Synthesis, characterization and fluorescence quenching of conjugated polymer containing triphenylamine group

Poly(triphenylamine-p-phenylenevinylene)s with two different end-groups were obtained through a Wittig polycondensation. The structures of two copolymers were characterized. Ultraviolet and visible spectroscopy (UV-Vis) and photoluminescence (PL) spectra show the end-capped polymer emits intensive green light in both solution and film state. Their applications in the detection of nitro compounds were investigated, and the results show high fluorescence quenching sensitivity of the end-capped polymer towards o-nitrotoluene (o-NT). When the concentration of o-NT was 21.5 × 10⁻³ mol/L, the fluorescence quenching reached 96%. Additionally, after the exposure of polymer film in three different quenchers such as dinitrotoluene (DNT), p-nitrobenzoquinone (p-BQ) and p-nitrotoluene (p-NT) for 600 s, its fluorescence quenching reached 93.6%, 11.5% and 77.9%, respectively. This kind of polymer has great advantages in preparation and may find applications in the detection of nitro explosives. __________ Translated from Journal of Functional Polymers, 2008, 21(1): 11–16 [译自: 功能高分子学报]     

Synthesis of a novel fluorene-based conjugated polymer with pendent bulky caged adamantane moieties and its application in the detection of trace DNT explosives

A novel fluorene-based conjugated polymer with phenylene spacers and steric bulky adamantane moieties in side chains has been synthesized by palladium-catalyzed Suzuki coupling reactions. This design strategy offers several advantages for the detection of trace 2,4-dinitrotoluene (DNT) vapor. The incorporation of the two groups into polymer side chains could retain an effective conjugation length and prevent the π-stacking of polymer chains. The detection of DNT vapor indicated that the polymer displayed higher fluorescence quenching sensitivity toward the explosives in films compared to reference polymers. The fluorescence quenching efficiency of the fluorescent polymer achieved 33.3% in 10 s and 71.1% in 60 s. The pathways or cavities generated by the two spacers are beneficial for the rapid diffusion of explosive vapor into the film interiors and increase the fluorescence quenching efficiency of the film.     

木质素磺酸钠荧光膜的制备及其在硝基爆炸物检测中的应用

以木质素磺酸钠(LS)为原料,聚乙烯醇为黏合剂,制备了木质素磺酸钠荧光膜。通过荧光光谱仪和激光粒度分析仪对LS的形态和光学性质进行了分析,研究了硝基化合物和无硝基化合物对LS的荧光猝灭作用及猝灭机理,并将木质素磺酸钠荧光膜应用于硝基爆炸物的检测。研究结果表明：LS随着制备溶剂中乙醇体积分数的增加,其荧光发射峰强度增加,分子之间发生缓慢聚集,且聚集体颗粒变大,具有聚集诱导发射(AIE)性质;硝基苯和对硝基苯酚均对LS的荧光猝灭程度高达90%,间二硝基苯对LS的荧光猝灭程度也有56%;苯、甲苯、苯酚、对苯二甲酸、对苯二甲醛和邻苯二甲醛等无硝基化合物对LS的荧光猝灭作用几乎没有。LS对硝基苯、间二硝基苯和对硝基苯酚等硝基化合物显示出专一、特异的高灵敏检测性能,该现象主要由光诱导电子转移机制造成的。浸泡过硝基苯/乙醇溶液、间二硝基苯/乙醇溶液和对硝基苯酚/乙醇溶液的木质素磺酸钠荧光膜的荧光猝灭程度分别为89%、 78%和100%。将硝基化合物溶液在荧光膜上涂写,在日光下观察不到笔迹存在,而在紫外光下能观察到笔迹部分有明显的荧光猝灭现象。     

Effect of film thickness, blending and undercoating on optical detection of nitroaromatics using fluorescent polymer films

In this work, using a fluorescent poly(phenylene ethynylene) containing the rigid pentiptycene and large cholesteryl ester pendent groups, the fluorescence quenching properties of the polymer thin films in response to vapor of 2,4-dinitrotulene (DNT) have been investigated by varying the film thickness, applying an undercoating and blending with another polar polymer. A significant change in fluorescence intensity (51% in 60 s) in response to DNT vapor exposure at ambient temperature was achieved when the polymer film coated on glass plate was about 2 nm in thickness. In comparison with the film of polymer alone, the film undercoated with (3-aminopropyl)triethoxysilane and the film of polymer blend containing a non-fluorescent polymer showed additional 18.5% (in 20-s exposure) and 18.7% (in 5-min exposure) decrease in fluorescence intensity, respectively. The use of polymer or polymer blend coated on optic-fiber tip for detection of DNT vapor has also been demonstrated.     

