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The poor cycling stability of faradaic materials owing to volume expansion and stress concentration during faradaic processes limits their use in large-scale electrochemical deionization (ECDI) applications. Herein, we developed a...

Purely organic room-temperature phosphorescence endowing very fast intersystem crossing from through-space systems has not been well investigated. Here we report three space-confined bridged phosphors, where phenothiazine is linked with dibenzothiophene, dibenzofuran, and carbazole by a 9,9-dimethylxanthene bridge. Nearly pure phosphorescence is observed in the crystals at room temperature. Interestingly, phosphorescence comes solely from the phenothiazine segment. Experimental results indicate that bridged counterparts of dibenzothiophene, dibenzofuran, and carbazole contribute as close-lying triplet states with locally excited (LE) character. The through-space spin–orbit coupling principle is proposed in these bridged systems, as their 1LE and 3LE states have intrinsic spatial overlap, degenerate energy levels, and tilting face-to-face alignment. The resulting effective through-space spin–orbit coupling leads to efficient intersystem crossing a with rate constant as high as 109 s–1 and an overwhelming triplet decay channel of the singlet excited state.

A pentagonal macrocycle (MC5-PER) with radialene topology was facilely synthesized through a selective one-pot Suzuki-Miyaura cross-coupling reaction. The resulting product is endowed with a pentagonal architecture as revealed by its single crystal structure, which affords the smallest ring strain and the best conjugation. As tetraphenylethene subunits are embedded, MC5-PER is highly emissive in the solid state due to the aggregation-induced emission effect. Because of the flexible structure and preferable fibre-like self-assembly, the aggregate of MC5-PER displays interesting polymorphism-dependent emission and acts as a sensitive fluorescence sensor for explosives detection.

Quinolones (QNs), dechloranes (DECs), and chlorinated paraffins (CPs) are three kinds of new halogenated organic pollutants (HOPs), which originate from the use of flame retardants, lubricants and pesticides. Since QNs, DECs, and CPs are frequently detected in waters and sediments, it is necessary to investigate the toxic effects of these HOPs with dwelling phytoplankton, especially for cyanobacteria, to explore their potential hormetic effects and contributions to algal blooms. In the present study, we investigate single and joint toxicity of QNs, DECs and CPs on Microcystis aeruginosa (M. aeruginosa), a cyanobacterium that is frequently implicated with algal blooms. The results indicate single QNs and DECs induce marked hormetic effects on the proliferation of M. aeruginosa but CPs do not. The stimulatory effect of hormesis is linked with accelerated replication of DNA, which is considered to stem from the moderate rise in intracellular reactive oxygen species (ROS). Joint toxicity tests reveal that both QNsCPs mixtures and DECsCPs mixtures show hormetic effects on M. aeruginosa, but QNsDECs mixtures show no hormetic effect. QNsDECs mixtures exhibit synergistic toxic actions, which may be caused by a sharp rise in intracellular ROS simultaneously produced by the agents. Joint toxic actions of both QNsCPs, and DECsCPs shift from addition to antagonism as concentration increases, and this shift may mainly depend on the influence of CPs on cell membrane hydrophobicity of M. aeruginosa. This study provides data and toxic mechanisms for the hormetic phenomenon of single and joint HOPs on M. aeruginosa. The hormetic effects of HOPs may benefit the proliferation of M. aeruginosa in the aquatic environment, aggravating the formation of algal blooms. This study also reflects the important role of hormesis in environmental risk assessment of pollutants.

Conductive and fluorescent hollow micro/nanospheres have attracted great attention owing to their potential applications such as environmental clean-up, energy storage, sensors, and medical diagnosis. We report novel, tunable, and uniform hollow microspheres of conjugated poly(aniline-co-3-amino-9-ethyl-carbazole) (PAC) copolymer synthesized by a template-free method, namely a simple chemical oxidative copolymerization of aniline and 3-amino-9-ethyl-carbazole. The molecular structure of the copolymers has been systematically characterized by UV–vis, ATR-IR, Raman, and solid-state 13C cross-polarization magic angle spinning NMR spectroscopies. The particle size and properties including dispersibility, thermostability, electrical conductivity, fluorescence emission and its sensitive quenching of PAC hollow microspheres can be significantly controlled by simply optimizing feed comonomer ratios and reaction parameters such as acidic media and oxidants used. The formation mechanism of PAC hollow microspheres and their sensitively and selectively sensing properties toward nitro-based explosives and Cu(II) ions with the limit of detection down to 5 μM and 5 nM are demonstrated, respectively. In particular, the limit of detection for Cu2+ is superior as compared to literature reports.

It remains a great challenge to cost-efficiently and cleanly synthesize sustainable polyesters based on both biomass-derived comonomers and biogenic catalysts because of the lack of clean, biogenic, and active catalysts so far. This work would like to address the tough problems of cleaner manufacturing and processing of the polyesters. We report the first example of the sustainable copolyesters from starch-based isosorbide/ethylene glycol and terephthalic acid by a highly active but environmentally benign Ti-Mg catalyst designed in our laboratory replacing current toxic catalysts. The optimal content of the Ti-Mg catalyst for productively synthesizing the copolyesters is down to 5 ppm that is just 1/30–1/75 content of traditional toxic catalysts including Sb2O3, GeO2, and pyridine reported heretofore. The copolyesters obtained by the Ti-Mg catalyst possess higher molecular weight up to Mn 25150, better performance, and are much more environmentally benign than most of similar copolyesters reported up to now. The copolyesters retain transparency owing to their irregular chain structure and random chain sequence and thus remain as a stable amorphous structure even after experiencing heating/cooling cycles. The Ti-Mg catalyst demonstrates 41–46 times higher catalytic activity than Sb2O3 catalyst and is active enough to catalyse the direct polycondensation between OH and COOH by eliminating water that is clearly distinguished from toxic methanol and corrosive HCl produced by polycondensation between OH and COOCH3/ COCl catalyzed with toxic Sb2O3/pyridine catalysts, achieving cost-efficient and cleaner synthesis of the copolyesters without toxic residues. A systematic environmental analysis of the Ti-Mg catalyst, the copolyesters, raw materials and catalytic process, has been estimated, signifying that the Ti-Mg catalyst replacing current Sb2O3, GeO2, and pyridine accomplishes the cleaner production of most polyesters without toxic discharge or other harmful environmental impacts.

