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Open AccessCCS ChemistryRESEARCH ARTICLE1 Apr 2020Multi-Stimuli-Responsive Field-Effect Transistor with Conjugated Polymer Entailing Spiropyran in the Side Chains Jing Ma†, Jianwu Tian†, Zitong Liu, Dandan Shi, Xisha Zhang, Guanxin Zhang and Deqing Zhang Jing Ma† Beijing National Laboratory for Molecular Sciences, CAS Key Laboratory of Organic Solids, CAS Center of Excellence in Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, (China) University of Chinese Academy of Sciences, Beijing 100049, (China) , Jianwu Tian† Beijing National Laboratory for Molecular Sciences, CAS Key Laboratory of Organic Solids, CAS Center of Excellence in Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, (China) University of Chinese Academy of Sciences, Beijing 100049, (China) , Zitong Liu *Corresponding author: E-mail Address: [email protected]; E-mail Address: [email protected]; Beijing National Laboratory for Molecular Sciences, CAS Key Laboratory of Organic Solids, CAS Center of Excellence in Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, (China) , Dandan Shi Beijing National Laboratory for Molecular Sciences, CAS Key Laboratory of Organic Solids, CAS Center of Excellence in Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, (China) University of Chinese Academy of Sciences, Beijing 100049, (China) , Xisha Zhang Beijing National Laboratory for Molecular Sciences, CAS Key Laboratory of Organic Solids, CAS Center of Excellence in Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, (China) University of Chinese Academy of Sciences, Beijing 100049, (China) , Guanxin Zhang Beijing National Laboratory for Molecular Sciences, CAS Key Laboratory of Organic Solids, CAS Center of Excellence in Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, (China) and Deqing Zhang *Corresponding author: E-mail Address: [email protected]; E-mail Address: [email protected]; Beijing National Laboratory for Molecular Sciences, CAS Key Laboratory of Organic Solids, CAS Center of Excellence in Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, (China) University of Chinese Academy of Sciences, Beijing 100049, (China) https://doi.org/10.31635/ccschem.019.201900056 SectionsSupplemental MaterialAboutAbstractPDF ToolsAdd to favoritesTrack Citations ShareFacebookTwitterLinked InEmail Multi-stimuli-responsive field-effect transistors (FETs) with organic/polymeric semiconductors have received increasing attention. Herein, we report a novel strategy for fabricating multi-stimuli-responsive polymeric semiconductors through the incorporation of spiropyran (SP) groups in the polymer side chains. The semiconducting performances of resultant FETs with a diketopyrrolopyrroles (DPP)-based conjugated donor–acceptor (D–A) polymer, that entails SP units in the side chains ( pDSP-1), could be modulated reversibly through UV and visible light irradiations, or UV light irradiation and heating, or acid treatment and heating. Our studies reveal that during the reversible transformations of closed, open, and the protonated forms of spiropyran, achieved by light irradiations, heating, and under acidic conditions, a large dipole moment changes occur, which triggers the reversible variation of semiconducting performance of the FETs. Download figure Download PowerPoint Introduction In the last few decades, the rapid developments of organic and polymeric semiconductors with high charge mobilities have been witnessed.1–5 Newly conjugated molecules and polymers have been designed, synthesized, and new device fabrication methods have been proposed in order to improve the semiconducting performance of organic semiconductors.6–20 Thin-film field-effect transistors (FETs) based on organic/polymeric semiconductors have shown potential applications in memory devices, flexible displays, and wearable electronics.21–24 In recent years, FETs with external-field tunable electrical properties other than electrical voltage have been of considerable interest.25–40 Since the output current could be controlled simultaneously and independently by voltage, as well as other external fields, it is possible to integrate complex functionalities, such as memory devices, switches, and complex logic operations, in a single FET device.41–43 Often, light is used as the external stimuli for optically tunable FETs.22–40 In fact, their fabrications have been achieved by utilizing photochromic molecules, able to undergo reversible light-induced interconversions between two isomers.41 For instance, Samorì and co-workers25 blended diarylethene derivative with P3HT [poly(3-hexylthiophene)] to generate a semiconducting film, which showed optically reversible FET with characteristic bi-stable states upon alternating UV and visible light irradiations. Additionally, Nuckolls and co-workers26 built optically reversible FETs using spiropyrans (SP) in the dielectric layer. Further, recent work by our lab and others27 incorporated azobenzene groups into the flexible alkyl side chains of a conjugated polymer, which was used successfully to fabricate optically tunable FETs with rapid photoresponsiveness. In addition to light, other external inputs, such as heating and introducing chemical species are also of high interest in the generation of multi-stimuli-responsive FETs.44–46 Herein, we report the fabrication of multi-stimuli-responsive FETs with the semiconducting D–A polymer (diketopyrrolopyrrole (DPP)-quaterthiophene conjugated polymer) with the substituted photochromic SP groups in the side chains ( pDSP-1), shown in Scheme 1. The incorporation of SP into the D–A polymer was based on the following considerations: (1) The closed-form, SP, should transform reversibly into the open-form, merocyanine (MC), and the protonated merocyanine (MCH+) forms, after UV or visible light irradiations, heating, addition of acid, and even the application of mechanical force.47,48 (2) By comparison, the open-form, MC, must possess a larger dipole moment (∼17.7 D) than the untransformed, closed-SP-form (∼4.3 D).49 Such a change in the dipole moment, presumably, generates carrier scattering sites within the semiconducting thin film and; as a result, the charge transporting behavior should be reduced. Thus, this became the basis of our fabrication of multi-stimuli-responsive FETs coupled with pDSP-1. Beside, pDSP-1 is a typical diketopyrrolopyrroles (DPP)-based conjugated donor–acceptor (D–A) polymer, which is known for its high charge mobility and good photostability.50–54 In pDSP-1, the SP moieties were incorporated into the side chains through covalent bonding; accordingly, the SP units were distributed uniformly within the semiconducting layer, and