Chemical modification and doping of poly(p-phenylenes): A theoretical study.

CONTEXT: Conjugated polymers (CPs) have been recognized as promising materials for the manufacture of electronic devices. However, further studies are still needed to enhance the electrical conductivity of these type of organic materials. The two main strategies for achieving this improvement are the doping process and chemical modification of the polymer chain. Therefore, in this article, we conduct a theoretical investigation, employing DFT calculations to evaluate the structural, energetic, and electronic properties of pristine and push-pull-derived poly(p-phenylene) oligomers (PPPs), as well as the analysis at the molecular level of the polymer doping process. As a primary conclusion, we determined that the PPP oligomer substituted with the push-pull group 4-EtN/CNPhNO2 exhibited the smallest HOMO-LUMO gap (Eg) among the studied oligomers. Moreover, we observed that the doping process, whether through electron removal or the introduction of the dopant anion ClO4-, led to a substantial reduction in the Eg of the PPP, indicating an enhancement in the polymer's electrical conductivity. METHODS: DFT calculations were conducted using the PBE0 functional along with the Pople's split valence 6-31G(d,p) basis set, which includes polarization functions on all atoms (B97D/6-31G(d,p)).

Comparison of three methods for collecting interstitial fluid from subcutaneous tissue in mini pigs.

Interstitial fluid, owing to its similarity to blood components and higher sensitivity and specificity, finds widespread application in disease diagnosis and tumor marker detection. However, collecting interstitial fluid, particularly from the deep subcutaneous connective tissue, remains challenging.•This study aimed to compare three different collection methods - push-pull perfusion, multi-filament nylon thread implantation, and tissue centrifugation - for collecting interstitial fluid from the subcutaneous connective tissue layer of mini-pigs. High-performance ion chromatography was employed to analyze the conventional cation components in the samples and compare ion composition analysis between the different methods.•Results indicated that while the distribution of conventional cations in the interstitial fluid collected by the three methods was generally consistent, there were slight variations in the detection rates and concentrations of different ions. Hence, suitable collection methods should be selected based on the ions or collection sites of interest.

The push-pull intercrop Desmodium does not repel, but intercepts and kills pests.

Over two decades ago, an intercropping strategy was developed that received critical acclaim for synergizing food security with ecosystem resilience in smallholder farming. The push-pull strategy reportedly suppresses lepidopteran pests in maize through a combination of a repellent intercrop (push), commonly Desmodium spp., and an attractive, border crop (pull). Key in the system is the intercrop's constitutive release of volatile terpenoids that repel herbivores. However, the earlier described volatile terpenoids were not detectable in the headspace of Desmodium, and only minimally upon herbivory. This was independent of soil type, microbiome composition, and whether collections were made in the laboratory or in the field. Furthermore, in oviposition choice tests in a wind tunnel, maize with or without an odor background of Desmodium was equally attractive for the invasive pest Spodoptera frugiperda. In search of an alternative mechanism, we found that neonate larvae strongly preferred Desmodium over maize. However, their development stagnated and no larva survived. In addition, older larvae were frequently seen impaled and immobilized by the dense network of silica-fortified, non-glandular trichomes. Thus, our data suggest that Desmodium may act through intercepting and decimating dispersing larval offspring rather than adult deterrence. As a hallmark of sustainable pest control, maize-Desmodium push-pull intercropping has inspired countless efforts to emulate stimulo-deterrent diversion in other cropping systems. However, detailed knowledge of the actual mechanisms is required to rationally improve the strategy, and translate the concept to other cropping systems.

Self-Assembled Monolayers of Push-Pull Chromophores as Active Layers and Their Applications.

In recent decades, considerable attention has been focused on the design and development of surfaces with defined or tunable properties for a wide range of applications and fields. To this end, self-assembled monolayers (SAMs) of organic compounds offer a unique and straightforward route of modifying and engineering the surface properties of any substrate. Thus, alkane-based self-assembled monolayers constitute one of the most extensively studied organic thin-film nanomaterials, which have found wide applications in antifouling surfaces, the control of wettability or cell adhesion, sensors, optical devices, corrosion protection, and organic electronics, among many other applications, some of which have led to their technological transfer to industry. Nevertheless, recently, aromatic-based SAMs have gained importance as functional components, particularly in molecular electronics, bioelectronics, sensors, etc., due to their intrinsic electrical conductivity and optical properties, opening up new perspectives in these fields. However, some key issues affecting device performance still need to be resolved to ensure their full use and access to novel functionalities such as memory, sensors, or active layers in optoelectronic devices. In this context, we will present herein recent advances in π-conjugated systems-based self-assembled monolayers (e.g., push-pull chromophores) as active layers and their applications.