Eu-Phen-AA-MMA共聚物的合成及性能

用先络合再聚合和先聚合再络合的方法,合成了稀土高分子铕(Eu)-邻菲罗啉(Phen)-丙烯酸(AA)-甲基丙烯酸甲酯(MMA)。用红外光谱和X射线衍射测试方法对其结构和物相进行了分析,表明铕与高分子基质发生配位。比较二者的荧光性质,发现得到的配位聚合物是一种良好的光致发光材料,在紫外光下发出亮度和单色性高的特征红色荧光,但当配位聚合物中铕离子(Eu3+)的质量分数达1.97%时,第二种方法合成的聚合物发生浓度猝灭现象。     

Solvent penetration and photoresist dissolution: A fluorescence quenching and interferometry study

A novel method, based upon fluorescence quenching measurements, is described for the study of the mechanistic details of solvent penetration into thin polymer films. Here poly(methyl methacrylate) (PMMA) labelled with phenanthrene (Phe) groups was coated as a film (0.8 μm thick) onto quartz disks. Diffusion of solvent (1 : 1 2-butanone/2-propanol) into the film was followed by a decrease in Phe fluorescence, while film dissolution was monitored simultaneously by laser interferometry. In the case of PMMA (M_w = 411,000, films annealed at 160°C) both processes occur at approximately the same rate and exhibit non-Fickian (relaxation-controlled) diffusion behavior. Correlating the results of these two experiments shows that, once the steady state is reached, the dissolution rate is controlled by the advance of the solvent front into the PMMA film. The “transition layer,” an important dissolution parameter, increases its thickness from 50 to 90 nm during the plasticization stage of solvent penetration and maintains its thickness until the solvent front reaches the quartz substrate.     

Low‐potential electrochemical polymerization of 6‐nitroindole and characterization of its polymers

Conducting polymers bearing nitro substituents are very important from both academic and industrial viewpoints. However, it is very difficult to electrosynthesize such conducting polymers because of the strong electron‐withdrawing effect of nitro groups. In this article, we describe the electrochemical synthesis of films of a new conducting polymer, high‐quality poly(6‐nitroindole) (P6NI), by direct anodic oxidation of 6‐nitroindole in boron trifluoride diethyl etherate containing 10% (v/v) diethyl ether. The oxidation potential onset of 6‐nitroindole in this medium has been measured to be just 0.98 V versus a saturated calomel electrode (SCE), which is much lower than that determined in acetonitrile containing 0.1 mol/L tetrabutylammonium tetrafluoroborate (1.6 V vs SCE). Thermal studies have revealed that P6NI displays good thermal stability. The electrical conductivity of the P6NI films has been measured to be 0.08 S/cm. Structural studies have shown that the polymerization of the 6‐nitroindole ring occurs mainly at the 2,3‐positions. Fluorescence spectral studies have shown that the principal excitation and emission peaks of P6NI are at 416 and 535 nm, respectively, with a fluorescence quantum yield of 0.05. All these properties of P6NI films may facilitate their potential applications in various fields, such as electrochemical sensors and green‐light‐emitting materials. To the best of our knowledge, this is the first report on the electrosynthesis and characterization of 6‐nitro‐substituted polyindole films. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Understanding of mechanistic perspective in sensing of energetic nitro compounds through spectroscopic and electrochemical studies

Understanding the probable mechanism of detection plays a significant role in selecting a particular fluorophore for the detection of the complicated and low volatile analyte namely, nitroaromatic and non-aromatic high energy materials (HEMs) in the development of detection devices when compared with the existing techniques. The fluorescence quenching employing conducting polymers-based response of HEMs have attained great significance in recent times. Amongst all conducting polymers, functionalized polyaniline can act as a fluorophore in quenching studies. This report also reveals the importance of studying electrochemical methods associated with the changes observed in the oxidation potential and its resemblance with fluorescence quenching study in establishing the probable mechanism associated with the sensing study of HEMs (viz., RDX, PETN, CL-20 and RDX: CL-20 Cocrystal). FTIR and resonance Raman characterization helped us to understand the interaction between nitro groups present in HEMs with benzenoid unit or polaronic or bipolaronic nitrogen of camphor sulfonic acid doped polyaniline (CSA[PANi]). Employing Stern Volmer plot, the efficiency of quenching and quenching mechanisms of complex structure formed between the fluorophore and HEMs is understood.     

