Dopant Solvent Research Articles

Correlation of dopant solution on doping mechanism and performance of F4TCNQ‐doped P3HT

AbstractUnderstanding the doping mechanism between the dopants and the conjugated polymers (CPs) is crucial for efficiently utilizing the doping process in a controllable manner. In this work, we doped the poly(3‐hexylthiophene) (P3HT) films with 2,3,5,6‐tetrafluoro‐7,7,8,8‐tetracyanoquinodimethane (F4TCNQ) from a chlorobenzene/acetonitrile (CB/AN) solvent blend and pure AN solvent by using the common sequential doping method. We found that the dissolution ability of the dopant solvent to P3HT and the concentration of the dopant solution were two critical factors to determine the doping process (solution doping or sequential doping) and the doping region (the amorphous or the crystalline phase). When the concentration of the dopant solution was low, solution doping was dominant in the P3HT film doped with F4TCNQ CB/AN solution, and the amorphous regions were doped in the P3HT film doped with F4TCNQ AN solution. With the increase of the dopant solution concentration, the ratio of ordered integer charge transfer (ICT) species, which formed from sequentially doped crystalline domains in the P3HT precast film, increased. Based on the above doping mechanism, a P3HT film with good electrical and tensile performance could be constructed by doping from F4TCNQ CB/AN solution with a relatively low concentration. Our work indicates that the dissolution or swelling ability of the dopant solvent to CP is an important factor in determining not only the doping mechanism but also the electrical and mechanical performances of doped CP films.

Study of the doping of PEDOT:PSS films and the reversibility in organic electrochemical transistors

In this work, the effect in the performance of organic electrochemical transistors (OECTs) due to the doping with a secondary dopant solvent of poly(3,4ethylenedioxythiophene): poly (styrene sulfonic acid) (PEDOT:PSS) films) has been studied. We found an improvement in the performance of the OECTs related to the increase of conductivity of the PEDOT:PSS film due to the doping with ethylene glycol (EG). We found that PEDOT:PSS films doped with EG showed higher conductivity due to the improvement of conducting paths between the PEDOT+ chains, which causes a higher transconductance and response of the OECTs. However, a higher concentration of EG is detrimental to the OECT performance due to the removal of PSS- chains caused by the EG secondary doping, which was corroborated by X-ray diffraction.We propose that the good reversibility between low-resistance state (ON) to high-resistance state (OFF), is caused by the injection/removal of cations in the polymeric film to maintain the electroneutrality. We found applying more negative gate voltage pulses in the transfer characteristics of the OECTs is necessary to reach the complete oxidation of the PEDOT:PSS film, as lower negative voltages only partially dedope the film.

Paper spray-atmospheric pressure photoionization-high resolution mass spectrometry for the direct analysis of neutral fluorinated compounds in waterproof impregnation sprays

In this work, paper spray (PS) is combined with atmospheric pressure photoionization-mass spectrometry (PS-APPI-MS) for the determination of non-polar and low polar compounds, such as the neutral per- and polyfluorinated alkyl substances (PFAS). The proposed PS-APPI-MS method has been developed for the analysis of fluorotelomer alcohols (FTOHs), fluoroctanesulfonamides (FOSAs) and fluorooctane sulfonamido-ethanols (FOSEs), using both negative ion mode and high-resolution mass spectrometry (HRMS). The most critical working parameters (i.e., UV-krypton lamp position, sample drying time, spray dopant solvent and spray voltage) have been evaluated to study both the ionization behaviour and ionization efficiency. The best results were achieved using dopant-assisted PS-APPI-HRMS with toluene as dopant solvent. The most intense ions observed in the mass spectra, [M‒H]‒ for FOSAs and [M+O2]‒• for FTOHs and FOSEs, were selected and proposed for fast screening and quantitative analysis of target compounds in waterproof impregnation sprays samples using internal standard calibration method and being able to detect down to μg L−1 levels. The satisfactory values of the method quality parameters (detection capability, repeatability, trueness and linearity) demonstrated the good performance of the PS-APPI-HRMS method and allowed the identification and quantitation of some FTOHs (6:2 FTOH, 7-Me-6:2 FTOH, 8:2 FTOH, 10:2 FTOH) and N-MeFOSE at mg L−1 in some of the waterproof impregnation spray products analyzed. This low-cost PS-APPI-HRMS method allows a fast screening, with minimum sample preparation, of non-polar and low polar compounds simultaneously, which can significantly improve the throughput on routine laboratories.