Near-IR Capturing N-Methylbenzene Sulfonamide-Phenothiazine Incorporating Strong Electron Acceptor Push-Pull Systems: Photochemical Ultrafast Carrier Dynamics.

Unraveling the intriguing aspects of the intramolecular charge transfer (ICT) phenomenon of multi-modular donor-acceptor-based push-pull systems are of paramount importance considering their promising applications, particularly in solar energy harvesting and light-emitting devices. Herein, a series of symmetrical and unsymmetrical donor-acceptor chromophores 1-6, are designed and synthesized by the Corey-Fuchs reaction via Evano's condition followed by [2+2] cycloaddition retroelectrocyclic ring-opening reaction with strong electron acceptors TCNE and TCNQ in good yields (~60-85 %). The photophysical, electrochemical, and computational studies are investigated to explore the effect of incorporation of strong electron acceptors 1,1,4,4-tetracyanobuta-1,3-diene (TCBD) and dicyanoquinodimethane (DCNQ) with phenothiazine (PTZ) donor. An additional low-lying broad absorption band extended towards the near-infrared (NIR) region suggests charge polarization after the introduction of the electron acceptors in both symmetrical and asymmetrical systems, leading to such strong ICT bands. The electrochemical properties reveal that reduction potentials of 3 and 6 are lower than those of 2 and 5, suggesting DCNQ imparts more on the electronic properties and hence largely contributes to the stabilization of LUMO energy levels than TCBD, in line with theoretical observations. Relative positions of the frontier orbitals on geometry-optimized structures further support accessing donor-acceptor sites responsible for the ICT transitions. Eventually, ultrafast carrier dynamics of the photoinduced species are investigated by femtosecond transient absorption studies to identify their spectral characteristics and target analysis further provides information about different excited states photophysical events including ICT and their associated time profiles. The key findings obtained here related to excited state dynamical processes of these newly synthesized systems are believed to be significant in advancing their prospect of utilization in solar energy conversion and related photonic applications.

Associational Effects of Desmodium Intercropping on Maize Resistance and Secondary Metabolism.

Intercropping is drawing increasing attention as a strategy to increase crop yields and manage pest pressure, however the mechanisms of associational resistance in diversified cropping systems remain controversial. We conducted a controlled experiment to assess the impact of co-planting with silverleaf Desmodium (Desmodium uncinatum) on maize secondary metabolism and resistance to herbivory by the spotted stemborer (Chilo partellus). Maize plants were grown either in the same pot with a Desmodium plant or adjacent to it in a separate pot. Our findings indicate that co-planting with Desmodium influences maize secondary metabolism and herbivore resistance through both above and below-ground mechanisms. Maize growing in the same pot with a Desmodium neighbor was less attractive for oviposition by spotted stemborer adults. However, maize exposed only to above-ground Desmodium cues generally showed increased susceptibility to spotted stemborer herbivory (through both increased oviposition and larval consumption). VOC emissions and tissue secondary metabolite titers were also altered in maize plants exposed to Desmodium cues, with stronger effects being observed when maize and Desmodium shared the same pot. Specifically, benzoxazinoids were strongly suppressed in maize roots by direct contact with a Desmodium neighbor while headspace emissions of short-chain aldehydes and alkylbenzenes were increased. These results imply that direct root contact or soil-borne cues play an important role in mediating associational effects on plant resistance in this system.

Nanoparticles of Push-Pull Triphenylamine-Based Molecules for Light-Controlled Stimulation of Neuronal Activity.

Organic semiconductor materials with a unique set of properties are very attractive for interfacing biological objects and can be used for noninvasive therapy or detection of biological signals. Here, we describe the synthesis and investigation of a novel series of organic push-pull conjugated molecules with the star-shaped architecture, consisting of triphenylamine as a branching electron donor core linked through the thiophene π-spacer to electron-withdrawing alkyl-dicyanovinyl groups. The molecules could form stable aqueous dispersions of nanoparticles (NPs) without the addition of any surfactants or amphiphilic polymer matrixes with the average size distribution varying from 40 to 120 nm and absorption spectra very similar to those of human eye retina pigments such as rods and green cones. Variation of the terminal alkyl chain length of the molecules forming NPs from 1 to 12 carbon atoms was found to be an efficient tool to modulate their lipophilic and biological properties. Possibilities of using the NPs as light nanoactuators in biological systems or as artificial pigments for therapy of degenerative retinal diseases were studied both on the model planar bilayer lipid membranes and on the rat cortical neurons. In the planar bilayer system, the photodynamic activity of these NPs led to photoinactivation of ion channels formed by pentadecapeptide gramicidin A. Treatment of rat cortical neurons with the NPs caused depolarization of cell membranes upon light irradiation, which could also be due to the photodynamic activity of the NPs. The results of the work gave more insight into the mechanisms of light-controlled stimulation of neuronal activity and for the first time showed that fine-tuning of the lipophilic affinity of NPs based on organic conjugated molecules is of high importance for creating a bioelectronic interface for biomedical applications.