thus, the stability of the resulting device was enhanced. In comparison, SP was used in constructing responsive FETs via physical blending with the semiconducting polymer or by interfacial/dielectric modifications.26,30–35 The results revealed that the current and performance of the thin FETs coupled with pDSP-1 device could be reversibly tuned in a relatively faster manner by alternating UV and visible light irradiations, or by UV light irradiation, followed by heating, or by addition of acid, followed by heating. Scheme 1 | Chemical structure of pDSP-1 and the schematic representation of the multi-stimuli-responsive FET architecture. For comparative mechanistic studies, pDSP-5, containing different contents of SP groups in the side chains, was also prepared. Download figure Download PowerPoint Results and Discussion Synthesis and characterization of pDSP-1 The SP side chains conjugated DPP-based D–A polymer, pDSP-1, was prepared by Stille co-coupling of compounds 3 (with SP-containing linear alkyl chains) and 4 (with branching alkyl chains) with the bis(stannyl) compound 5 (see ). The molar ratio of compounds 3 and 4 was set at 1∶1 to enable the formation of the polymer pDSP-1, in which the molar ratio of the linear chains with SP units versus the branching alkyl chains is 1∶1. For comparison (see below), the polymer, pDSP-5, for which the molar ratio of the linear chains with SP units versus the branching alkyl chains was decreased to 1∶5, was prepared under similar conditions. After purification, pDSP-1 and pDSP-5 were obtained in 80% and 87% yields, respectively. pDSP-1 and pDSP-5 were characterized by 1H NMR, solid 13C NMR, and by elemental analysis. The molar ratios of SP-containing side chains versus branching side chains in pDSP-1 and pDSP-5 were calculated to be ∼1.09∶1 and ∼1∶4.67, being close to the respective feed ratios, based on the elemental analysis data. The number averaged molecular weights (Mns) and polydispersities (PDIs) of pDSP-1 and pDSP-5, determined by high-temperature gel permeation chromatography in o-dichlorobenzene at 140 °C, were 16.8 kg mol−1 and 2.9, and 26.0 kg mol−1 and 1.4, respectively. pDSP-1 and pDSP-5 could be dissolved in 1,1,2,2-tetrachloroethane (TeCA) to reach a concentration of ∼5 mg mL−1 at 100 °C. They could not dissolve in chloroform and nonhalogenated solvents, such as toluene and tetrahydrofuran (THF). Both pDSP-1 and pDSP-5 were thermally stable with decomposition temperatures of 309 °C and 371 °C (at a weight loss of 5%) based on thermogravimetric analysis (TGA) data (). Apparently, the incorporation of SP units in the side chains did not affect the highest occupied molecular orbital/lowest unoccupied molecular orbital (HOMO/LUMO) levels of pDSP-1 and pDSP-5. On the basis of cyclic voltammograms obtained from cyclic voltammetry (CV) analysis (), the HOMO/LUMO energy levels of pDSP-1 and pDSP-5 were estimated to be −5.18/−3.69 and −5.22/−3.67 eV, respectively (), being close to those of DPP-based D–A polymers reported previously.55–57 Absorption spectral variations for pDSP-1 upon light irradiations, heating, and protonation The SP groups in pDSP-1 were expected to switch reversibly between the closed-form (SP) and the opened form (MC) upon UV and visible light irradiations. As shown in , new absorption peaks in the range of 500–600 nm appeared in the UV-vis absorption spectrum after UV light irradiation of a solution of pDSP-1, and these peaks disappeared after further application of visible light irradiation or heating the solution. Similarly, new absorptions peaks ∼420 nm were observed for the solution of pDSP-1 after the addition of trifluoroacetic acid (TFA or CF3COOH) (see ), and these absorptions disappeared after heating the solution further. We attributed the absorption at ∼420 nm to the formation of the MCH+ form, based on previous reports.47,48 Additionally, such absorption spectral changes could be reversibly repeated for 5 cycles. Moreover, the correlation of the absorption spectral variations with the transformations of SP into MC or MCH+ forms also matched with the data obtained for thin films of pDSP-1. Figure 1a shows the absorption spectra of thin film of pDSP-1 before and after UV light irradiation at 365 nm for 30 s, followed by exposure to visible light irradiation at 470 nm for 10 min. A new absorption at ∼590 nm emerged after UV light irradiation. According to previous studies,47,48 the absorption from 550 to 600 nm is due to the formation of the MC form. Furthermore, visible light irradiation resulted in the gradual decrease of the absorption at 590 nm (see Figure 1b). Visible light irradiation for 10 min was required for the complete disappearance of the absorption due to the MC form. In contrast, this 590 nm peak due to the MC form disappeared quickly after heating the thin film of pDSP-1 at 80 °C for 2 min, as shown in Figure 1c. Indeed, the reversible variation of the absorption at 590 nm for thin film of pDSP-1 could be repeated for five cycles after alternating UV light irradiation and heating at 80 °C, as depicted in Figure 1d. These results indicate that the reversible interconversion between the SP form in pDSP-1 and MC form occurs at fast rates upon UV light irradiation and heating at 80 °C. Moreover, new absorption around 420 nm appeared after the thin film of pDSP-1 was treated with the vapor of TFA (500 ppm for 1 min), and this new peak vanished after further heating at 80 °C for 5 min (Figure 1e,f). We used monomer 3 (see ) as a model for pDSP-1 and pDSP-5 to estimate the conversion ratio by 1H NMR. The 1H NMR spectra of monomer 3 and those after UV light irradiation and treatment with CF3COOD are shown in , respectively. The chemical shifts around 8.65–8.60 ppm, 7.79–7.58, and 6.67–6.64 ppm were due to the MC form (see ), whereas the chemical shifts around 8.50 ppm, 8.29–8.16 ppm, and 7.64 ppm were attributable to the MCH+ form. Based on these 1H NMR data, ∼39.5% of SP units were converted to the MC form after UV irradiation at 365 nm for 30 s. Similarly, ∼82.5% SP units were transformed into the MCH+ moieties after addition of 0.03 M deuterium TFA (d-TFA or CF3COOD). However, the estimated conversion ratios might not reflect the conversion efficiencies of SP into MC (after UV light irradiation) and SP into MCH+ (after treatment with CF3COOH) in thin films of pDSP-1 and pDSP-5. This is because the structures of monomer 3 and pDSP-1/ pDSP-5 are different; thus, their conversion efficiencies are expected to be different both in solution and as thin films. Figure 1 | UV-vis absorption spectra of thin film of pDSP-1: (a) After successive UV light (365 nm for 30 s) and visible light (470 nm for 10 min) irradiations