Target Chromophores Research Articles

A Single-Shot Technique for Measuring Broadband Two-Photon Absorption Spectra in Solution.

Applications involving two-photon activation, including two-photon fluorescence imaging, photodynamic therapy, and 3D data storage, require precise knowledge of the two-photon absorption (2PA) spectra of target chromophores. Broadband pump-probe spectroscopy using femtosecond laser pulses provides wavelength-dependent 2PA spectra with absolute cross sections, but the measurements are sometimes complicated by cross-phase modulation effects and dispersion of the broadband probe. Here, we introduce a single-shot approach that eliminates artifacts from cross-phase modulation and enables more rapid measurements by avoiding the need to scan the time delay between the pump and the probe pulses. The approach uses counterpropagating beams to automatically integrate over the full interaction between the two pulses as they cross. We demonstrate this single-shot approach for a common 2PA reference, coumarin 153 (C153), in three different solvents using the output from a Yb:KGW laser. This approach provides accurate 2PA cross sections that are more reliable and easier to obtain compared with scanning pump-probe methods using copropagating laser beams. The single-shot method for broadband two-photon absorption (BB-2PA) spectroscopy also has significant advantages compared with single-wavelength measurements, such as z-scan and two-photon fluorescence.

33527 What is the most effective picosecond laser protocol for tattoo removal? A comparative study by histopathologic review

Background: Picosecond lasers have become widely adapted as the mainstay of tattoo removal due to their faster heating of target chromophores and consequently more effective tattoo removal. Different protocols for tattoo removal using the picosecond laser are actively being studied. Our investigation focuses on the R20 method: repeated exposure to laser light at 20-minute intervals in a single session. Several preliminary studies have shown that R20 technique could be effective in reducing treatment time while maintaining efficacy.

33527 What is the most effective picosecond laser protocol for tattoo removal? A comparative study by histopathologic review

Background: Picosecond lasers have become widely adapted as the mainstay of tattoo removal due to their faster heating of target chromophores and consequently more effective tattoo removal. Different protocols for tattoo removal using the picosecond laser are actively being studied. Our investigation focuses on the R20 method: repeated exposure to laser light at 20-minute intervals in a single session. Several preliminary studies have shown that R20 technique could be effective in reducing treatment time while maintaining efficacy. Objective: This study aims to compare different picosecond laser techniques in clearing tattoos. Methods and materials: Three patients with tattoos (1 on foot, 2 on arms) underwent skin biopsy followed by laser tattoo removal. The target site was divided into 4 areas, each of which received different protocols: picosecond laser alone, R20 method, picosecond MLA followed by picosecond toning, and picosecond laser after gel application. The protocols were all performed five times at 1-month intervals. After treatment completion, 1 patient underwent biopsy of all four treatment sites while the other 2 underwent biopsy only at the R20 treatment area. Results: Histopathologic evaluation showed that the R20 treatment site had the least remaining intradermal pigmentation. Picosecond MLA followed by picosecond toning laser was shown to have the following best outcome. Conclusion: Our report compares skin biopsy findings before and after laser treatment and clinical results for tattoo removal. Although the number of cases is small, our preliminary findings suggest that the Pico R20 is favorable for tattoo removal.

Quadrupolar fluorophores with tetrafluorobenzene central electron acceptor

Seven novel quadrupolar chromophores based on 1,2,4,5-tetrafluorobenzene (TFB) central electron acceptor unit and methoxythiophene peripheral donor were synthetized and described. Fundamental structure-property relationships were elucidated via thermal, electrochemical and optical measurements. These revealed that the properties are mostly affected by the used π-linker. Variation of the π-linker resulted in tuning of the HOMO-LUMO gap. The LUMO clearly reflects planarity, polarizability and electronic transparency of the utilized π-linker. The absorption maxima of target chromophores were found within the range of 346–412 nm and the emission maxima of emissive derivatives were found within the range of 411–499 nm. Novel TFBs were compared with TFBs previously described in the literature. The experimental data are further corroborated by theoretical calculations.