A Novel Light-Cured Dental Material Based on Maleic Copolymer Functionalized With Urethane Derivative for Dental Applications

The purpose of this work was to obtain a polymeric material aimed at being easily applied in a thin film on an organic substrate for dental applications. A maleic anhydride copolymer functionalized with a urethane derivative bearing methacrylate groups was synthesized, and by its mixing with commercial dental monomers, two light-curing formulations were prepared and investigated. The surface morphology and physicochemical properties of the obtained materials are affected by their composition. An increase of the diffusion coefficient from 0.38 at 3.58 µm²/s (estimated by fluorescence recovery after photobleaching) could ensure minimal moisture of an organic injectable paste situated under this polymer film.     

Surface properties and chain structure of fluorinated acrylate copolymers prepared by emulsion polymerization

The fluorinated copolymer poly (MMA–co–FMA), composed of methyl methacrylate (MMA) and 2-perfluorooctylethyl methacrylate (FMA), was prepared by emulsion polymerization using a pre-emulsified monomer addition process. The results showed that the contact angle of water on its solvent-borne film increased dramatically and reached 118o when the FMA content in the copolymer was only 0.65 mol%, approaching that of poly(2-perfluorooctylethyl methacrylate) homopolymer. Unlike the copolymer prepared by solution polymerization, X-ray photoelectron spectroscopy (XPS), and sum frequency generation (SFG) vibrational spectroscopy analysis results indicated that the fluorinated moieties in this polymer were very easily segregated at the surface of the film. The interfacial structure and properties of this polymer in solution were investigated using SFG, surface tension, and dynamic laser light scattering (DLS). It was found that emulsion polymerization produced a chain structure of the fluorinated copolymer similar to that of FMA capped PMMA, thereby providing a possible way to produce fluorinated end-capped polymers using a popular polymerization method.     

Conjugated fluorescent polymer sensor for proteolytic activity detection with designed specificity

A portable fluorescence assay for direct endopeptidase activity detection has been developed with the use of a cyclophane‐based conductive conjugated fluorescent polymer and peptide substrates. The substrates, carrying internal quenching amino acid, were designed to be cleaved in a sequence‐specific manner by a protease of interest. Intact substrates were incapable of quenching the fluorescence of the polymer due to steric constraints. Upon specific cleavage, the quencher became exposed and could interact with the ring structure of the fluorescent polymer, disrupting the conjugation and quenching the fluorescence along the polymer chain. The approach was developed using a model Glu‐C endopeptidase from Staphylococcus aureus strain V8, detected in the picomolar to micromolar concentration range. The developed assay was tested for the detection of endopeptidase activity of botulinum toxin. The feasibility study showed that botulinum neurotoxin (BoNT)‐A could be detected down to picomolar concentration, with limit of detection of 5 pg, or 33 amol in 5 µL of sample, and a total assay time under 2 h. The assay exhibited high specificity and no cross‐reactivity with BoNT‐B was detected. Following this proof‐of‐concept work, the assay can be further optimized and expanded to differentiate between various botulinum toxin serotypes in their active proteolytic form, or modified for detection of proteases with other specificities. © 2015 Society of Chemical Industry     

Fluorescence Intensity Modulation in Photochromic Conjugated Polymer Systems

The ability to modulate fluorescence intensity with a light signal enables a variety of applications based on fluorescence imaging. One approach to fluorescence photomodulation involves using a photochromic moiety that responds to a light signal in conjunction with a nearby fluorophore. We employ conjugated polymers based on poly(p-phenylene vinylene) (PPV) as the fluorophore in photochrome-fluorophore systems for fluorescence modulation. Advantages of using conjugated polymers for this purpose include their intrinsic energy migration processes that enable amplified fluorescence quenching as well as their processability. Here we present examples of PPV-based photomodulation systems that employ photochromic dyes from three common photochromic families: azobenzenes, spironaphthoxazines, and diarylethenes. In all cases we observe reversible fluorescence quenching due to fluorescence resonance energy transfer to the photogenerated form of the photochrome. Examples of the photomodulation of photochromic PPV systems in organic solution, polymer films, and conjugated polymer nanoparticles are presented.     