for five cycles. (b) The reversible variations of absorption intensity at 590 nm after alternating UV and visible irradiations. (c) After successive UV light irradiation (365 nm for 30 s) and heating (80 °C for 2 min) for five cycles. (d) The reversible variations of absorption intensity at 590 nm after alternating UV and heating treatments. (e) After successive acid [(CF3COOH) vapor (500 ppm) for 1 min] treatment and heating (80 °C for 5 min) for five cycles. (d) The reversible variations of absorption intensity at 420 nm after alternating acid and heating treatments. Download figure Download PowerPoint Multi-stimuli-responsive FETs We first explored the semiconducting performances of pDSP-1 by fabrication of bottom-gate, bottom-contact (BGBC) FETs before UV light irradiation. Predictably, a thin film of pDSP-1 exhibited a typical p-type semiconducting behavior under ambient conditions based on the transfer and output curves (). As shown in , hysteresis was minimal for the transfer and output characteristics. The maximum/average saturated and linear hole mobilities of thin films of pDSP-1 were measured to be 0.20/0.16 and 0.09/0.07 cm2 V−1 s−1, respectively, after thermal annealing at 160 °C, with on/off ratio of 106–107 (). We further studied the tunable semiconducting properties of FETs with thin films of pDSP-1 after UV light irradiation and heating at 80 °C. Figure 2a and show the transfer and output curves after UV light irradiation at 365 nm for 30 s, followed by heating at 80 °C for 2 min. Undoubtedly, the transfer curve was altered upon UV light irradiation, due to the transformation of the SP moieties of pDSP-1 to MC. Upon heating, the transfer curve was restored, attributable to the conversion of MC to SP. The output curve shows the same tendency (), suggesting that the reversible transformation between SP and MC forms. Such reversible tuning could be repeated for 5 cycles upon the successive UV light irradiation and heating treatment. As shown in Figure 2b and Table 1, the pristine average IDS was measured to be 6.5 × 10−5 A (VGS = VDS = −60 V), and it decreased to 2.1 × 10−5 A after UV light irradiation for 30 s. The drain current increased almost to the initial value after heating the device for 2 min. Figure 2b depicts the reversible variation of the device current for five cycles after alternating UV light irradiation and heating. In addition, the average hole mobility of pDSP-1 thin film could also be reversibly tuned between 0.16 and 0.05 cm2 V−1 s−1. Interestingly, the variation of IDS after UV light irradiation and heating matched well with the variation of the absorption spectra change of pDSP-1 in association with the transformation of the SP and MC forms of SP units in pDSP-1 (Figure 2b). Figure 2 | UV-vis absorption spectra showing: (a) variations in the transfer curves based on different pDSP-1 treatments after alternating UV light irradiation (365 nm for 30 s) and heating (80 °C for 2 min) and (b) the reversible modulation of IDS (VDS = VGS = −60 V) and absorption intensity at 590 nm for five UV/heating cycles. W = 1440 μm, L = 5 μm. I is the drain current upon UV or thermal treatment, while I0 is the initial drain current. A is the absorbance upon UV or thermal treatment, while A0 is the initial absorbance. Download figure Download PowerPoint Table 1 | Average Mobilities (μh), Drain Currents, and Current Variation Ratios for pDSP-1- and pDSP-5-Based FET Devices After UV Light Irradiation or Acid Treatment Polymer μh/cm2 V−1 s−1 I0 Current (10−5 A) Stimulus μh/cm2 V−1 s−1 I Current (10−5 A) Current Variation Ratio (%) pDSP-1 0.16a 6.5a UV 0.05b 2.1b 67d Acid 0.06c 2.3c 65d pDSP-5 0.60a 17.5a UV 0.30b 10.0b 43d Acid 0.28c 9.5c 46d aInitial average mobilities and drain currents (VDS = VGS = −60 V) of pDSP-1 and pDSP-5; baverage mobilities and drain currents after UV irradiations; caverage mobilities and drain currents after acid treatment; dcurrent variation ratio = (I0–I)/I0. We also explored the reversible variations of the semiconducting performances of FETs coupled with pDSP-1 upon either alternating UV and visible light irradiations or alternating acid treatment and heating at 80 °C. As discussed above, the device current and the hole mobility of the thin film of pDSP-1 decreased after UV light irradiation. As shown in Figure 3a,b and , the transfer and output curves for FETs that were treated with UV light, were almost restored to their respective initial ones after further irradiation with visible light at 470 nm for 10 min. Accordingly, the device current (IDS at VGS = VDS = −60 V) was restored to the initial value after further visible light irradiation. Figure 3 | UV-vis absorption spectra showing: (a) variation of transfer curves based on pDSP-1 after alternating UV light (365 nm for 30 s) and visible light (470 nm for 10 min) irradiations; (b) the reversible modulation of IDS (VDS = VGS = −60 V) and absorption intensity at 590 nm for five UV/vis cycles. (c) Variation of transfer curves based on pDSP-1 after alternating acid (500 ppm for 1 min) and heating (80 °C for 5 min) treatment; (d) the reversible modulation of IDS (VDS = VGS = −60 V) and absorption intensity at 420 nm for five acid/heating cycles. W = 1440 μm, L = 5 μm. I is the drain current upon external stimuli treatment, while I0 is the initial drain current. Similarly, A is the absorbance upon external stimuli treatment, while A0 is the initial absorbance. Download figure Download PowerPoint As discussed earlier, and also, displayed in Scheme 1 and Figure 1e, the SP units in pDSP-1 could be transformed into the protonated MC (MCH+) units after exposure to CF3COOH vapor, and the MCH+ moieties, in turn, could switch back to SP upon heating. For this reason, we investigated the variation of semiconducting performances of FETs- pDSP-1 after exposure to the vapor of CF3COOH and heating at 80 °C. First, BGBC FETs were treated with CF3COOH vapor at a concentration of 500 ppm for 1 min, followed by thermal treatment of the devices at 80 °C for 5 min. The transfer and output curves were measured separately before the treatments and after exposure to CF3COOH vapor and heating at 80 °C. As shown in Figure 3c,d, and , both transfer and output curves were varied after exposure to CF3COOH vapor, but the curves were almost restored after further thermal treatment. As listed in Table 1, the average device current (IDS) decreased from 6.5 × 10−5 to 2.3 × 10−5 A with a resultant current variation ratio [(I0−I)/I0] of 65%. After heating at 80 °C, the device current reincreased to 6.5 × 10−5 A. Such current variation could be repeated reversibly by alternating exposures to CF3COOH vapor and thermal