Optimized selection of dopant solvents for improving the sequential doping efficiency of conjugated polymers

Abstract Molecular doping for conjugated polymers is an important tool for modifying their electrical and optical properties, which extends conjugated polymer's application to various optoelectronic devices. Sequential doping, i.e., dopant diffusion into a pre-deposited polymer film is one of the most widely used molecular doping methods. To improve dopant diffusion efficiency, solvent engineering for conjugated polymers has been studied, however, less attention has been given to solvent selection for the dopant, which is equally important as dopant carriers. In this study, we suggest a selection rule for dopant solvents in the application of sequential doping based on the systemic characterizations of Hansen solubility parameters, UV–Vis absorption spectra, and electrical conductivity. Furthermore, by applying the rule to different conjugated polymers, we demonstrate the wide applicability of our findings on dopant solvent selection.

Comparison of atmospheric pressure photoionization and electrospray ionization mass spectrometry for the analysis of UV filters

A comparison was made between the electrospray ionization (ESI) and atmospheric pressure photoionization (APPI) tandem mass spectrometric (MS/MS) responses of eleven ultraviolet (UV) filters. Four of the target compounds were favourably ionized in negative ion mode, and the other seven compounds in positive ion mode. For nine of the compounds APPI generated a similar response to that of ESI, but the APPI signal-to-noise (S/N) ratios were 1.3-60 times higher. The two most polar of the UV filter compounds (PBSA and BP-4) were more efficiently ionized by ESI, offering higher signal intensities and lower detection limits. APPI was, however, less susceptible to ion suppression than ESI when real samples were injected. In order to optimize the APPI conditions different dopant solvents were examined to enhance the efficiency of the photoionization process. Among the evaluated dopants, toluene was selected as the best compromise. At a toluene flow rate of 10% of the solvent flow rates the ionization response increased by a factor of 40-50 over the use of no dopant for the compounds in positive ion mode and by more than 300 for the compounds in negative ion mode.

Atmospheric Pressure Photoionization Proton Transfer for Complex Organic Mixtures Investigated by Fourier Transform Ion Cyclotron Resonance Mass Spectrometry

To further clarify the role of dopant solvent in proton transfer in atmospheric pressure photoionization (APPI), we employ ultrahigh-resolution FT-ICR mass analysis to identify M(+*), [M + H](+), [M - H](-), and [M + D](+) species in toluene or perdeuterotoluene for an equimolar mixture of five pyrrolic and pyridinic nitrogen heterocyclic model compounds, as well as for a complex organic mixture (Canadian Athabasca bitumen middle distillate). In the petroleum sample, the protons in the [M + H](+) species originate primarily from other components of the mixture itself, rather than from the toluene dopant. In contrast to electrospray ionization, in which basic (e.g., pyridinic) species protonate to form [M + H](+) positive ions and acidic (e.g., pyrrolic) species deprotonate to form [M - H](-) negative ions, APPI generates ions from both basic and acidic species in a single positive-ion mass spectrum. Ultrahigh-resolution mass analysis (in this work, m/Deltam(50%) = 500,000, in which Deltam(50%) is the mass spectral peak full width at half-maximum peak height) is needed to distinguish various close mass doublets: (13)C versus (12)CH (4.5 mDa), (13)CH versus (12)CD (2.9 mDa), and H(2) versus D (1.5 mDa).

Comparison of fast liquid chromatography/tandem mass spectrometric methods for simultaneous determination of cladribine and clofarabine in mouse plasma

Several fast high performance liquid chromatography/atmospheric pressure ionization/tandem mass spectrometric (HPLC-API/MS/MS) methods were evaluated for the simultaneous determination of cladribine and clofarabine in mouse plasma samples. The chemical separation for analytes under reversed-phase conditions were achieved by using either ultra-performance liquid chromatography (UPLC) or micro-column HPLC coupled to either a quadrupole linear ion trap mass spectrometer (QTrap MS) or a triple quadrupole mass spectrometer. Atmospheric pressure chemical ionization (APCI) or atmospheric pressure photoionization (APPI) interfaces in the positive mode were employed prior to mass spectrometric detection. The effects of various dopant solvents on the APPI sensitivities of analytes and the internal standard were investigated. The matrix ionization suppression potential for the test compounds in plasma samples on fast HPLC-MS/MS methods was examined by a post-column infusion technique. In this work, these proposed approaches were successfully employed to determine the concentrations of cladribine and clofarabine in mouse plasma in the low ng/ml region. The mouse plasma levels of all analytes obtained by these fast HPLC-MS/MS methods were compared and found to be well correlated in terms of analytical accuracy.