Perspectives of push-pull-mooring effects on a desire for switching to alternative crops among tobacco farmers in Thailand: A qualitative study.

INTRODUCTION: Tobacco use contributes significantly to premature deaths worldwide. A key strategy to curb tobacco consumption involves limiting the tobacco supply through the transition to substitute crops. This study aims to provide insight into why tobacco farmers desire to switch to alternative crops and the support required for a successful transition. METHODS: Semi-structured interviews were conducted with 34 tobacco farmers expressing a desire to transition to other crops in two communities in Thailand. Data were recorded and transcribed verbatim in Thai and subsequently translated into English. A deductive content analysis applied the Push-Pull-Mooring (PPM) framework, contextualizing factors for the transition among tobacco farmers. RESULTS: Four main categories emerged: 1) push factors, encompassing negative experiences in growing tobacco, such as poverty, health problems, and hopelessness; 2) pull factors, representing positive experiences in transitioning to alternative crops, particularly having a role model; and 3) mooring factors, highlighting characteristic disadvantages of tobacco farmers, particularly the receipt of small tobacco growing quotas. The fourth category focused on the support needed for a successful transition, including the suspension of tobacco debt payments, access to low-interest loans, and the development of marketing capabilities. CONCLUSIONS: The study provides a comprehensive understanding of farmers' motivations to switch from tobacco to alternative crops and outlines the necessary support for a successful transition. Offering financial assistance and enhancing the production and marketing capabilities of alternative crops are essential steps toward facilitating a successful switch for farmers and ensuring a secure livelihood beyond tobacco farming.

Exploring ethynyl-based chalcones as green semiconductor materials for optical limiting interests.

The fabrication of molecular electronics from non-toxic functional materials which eventually would potentially able to degrade or being breaking down into safe by-products have attracted much interests in recent years. Hence, in this study, the introduction of mixed highly functional substructures of chalcone (-CO-CH=CH-) and ethynylated (C≡C) as building blocks has shown ideal performance as solution-processed thin film candidatures. Two types of derivatives, (MM-3a) and (MM-3b) repectively, showed a substantial Stokes shifts at 75 nm and 116 nm, in which such emission exhibits an intramolecular charge transfer (ICT) state and fluoresce characteristics. The density functional theory (DFT) simulation shows that MM-3a and MM-3b exhibit low energy gaps of 3.70 eV and 2.81 eV, respectively. TD-DFT computations for molecular electrostatic potential (MEP) and frontier molecular orbitals (FMO) were also used to emphasise the structure-property relationship. A solution-processed thin film with a single layer of ITO/PEDOT:PSS/MM-3a-MM-3b/Au exhibited electroluminescence behaviour with orange and purple emissions when supplied with direct current (DC) voltages. To promote the safer application of the derivatives formed, ethynylated chalcone materials underwent toxicity studies toward Acanthamoeba sp. to determine their suitability as non-toxic molecules prior to the determination as safer materials in optical limiting interests. From the preliminary test, no IC50 value was obtained for both compounds via 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assay analysis and molecular docking analysis between MM-3a and MM-3b, with profilin protein exhibited weak bond interactions and attaining huge interaction distances.

Unique structural effect on the fluorosolvatochromism and dual fluorescence emission of D-π-A+ cationic chromophores with furyl bridge. An approach to white light emitters.