treatment. Beside, for drain current, the variation of threshold voltages (Vths) was also observed, as shown in . For instance, Vth for the BGBC FET with pDSP-1 was varied from −5 to −3 V to −10 to −8 V after UV light irradiation. The reversible variation of the semiconducting performance was also observed by treatments with other acids, such as acetic acid (CH3COOH) and hydrochloric acid (HCl), followed by heating, as shown in . These results demonstrated that the semiconducting performances of FETs with pDSP-1 entailing SP units in the side chains could tune reversibly not only by alternating UV light irradiation, visible light irradiation or heating but also by treatment with CF3COOH vapor and heating. Notably, the transfer curves of FETs with pDSP-1 in which the SP units transformed into MC forms could be restored gradually after the devices were left in air for 2 h (see ). This also applied to FETs with pDSP-1 in which the SP units could convert into the MCH+ forms, as depicted in . These results could be attributable to both MC and MCH+ forms able to switch back to the SP forms at room temperature. Thus, the incorporation of SP units in the side chains of pDSP-1 enabled the semiconducting polymer to be multi-stimuli-responsive; accordingly, multi-stimuli-responsive FETs could be fabricated via coupling with such stimuli-responsive semiconducting polymer. Mechanism of FETs/pDSP-1 reversible modulation We further investigated the mechanism of the reversible modulation of the semiconducting performance of FETs with pDSP-1, which is associated with the reversible transformation among SP, MC, and MCH+ upon light irradiations, heating, and acid treatment. We first examined whether the transformation of SP units in pDSP-1 into MC units could influence the interchain packing, thin-film crystallinity, and morphology. We performed geometry measurements by grazing incidence wide-angle X-ray scattering (GIWAXS) on thin film of pDSP-1 untreated and external stimuli-treated samples. The GIWAXS patterns collected for thin film of pDSP-1 before and after UV light irradiation for 30 s and subsequent heating at 80 °C for 2 min are shown in . Our results showed that the 2D-GIWAXS patterns and the corresponding line-cut profiles of thin film of pDSP-1 after UV light irradiation and subsequent heating were almost the same as that of the untreated thin-film (). Both lamellar, including (100), (200), (300), and (400) peaks, and π–π stacking (010) signals for the pristine thin film of pDSP-1 were almost identical to those of the respective thin film after sequential treatments with UV light and heating (). shows the atomic force microscopy (AFM) height images for the untreated spin-coated thin film of pDSP-1 and those after UV light irradiation, followed by heating. The results also revealed no distinct differences in thin-film morphology, consistent with the root-mean-square roughness (RRMS), which remained unchanged for the thin film of pDSP-1 after treatments with UV light and heating. These studies demonstrated that thin-film crystallinity and were not by the transformation of SP units in pDSP-1 into the MC We also measured the of the pristine thin film of pDSP-1 and those after exposure to CF3COOH vapor and sequential thermal treatment at 80 °C (see ) and obtained similar the thin-film of pDSP-1 was also not further that its geometry was not by the treatments. the transformation of SP units in pDSP-1 into the MC units is associated with variations of the dipole moment, that the dipole moment of the SP form is whereas the MC form a dipole moment of In fact, as shown in Figure the for thin film of pDSP-1 were measured to be and before and after UV light irradiations, respectively. Such variation is consistent with the MC form a larger dipole moment than the SP form. is that the MCH+ form, achieved by treatment of the SP form with as the also possess a large dipole According to previous species such as MC and with large dipole might as charge carrier scattering sites by the which to decrease of the FETs device We also observed threshold voltage changes (), which might be due to the variations of charge or semiconducting and we could the reversible tuning of the semiconducting performances of FETs coupled with pDSP-1 to the dipole moment change among SP, MC or MCH+ forms, as in Figure Figure 4 | UV-vis absorption spectra the reversible of based on thin-film of pDSP-1 under UV light irradiation (365 nm for 30 s) and heating treatment (80 °C for 2 Download figure Download PowerPoint Figure 5 | mechanism for multi-stimuli-responsive FETs based on SP-containing semiconducting polymer. Download figure Download PowerPoint further that SP moieties of pDSP-1 are for the charge the polymer pDSP-5 of pDSP-1, Scheme in which the molar ratio of the SP-containing alkyl chains versus the branching ones is 1∶5, was prepared. Thus, polymer pDSP-5 contents of SP units than pDSP-1. After to we that the semiconducting performances of FETs coupled with pDSP-5 could also be tuned reversibly by light irradiations, and heating in the same as FETs with pDSP-1 (see ). However, as shown in Table 1, after UV light irradiation for 30 s, the average device current (IDS at VGS = VDS = −60 V) of pDSP-5 decreased to of the initial current. This further upon exposure of FETs coupled with pDSP-5 to UV and light irradiation, during which the current variation ratio to than that for the FETs device coupled with pDSP-1 under the same conditions. On the other the device current variation ratio exhibited similar after treatment with CF3COOH for FETs coupled with pDSP-5 and pDSP-1. Additionally, as shown in , the for thin film of pDSP-5 were measured to be and before and after UV light irradiations, respectively, and to be than the respective pDSP-1 (see Figure Thus, we from this comparative analysis because pDSP-5 a of SP units than pDSP-1, this resulted in the formation of of MC or MCH+ units after UV light irradiation or treatment with CF3COOH the charge within the thin film of pDSP-5 was by the UV light irradiation or treatment with CF3COOH vapor, with pDSP-1. We report a novel strategy for the of multi-stimuli-responsive polymeric semiconductors through the of SP groups in the side chains of a DPP-based D–A polymer by the of the reversible transformation of SP into MC or MCH+ under light irradiations, and heating. The semiconducting performances of FETs coupled with pDSP-1 that SP units could tune reversibly after alternating UV and visible light irradiations, alternating UV light irradiation, and heating, or alternating protonation with CF3COOH and heating. it was to fabricate multi-stimuli-responsive FETs with such semiconducting SP units in the side chains. Our current results that the molecular transformations among SP, MC, and MCH+ in the side chains of conjugated polymers could affect the charge within the semiconducting thin films. Accordingly, our studies new for applications of semiconducting is of are no

