. Meanwhile, the crystallite size and lattice strain changed due to the change in the Nd number. Additionally, the morphology images showed the pores on the films’ surface and the different film thicknesses of each BNFO film. From the optical characterization, the transmittance spectra of the BNFO films tended to rise as the more Nd amount doped, in which the BNFO20 had the highest transmittance. The BNFO10 had the highest refractive index, followed by the BNFO5 and BNFO20. Contrarily, the BNFO20 had the highest extinction coefficient and spectra, followed by the BNFO5 and BNFO10. Further, the bandgap values of the BNFO5, BNFO10, and BNFO20 were 2.75, 2.85, and 2.64 eV, respectively. Accordingly, due to the highest Nd amount that most impacted its microstructure, the BNFO20 exhibited the lowest bandgap value compared to the other films that are good for photovoltaic applications.

Lead-Free Cs2 AgSbCl6 Double Perovskite Nanocrystals for Effective Visible-Light Photocatalytic C-C Coupling Reactions.

Lead halide perovskite nanocrystals (NCs) have been regarded as a promising potential photocatalyst, owing to their high molar extinction coefficient, low economic cost, adjustable light absorption range, and ample surface active sites. However, the toxicity of lead and its inherent instability in water and polar solvents could hinder their wide application in the field of photocatalysis. Herein, with α-alkylation of aldehydes as a model reaction, C-C bond-forming is demonstrated in high yield by using lead-free double perovskite Cs2 AgSbCl6 NCs under visible light irradiation. Moreover, the photocatalytic performance is simply improved by rational control of the surface ligands and a reaction mechanism involving a radical intermediate is proposed. Although the stability requires further amelioration, the results indicate the enormous potential of lead-free double perovskite NC photocatalysts for organic synthesis and chemical transformations.

Enhancing Intersystem Crossing by Intermolecular Dimer-Stacking of Cyanine as Photosensitizer for Cancer Therapy

Enhancing Intersystem Crossing by Intermolecular Dimer-Stacking of Cyanine as Photosensitizer for Cancer Therapy

Cyclodextrins with Multiple Pyrenyl Groups: An Approach to Organic Molecules Exhibiting Bright Excimer Circularly Polarized Luminescence.

We report a simple and effective approach to organic molecules exhibiting bright circularly polarized luminescence (CPL) by combining a chiral cyclic molecular scaffold and multiple excimer-enabling moieties. An α-cyclodextrin (CyD) scaffold was modified with six pyrenyl groups to obtain pyrene-cyclodextrins (PCDs) in a one-step synthesis from commercially available compounds. The PCDs exhibited high molar extinction coefficients (ϵ≈105 M-1 cm-1 ), polarized emission with a good dissymmetry factor (|glum |≈10-2 ), and quantum yield (Φf ≈0.5). Owing to the excellent photophysical properties of the PCDs, the circularly polarized luminescence brightness (BCPL ) reached 340 M-1 cm-1 . Photophysical and chiroptical studies of the PCDs with only five pyrene units and with linkers of various lengths connecting the CyD with the pyrene units revealed that the formation of a pyrene excimer in a spatially crowded environment is crucial for CPL anisotropy. This study paves the way for the development of bright CPL organic molecules.