Acceptor-induced photoisomerization in small thienothiophene push-pull chromophores

Six new push-pull chromophores based on thieno[3,2-b]thiophene were prepared by a facile two step synthesis of extended aldehyde and its subsequent Knoevenagel condensation. Optoelectronic and thermal properties of target chromophores were tailored by attaching various electron-withdrawing moieties. Variation of the acceptor resulted in tuning of the HOMO-LUMO gap by exclusive altering the LUMO level; the absorption maxima were found within a range of 428–479 nm independently on the used solvent. A reversible E-Z photoisomerization has been observed for the chromophores with particular electron withdrawing moieties. Whereas irradiation of the chromophores with RoyalBlue LED afforded a dynamic equilibrium of E and Z isomers, the Z-isomer is fully regenerated in the dark. Thus, the switching properties can be easily modulated by attaching proper electron acceptor. According to the performed DFT calculations, both isomers differ in the fundamental (non)linear optical properties.

Diarylpyrazine-based position isomers: A detailed study of optical properties and structure-property relationship

A versatile and expeditious synthetic route to pyrazine-based symmetric and asymmetric chromophores decorated with donor-acceptor (D-A) has been designed to study their structural effects on optical properties. Suzuki-Miyaura coupling of dihalopyrazine with various aryl boronic acids was synthesized under microwave condition. Pyrazine functionalized at C-2, C-5 and C-6 serve as acceptor to construct linear and angular push-pull chromophores. The photophysical, electrochemical and thermal properties of all the target chromophores were systematically investigated and the results were correlated theoretically by density functional theory computations. The emission wavelength was significantly red-shifted by introduction of strong electron withdrawing group (CN). The permutation of terminal donor acceptor units tunes the optoelectronic properties in a predictable way, aiding in the rational design of small molecule for luminescent materials. These chromophores displayed multicolour change in different solvents, exhibiting good solvatochromism with a large Stokes shift.

Novel dibenzothiophene chromophores with peripheral barbituric acceptors

A series of novel chromophores based on central 2,8-disubstituted dibenzothiophene (DBT) or dibenzothiophene-S,S-dioxide (DBTO) has been designed and prepared. The interconnection of DBT(O) central scaffold with two peripheral barbituric acceptors via various π-spacer allowed significant property tuning of target chromophores. Four new final chromophores and six DBT(O)-intermediates have been successfully synthesized and fully characterized. Experimental and calculated data showed that the fundamental properties are affected by the chromophore A-π-D-π-A or A-π-A-π-A arrangement (DBT vs. DBTO) and the π-linker (ethenylene vs. ethynylene). Thorough structure-property relationships have been elucidated and discussed in detail.

Direct connection of an amine to oligothiophene to generate push-pull chromophores for organic photovoltaic applications

Through the direct connection of the donor nitrogen atom to oligothiophenes, herein we report three novel, donor materials for evaluation in bulk-heterojunction solar cells. The direct substitution enhances the charge transfer transition, thus improving the light-harvesting ability of the target chromophores. The influence of various terminal acceptor functionalities on the optoelectronic and photovoltaic properties was systematically studied. The target chromophore, T3, bearing oxoindenemalononitrile acceptor unit afforded a power conversion efficiency of 6.12% when paired with the conventional acceptor, PC61BM, a result that is the highest in the current literature for push-pull chromophores.

Dipolar NLO Chromophores Bearing Diazine Rings as π-Conjugated Linkers.

The synthesis of a series of push-pull derivatives bearing triphenylamine electron-donating group, cyclopenta[c]thiophen-4,6-dione electron acceptor and various π-linkers including (hetero)aromatic fragments is reported. All target chromophores with systematically varied π-linker structure were further investigated by electrochemistry, absorption measurements, and EFISH experiments in conjunction with DFT calculations. Based on electrochemical and photophysical measurements, when a polarizable 2,5-thienylene moiety is embedded into the chromophore π-backbone the highest intramolecular charge transfer (ICT) is observed. Benzene, pyrimidine, and pyridazine derivatives exhibit lower polarizability and extent of the ICT across these π-linkers. The elongation of the π-conjugated system via additional ethenylene linker results in a significant reduction of the HOMO-LUMO gap and an enhancement of the NLO response. Whereas it does not significantly influence electrochemical and linear optical properties, the orientation of the pyrimidine ring seems to be a key parameter on the μβ value due to significant variation of the dipolar moment (μ) value. In 2a and 2c, pyrimidine is oriented to behave as an acceptor and thus generate dipolar molecule with μ above 5 D, whereas in 2b and 2d ground state dipole moment is significantly reduced. This study seems to indicate a high aromaticity of pyrimidine and pyridazine derivatives, close to the benzene analogues and significantly higher than thiophene analogues.