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Oxidation of organic dye using nanocrystalline rare earth metal ion doped CeO2 under UV and Visible light irradiations

Photocatalytic degradation of reactive red 3 and alachlor over uncalcined Fe–TiO2 synthesized via hydrothermal method

Background: Quinazolinones are a class of heterocyclic compounds that have a wide variety of applications. They are also used in agrochemicals. There are several methodologies reported for the synthesis of 2,3-dihydroquinazolines using various catalysts. Method: Here, by using 1-butyl-1,2,4-triazolium as cation and trifluoroacetate as anion, 2,3-dihydroquinazolin-4(1H)-one has been synthesized. For the synthesis of 2,3-dihydroquinazolin-4(1H)-one condensation of anthranilamide with the corresponding aldehyde in the presence of organocatalyst and solvent is done. Using benzaldehyde as the parent aldehyde, to validate the outcome, the benzaldehydes were selected as follows a) benzaldehyde, b) 4-methoxybenzaldehyde – electron releasing group and c) 4-nitrobenzaldehyde – electronwithdrawing group. Solvent study has been done with solvents varied from polar to apolar. Both polar protic and polar aprotic solvents are used for the reactions. The polar protic solvents used were water, methanol, ethanol, isopropanol, butanol, hexane-1-ol, and glycerol. The polar aprotic solvents used are ethyl acetate, DMF,acetonitrile, and DMSO. The moderately apolar solvents used are DCM, carbon tetrachloride, 1,4 dioxane, and chloroform. Results: The synthesized triazolium salts are found soluble in polar aprotic, polar protic solvents and few moderately apolar solvents such as DCM, chloroform, acetonitrile, water, methanol and ethanol whereas insoluble with apolar solvents like toluene, benzene, and hexane.The yield of 2-phenyl-2,3-dihydroquinazolin-4(1H)-one was low for 1-butyl-1,2,4-triazolium trifluoroacetate based organocatalyst. But for substituted benzaldehyde, the yield was comparatively high. Comparatively, the yield for 2-(4-methoxyphenyl)-2,3-dihydroquinazolin-4(1H)-one, where the aromatic benzaldehyde had electron-donating group, is less than 2-(4-nitrophenyl)-2,3-dihydroquinazolin-4(1H)-one, where the aromatic benzaldehyde had an electron-withdrawing group. Conclusion: Substituted benzaldehyde gave better yields than benzaldehyde. And nitro group which is electrowithdrawing attached to benzaldehyde enhanced the electrophilic nature at carbonyl center showed higher yields than methoxy group which is electron donating attached to benzaldehyde as it deactivates the carbonyl carbon. The polar protic solvents like water, ethanol and methanol stabilizes the ionic intermediates and gave better yield. Even the moderately apolar solvents like DCM, chloroform resulted in good yields, green solvents like water, ethanol and methanol would be a better choice as solvents. The carbon chain on the solvent has got an effect on product yield. As the carbon chain increases in solvent, the yield decreases due to the separation difficulties. The polar aprotic solvents did gave better yields but not as good as polar protic solvents.

Anthelmintic drugs such as mebendazole, niclosamide, albendazole, pyrantel, pyrvinium etc. have been applied to kill the helminthes, worm-like parasites such as flukes, roundworms, and tapeworms, in humans and livestock [1, 2]. Pyrvinium pamoate as a quinoline-derived cyanine dye, has been used to treat pinworm, nematode, or a roundworm infection in humans [3, 4]. This drug as an FDA-approved classical anthelmintic, can be useful for cancer therapy, antitumor activity [3, 5, 6]. During the past decades a wide range of these compounds as well as other pharmaceuticals have been described as emerging environmental contaminants [7-10]. High levels of pharmaceutical compounds have been discovered in sewage, sludge fields, surface water, groundwater, and even drinking water [11]. The majority of the adverse effects of toxic organic micro-pollutants has increased the requirement of the complete removal of these contaminants from the aquatic environment [12]. Different procedures such as physical approaches (flocculation, adsorption, coagulation, and membrane filtration, etc.), chemical approaches (electrochemical treatment and ozonation), and biological methods (using microorganisms and/or enzymes) have been applied for degradation of dyes and drugs [13, 14]. Advanced oxidation processes (AOPs), such as Fenton's oxidation, ozonation, photocatalytic oxidation, and sonolysis have been widely used for treatment of wastewaters [15-18]. AOPs have related to the ultraviolet light and semiconductors such as titanium dioxide (TiO2) and zinc oxide (ZnO) etc. and applied for the change of molecules and the formation of hydroxyl radicals (OH) [17, 19, 20]. In general, photocatalytic oxidation together with ultraviolet radiation formed a redox environment in the aqueous solution and usually decomposed the undesired contaminant into water [21, 22]. Investigation of photocatalytic methods by using the photo-catalysts such as TiO2, ZnO, WO3, Fe2O3, ZnS, and CdS have included in the previous studies for the removal of pollution resources from wastewaters [17, 23]. For example, Jiang et al. [24] described about photocatalytic degradation of dimethyl phthalate by TiO2 coated glass microspheres–UV irradiation process. In the other study done by Zhang et al. [25], the photo-catalyst nano-TiO2 has been successfully applied for the degradation of chloramphenicol under UV irradiation [25]. Zeolites as crystalline aluminosilicates with 3D microporous structure, which attracted great attentions due to their unique properties such as ion exchangeability, high thermal, mechanical, and chemical stability, high capacity for catalytic reactions. The uses of zeolites for removal of pharmaceuticals from wastewaters have been reported in the last decades [26-28]. For example, Li et al. [27] applied the HZSM-5 zeolite supported boron-doped TiO2 for photocatalytic degradation of ofloxacin. Liu et al. [28] also used novel CoS2/MoS2@Zeolite for tetracycline removal in wastewater. The statistical and mathematical methods have successfully been applied to determine the optimal conditions for a variety of processes [8, 9, 24, 25]. In the study of Farzadkia et al. [11], the influences of some effective parameters, such as varying of pH value, nano-ZnO loading amount, UV-A light time, and intensity