It remains great challenges to fabricate advanced potentiometric sensors based on ion-selective electrodes (ISEs) with ultrasensitivity, high selectivity, long-term durability, and even reproducible potential. Sensing and transducing materials are vital components for substantial performance optimization. This review systematically summarizes the progress in ionophore, formulation, preparation, nanostructure, and electrochemical properties of state-of-the-art sensing membranes and ion-to-electron transducing layers for comprehensively stabilizing potential and enhancing the sensing performance. This article elaborates the development of cutting-edge solid-contact (SC)-ISEs including wearable chip and needle electrodes to achieve versatile applications like health and environmental monitorings, medical diagnosis, food and plant analysis. As an indispensable element in SC-ISEs, the transducing materials particularly including conducting polymers, noble metals and carbon nanomaterials for stabilizing potential are thoroughly expounded. It is suggested that the highly transducing materials with practical applicability should possess two key features including high hydrophobicity and strong adherence onto the electrode substrates and ion-selective membranes besides high ion and electron conductivity, which could be used to guide the design and fabrication of next-generation ISEs based on multifeatured composites. The current startup status and future research direction of calibration-free ISEs with excellent potential reproducibility that would become a major hotspot in the field soon are highlighted.

Graphene, a two-dimensional (2D) layered nanomaterial, which has attracted great attention in the environmental field due to its excellent physical and chemical properties, including easily modified surface characteristics, tunable structure, and excellent stability. However, the inherent problems of nanomaterials, such as serious aggregation, difficulty in recycling, and potential ecological risks, have severely hindered the large-scale application of graphene. Therefore, immobilization of nanomaterials into macroscopic structures is one of the most feasible strategies to solve these problems, which is of great significance to promote the progress of nano-water treatment chemistry and technology. With the deepening of related studies, diverse dimensional graphene materials with large specific surface area, internal interconnected porous network and novel functionalities have been successively developed. Herein, we review the structural characteristics and synthesis methods of multi-dimensional graphene materials and highlight some examples with impressive and unique properties. Furthermore, we specifically emphasize their removal performance and mechanisms for organic contaminants in adsorption and membrane separation. Finally, the future outlooks, research directions and foreseeable challenges in this filed are summarized and prospected as concluding remarks based on our understanding.

Hormesis is a biphasic dose-response relationship featured by low-dose stimulation and high-dose inhibition. Although the hormetic phenomenon has been extensively studied over the past decades, there is little information regarding the influence of energy source on the occurrence of hormesis, especially the time-dependent one. In this study, to explore the role of cultivation system's energy source in time-dependent hormesis, the toxic dose-responses of Aliivibrio fischeri (A. fischeri) bioluminescence to Sulfadoxine (SDX) during 24 h were determined in four cultivation systems with different energy source conditions. The results indicated that the time-dependent hormetic effects were induced by SDX in all cultivation systems: SDX triggered hormetic phenomenon on the bioluminescence at each growth stage over 24 h in the cultivation systems with sufficient and insufficient energy source; due to the diauxic growth of A. fischeri under multiple energy source conditions, the hormetic effects of SDX gradually disappeared after the preferred energy source was used up. It was speculated that the inhibitory action of SDX was derived from its interaction with DHPS to impede the synthesis of proteins, and SDX bound with AC to upregulate the quorum sensing (QS) system to exhibit the stimulatory action. Comparing the time-dependent hormesis in each cultivation system, it was obtained that the energy source could impact the hourly maximum stimulatory rate, the EC50 of SDX, and the time point that hormesis occurred, which might result from the influence of energy source on the stimulatory and inhibitory actions of SDX through regulating the metabolic system (individual level) and QS system (group level) of bacteria. This study clarifies the importance of energy source for hormesis occurrence, which may further promote the development of hormesis.

Efficient sustainable synthesis of high-performance poly(trimethylene terephthalate) (PTT) with simultaneously high molecular weight, narrow molecular weight distribution, and tiny cyclic dimer suitable for high end applications at low cost still faces challenges. Novel nontoxic and 1,3-propanediol-soluble Ti/Mg bimetal catalyst mainly based on biobased 1,3-propanodiol and food grade materials has been productively synthesized and also carefully characterized. The Ti/Mg catalyst was found to be exceptionally active catalysts for the polycondensation of terephthalic acid and 1,3-propanediol from a renewable resource capable of producing high-molecular-weight PTT as an environmentally friendly and recyclable material in both laboratory reactor and continuous pilot plant. The high-quality PTT samples with the highest number-average molecular weight up to 68 870 g/mol ever reported so far, the narrowest molecular weight distribution index down to 1.92, and the second lowest cyclic dimer content down to 2.21% ...

Poly(1,5-diaminonaphthalene) microparticles with abundant reactive amino and imino groups on their surface were synthesized by one-step oxidative polymerization of 1,5-diaminonaphthalene using ammonium persulfate as the oxidant. The molecular, supramolecular, and morphological structures of the microparticles were systematically characterized by IR and UV-vis spectroscopies, elementary analysis, wide-angle X-ray diffractometry, and transmission electron microscopy. The microparticles demonstrate electrical semiconductivity and high resistance to strong acid and alkali, and strong adsorption capability for lead(II), mercury(II), and silver(I) ions. The experimental conditions for adsorption of Pb(II) were optimized by varying the persulfate/monomer ratio, adsorption time, sorbent concentration, and pH value of the Pb(II) solution. The maximum adsorption capacity is 241 mg·g−1 for particles after a 24 h-exposure to a solution at an initial Pb(II) concentration of 29 mM. The adsorption data fit a Langmuir isotherm and follow a pseudo-second-order reaction kinetics. This indicates a chemical adsorption that is typical for a chelation interaction between Pb(II) and amino/imino groups on the sorbent.

Scalable and transparent polyether-based waterborne polyurethane (WPU) thin films that adhere firmly to Al nanofilm but not to PET film without release agents have been designed and prepared. In order to realize cleaner production, eco-friendly acetyl tributyl citrate (ATBC) instead of toxic additives like N-methylpyrrolidone was introduced into polymerization system as both an effective dispersant of dimethylolpropionic acid crystal as hydrophilic chain extender and a viscosity thinner of the synthesized precursors to promote homogeneous hydrophilic extension reaction in the absence of toxic catalysts. The appropriate ATBC and dimethylolpropionic acid contents are critical to formation of stable translucent dispersion of the WPU with total hard segments as high as 56 wt% at –NCO/-OH molar ratio of 1.05. Molecular structure and ATBC existence of the WPU film have been characterized by IR, NMR, gas chromatography, and thermogravimetry, suggesting that ATBC will not release into the environment even if at 140 °C because of its high boiling point and ultralow volatility. The reserved ATBC in the WPU film also acts as an effective plasticizer and lubricant so that the WPU film can be quickly peeled off from PET. The lowest T-peel strength of 1.3 N m−1 on PET is achieved for the WPU film with a high tensile strength of 15.8 MPa and a medium elongation at break of 237%. The WPU films have tunable stickiness onto PET film from sticky to completely nonsticky. Importantly, the WPU films offer simultaneously strong adhesion to Al nanofilm and high thermal stability but high peelability from the PET, allowing to fabricate a stable holographic/photolithographic composite film by Al deposition at >1000 °C and ensure high flatness and luster of the composite film. Optimal formulations of WPU materials with high comprehensive performance including good film-processability, ultralow VOC emission, high mechanical and thermal properties, controllable surface tension, and tunable adhesion to Al nanofilm have been proposed for transferable holographic films.