Photophysical behavior of two D - π - A+ cationic compounds with the same furyl bridge and nicotinamidine group as an electron acceptor moiety and two electron donating groups, namely methoxy (I) and N,N-dimethylamino (II) groups was examined using steady-state and time-resolved techniques in variety of solvents. Time-dependent density functional theory (TDDFT) calculations were performed in some representative solvents and compared with the experimental results. Steady state and time-resolved studies in different solvents reveal that fluorescence emission of (I) is ascribed to an emission from an excited state (ICT) with higher dipole moment than the ground state while the emission of (II) is a dual emission from a state with high charge transfer nature (ICT) in addition to the locally excited state (LE). The fluorescence emission spectra of (II) were found to depend on the excitation wavelength and an increase in the excitation wavelength led to the formation of a longer wavelength emission band with lower quantum yield. It has also been found that the fluorescence excitation spectra were dependent on the emission wavelength. The effect of solvent on the nature of dual emission was examined. Correlation of the photophysical properties of the excited states of (I) and (II) with the solvent polarity, ε, reveals the charge transfer nature of (I) and the long wavelength emission band of (II), while their correlation with the solvent polarity parameter (ETN) shows two different trends when the solvents are divided to aprotic and protic solvents. For precise investigation of the impact of each solvent parameter on each photophysical property, Catalán's and Laurence's four parametric linear solvation energy relationships were studied. We have found that the non-specific interactions of the solvent are primarily responsible for controlling the photophysical properties, as demonstrated by Catalán's and Laurence's treatments. DFT and TDDFT calculations were used to anticipate the dipole moments in the ground and excited states and geometry of both states.

Monitoring oxytocin signaling in the brain: More than a love story.

More than any other neuropeptide, oxytocin (OXT) is attracting the attention of neurobiologists, psychologists, psychiatrists, evolutionary biologists and even economists. It is often called a "love hormone" due to its many prosocial functions described in vertebrates including mammals and humans, especially its ability to support "bonding behaviour". Oxytocin plays an important role in female reproduction, as it promotes labour during parturition, enables milk ejection in lactation and is essential for related reproductive behaviours. Therefore, it particularly attracts the interest of many female researchers. In this short narrative review I was invited to provide a personal overview on my scientific journey closely linked to my research on the brain OXT system and the adventures associated with starting my research career behind the Iron Curtain.

Push-Pull Inverter Using Amplitude Control and Frequency Tracking for Piezoelectric Transducers.

Frequency tracking and amplitude control are essential for piezoelectric transducers. Frequency tracking ensures the piezoelectric transducer operates at the resonant frequency for maximum power output, and amplitude control regulates the mechanical motion of the output. This paper presents a novel driver based on a push-pull inverter for piezoelectric transducers. The proposed driver realizes the frequency tracking and amplitude control scheme by a voltage sensing bridge in the case of transformer secondary matching, guaranteeing automatic frequency tracking and precise mechanical functions regardless of environmental and load variations. The proposed scheme is verified by the ultrasonic scalpel and the ultrasonic motor (USM). The experimental results show that this scheme reduces the build-up time from 10 ms to 3 ms and loaded frequency variations from 250 Hz to 200 Hz. In addition, the amplitude control performance was further observed on USM for various loads. The overshoot is less than 5.4% under different load torques. Therefore, the proposed scheme improves the load adaptability and stability of piezoelectric transducers and promotes the application of piezoelectric transducers under various conditions.

Rewiring cell-free metabolic flux in E. coli lysates using a block-push-pull approach.

Cell-free systems can expedite the design and implementation of biomanufacturing processes by bypassing troublesome requirements associated with the use of live cells. In particular, the lack of survival objectives and the open nature of cell-free reactions afford engineering approaches that allow purposeful direction of metabolic flux. The use of lysate-based systems to produce desired small molecules can result in competitive titers and productivities when compared to their cell-based counterparts. However, pathway crosstalk within endogenous lysate metabolism can compromise conversion yields by diverting carbon flow away from desired products. Here, the 'block-push-pull' concept of conventional cell-based metabolic engineering was adapted to develop a cell-free approach that efficiently directs carbon flow in lysates from glucose and toward endogenous ethanol synthesis. The approach is readily adaptable, is relatively rapid and allows for the manipulation of central metabolism in cell extracts. In implementing this approach, a block strategy is first optimized, enabling selective enzyme removal from the lysate to the point of eliminating by-product-forming activity while channeling flux through the target pathway. This is complemented with cell-free metabolic engineering methods that manipulate the lysate proteome and reaction environment to push through bottlenecks and pull flux toward ethanol. The approach incorporating these block, push and pull strategies maximized the glucose-to-ethanol conversion in an Escherichia coli lysate that initially had low ethanologenic potential. A 10-fold improvement in the percent yield is demonstrated. To our knowledge, this is the first report of successfully rewiring lysate carbon flux without source strain optimization and completely transforming the consumed input substrate to a desired output product in a lysate-based, cell-free system.