Malonic Acid Derivatives on Duty as Electron‐Withdrawing Units in Push–Pull Molecules

Based on the 2‐(N‐piperidinyl)thiophene central donor, 32 model push–pull molecules with systematically varied malonic acid‐derived peripheral acceptors have been prepared. Further property tuning has been achieved by modifying the π‐linker and the structural arrangement (linear vs. quadrupolar D–π–A systems). Malonic acid derivatives such as cyanoacetic acid, malondinitrile, diethyl malonate, Meldrum′s acid, and N,N′‐dibutyl(thio)barbituric acid as well as 1,3‐diketo analogues dimedone and indan‐1,3‐dione were employed as acceptor moieties. Knoevenagel condensation with four thiophene aldehydes afforded the target chromophores in satisfactory yields. The electron‐withdrawing abilities of malonic acid acceptors were examined both by experiment including X‐ray analysis, differential scanning calorimetry, electrochemistry, and UV/Vis absorption spectroscopy, and by DFT calculations. Details of the structure–property relationships have been elucidated. According to the increasing electron‐withdrawing ability, the widely used malonic acid acceptor units can be ordered: diethyl malonate ≤ cyanoacetic acid < malondinitrile < Meldrum's acid < dimedone ≤ N,N′‐dibutylbarbituric acid < indan‐1,3‐dione ≤ N,N′‐dibutylthiobarbituric acid.

Paediatric laser dentistry. Part 1: General introduction.

Knowledge of the physical characteristics of different laser lights and optical and thermal properties of oral tissues is very important to understand the interaction of dental lasers with biological tissues. Choosing the correct dental laser is crucial to match specific wavelengths with target chromophores of different tissues; this affinity makes laser irradiation selective and therefore minimally invasive. Various types of lasers are used in dentistry, offering a viable alternative to low and high-speed handpieces and surgical blades, and also minimising fear and discomfort of the patient. Lasers can provide innovative and minimally invasive therapies in different branches of dentistry including preventive and restorative dentistry, traumatic injury treatments and surgical procedures. Laser has also biostimulating and anti-inflammatory effects, as well as analgesic effect.

Proaromatic pyranylidene chalcogen analogues and cyclopenta[c]thiophen-4,6-dione as electron donors and acceptor in efficient charge-transfer chromophores

Fifteen new push-pull chromophores based on a proaromatic pyranylidene donor and its chalcogen analogues and various electron acceptor moieties were synthesized in a straightforward manner. These model molecules were designed and prepared to investigate the concept of proaromaticity as a tool to tune the fundamental properties of push-pull systems. All target chromophores with systematically varied structure were further investigated by electrochemistry, absorption spectra, and EFISH experiment in conjunction with DFT calculations. Employing structural variations such as chalcogen/acceptor replacement, extension of the π-system, and the position of substitution along the pyran ring, the HOMO-LUMO gap can be tuned within the range of 2.18 to 1.41 eV. A new and powerful electron withdrawing moiety, combining features of polarizable thiophene and successful indane-1,3-dione acceptor, cyclopenta[c]thiophen-4,6-dione (ThDione) has also been developed.

The picosecond laser for tattoo removal.