Poly(m-phenylenediamine) (PmPD) microspheres were productively and sustainably synthesized by a facile one-step chemical oxidative polymerization of m-phenylenediamine with ammonium persulfate in pure water without any acid or alkali. A comprehensive characterization of the structures, morphology, and nature of PmPD microspheres suggested that they exhibited highly chemical/thermal resistance and strong Hg(II) adsorbability. The batch static sorption/desorption of mercury ions were systematically optimized by adjusting the sorption/desorption time and temperature, mercury-ion concentration, sorbent dosage, and the species, concentration and dose of desorbents. The microparticles exhibit high Hg(II) sorption capacity up to 1499.2 mg/g at an initial Hg(II) concentration of 1986 mg/L, high Hg(II) partition coefficient up to 5040 mg/(g.μM) at an initial Hg(II) concentration of 20 mg/L, and high initial sorption rate up to 763.3 mg/(g.min). The dynamic sorption results suggest that the breakthrough and saturation times of the column loaded with the microparticles toward 1.99 mM Hg(II) solution at the flow rate of 1 mL/min are 19.8 h and 58.0 h, respectively. After 5 dynamic sorption-desorption cycles, the column efficiency is still high, indicating good reusability. A sorption mechanism including the first reduction from mercury-ion to mercurous-ion by amino and imino groups, and the second complexation and ion exchange of mercurous-ions is proposed. Without the pollution caused by the preparation or part solubility of sorbents themselves, the PmPD microspheres are cost-effectively and eco-benignly applicable to elimination and recovery of mercury ions in wastewater. This generates a unique solution to sustainable problems of sorbents themselves.

N-methyl pyrrolidone (NMP)-free waterborne polyurethane (WPU) in a two-tons scale was prepared without catalyst in the presence of a non-toxic acetyl tributyl citrate (ATBC) with high boiling point and extremely low vapor pressure. It is found that a small amount of ATBC is key to the obtainment of WPU nano-sized dispersions with proper viscosity, good storage stability, and low volatile organic compounds (VOC). Macromolecular structure, molecular weight and its distribution, mechanical and thermal properties, and water-resistance of the cast films of the ATBC-based WPUs have been systematically evaluated. The ATBC-based WPUs exhibit several advantages including higher molecular weight, much lower VOC, higher thermal stability, and stronger water resistance than the NMP-based ones. ATBC plays six roles as hydrophilic chain extender's medium, emulsifier, and viscosity thinner in the polymerization stage, plasticizer, water- and heat-resisting additives in the WPU films, which is responsible for the performance improvement. The tough problem of -NCO group residue in PUs that result from slightly excessive isocyanates, has been tackled here. This has been confirmed by a simultaneous disappearance of the characteristic carbon peak at 122.7 ppm and IR absorbance at 2252 cm−1 of -NCO group. Usage of ATBC and the phase transition in water tackle the toxic problems from NMP and -NCO residue, opening up a large-scale and eco-friendly method for cost-effectively producing VOCs-free WPU films.

A novel polyfluoranthene (PFA) exhibiting strong visual fluorescence emission, a highly amplified quenching effect, and widely controllable electrical conductivity is synthesized by the direct cationic oxidative polymerization of fluoranthene in a dynamic interface between n-hexane and nitromethane containing fluoranthene and FeCl3, respectively. A full characterization of the molecular structure signifies that the PFAs have a degree of polymerization from 22–50 depending on the polymerization conditions. A polymerization mechanism at the interface of the hexane/nitromethane biphasic system is proposed. The conductivity of the PFA is tunable from 6.4 × 10−6 to 0.074 S cm−1 by doping with HCl or iodine. The conductivity can be significantly enhanced to 150 S cm−1 by heat treatment at 1100 °C in argon. A PFA-based chemosensor shows a highly selective sensitivity for Fe3+ detection which is unaffected by other common metal ions. The detection of Fe3+ likely involves the synergistic effect of well-distributed π-conjugated electrons throughout the PFA helical chains that function as both the fluorophore and the receptor units.

Strongly fluorescence-emitting oligofluoranthene nanorods efficiently synthesized by template-free oligomerization of fluoranthene in nitromethane demonstrate tunable conductivity and porous carbon formability., Strongly fluorescence-emitting oligofluoranthene (OFA) nanorods are readily synthesized by a direct template-free chemical oxidative oligomerization of fluoranthene in nitromethane containing ferric chloride as an oxidant. The OFAs likely consist of five fluoranthene units containing cyclic pentamers with crystalline order and tunable electrical conductivity across 12 orders of magnitude. The OFA nanorods are heat-resistant materials and efficient precursors for macroporous carbon materials with high carbon yield in argon at 1100 °C. In particular, the optimal ring-like pentamer shows 12.2 times stronger cyan fluorescence-emission than recognized highly fluorescent fluoranthene under the same conditions, which makes the OFAs into ideal strong fluorescent emitters, tunable conductors, and high carbon-yield precursors for the preparation of sensors and carbon materials. These findings demonstrate an advance in the direct synthesis of oligomers from fused-ring aromatic hydrocarbons and provide a potential direction to optimize the synthesis and functionalities of wholly aromatic nanomaterials.

Poly(1,5-diaminonaphthalene) (P15DAN) is a novel multifunctional but intractable polymer, from which it is difficult to preparing a large uniform membrane directly. A unique electroactive composite membrane was facilely prepared by drop-casting the dispersion of the P15DAN nanoparticles in 0.1% poly(vinyl alcohol) aqueous solution. The cyclic voltammogram of an electrode modified by the nanocomposite membrane strongly depends on the potential sweeping rate and pH value of the electrolyte solution. The anodic/cathodic peak currents rise linearly with increasing the sweeping rate, but decline with increasing the pH value. The redox and coordination sensitivity of the nanocomposite membrane to heavy metal ions including silver, mercury, and copper ions was explored by open-circuit potential and cyclic voltammetry techniques. The results indicate that the three ions are all spontaneously and non-electrochemically reduced by the P15DAN and then adsorbed on the membrane surface upon contacting each other, but t...