Effect of Polymer Composition on the Optical Properties of a New Aggregation-Induced Emission Fluorophore: A Combined Experimental and Computational Approach.

Nowadays, fluorophores with a tetraphenylethylene (TPE) core are considered interesting due to the aggregation-induced emission (AIE) behavior that enables their effective use in polymer films. We propose a novel TPE fluorophore (TPE-BPAN) bearing two dimethylamino push and a 4-biphenylacetonitrile pull moieties with the typical AIE characteristics in solution and in the solid state, as rationalized by DFT calculations. Five different host polymer matrices with different polarity have been selected: two homopolymers of poly(methylmethacrylate) (PMMA) and poly(cyclohexyl methacrylate) (PCHMA) and three copolymers at different compositions (P(MMA-co-CHMA) 75:25, 50:50, and 25:75 mol%). The less polar comonomer of CHMA appeared to enhance TPE-BPAN emission with the highest quantum yield (QY) of about 40% measured in P(MMA-co-CHMA) 75:25. Further reduction in polymer polarity lowered QY and decreased the film stability and adhesion to the glass surface. LSC performances were not significantly affected by the matrix's polarity and resulted in around one-third of the state-of-the-art due to the reduced QY of TPE-BPAN. The theoretical investigation based on density functional theory (DFT) calculations clarified the origin of the observed AIE and the role played by the environment in modulating the photophysical behavior.

Fabrication, optimization and characterization of an osmotic push-pull drug delivery system for paliperidone.

Objectives: Paliperidone is a BCS class II drug with low solubility and high permeability. It has 28% absolute oral bioavailability and an elimination half-life of 23 h. An osmotic push-pull trilayer tablet currently available on the market has achieved controlled release of a low dose over an extended time period, while avoiding the need for a loading dose. However, this trilayer tablet has several disadvantages, such as complicated processing, high production costs and difficulty in achieving uniformity of the contents. Thus, the objective of this study was to overcome the above difficulties associated with paliperidone and to formulate a bilayer tablet with a similar drug profile to that of the reference listed drug Invega®. Methods: The bilayer tablets were prepared by optimization of the core and semi-permeable membrane. Effects of the curing time, and the size and number of orifices on the prepared tablets' dissolution profile were analyzed. Two different grades of polyethylene oxide were used in the core and push layer as pore formers. Results: The weight variation, friability and hardness values of the prepared tablets were well within compendium limits. The optimized bilayer parameters for the prepared tablets were curing time, 5 h; seal coat, 7% w/w; ER coat, 13% w/w; orifice size, 0.6 mm; and orifice number, 2. Further tablet formulation resulted in an F2 value of 75.67, indicating a dissolution profile similar to that of Invega®. Conclusion: Bi-layer tablets of paliperidone overcoming the drawbacks of the marketed formulation were successfully prepared, and offer advantages such as a simpler preparation process, cost effectiveness and faster preparation of the tablet core.

Visible-light-switchable Chalcone-Flavylium Photochromic Systems in Aqueous Media.

The chalcone-flavylium photochromic system switches in aqueous media. However, the chalcone→flavylium conversion requires detrimental ultra-violet (UV) light for the switching which deters their applications in the biological domain. To address this issue, we have synthesized strategically modified chalcone scaffolds that can be reversibly switched to the flavylium forms with visible light ranging from 456 nm (blue) to 640 nm (red).

Understanding the drivers of preferential migration of people living with HIV to fishing communities of Lake Victoria in Uganda.

Fishing communities around Lake Victoria have among the highest burdens of HIV globally. Growing evidence suggests that high HIV prevalence is partially due to selective migration of people living with HIV to fishing communities. However, the reasons for this preferential migration are unclear. We recruited 60 men and women for qualitative in-depth interviews (30% living with HIV; 70% recent migrants of unknown HIV status) from seven Ugandan fishing communities. Interviews discussed mobility histories and the social context surrounding migration. Interviews were audio-recorded, transcribed, and translated. A version of the 'Push-Pull' theory of migration helped structure a conceptual thematic framework for data analysis. Unfavourable conditions related primarily to stigma, social discrimination, humiliation, rejection or HIV labelling, and violence, induced individuals to leave their home communities. Factors which eventually resulted in migration to fishing communities included anticipating less HIV-related stigma and a safe, friendly environment that accommodates all people. Access to healthy food (fish) and the perceived availability of community-based HIV care services were also attractions. We found that stigma is the major social phenomenon shaping preferential migration to fishing communities in Uganda.