The prevalence of tattoos continues to grow as modern society's stigma towards this form of body art shifts towards greater acceptance. Approximately one third of Americans aged 18-25 and 40% of Americans aged 26-40 are tattooed. As tattoos continue to rise in popularity, so has the demand for an effective method of tattoo removal such as lasers. The various colors of tattoo inks render them ideal targets for specific lasers using the principle of selective photothermolysis. Traditional laser modalities employed for tattoo removal operate on pulse durations in the nanosecond domain. However, this pulse duration range is still too long to effectively break ink into small enough particles. Picosecond (10-12) lasers have emerged at the forefront of laser tattoo removal due to their shorter pulse lengths, leading to quicker heating of the target chromophores, and consequently, more effective tattoo clearance. Recent studies have cited more effective treatment outcomes using picosecond lasers. Future comparative studies between picosecond lasers of various settings are necessary to determine optimal laser parameters for tattoo clearance.

A Successful Attempt to Obtain the Linear Dependence Between One-Photon and Two-Photon Spectral Properties and Hammett Parameters of Various Aromatic Substituents in New π-Extended Asymmetric Organic Chromophores.

A series of new asymmetric chromophores containing aromatic substituents and possessing the excellent π-extension in space were prepared through multi-steps routes. One-photon and two-photon spectral properties of these new chromophores could be tuned by these substituents finely and simultaneously. The linear correlation of the wave numbers of the one-photon absorption and emission maxima to Hammett parameters of these substituents was presented. Near infrared two-photon absorption emission integrated areas of the target chromophores were correlated linearly to Hammett constants of these substituted groups.

New armed near-IR two-photon organic chromophores undergoing ESIPT and ‘naked eye’ fluorescence sensing to zinc ions

New armed near-infrared two-photon organic chromophores bearing with o-hydroxy-phenyl-imino groups are presented in this work. These molecules are demonstrated to undergo internal molecular proton transfer in the excited state under irradiation by one-photon absorption and near-IR femtosecond laser two-photon absorption, respectively. The target chromophores show ‘naked eye’ fluorescence sensing to Zn ions in DMF aqueous solution through the inhibition of excited state intramolecular proton transfer (ESIPT).

Механизмы действия различных лазеров и дифференцированные показания к их применению (обзор литературы)

To date, the methods of laser irradiation applied to the skin is much more frequent than in any other tissues, due to an exceptional variety and prevalence of skin diseases and a variety of cosmetic defects, as well as the relative simplicity of the procedures, which is associated with a surface location of objects requiring lecheniya.Lazernoe rejuvenation can be attributed to the most efficient and versatile methods of struggle with involutional changes in the skin. Target chromophores for laser radiation are almost all the chemical structures of the skin - the water, hemoglobin, melanin, collagen. The selectivity of the laser action allows you to choose individual scheme correction of involutional disorders of the skin in any type of aging skin. Wide demand for laser treatments, their high efficiency dictate the need to synthesize the available current data on the benefits and features of the application, as well as to the tactics of patients that can benefit greatly assist the individual laser medicine in the choice of the most efficient technology with the correct ratio of efficacy and safety. 
 In this review article provides current data on the method of laser skin resurfacing using a CO2 laser with a description of the phase of patient management. Describes in detail the predicted side effects, adverse events, and methods for their prevention and correction.

Quadrupolar D-π-A-π-D chromophores with central tetrafluorobenzene acceptor and two peripheral N,N-dimethylamino and methoxy donors

1,2,4,5-Tetrafluorobenzene has been utilized as suitable central acceptor moiety in push–pull chromophores having D-π-A-π-D quadrupolar arrangement. Starting from commercially available 1,4-diiodotetrafluorobenzene, nine novel chromophores with systematically extended π-system were synthesized via cross-coupling reactions. Further electronic tuning has been achieved by variation of the appended donor (N,N-dimethylamino and methoxy groups). Target chromophores were further investigated by X-ray analysis, electrochemical measurements, absorption and emission spectra and theoretical calculations and structure–property relationships were elucidated. Whereas target chromophores showed weak second-order nonlinear responses with β of 0.18–6.09×10−30esu, which is primarily given by their centrosymmetric arrangement, third-order polarizabilities γ of 0.84–22.5×10−27esu notably exceeded the standard Disperse Red 1 (γ=3.47×10−27esu).