Highly dispersible polypyrrole (PPy) nanospheres were synthesized and used to produce polysulfone (PSf) nanocomposite ultrafiltration membranes by a non-solvent induced phase separation (NIPS) process. The composite networks formed between PPy and PSf lead to higher porosity, hydrophilicity, surface charge, thermal stability, and water permeability, but slightly lower protein rejection. Nanocomposite membranes containing up to 20% PPy nanospheres were >10 times more permeable than pure PSf membranes, while the bovine serum albumin (BSA) rejection decreased from 94 to 82%. With nanoscale pores, high porosity, improved hydrophilicity, and tunable surface charge properties, the PPy/PSf nanocomposite membranes hold great promise for advanced protein separation, dialysis, water filtration and other macro molecular separations.

A simple and effective template-free synthesis method for nanosized conducting polymers with self-stability and functionality is a main challenge. Herein, a strategy is reported for the facile synthesis of poly(1,5-diaminonaphthalene) nanospherical particles by an interfacial miniemulsion oxidative polymerization of 1,5-diaminonaphthalene at mobile microinterfaces between a stirred biphase without external emulsifiers. The size of the nanospheres was carefully optimized by controlling the polymerization conditions. Formation and self-stabilization mechanisms of the nanoparticles are proposed. The constantly movable and refreshed microinterface is a key to successful synthesis of the nanospheres, for significantly suppressing secondary growth leading to agglomerated particles because vigorous stirring makes as-formed self-stabilized nanospheres instantly leave the microinterfaces. The resulting nanospheres possess several advantages: clean surface, self-stability, redispersibility, semiconductivity, electroactivity, and fluorescence emission. The fluorescence emission can be quenched by specific quenchers, thus enabling low-cost, high-performance chemosensors to be obtained for the sensitive detection of Zn(II) ions in a wide linear concentration range of more than five orders of magnitude with a superior detection limit down to 1 nM.

Sulfonated polyaniline (SPANi), a self-doped conjugated polymer, has received great interest in recent years; however, controlling its shape, size, and conductivity at the nanoscale remains a significant challenge. Here, we report an initiator-assisted route to SPANi nanostructures by rapidly copolymerizing o-aminobenzenesulfonic acid with aniline or its derivatives in the presence of a catalytic amount of the initiator–aniline dimer. UV–vis, FT-IR, and XRD spectra reveal that the chemical compositions of the SPANi nanostructures are similar to that of conventional SPANi possessing an agglomerated morphology. By regulating the comonomer molar ratios, the aniline derivatives used and the acidic media employed, the morphology of the SPANi changes from 1-D nanofibers, nanosticks, nanothorns, and nanorods to 2-D nanoplates and 3-D porous nanospheres. The length and aspect ratio of the SPANi nanofibers can reach values up to 4.5 μm and 60, respectively. These SPANi nanostructures are readily processable in bot...

Potentiometric Pb 2+ sensors based on ionophores bearing oxygen/sulfur-containing functional groups, which include anthraquinone, aromatic carboxylic acids, carboxylates, phosphates, and macrocyclic compounds containing amide or thioamide groups, are systematically summarized. Anthraquinone is found to be quickly responsive to lead ions, with the shortest response time of two seconds. Aromatic carboxylic acids with a sulfur atom as an ionophore in an asymmetric membrane respond sensitively to lead ions, with the lowest detection limit of 6.0 × 10 −10 M. Phosphate has the advantage of better anti-interference ability, with a logarithmic selectivity coefficient, log K , smaller than −3.0. Macrocyclic amides, after assembly into microelectrodes, have been used as ionophores for the analysis of samples confined in cells of volume 3 μL, with a superior lower detection limit of 2.7 × 10 −9 M.

An important aspect of the current global change research is using river chemical composition to reveal the chemical weathering process and its effect of carbon sink. In this study, water samples were collected and analyzed 2 ~3 times per month from January to December in 2013. The hydrochemistry belonged to HCO3-Ca type. Ca+ and HCO3- were the main cation and anion, which reflected that the hydrochemical characteristics of river were mainly affected by the dissolution of carbonate rock. The concentration of main ions varied with the seasons, which reflected that the crest value occurred in winter, followed by those in autumn and spring, and the lowest value was observed in summer. Due to the interaction of effect of dilution and effect of C2, the seasonal variation of Ca2+ and HCO3- showed that the highest value was in autumn and the lowest value was in summer. The seasonal variation law of other ions should be attributed to the effect of dilution or agricultural activities or combined action of them. Both carbonic acid and sulfuric acid took part in the chemical weathering of carbonate rocks as evidenced by stoichiometric analysis. Besides, the δ34S of sulfate ion of the river waters (δ34S: from 7. 65 per thousand to 8. 55 per thousand) showed that SO2- was originated mainly from oxidation of sulfide minerals in ore deposits and acid rain. Chemical mass balance method was applied to estimate the proportion of HCO- coming from carbonate weathering by sulfuric acid. The result was 28. 26% . On this basis, the total carbon flux of carbon ( by CO2 calculation) in Liuzhou section calculated month by month was about 8. 95 x 10(5) t . a-1. What's more, the carbon flux showed a positive correlation with flow, which implied that the discharge of catchment was the main influencing factor of carbon flux rather than the HCO3- concentration.

Blue light-emitting oligotriphenylene nanofibers are synthesized by oxidizing triphenylene using ferric chloride. By adjusting the monomer concentration, the acid used, and the temperature employed, the average diameter and length of the nanofibers can be readily tuned from 50 to 200 nm and 0.5 to 5 μm, respectively. Structural characterization, electrical conductivity, thermal stability, and fluorescence of oligotriphenylene, along with a pro posed nanofiber formation mechanism, are presented. Both oligotriphenylene nanofiber dispersions and oligotriphenylene/polysulfone composite films are developed as fluorescent sensors for detecting traces of nitro-based explosives including nitromethane, nitrobenzene, and 2,4,6-trinitrophenol, as well as an electron-deficient metal ion, Fe(III). The sensors exhibit much better selectivity and sensitivity compared to conventional sensors, with detection limits down to 1.0 nm with a detection range covering ∼4 orders of magnitude. The detection mechanism of the fluorescent sensors is also disscussed.