of radiation on the degradation efficiency of metronidazole in aqueous solution were discussed through photocatalytic trials using nano-ZnO as the photo-catalyst [11]. Optimization of photocatalytic degradation of phenazopyridine under UV light irradiation using immobilized TiO2 nanoparticles studied by Fathinia and Khataee [29]. In the present study the potential ability of the synthesized zeolite-based nanostructures for elimination of pyrvinium pamoate (PP) in the presence of UV light and H2O2 was evaluated. For this purpose, response surface methodology (RSM), a mathematical and statistical technique, was applied for the optimization of the removal process of PP and determines the optimum operational condition of the removal (%) by a predictive model. Pyrvinium pamoate was purchased from Aboureihan Pharmaceuticals Co. (Tehran, Iran). Sodium hydroxide, silicon dioxide, sodium aluminate, and hydrogen peroxide (H2O2) solution (30 wt%) were obtained from Merck chemicals (Darmstadt, Germany). All other chemicals and the used solvents were of analytical grade. In order to synthesize zeolite-based nanostructures, 5 mL sodium hydroxide (2 m) was added to a 50 mL round bottom balloon and 0.05 g silicon dioxide was added to the above solution until clarified completely. In the next step, the obtained silicate solution was slowly added to the alumina solution (0.1 mm) to form a clear white gel. The formed white gel was then transferred to a 250 mL container and exposed to microwave irradiation in a domestic microwave oven operating at 2,450 MHz for different output such as 600 and 300 W for 15 min. Then, the solution was transferred to an autoclave and heated at 200°C for 6 h. Then, to eliminate the alkalinity, the solution was passed through a filter paper and washed several times with deionized water. The pH of the solution was measured after each washing step until the solution reached a dull state and the pH adjusted to approximately 7. The remaining precipitate from the washed solution was transferred to a glass filter on a filter paper and kept aside for 9 h. At the final step, the precipitates were dried in vacuum at 50°C for 48 h. XRD patterns of as-synthesized zeolite-based nanostructures were collected from a diffractometer of Philips company with X'PertPro monochromatized Cu Ka radiation (k = 1.54 A°). Microscopic morphology of the products was visualized by a LEO 1455VP scanning electron microscope (SEM) operated at 20 keV. The synthesized zeolite-based nanostructures were examined for removal of PP by direct irradiation of UV light in a UV cabinet equipped by three 15 W UV lamps with wavelength of 254 nm (Philips, Holland) which sited in 25 cm on the top and behind the batch photoreactor [8, 30]. The reaction mixture was prepared by mixing PP solution of different concentrations (5−100 μg/mL) with the altered doses of nanostructure solution (0.5−5 μg/mL) and hydrogen peroxide (0−5 mm). The prepared mixtures were continuously stirred for 60 min in the presence of UV light (15−30 W/m2) and samples then taken each 15 min for 60 min. The nanocatalyst was then removed by centrifugation (8,000 × g for 5 min) and filtration (0.22 μm filters). The concentration of PP in samples was monitored using a Shimadzu UV–vis Double Beam PC Scanning spectrophotometer (UV-1800, Shimadzu CO, USA) at maximum absorbance of 507 nm (Figure 1). The experimental design technique, response surface methodology (RSM), was employed to optimize the removal process [8, 25, 31]. The removal effectiveness of pyrvinium pamoate was assessed using D-optimal design. Four factors were chosen including nanostructure dose (1−2 μg/mL), drug concentration (10−50 μg/mL), hydrogen peroxide concentration (0−1 mm), and light intensity (15−30 W/m2) (Table 1). XRD pattern of the as-synthesized zeolite-based nanostructures sample is shown in Figure 2. It can be seen from the XRD pattern that crystallinity phase shows the formation of structures in a completely pure way. No other crystalline phases were detected in the heated sample. The diffraction peaks of the as-synthesized zeolite-based nanostructures were matched with the signals of standards including Na2CO3 (JCPDS No. 00-018-1208), NaNO3 (JCPDS No. 01-070-1518) and Na3H (CO3)2.2H2O (JCPDS No. 01-078-1064) (Figure 2). Talebian-Kiakalaieh and Tarighi [32] synthesized and characterized the initially parent NaY and ZSM-5 zeolites. All XRD patterns demonstrated the high crystallinity of obtained zeolites without any amorphous phase. Ahmadi et al. [33] showed the characteristic peaks of zeolite NaY at 2 theta 6.1°, 11.8°, 15.5°, and 23.4°. Selim et al. [34] prepared the Na-A zeolite from aluminium scrub and sodium silicate and revealed the formation of pure Na-A zeolite without interference of other crystalline by-products [34]. Microscopic images show that samples are nanometre-sized and generally formed on a regular, uniform substrate (Figure 3). Ramezani et al. [35] synthesized NaY zeolite and revealed the formation of well-shaped crystals with an approximate size of 1 μm. Ameri et al. [36] observed the faujasite and hexagonal shapes for NaY and ZSM-5 zeolite, respectively, in the SEM images [36]. FESEM images of NH4Y zeolite, and amorphous silica–alumina assessed by Aghakhani et al. [37]. The NH4Y zeolite showed the agglomerated particles with smooth surface and sharp edges having average particle size of 0.7 μm while silica–alumina displayed rough surface irregular agglomerates with sizes in the range of 0.2–2 μm [37]. TEM analysis was used to further investigate the surface properties of zeolite-based nanostructures. According to the TEM image it can be concluded that the porous structures were well formed. The average pore size is below 50 nm. TEM image of the as-synthesized zeolite-based nanostructures is shown in Figure 4. In order to study the porosity of as-synthesized zeolite-based nanostructures, the Brunauer–Emmett–Teller (BET) analysis was used. The obtained data through the BET and BJH with the adsorption/desorption isotherm method demonstrate that cross section area, total pore volumes and dead volume were calculated 0.162 nm2, 0.062 cm3/g, and 17.442 cm3, respectively. BET analysis of the as-synthesized zeolite-based nanostructures is shown in Figure 5. It seems that with increasing the amount of porosity at the level of zeolite structures, these porosities are evenly distributed at the surface of the sample. Energy-dispersive X-ray spectroscopy (EDX) elemental mapping was used to show the distribution of elements within some selected area as a complement to the SEM analysis in the distribution of the as-synthesized zeolite-based nanostructures. The EDX elemental