基于氮掺杂碳量子点的荧光微球制备和Fe3+检测

分别以尿素、氨水、二乙烯三胺、多乙烯多胺为氮源,绿色廉价的白菜为碳源,采用水热法合成氮掺杂的蓝色荧光碳量子点,结果表明多乙烯多胺氮掺杂碳量子点（NCDs）荧光量子产率最高为53.3%。然后将NCDs作为荧光探针应用于荧光微球制备和Fe³⁺检测方面,以三聚氰胺甲醛（MF）为载体,合成了氨基化MF荧光微球;基于Fe³⁺对NCDs良好的荧光猝灭效应,建立了一种荧光测定Fe³⁺的方法,并对NCDs和MF荧光微球的结构和性能进行表征。结果表明,NCDs的荧光性能得到了显著的改善;MF荧光微球单分散性好、荧光性能好且稳定,在生物医学领域方面有重要的应用价值;NCDs对Fe³⁺具有单一选择性,Fe³⁺浓度在0~2μmol/L内与NCDs的荧光猝灭程度呈良好的线性关系（R²=0.9945）,检出限为0.035μmol/L。将该体系应用于实际水样中Fe³⁺的测定,相对标准偏差（RSD,n=6）在1.42%~3.02%内,加标回收率在98.7%~104.5%之间。该体系对Fe³⁺检测灵敏性好、选择性高以及抗干扰性强,在离子分析检测方面有潜在的应用前景。     

Insoluble porous conjugated polymer films via phase separation and photo‐crosslinking for the trace detection of 2,4‐dinitrotoluene

A novel conjugated polymer film with microscale/submicroscale porous morphology fabricated from crosslinked poly(fluorene‐co‐carbazole) (PFC1) was developed for the detection of 2,4‐dinitrotoluene (DNT). The fluorescent conjugated polymer PFC1 with pendant photo‐crosslinkable coumarin groups was synthesized by Suzuki coupling polymerization. Taking advantage of the phase separation of PFC1/polystyrene (PS) blends in the film and the solvent‐resistant network, porous structured films were prepared by removal of PS. Films with porous morphologies exhibited marked responsive sensitivity to trace DNT vapor due to the unique porous structure favoring the diffusion of and association with DNT molecules. The formation of a crosslinked network by dimerization of the coumarin moieties may be beneficial for isolating the polymeric backbones, thus to some extent preventing chain aggregation. This facile fabrication method enabled the crosslinked porous films to be efficient fluorescence chemosensors towards the detection of trace amounts of DNT vapor.© 2012 Society of Chemical Industry     

全氟酰基过氧化引发剂

综述了全氟酰基过氧化物引发剂的优点、合成方法及其用途。通过全氟酰基过氧化物引发剂引发烯类单体（如丙烯酸、乙烯硅等）可在相应聚合物链上引入氟端基,氟端基聚合物具有极强的表面活性,当水溶液中或聚合物混合物中含有极少量的氟端基聚合物时,即会发生向表面的强烈吸附现象。并简要地介绍了它作为对芳环、芳杂环有效的全氟烷基化试剂及烯烃聚合的引发剂在合成含（全）氟功能化合物领域中的重要作用。     

双组分水性阴极聚氨酯电泳漆的制备及其工艺优化

以低聚物二元醇、异佛尔酮二异氰酸酯（IPDI）、N-甲基二乙醇胺（MDEA）和1,4-丁二醇（BDO）为主要原料制备了阳离子型端羟基聚氨酯树脂;再以IPDI、MDEA、BDO以及甲乙酮肟（ME．KO）为主要原料制备了阳离子型端异氰酸酯固化剂,将树脂与固化剂混合、分散乳化后进行电泳成膜。考察了电泳工艺参数、助溶剂丙二醇苯醚（PPH）用量、低聚物二元醇种类、树脂与固化剂的nNCO／／noH对漆膜表观及性能的影响。结果表明,电泳电压为60V,电泳时间为40S,PPH质量分数为3．0％（相对于树脂）,以聚四氢呋喃醚二醇（PTMG-1000）为二元醇组分,nNco／nOH为1．1时,漆膜表现出较好的性能及表观。     