A novel membrane electrode for Pb(II) ion detection based on semi-conducting poly(m-phenylenediamine) microparticles as a unique solid ionophore was fabricated. The electrode exhibited significantly enhanced response towards Pb(II) over the concentration range from 3.16×10(-6) to 0.0316 M at pH 3.0-5.0 with a low detection limit of 6.31×10(-7) M, a high sensitivity displaying a near-Nernstian slope of 29.8 mV decade(-1) for Pb(II). The electrode showed a long lifetime of 5 months and a short response time of 14s. A systematical investigation on the effect of anion excluder and various foreign ions on the selectivity of the electrode by a fixed interference method suggests that all other metal ions hardly ever interfere with the determination of Pb(II) except high concentration Hg(II). The electrode was successfully used as an indicator electrode in the potentiometric titration of Pb(II) with EDTA. Furthermore, the electrode has been used to satisfactorily analyze four types of real-world samples like spiked human urine, spiked tap water, and river water containing interfering ions like Na(I), Ca(II), Mg(II), Zn(II), Pd(II), Fe(III), K(I), Cu(II) and Hg(II) up to 8.04×10(-4) M, demonstrating fast response, high selectivity, good recovery (96.6-121.4%), good repeatability (RSD 0.31-6.45%), and small relative error (5.0%).

Intrinsically self-stabilized nanofibril bundles of poly(1- aminoanthraquinone) (PAQ) were facilely synthesized by the chemical oxidative polymerization of 1-aminoanthraquinone. Critical polymerization parameters such as the monomer concentration, medium, oxidant species, temperature, and time were studied to significantly optimize the synthesis, size, properties, and multifunctionality of the resulting nanofibrils by IR, UV-vis, and fluorescence spectroscopy, X-ray diffraction, SEM, TEM, DSC, and thermogravimetry. It is found that the polymerization of 1-aminoanthraquinone with (NH4) 2S2O8 as an oxidant in HClO4/ acetonitrile without external stabilizer simply affords finer PAQ nanofibrils with an optimal combination of diameter of ca. 15 nm, a length of ∼6 μm, a higher preparation yield, a purer composition, a higher conductivity, and higher melting and decomposition temperatures than that with CrO3 and H2O2/Fe2+. Furthermore, the polymer nanofibrils exhibit high self-stability, powerful redispersibility, and a clean surface because of the complete avoidance of contamination from an external stabilizer. PAQ exhibits remarkably good solubility in polar solvents, colorful solvatochromism, widely controllable conductivity moving across 10 orders of magnitude from 10-9 to 50 S/cm, fluorescence, lead-ion adsorbability, high thermostability in air, and a very high carbon yield in nitrogen at 1000 °C. In particular, the nanoeffect of the PAQ nanofibrils with a large specific surface area and aspect ratio further enhances their fluorescence, lead-ion adsorbability, and nanocomposite ability of facilely forming a unique nanonetwork. PAQ would be useful as advanced materials including fluorescent emitters, sorbents of toxic metallic ions, cost-effective carbon foam precursors, and conducting nanocomposites with low percolation thresholds. © 2011 American Chemical Society.

Pure polypyrrole (PPy) nanoparticles that are well-applicable for nanocomposite and nanocarbon precursor were productively synthesized by necessarily unstirred oxidative polymerization of pyrrole in acidic aqueous media at 0 °C without any template. The species and concentration of acid and oxidant have been carefully investigated to optimize the polymerization yield, conjugated structure, size, and conductivity of the PPy particles. Laser particle-size analysis, field-emission scanning electron microscopy, transmission electron microscopy, and atomic force microscopy all revealed that the PPy particles produced in still acid media have narrow size distribution and uniform spheroid morphology. Homogeneous nucleation and static repulsion are proposed as the formation and self-stabilization mechanisms of the PPy nanoparticles. Combination of HNO3 medium and (NH4)2S2O8 oxidant is optimal for the synthesis of PPy nanoparticles possessing maximal yield of 87.2%, small diameter, and high conductivity which has ...

Novel poly(pyrrole-co-aniline-2-sulfonic acid) (PPYAS) nanoparticles were prepared via chemical oxidative polymerization of pyrrole and aniline-2-sulfonic acid in different aqueous solutions without any external additives. The morphology, structure and electroconductivity of the HCl-doped particles were studied by changing the molar ratio of the oxidant and monomers, and the solvent for polymerization. It was found that the yield, mean diameter and electrical conductivity of the resulting particles varied strongly with the molar ratio of the components. The nanoparticles exhibit a minimum mean diameter of around 62 nm, and good self-stability because of the introduction of sulfo groups into the chains of the copolymer. The preparation affords yield of up to 85%, and the HCl-doped copolymer salts possess an electroconductivity between 0.68 and 0.2 S/cm, depending on the fraction of anilinesulfonic acid.

Pb(II) solution has been treated by a column packed with 5 mm-diameter spheroids of poly(m-phenylenediamine) powder that has been entrapped in polyvinylalcohol, via dynamic adsorption. The effect of operation conditions on the adsorbability and desorbability has been investigated and optimized systematically. The results show that a lower flow rate gives a higher adsorptivity at a fixed Pb(II) concentration because of longer contact time, and higher Pb(II) concentration gives higher adsorptivity at a fixed flow rate. The highest adsorptivity reaches up to 75.9% for Pb(II) concentration of 500 mg·L–1 at the flow rate of 1 mL·min–1. The release of Pb(II) from the Pb(II)-adsorbing column has been revealed using 0.1 M HNO3 as an eluant, with an elution efficiency of 98.1%, effectively regenerating the column. The regenerated column could be circularly used several times. The Adams-Bohart and Wolborska sorption models have been used to describe the dynamic sorption of Pb(II) through the packed column. It is ve...

Self-stabilized copolymer nanoparticles are easily and productively synthesized by a chemical oxidative polymerization of pyrrole (Py) and 2-hydroxy-5-sulfonic aniline (HS) in 1 M HCl without any external template. UV-vis, IR, 1D 1H NMR, 2D 1H-1H COSY NMR, and 2D 1H-13C HSQC NMR all indicate that a real copolymerization occurs between HS and Py comonomers and Py units construct the main position of the copolymer. On the basis of the elemental analysis, the reactivity ratios of HS and Py comonomers are calculated to be 0.043 and 1.14, respectively. The polymerization yield, size, morphology, and electrical conductivity of the copolymer particles can significantly be optimized by the comonomer ratio, polymerization temperature, and ammonium persulfate oxidant/comonomer ratio. The copolymer particles always keep narrow size distribution with a small polydispersity index (PDI) of 1.05-1.08. HS/Py(50/50) copolymer nanoparticles synthesized at 0 °C are found to generally have irregular granular morphology with the smallest diameter of 35-60 nm and the lowest PDI of 1.05 by laser particle-size analyzer, FE-SEM, and TEM. The mechanisms of the formation and intrinsic self-stabilization of the nanoparticles are proposed based on the powerful static repulsion from negatively charged sulfonic and hydroxyl groups on the nanoparticles. Through simple dedoping and redoping procedures, the copolymer particles exhibit a widely adjustable conductivity from 10-9 to 1.12 S cm-1. These copolymer nanoparticles show high conductivity, good self-stability, and powerful redispersibility in water and organic media. Nanocomposite films of the copolymer nanoparticles in polyvinylalcohol possess a low percolation threshold down to 0.09 wt % as well as retain 80-95% transparency and 10 2-108 times the conductivity of the pure polyvinylalcohol film in the nanoparticle loading from 0.09 to 3 wt %. © 2009 American Chemical Society.