Identification and evaluation of cruciferous plant volatiles attractive to Plutella xylostella L. (Lepidoptera: Plutellidae).

BACKGROUND: The diamondback moth, Plutella xylostella, has developed resistance to almost all insecticides used for its control. The 'push-pull' method has been shown as an effective control strategy to address this resistance challenge of P. xylostella. The key focus of the strategy is the identification of attractive or repellent volatile components. The aim of this study was to identify attractive volatile compounds released from host plants. Identified compounds were applied in the biological control of this pest. RESULTS: Nine active compounds released into the headspace of seven cruciferous plant species were identified using gas chromatography-electroantennographic detection and gas chromatography-mass spectrometry. Electroantennographic detection-active compounds included five green leaf volatiles (hexanal, trans-2-hexen-1-ol, cis-3-hexen-1-ol, cis-3-hexenyl acetate, and 1-penten-3-ol), three isothiocyanates (isopropyl isothiocyanate, allyl isothiocyanate, and butyl isothiocyanate), and nonanal. Except for nonanal, all the identified green leaf volatiles and isothiocyanates elicited strong electrophysiological and behavioral responses in P. xylostella. The strongest attractive compounds, trans-2-hexen-1-ol and isopropyl isothiocyanate, were further evaluated in oviposition and field-trapping assays. Results showed that they both lured female moths to lay eggs, and were highly attractive to P. xylostella adults in field, especially when used in combination with yellow and green sticky boards. However, a blend of the two compounds showed no synergistic effect, but rather an antagonistic effect. CONCLUSIONS: Green leaf volatiles and isothiocyanates were identified as key olfactory cues for host selection of P. xylostella. Trans-2- hexen-1-ol and isopropyl isothiocyanate were identified as candidate attractive compounds to serve in a 'push-pull' strategy for P. xylostella control. © 2023 Society of Chemical Industry.

Unraveling the structure-property relationship of a chalcone-based push-pull molecule for optical limiting application in high-powered laser.

In this work, the optical limiting response of a highly π-conjugated push-pull chalcone derivative (2E)-3-(2,3-dimethoxyphenyl)-1-(3-nitrophenyl)prop-2-en-1-one (abbreviated as 3DPNP) has been investigated. The structure-property relationship of 3DPNP was explored through spectroscopic investigation and quantum chemical computations. The existence of weak-non-covalent interactions and charge transfer species that responsible for the chemical stability of 3DPNP were studied by AIM and NBO analyses. The quantitative and qualitative analysis of vibrational and electronic contribution to non-linear optical (NLO) response of 3DPNP were discussed in detail. The normal vibrational modes associated with a change in the dipole moment, polarizability, first- and second-order hyperpolarizabilities of 3DPNP were identified using DFT calculations followed by potential energy distribution (PED) analysis using Gaussian 09 W software and Gar2ped program, respectively. The changes in the NLO parameters with respect to the varying frequencies and electric dipole fields were studied. The abrupt changes in the NLO properties were noticed when the frequency doubled, confirming the second harmonic generation (SHG) efficiency of 3DPNP. From the non-linear absorption and refraction studies through the z-scan experiment, the optical limiting threshold value of 3DPNP is determined to be 3.26 kJ/cm2, which shows the suitability of the material for optical limiting applications in the continuous wave (CW) laser regime.

Push-Pull Heptamethines Near the Cyanine Limit Exhibiting Large Quadratic Electro-Optic Effect.

Harnessing the quadratic electro-optic (QEO) of near-infrared polymethine chromophores over broad telecom wavelength bands is a subject of immense potential but remains largely under-investigated. Herein a series of push-pull heptamethines containing the tricyanofuran (TCF) acceptors and indoline or benzo[e]indoline donors are reported. These dipolar chromophores can attain a highly delocalized "cyanine-like" electronic ground state in solvents spanning a wide range of polarities, in some cases even closer to the ideal polymethine state than symmetrical cyanines. A transmission-mode electromodulation spectroscopy is used to study the electric-field-induced changes in optical absorption and refraction of polymer films doped with heptamethine chromophores, and large and thermally stable QEO effect with high efficiency-loss figure-of-merits that compare favorably to those from dipolar polyenes in poled or unpoled polymers and III-V semiconductors is obtained. The study opens a path for developing organic materials based on cyanine-like merocyanines for complementary metal oxide semiconductor -compatible, fast, efficient, and low-loss electro-optic modulation.