Self-assembled folding of a biaxially compressed film on a compliant substrate

Amorphous carbon films grown by ion beam deposition from hydrocarbon precursors on compliant polymer substrates are shown here to undergo spontaneous self-assembled folding during growth. When deposited up to 30 min, the deposition-induced stretch strain of an amorphous carbon film on poly(dimethylsiloxane) (PDMS) with a Young’s modulus of 1–2 MPa reached more than 50%, which is much higher than usually observed compressive mismatch strains of approximately 1–2% on silicon. During deposition of the carbon film, compliant PDMS substrates allowed large amplitude film buckling to let in lateral growth of the film with the significant compressive mismatch strain. The film wrinkled at a low strain of approximately 1% at an early stage of deposition. Then, the wrinkled film was observed to transform its configuration through two different nonlinear modes; formations of ridges and asymmetric localized folds. Due to the biaxial nature of the deposited thin film, the wrinkled film showed herringbone or labyrinth patterns for strains less than 10%, while the folds were made in random orientations to create asymmetric disordered tessellation for strains more than 30%.     

Thermal Degradation of Plasticized Poly(<Emphasis Type="Italic">para</Emphasis>-Methoxystyrene) in Solid Films

The thermal effect on the stability of poly(para-methoxystyrene) in solid films was studied within a temperature range of temperature range of 298–363 K. The fluorescence spectrum of poly(para-methoxystyrene) was found to be mainly excimeric emission at room temperature. However, this emission is quenched at higher temperatures. Added terephthalate and phthalate plasticizers to poly(para-methoxystyrene) caused a quenching of the excimer emission and enhanced exciplex emission. Thermal heating of the solid films of the plasticized and non-plasticized polymer was accompanied by quenching of fluorescence emission at low temperature and brought about a change in the structure of the fluorescence spectrum at high temperatures. This may indicate that thermodestruction of these polymers starts from a random chain scission. In addition to that the presence of the plasticizer in the polymer backbone was found to accelerate thermal degradation of the polymer. This was proved by the infrared spectra of the heated and unheated plasticized solid films of poly(para-methoxystyrene). The binding energy or excimer formation was calculated in solid film.     

Simplistic hydrothermal synthesis approach for fabricating photoluminescent carbon dots and its potential application as an efficient sensor probe for toxic lead(II) ion detection

The past decade has witnessed a variety of members of the carbon family along with exposure of carbon dots due to their magnificent properties in sensing, bioimaging, catalytic applications, biomedical fields, and so on. Herein, we report the simple hydrothermal method to fabricate photoluminescent doped carbon quantum dots for the detection of noxious lead(II) ions. Lead(II) ion is very venomous for both the environment and human health for which its detection is demanded area in the research field. The as-prepared carbon dots show excellent photostability, low toxicity and significant photoluminescence properties along with good water solubility. Along with these properties, carbon dots have a quantum yield of approximately 15%. In the practical field of application, these carbon dots have been used as sensing probes for the detection of lead(II) ions with a detection limit of 60 nmol·L^–1. The fluorescence intensity of carbon dots was remarkably quenched in the presence of the lead(II) ion selectively among all the tested metal ions. Furthermore, we have studied the Stern–Volmer relationship for lead(II) quenching along with the explanation of the probable quenching mechanism. Ability of the doped carbon dots in heavy metal ions sensing in an environmental sample was demonstrated.     

六羰基钨催化制备聚苯乙炔及其荧光性能的研究

用W(CO) 6 催化体系聚合苯乙炔 ,以高产率获得较高相对分子质量的聚苯乙炔。使用UV、IR、GPC等分别对聚苯乙炔结构进行表征。采用不同波长的激发光对聚苯乙炔荧光性能进行了详细研究 ,结果表明 :当聚苯乙炔用 31 0nm激光激发时 ,呈现 3个荧光发光峰 ,峰值分别在348、396和 61 0nm处 ,与其溶液的紫外吸收有类似的光谱曲线特征。荧光峰在 348nm处的荧光 ,当聚苯乙炔质量浓度大于 0 0 5g L时 ,呈现荧光猝灭效应 ;在聚苯乙炔质量浓度为 1 0 - 4g L时 ,呈现出最大的荧光发光量子效率。当激发光波长低于 2 70nm和高于 340nm时 ,348nm波长荧光消失 ;荧光峰在 396nm处的荧光 ,当聚苯乙炔的质量浓度为 1 0 - 2 g L时 ,呈现最大的发光量子效率 ,聚苯乙炔的质量浓度增大或降低 ,其发光强度均呈现减弱现象 ;荧光峰在 61 0nm的荧光 ,在聚苯乙炔质量浓度为 1 0 - 4g L时 ,呈现最大的发光量子效率。荧光性能研究结果证明这种催化剂获得的聚苯乙炔具有多种异构链结构。