Perpendicularly cross-bedded CuO microstructure has been prepared via a precursor-based route. First, Cu2(OH)3Br, as the precursor, was hydrothermally synthesized in 0.1 M hexadecyl trimethyl ammon...

A facile approach for synthesis of hyperbranched polycarbosilane from AB2 monomer via UV-activated hydrosilylation is presented in this communication. The polymerization process was monitored using real-time FTIR spectroscopy and the resulting hyperbranched polycarbosilanes were characterized using 1H-NMR, 13C-NMR, 29Si-NMR and SEC/MALLS. It is found that hyperbranched polycarbosilane can be synthesized from methyldiallylsilane via UV-activated hydrosilylation with bis(acetylacetonato)platinum(II) as catalyst. The polymerization activated by UV irradiation was much faster than that under thermal conditions. The similar degree of branching, average number of branch units and the exponent of the Mark–Houwink equation demonstrate that the hyperbranched polycarbosilane synthesized via UV-activated polyhydrosilylation possesses almost the same branching structure as that synthesized via thermal-activated polyhydrosilylation. Copyright © 2009 John Wiley & Sons, Ltd.

Fine polythiophene (PTh) microparticles were successfully synthesized by a novel interfacial polymerization at a dynamic interface between two immiscible solvents, i.e., n-hexane and acetonitrile or nitromethane containing thiophene and oxidant, respectively. The polymerization yield, size, and electrical conductivity of the microparticles are optimized by facilely regulating the medium species, oxidant species, oxidant/monomer ratio, monomer concentration, and polymerization temperature. The microparticles were thoroughly characterized by IR, UV-vis spectroscopy, wide-angle X-ray diffractometry, laser particle-size analyzer, and simultaneous TG-DSC technique. The yield rises with increasing oxidant/monomer ratio, monomer concentration, and polymerization temperature. However, low monomer concentration, low polymerization temperature, and modest oxidant/monomer ratio are all favorable for the formation of the PTh with good, large pi-conjugation and high conductivity. With decreasing the thiophene concentration from 200 to 50 mM at a fixed FeCl3/thiophene molar ratio of 3 at 0 degrees C in hexane/nitromethane biphase system, the PTh obtained exhibits a steadily enhanced conductivity from 10(-12) to 0.01 S cm(-1) and gradually darkening color from crimson to black. Under the same conditions, the PTh obtained in hexane/acetonitrile usually possesses lower yield but higher conductivity than that in hexane/nitromethane. The conductivity will be further enhanced to 1.1 and 4.4 S cm(-1) if the PTh powders are doped in iodine vapor and simply carbonized at 25 through 999 degrees C in nitrogen, respectively. The PTh is fine particles with the number-average diameter of 2.67-3.95 microm and low size polydispersity index between 1.12 and 1.23. The black particles carbonized at 25 to 999 degrees C are much smaller than original PTh particles, with the number-average diameter of 279 nm and size polydispersity index of 1.09. This interfacial approach provides an optimal synthesis of unique PTh microparticles with large pi-conjugation, high conductivity, black color, uniform size, good insolubility, excellent infusibility, high thermostability, and high yield of electrically conducting char at 999 degrees C.

The straight dope: Polythiophene (PTh) nanoparticles with a narrow size distribution were successfully synthesized by a chemical oxidative polymerization (see image). The highest conductivity of virgin PTh is 3.1x10(-4) S cm(-1) and can be dramatically enhanced to 50 S cm(-1) by doping in iodine vapor.Polythiophene (PTh) nanoparticles were successfully synthesized by a simple chemical oxidative polymerization in the presence of a very small amount of cetyltrimethylammonium bromide (CTAB). The polymerization yield, particle size, bulk electrical conductivity, and solubility of the PTh nanoparticles have been optimized by adjusting the CTAB/FeCl(3) oxidant/thiophene monomer ratio, thiophene concentration, polymerization temperature, and reaction time. The structure of the PTh nanoparticles was systematically characterized by IR and UV/Vis spectroscopy, wide-angle X-ray diffraction, laser particle-size analysis, field-emission scanning electron microscopy (SEM), and transmission electron microscopy (TEM). It was found that the number-average diameter (D(n)) and size polydispersity index (PDI) of the particles decrease significantly from 4.19 microm and 1.21 to 203 nm and 1.056, respectively, with a slightly increasing CTAB concentration. SEM and TEM reveal that the PTh particle size is reduced to 67 and 36 nm, respectively. The conductivity increases on raising the FeCl(3)/thiophene ratio or on lowering the CTAB concentration and polymerization temperature. A moderate monomer concentration and polymerization time are very beneficial for achieving highly conducting PTh. The highest conductivity of virgin PTh is 3.1x10(-4) S cm(-1) and can be further elevated to 50 S cm(-1) by doping in iodine vapor. Under optimized polymerization conditions, the significant variation of the conductivity of the PTh particles in virgin and doped states was well confirmed by the intensity and wavelength of the UV/Vis spectral band owing to the large pi conjugation. The PTh particles demonstrate uncommon characteristics including easy synthesis, low cost of production, large pi-conjugated structure, high conductivity, solution processability, and extensive potential for further application.