mapping is shown in Figure 6. In this example, the number of elements formed with a uniform scattering distribution. There is a small amount of Ti as impurities in the sample. At first, the effects of each parameter were individually assessed on the removal of PP and thus, the parameters, such as the initial concentration of PP, existence of zeolite-based nanostructures, the presence of UV light irradiation, UV light intensity, the presence of H2O2, and irradiation time were solely evaluated on the elimination of PP in solution. The obtained results showed that the total parameters have the positive effects on the removal process. So, these factors were selected for the optimization of removal conditions of PP using RSM. However, the irradiation time was considered to be constant during the PP removal process (15 min). These results were in accordance with the results reported by Samara et al. [38], who showed that the photodegradation in the absence of a catalyst resulted in changes of the peak intensity under 302-nm UV light. Wang et al. [26] assessed the effective degradation of sulfamethoxazole by Fe2+-zeolite/peracetic acid, and reported that the increase in Fe2+-zeolite/peracetic acid dosage enhanced the degradation of sulfamethoxazole. Sturini et al. [39] evaluated the photocatalytic removal for the degradation of ofloxacin from polluted water. They found that the highest degradation rate (95%) obtained in the presence of undoped composites, the synthesized sepiolite–TiO2 (ST-1) and the synthesized zeolite–TiO2 (ZT) [39]. Before performing of the experimental design, initial experiments (selected as one factor study) were accomplished to evaluate the effect of each parameter on PP elimination. Results obtained by individual factors including the elimination in the absence of UV light (in the presence of zeolite-based nanostructures and dark conditions), photolysis (UV light irradiation), and photodegradation (assisted by UV/zeolite-based nanostructures) for a time period of 90 min proved that factors of UV light intensity, irradiation time, and existence of zeolite-based nanostructures positively affected the elimination of PP. So, these factors were selected for the optimization of PP elimination using UV/zeolite-based nanostructures/H2O2. However, the radiation time was remained constant (15 min) during the removal processes of PP. The graphical tools were applied for diagnostics of the normal distribution of data. The residuals versus the predicted plot were the residuals versus the ascending predicted response values. As shown in Figure 7a, the plot must have a random scatter, which is appropriate for continuing analysis. Figure 7b represents a graph of the actual response values versus the predicted response values. The data points should be split evenly by the 45° line. It can be seen that there was a high correlation between the predicted and experimental PP removal (%). The relationship between factors and PP removal (%) was investigated by 3D surface plots. Figure 8a shows the effect of H2O2 concentration and nanostructure dose on pyrvinium pamoate removal (%), while factors such as drug concentration and light intensity were kept at their centre points. As can be seen in the plot, the PP removal (%) improved with increase in nanostructure dose from 1 to 2 μg/mL. However, the removal of PP decreased with the increase in H2O2 concentration (Figure 8a). In the study performed by Zhang et al. [25], they found that the degradation rate of chloramphenicol was 85.97% under optimal conditions especially at TiO2 concentration of 0.94 g/L. Gupta et al. [9] reported that the maximum quinoline degradation efficiency (about 92%) obtained at the optimum condition of 400°C calcination temperature, 8 pH, 1:1 ZnO:TiO2 molar ratio, 50 mg/L initial quinoline concentration, and 2.5 g/L catalyst dose [9]. Photocatalytic degradation of 2,3,7,8-tetrachlorodibenzofuran (2,3,7,8-TCDF) evaluated by Samara et al. [38]. They also applied the both types of silver zeolite (AgY1 and AgY2) to degrade 2,3,7,8-TCDF. The amount of the adsorbed 2,3,7,8-TCDF on AgY1 and AgY2 catalyst was 37.9% and 18.9%, respectively [38]. In general, the amount of catalyst has affected on the degradation efficiency due to provide a greater number of actives sites. Therefore, an enhancement in the amount of catalyst has led to increase in the number of •OH radicals, which produced more free electrons [8, 9]. The effects of the light intensity and H2O2 concentration (other factors such as drug concentration and nanostructure dose were at centre points) on the removal (%) of PP are shown in Figure 8b. The results show that the PP elimination (%) increased with the increasing of light intensity (Figure 8b). Indeed, this behaviour is as an indication of producing the activated •OH and the atomic oxygen due to absorbed UV light energy via H2O2 and O─O bond. The created molecular oxygen, an electron acceptor, operates for the avoidance of recombination of electrons and holes during the photochemical process [17, 40, 41]. When, the higher light intensity was used for the degradation process, the more electron–hole pairs were created by photocatalyst elements [17, 40, 41]. Since the same study reported by Trapido et al. [42] for diclofenac degradation. They applied the several protocols such as UV photolysis, H2O2/ photolysis, and Fenton/photo-Fenton treatment for the diclofenac degradation and reported that the UV photolysis was the main pathway for diclofenac degradation. Achilleos et al. [40] applied the hydrogen peroxide as an oxidizer on diclofenac degradation. They found that the ratio of H2O2 to drug concentration influenced the rate of degradation. Samy et al. [43] synthesized the nanocomposites of carbon nanotubes/lanthanum vanadate for the photocatalytic degradation of a sulfamethazine and optimized the degradation parameters such as solution pH, catalyst dose and light intensity using a central composite design. The predicted and experimental sulfamethazine removal rates were 95.54% and 96.2%, respectively, in the optimum parameters obtained 3.0 (pH), 0.2495 g/L (catalyst dose), and 152.727 W/m2 (light intensity). Apollo et al. [44] assessed a UV/H2O2/TiO2/Zeolite combined system for treatment of molasses wastewater and achieved the highest decolorization in the order H2O2/UV/TiO2/zeolite > H2O2/UV/TiO2 > UV/TiO2 > H2O2/UV system [44]. The effect of drug concentration and nanostructure dose, while factors such as H2O2 concentration and light intensity were at centre points, on PP removal (%) is presented in Figure 8c. It can be observed that nanostructure dose had a major effect on the response, with a high increase in PP removal