Erratum: Fiberoptic microneedles: Novel optical diffusers for interstitial delivery of therapeutic light

Background and Objectives Photothermal therapies have limited efficacy and application due to the poor penetration depth of light inside tissue. In earlier work, we described the development of novel fiberoptic microneedles to provide a means to mechanically penetrate dermal tissue and deliver light directly into a localized target area. This paper presents an alternate fiberoptic microneedle design with the capability of delivering more diffuse, but therapeutically useful photothermal energy. Laser lipolysis is envisioned as a future clinical application for this design. Materials and Methods A novel fiberoptic microneedle was developed using hydrofluoric acid etching of optical fiber to permit diffuse optical delivery. Microneedles etched for 10, 30, and 50 minutes, and an optical fiber control were compared with three techniques. First, red light delivery from the microneedles was evaluated by imaging the reflectance of the light from a white paper. Second, spatial temperature distribution of the paper in response to near-IR light (1,064 nm, 1 W CW) was recorded using infrared thermography. Third, ex vivo adipose tissue response during 1,064 nm, (5 W CW) irradiation was recorded with bright field microscopy. Results Acid etching exposed a 3 mm length of the fiber core, allowing circumferential delivery of light along this length. Increasing etching time decreased microneedle diameter, resulting in increased uniformity of red and 1,064 nm light delivery along the microneedle axis. For equivalent total energy delivery, thinner microneedles reduced carbonization in the adipose tissue experiments. Conclusions We developed novel microscale optical diffusers that provided a more homogeneous light distribution from their surfaces, and compared performance to a flat-cleaved fiber, a device currently utilized in clinical practice. These fiberoptic microneedles can potentially enhance clinical laser procedures by providing direct delivery of diffuse light to target chromophores, while minimizing undesirable photothermal damage in adjacent, non-target tissue. Lasers Surg. Med. 43:914-920, 2011. © 2011 Wiley Periodicals, Inc.

Fiberoptic microneedles: Novel optical diffusers for interstitial delivery of therapeutic light

Photothermal therapies have limited efficacy and application due to the poor penetration depth of light inside tissue. In earlier work, we described the development of novel fiberoptic microneedles to provide a means to mechanically penetrate dermal tissue and deliver light directly into a localized target area.This paper presents an alternate fiberoptic microneedle design with the capability of delivering more diffuse, but therapeutically useful photothermal energy. Laser lipolysis is envisioned as a future clinical application for this design. A novel fiberoptic microneedle was developed using hydrofluoric acid etching of optical fiber to permit diffuse optical delivery. Microneedles etched for 10, 30, and 50 minutes, and an optical fiber control were compared with three techniques. First, red light delivery from the microneedles was evaluated by imaging the reflectance of the light from a white paper.Second, spatial temperature distribution of the paper in response to near-IR light (1,064 nm, 1 W CW) was recorded using infrared thermography. Third, ex vivo adipose tissue response during 1,064 nm, (5 W CW)irradiation was recorded with bright field microscopy. Acid etching exposed a 3 mm length of the fiber core, allowing circumferential delivery of light along this length. Increasing etching time decreased microneedle diameter, resulting in increased uniformity of red and 1,064 nm light delivery along the microneedle axis. For equivalent total energy delivery, thinner microneedles reduced carbonization in the adipose tissue experiments. We developed novel microscale optical diffusers that provided a more homogeneous light distribution from their surfaces, and compared performance to a flat-cleaved fiber, a device currently utilized in clinical practice. These fiberoptic microneedles can potentially enhance clinical laser procedures by providing direct delivery of diffuse light to target chromophores, while minimizing undesirable photothermal damage in adjacent, non-target tissue.

Two-photon absorption in V-type chromophores with electron-rich heterocyclevinylene bridges

A series of V-type chromophores with electron-rich heterocyclevinylene bridges have been synthesized via Wittig-Horner-Emmons and Vilsmeier reactions. All the target chromophores showed strong one-photon and two-photon excited emission, and their electron properties could be tuned by using different heterocycles such as furan, thiophene and pyrrole moieties in I–III. The maximum two-photon absorption (TPA) cross sections occurred at 760 nm and were measured to be in the range of 400–800 GM.