The highest Hg-ion adsorbance so far, namely up to 2063 mg g(-1), has been achieved by poly(aniline-co-5-sulfo-2-anisidine) nanosorbents. Sorption of Hg ions occurs mainly by redox and chelation mechanisms (see scheme), but also by ion exchange and physisorption.Poly(aniline (AN)-co-5-sulfo-2-anisidine (SA)) nanoparticles were synthesized by chemical oxidative copolymerization of AN and SA monomers, and their extremely strong adsorption of mercury ions in aqueous solution was demonstrated. The reactivity ratios of AN and SA comonomers were found to be 2.05 and 0.02, respectively. While AN monomer tends to homopolymerize, SA monomer tends to copolymerize with AN monomer because of the great steric hindrance and electron-attracting effect of the sulfo groups, despite the effect of conjugation of the methoxyl group with the benzene ring. The effects of initial mercury(II) concentration, sorption time, sorption temperature, ultrasonic treatment, and sorbent dosage on mercury-ion sorption onto AN/SA (50/50) copolymer nanoparticles with a number-average diameter of around 120 nm were significantly optimized. The results show that the maximum Hg-ion sorption capacity on the particulate nanosorbents can even reach 2063 mg of Hg per gram of sorbent, which would be the highest Hg-ion adsorbance so far. The sorption data fit to the Langmuir isotherm, and the process obeys pseudo-second-order kinetics. The IR and UV/Vis spectral data of the Hg-loaded copolymer particles suggest that some mercury(II) was directly reduced by the copolymer to mercury(I) and even mercury(0). A mechanism of sorption between the particles and Hg ions in aqueous solution is proposed, and a physical/ion exchange/chelation/redox sorption ratio of around 2/3/45/50 was found. Copolymer nanoparticles may be one of the most powerful and cost-effective sorbents of mercury ions, with a wide range of potential applications for the efficient removal and even recovery of the mercury ions from aqueous solution.

Bis-Schiff base, pyridyl carboxamide, acylhydroxylamine, and phenylhydrazone, acting as sensing agents in ionophore-doped membranes of lead-ion selective electrodes with excellent response characteristics, are systematically summarized according to the latest literatures and our latest researches. The relationship between the response characteristics of the lead (II) ion-selective electrode assembled by the carriers and their molecular structures is also elaborated. It is noteworthy that the selectivity of the electrode towards lead ions over other cations is closely related to the molecular structure of the carrier. The presence of cyano group would largely improve the lower detection limit whether it is introduced into the carrier or membrane matrix. The sensing mechanism should be emphasized in order to find out the direction for developing high performance carriers.

Chemical oxidative polymerization at 15 degrees C was used for the simple and productive synthesis of polyaniline (PAN) nanosticks. The effect of polymerization media on the yield, size, stability, and electrical conductivity of the PAN nanosticks was studied by changing the concentration and nature of the acid medium and oxidant and by introducing organic solvent. Molecular and supramolecular structure, size, and size distribution of the PAN nanosticks were characterized by UV/Vis and IR spectroscopy, X-ray diffraction, laser particle-size analysis, and transmission electron microscopy. Introduction of organic solvent is advantageous for enhancing the yield of PAN nanosticks but disadvantageous for formation of PAN nanosticks with small size and high conductivity. The concentration and nature of the acid medium have a major influence on the polymerization yield and conductivity of the nanosized PAN. The average diameter and length of PAN nanosticks produced with 2 M HNO(3) and 0.5 M H(2)SO(4) as acid media are about 40 and 300 nm, respectively. The PAN nanosticks obtained in an optimal medium (i.e., 2 M HNO(3)) exhibit the highest conductivity of 2.23 S cm(-1) and the highest yield of 80.7 %. A mechanism of formation of nanosticks instead of nanoparticles is proposed. Nanocomposite films of the PAN nanosticks with poly(vinyl alcohol) show a low percolation threshold of 0.2 wt %, at which the film retains almost the same transparency and strength as pure poly(vinyl alcohol) but 262 000 times the conductivity of pure poly(vinyl alcohol) film. The present synthesis of PAN nanosticks requires no external stabilizer and provides a facile and direct route for fabrication of PAN nanosticks with high yield, controllable size, intrinsic self-stability, strong redispersibility, high purity, and optimizable conductivity.

Macrocyclic compounds, such as crown ethers, azacrown ethers, thiacrown ethers, calixarenes and porphyrins, which act as ionophores in lead(II) ion-selective electrodes, are systematically summarized based on the latest literatures. The molecular structure characteristics of the ionophores are generalized. The modification regulations for the substituted ionophores are elaborated with the purpose of improving the response features of the lead(II) ion-selective electrodes assembled by them. It is pointed out that the introduction of pendant moieties which contain soft base coordination centers like N, S and P atoms is in favor of adjusting the cavity size and conformation of the macrocyclic compounds. Furthermore, there is synergic effect between the cavity and the donor sites of the ligand and thus the selective complexation of lead ions is easily realized, resulting in significant avoidance of the interference from other metal ions. The macrocyclic ionophore having the best response characteristics thus far was found to be N,N′-dimethylcyanodiaza-18-crown-6 with the detection limit of 7.0×10−8 (14.5 μg/L), which is one of the uncommon ionophores that can really eliminate the interference from silver and mercury ions. The selectivity coefficients of the ionophore for lead ions over other metal ions, such as alkali, alkaline earth and transition metal ions are in the order of 10−4 or smaller, where the selectivity coefficient of lead(II) over mercury(II) ions is much lower, down to 8.9×10−4. The structure design idea for high-performance ionophore is proposed according to present results. The incorporation of nitrogen atom, especially cyano group or thiocyano group or amino/imino groups, rather than thio atom alone could result in new excellent lead ionophores. The aborative design for metacyclophanes containing aromatic nitrogen atoms with the aim of creating excellent ionophores would also become a potential research trend. The lead(II) ion-selective electrodes have shown widely potential applications in the potentiometric titration, and flow injection potentiometry, and in the direct determination of lead in stack emissions of lead smelters, and assay of lead in rocks, particularly in the direct measurements of trace amount of lead(II) in human hair, blood, edible oil, food, water, and air.

Novel copolymer nanoparticles with inherent self-stability, narrow size distribution, and high electrical conductivity are facilely and productively synthesized by the oxidative precipitation polymerization of 5-sulfonic-2-anisidine and aniline in acidic medium without any external stabilizer. The structures of the copolymer particles are systematically characterized by IR and UV/Vis spectroscopy, X-ray diffraction, laser particle-size analysis, atomic force microscopy, field-emission scanning electron microscopy, and high-resolution transmission electron microscopy. The comonomer ratio, oxidant/monomer ratio, and polymerization temperature and medium can be used to optimize the size and conductivity of the nanoparticles. It is found that the nanoparticles exhibit a minimal size and polydispersity index of around 53 nm and 1.045, respectively. Nanocomposite films of the nanoparticles with diacetyl and ethyl celluloses show good thermostability and a low percolation threshold of 0.08 wt%, at which the films retain 89% of the transparency, 96-98% of the strength, and 10(8) times the conductivity of the matrix film. The synthesis of sulfoanisidine copolymer nanoparticles is thus achieved without the use of external stabilizer, which opens up a simple and general route to the fabrication of nanostructured polymer materials with controllable size, narrow size distribution, intrinsic self-stability, strong dispersibility, high purity, and optimizable electroconductivity.