for high nanostructure dose (2 μg/mL) (Figure 8c). When, an increase in drug concentration from 10 μg/mL to 50 μg/mL decreased the elimination of PP from 65.00% to 60.20%, at high nanostructure dose (2 μg/mL). As observed, at high concentration of drug (50 μg/mL) and in the presence of low dose of nanostructure (1 μg/mL), the PP removal (%) was occurred 53.15% (Figure 8c). Mostafaloo et al. [45] optimized the degradation parameters of ciprofloxacin by BiFeO3 nanocomposites using RSM. The maximum ciprofloxacin removal (100%) obtained at pH 6, initial ciprofloxacin concentration of 1 mg/L, BiFeO3 dosage of 2.5 g/L, and at 30°C for 46 min. They found that the removal efficiency enhanced at low level of ciprofloxacin and at high level of BiFeO3. Apollo et al. [44] reported that when the molasses concentration increased from 1 to 20 g/L, the degradation efficiencies decreased from 57% to 49%, respectively [44]. In the other study of Gupta et al. [9], the initial quinoline concentration (ranging from 50 to 500 mg/L) evaluated for photocatalytic degradation of quinoline. They observed that increasing the concentration of quinoline from 50 to 500 mg/L, the degradation rate reduced from 81.2% to 45.3%, respectively [9]. Figure 8d illustrates the effects of nanostructure dose and light intensity on PP removal efficiencies. As shown in from Figure 8d, the highest removal percent of PP (62.85%) obtained when the nanostructure dose and light intensity were 2 μg/mL and 24 W/m2, respectively. Similar observations were reported by Li et al. [27], who applied HZSM-5 zeolite supported boron-doped TiO2 with ultraviolet irradiation for photocatalytic degradation of ofloxacin [27]. The photocatalytic degradation of tetracycline using a series of CoS2/MoS2@Zeolite photocatalysts showed that CoS2/MoS2@Z-50 was the most effective photocatalyst. Nenavathu et al. [46] found that there is the significant difference between removal of trypan blue with and without UV light irradiation using Se-doped ZnO NPs [46]. Generally, an enhancement of electron–hole pairs generation and an increase of the hydroxyl radical formation depends on the higher energy obtained from UV light intensity, which led to enhancement of removal efficiency [17, 31]. The adequacy of the model was validated under the optimal conditions obtained from D-optimal design (Table 4). Experimental PP removal (%) was found 70.14±1.71% at the optimal conditions. Also predicted PP removal (%) was calculated 72.25 ± 1.23% at the optimal conditions. According to results, verification experiments confirmed the validity of the predicted model (Table 4). Based on Figure 9, the PP removal (%) was increased (97.67 ± 1.1%) with enhancement of irradiation time of 15 to 60 min. X1: 2.00 μg/mL X2: 10.00 μg/mL X3: 0.00 mm X4: 22.50 W/m2 The present study was designed to assess the elimination of PP in the presence of the synthesized zeolite-based nanostructures assisted by UV light radiation in the aqueous solution. Statistical method, D-optimal design, was applied to optimize the essential components for elimination. The effect of four factors including nanostructure dose, drug concentration, H2O2 concentration, and light intensity were evaluated on removal efficiency of PP. Among the total variables, nanostructure dose, and light intensity were significantly showed positive effects on PP removal (p < 0.05), while H2O2 concentration, and drug concentration had negative effect (p < 0.05). Lastly, the best optimum conditions for maximum elimination of PP (70.14 ± 1.71%) was experimentally reached at nanostructure dose of 2.00 μg/mL, drug concentration of 10.00 μg/mL, H2O2 concentration of 0.00 mm, light intensity of 22.50 W/m2, which was very near to the predicted amount (72.25 ± 1.23%). The PP removal (%) was also increased (97.67 ± 1.1%) with the enhancement of irradiation time of 15–60 min. The obtained results confirmed the potential application of zeolite-based nanostructures in the presence of UV light radiation for elimination of the PP. However, more studies are needed to investigate the related mechanism(s) on this process and to identify the probable by-products. Research reported in this publication was supported by Elite Researcher Grant Committee under award number [982564] from the National Institute for Medical Research Development (NIMAD), Tehran, Iran. The authors declare no conflict of interest. None Research reported in this publication was supported by Elite Researcher Grant Committee under award number [982564] from the National Institute for Medical Research Development (NIMAD), Tehran, Iran. Furthermore, we thank the Pharmaceutics Research Center, Institute of Neuropharmacology, Kerman University of Medical Sciences (Kerman, Iran). The data that support the findings of this study are available from the corresponding author upon reasonable request.

A polyimide containing main-chain chalcone groups and hydroxyl side-groups was synthesized.In the synthesis,1,3-dioxoisobenzofuran-5-carbonyl chloride was obtained by the reaction between 1,2,4-benzenetricarboxylic anhydride and SOCl_2.1,3-Bis(4-(2-hydroxyethyl) phenyl)prop-2-en-1-one was synthesized by the nucleophilic substitution reaction between 2-chloroethanol and 1,3-bis(4-hydroxyphenyl)-prop-2-en-1-one,which was synthesized from the Claisen-Schmidt condensation of 4-hydroxybenzaldehyde and 1-(4-hydroxyphenyl)ethanone.The new dianhydride monomer containing chalcone group was prepared by reactions between 1,3-dioxoisobenzofuran-5-carbonyl chloride and 1,3-bis(4-(2-hydroxyethyl)phenyl)prop-2-en-1-one.The polyimide was obtained by polycondensation of the dianhydride monomer with 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane and subsequent thermo imidization.The chemical structure and properties of the polyimide were characterized by 1H-NMR,FTIR,GPC and thermal analysis.The number average molecular weight(M_n) of the polyimide is 27310 with a polydispersity index of 1.55.The glass transition temperature(T_g) of the polyimide is 207℃ obtained from the DSC thermogram.The thermal degradation temperature(T_d) is 382℃ measured at the point with a weight lost of 2.5% from the thermogravimetric curve.The polymer shows good solubility in aprotic polar organic solvents such as DMF,DMAc and THF.The polyimide has an absorption maximum at 342 nm due to the chalcone group.Upon the UV light irradiation,the polyimide can undergo sensitive photocycloaddition reaction.After UV light irradiation with the dose of 20 J/cm2,the absorbance band at 342 nm disappears completely,and the film is insoluble in DMF.The polyimide synthesized in this work can be expected for applications as photoimagable materials and others.