A systematic analytical method is proposed and applied to directly determine the total concentration of Hg(II) and Hg(I) ions in water. Experimental results demonstrate that this method provides a low detection limit of 0.05 mM and small relative error within 1.5% in an ion concentration range of 0.2–50 mM. The technique is especially applicable for sample solutions that the traditional titration method like Volhard and EDTA complexation titrimetry could not analyze directly. This method could be employed to analyze solutions in any ratio of Hg(II) and Hg(I) ions including pure Hg(II) or pure Hg(I) ions, exhibiting several advantages, such as simple operation, good reproducibility, and low cost.

The conformational transition of molecular chains of regenerated silk fibroin (SF) aqueous solution is systematically investigated by circular dichroism, Raman, IR, and UV-vis spectroscopies. It is found that an initial random coil conformation of the SF can be readily changed into an ordered beta-sheet structure by optimizing the solution conditions, such as the SF concentration, pH, temperature, or metal-ion content. Circular dichroic spectra quantitatively confirm a steadily decreased content of the random coil conformation but a significantly increased beta-sheet content after an ultrasonic or extruding treatment. Furthermore, the extrusion is more powerful to achieve high beta-sheet content than the ultrasonic. It is interesting that the polarized optical micrographs of the SF aqueous solution extruded by injection illustrate the formation and existence of liquid crystalline state. A study of extrusion in vitro could be used as a model system to understand the natural silk spinning process in silkworm.

Wholly aromatic poly(1,5-diaminoanthraquinone) (PDAA) particles were productively synthesized for the first time by chemically oxidative polymerization of 1,5-diaminoanthraquinone (DAA) by using CrO 3 , K 2 Cr 2 O 7 , K 2 CrO 4 , or KMnO 4 as oxidants in acidic DMF. The effects of the oxidant species, oxidant/DAA ratio, polymerization temperature, and medium on the polymerization yield, macromolecular structure, size, electroconductivity, solubility, solvatochromism, thermostability, photoluminescence, and silver-ion sorption of the PDAA particles were systematically studied by IR, UV/Vis, fluorescence, and solid-state 13 CNMR spectroscopies, wide-angle X-ray diffraction, scanning and transmission electron microscopies, and laser particle-size, differential scanning calorimetry (DSC), and thermal gravimetric (TG) analyses. It seems that the DAA is oxidatively polymerized at the 1,4- and 5,8-positions. Surprisingly, the chemical oxidative polymerization of DAA with CrO 3 at 0°C in H 2 SO 4 /DMF in the absence of external stabilizer simply affords novel PDAA nanoparticles of around 30 nm in diameter with high purity, clean surfaces, inherent semiconductivity, and self-stability that can be ascribed to the presence of a large number of 1,4-benzoquinone units that are negatively charged on their macromolecular chains. The polymers exhibit a high thermal stability at temperatures below 400 °C. Two unique nanoeffects were found, namely the strongest silver-ion adsorbability and photoluminescence of the PDAA nanoparticles. This gives a facile and general route for the application of the versatilities of PDAA nanomaterials. The PDAA particles are good semiconductors with a widely adjustable conductivity that moves across seven orders of magnitude through simple HClO 4 redoping or Ag + sorption, as expected.

Nitric acid, hydrochloric acid and EDTA were carefully chosen as desorbent to systematically evaluate the adsorption/desorption performance of the Pb 2+ -adsorbing fine microparticles of poly( m -phenylenediamine). The sorption/desorption efficiency was maximized by optimizing desorption condition including the desorbent concentration, contact time, and desorption mode. The variation of the solution pH with Pb 2+ desorption was recorded to speculate the desorption mechanism. The practical reusability of the microparticles was elaborated through the sorption–desorption cycle experiments in an optimum condition. It was found that the desorption was very rapid with an equilibrium time of several minutes. A strong dependence of the desorbability on the species and concentration of the desorbents was observed. When 20 mM EDTA was chosen as the desorbent, the highest desorptivity was up to 94.2% that was much higher than those using nitric and hydrochloric acids. A successive sorption–desorption study employing nitric acid indicated that the microparticles could be simply regenerated and reutilized for more than 5 cycles together with Pb 2+ re-adsorption efficiency of about 50% and accumulative Pb 2+ adsorption capacity of up to 720.4 mg L −1 . Facilely prepared, extremely chemoresistant and cost-effective PmPD microparticles would be potentially used for multicyclic sorption of lead ions from aqueous solution.

We discuss the background associated with an electrochromic device that can reversibly change its color and optical density at a specific potential. We discuss the underlying science needed to make a new polyaniline (PAN)/polyvinyl alcohol(PVA) electrochromic composite film on an indium-tin oxide (ITO) conducting glass by electropolymerization and describe a reversible redox transition of the PAN. The experiment gives students an opportunity to fabricate an electrochromic device containing PAN, one of the most important conducting polymers. The experimental conditions are flexible so that each group of students can construct their own electrochromic device with particular behavior. Two techniques for polymerizing the PAN and three methods of demonstrating the electrochromism are given, depending on the available apparatus. A sophisticated three-electrode potentiostat or a crude apparatus containing a battery, wire, a variable resistor, and a voltage meter is used to synthesize the PAN deposit. The electrochromic property is repetitively observed by reversibly changing the applied potentials on the device. A potentiostatic apparatus, a single flashlight battery, or a flashlight battery accompanied by a variable resistor allows students to observe multicolor electrochromism. The experiments significantly enhance students’ understanding of polymer chemicophysics principles and their appreciation of novel variable colorful films. The experiments are safe and easy to perform, provided that appropriate precautions are taken.

A highly volatile asymmetric iron(II) amidinate, iron(II) bis(N-tert-butyl-N! -ethylacetamidinate), was synthesized for the first time by systematically changing starting iron(II) compounds such as acetylacetonate, acetate, and chloride, in different media such as diethyl ether, toluene, and tetrahydrofuran. The amidinate has been characterized and compared with the symmetric iron(II) bis(N,N! -diisopropylacetamidinate) by NMR spectroscopy, MS, IR spectroscopy, and dynamic and isothermal thermogravimetric techniques. Different amidinates from three starting compounds exhibit almost the same NMR, MS, and IR spectra, a melting point of 85 °C, and the same solution color in the same solvents, but quite different synthetic yields, volatilities, and colors in different solvents. This implies that the amidinates show an interesting solvatochromism. In particular, the asymmetric iron(II) amidinates obtained should be a mixture of paramag