All‐Solid‐State Ion Selective and All‐Solid‐State Reference Electrodes

This paper is aiming to give a brief overview of recent research in the field of all‐solid‐state, internal solution free, ion‐selective electrodes and reference electrodes, employing conducting polymers or nano‐/microstructures as solid contacts beneath the polymeric, ion‐selective or reference membranes. The emphasis is on papers published in the last five years (after 2006). According to the papers published, poly(3‐octylthiophene) conducting polymer transducers offer highly reliable sensors for various applications, involving demanding analytical approaches and miniature sensors. On the other hand, the search for alternative materials continues: the sensors obtained by placing nano‐/microstructures (conducting polymers but also other materials, like, e.g., carbon nanotubes) underneath the receptor membrane are intensively tested. The recent years have also shown how useful the application of advanced instrumental methods is for the investigation of processes occurring within all‐solid‐state ion‐selective electrodes.     

Highly Selective “Turn‐On” Fluorescent and Colorimetric Sensing of Fluoride Ion Using 2‐(2‐Hydroxyphenyl)‐2,3‐dihydroquinolin‐4(1 H)‐one based on Excited‐State Proton Transfer

A simple, highly selective and sensitive colorimetric system for the detection of fluoride ion in an aqueous medium has been developed using 2‐(2‐hydroxyphenyl)‐2,3‐dihydroquinolin‐4(1 H)‐one. This system allows selective “turn‐on” fluorescence detection of fluoride ion, which is found to be dependent upon guest basicity. An excited‐state proton transfer is proposed to be the signaling mechanism, which is rationalized by DFT and TD‐DFT calculations. The present sensor can also be applied to detect fluoride levels in real water samples.     

Tailoring Solution Cast Poly(3,4‐dioctyloxythiophene) Transducers for Potentiometric All‐Solid‐State Ion‐Selective Electrodes

A novel concept of tailoring potentiometric responses of all‐solid‐state ion‐selective electrodes was introduced. The effect of composition and resulting properties of the conjugated polymer transducer, placed between the electrode support and ion‐selective membrane, on analytical characteristic of obtained sensors was studied.     

All Solid State Chromium(III) Selective Potentiometric Sensor Based on 2‐(1‐(2‐((3‐(2‐Hydroxyphenyl)‐1H‐pyrozol‐1‐yl)methyl)benzyl)‐1H‐pyrazol‐3‐yl)phenol

Highly selective all solid state electrochemical sensor based on a synthesized compound i.e. 2‐(1‐(2‐((3‐(2‐hydroxyphenyl)‐1H‐pyrozol‐1‐yl)methyl)benzyl)‐1H‐pyrazol‐3‐yl)phenol (I) as an ionophore has been prepared and investigated for the selective quantification of chromium(III) ions. The effect of various plasticizers, viz. dibutyl phosphonate (DBP), dibutyl(butyl) phosphonate (DBBP), nitrophenyl octyl ether (NPOE), tris‐(2‐ethylhexyl)phosphonate (TEP), tri‐butyl phosphonate (TBP), dioctyl phthalate (DOP), dioctyl sebacate (DOS), benzyl acetate (BA) and acetophenone (AP) along with anion excluders NaTPB (sodium tetraphenyl borate) and KClTPB (potassium(tetrakis‐4‐chlorophenyl)borate was also studied. The optimum composition of the best performing membrane contained (I):KClTPB:NPOE:PVC in the ratio 15 : 3 : 40 : 42 w/w. The sensor exhibited near Nernstian slope of 20.1±0.2 mV/decade of activity in the working concentration range of 1.2×10^?7–1.0×10^?1 M, and in a pH range of 3.8–4.5. The sensor exhibited a fast response time of 10 s and could be used for about 5 months without any considerable divergence in potentials. The proposed sensor showed very good selectivity over most of the common cations including Na⁺, Li⁺, K⁺, Cu²⁺, Sr²⁺, Ni²⁺, Co²⁺, Ba²⁺, Hg²⁺, Pb²⁺, Zn²⁺, Cs⁺, Mg²⁺, Cd²⁺, Al³⁺, Fe³⁺and La³⁺. The activity of Cr(III) ions was successfully determined in the industrial waste samples by using this sensor.     

Polymorph‐Dependent Thermally Activated Delayed Fluorescence Emitters: Understanding TADF from a Perspective of Aggregation State

Current research on thermally activated fluorescence (TADF) emitters is mainly based on the molecular levels, while the aggregation states of TADF emitters are to be explored deeply. Now two multifunctional emitters are reported with simultaneous TADF, aggregation induced emission (AIE), and multicolor mechanochromic luminescence (MCL) features. Both emitters also show polymorph‐dependent TADF emission. Crystal structure analysis reveals that the polymorphism is ascribed to the mutable conformations in different aggregation states. This work brings new insight to TADF emitters from a perspective of aggregation states.     

Comparison of Multi‐walled Carbon Nanotubes and Poly(3‐octylthiophene) as Ion‐to‐Electron Transducers in All‐Solid‐State Potassium Ion‐Selective Electrodes

Multi‐walled carbon nanotubes (MWCNTs) were compared with poly(3‐octylthiophene) (POT) as ion‐to‐electron transducer in all‐solid‐state potassium ion‐selective electrodes with valinomycin‐based ion‐selective membranes. MWCNTs and POT were mixed with the other components of the potassium ion‐selective membrane cocktail (valinomycin, KTpClPB, o‐NPOE, PVC, THF) which was then applied on a glassy carbon (GC) substrate to prepare single‐piece ion‐selective electrodes (SPISEs). Results from potentiometric and impedance measurements showed that the MWCNT‐based electrodes have a more reproducuible standard potential and a lower overall impedance than the electrodes based on POT. Both types of electrodes showed similar sensitivity to potassium ions and no redox sensitivity.     

Conducting Polymer‐Based Solid‐State Ion‐Selective Electrodes

Conducting polymers, i.e., electroactive conjugated polymers, are useful both as ion‐to‐electron transducers and as sensing membranes in solid‐state ion‐selective electrodes. Recent achievements over the last few years have resulted in significant improvements of the analytical performance of solid‐contact ion‐selective electrodes (solid‐contact ISEs) based on conducting polymers as ion‐to‐electron transducer combined with polymeric ion‐selective membranes. A significant amount of research has also been devoted to solid‐state ISEs based on conducting polymers as the sensing membrane. This review gives a brief summary of the progress in the area in recent years.     

Synthesis and Spectral Properties of 4‐(2,5‐Dimethoxyphenylmethelene)‐2‐phenyl‐5‐oxazolone (DMPO)

An interesting flourophore, 4‐(2,5‐dimethoxyphenylmethelene)‐2‐phenyl‐5‐oxazolone (DMPO) was synthesized by mixing an equivalent molar quantity of hippuric acid and 2,5‐dimethoxybenzaldehyde in acetic anhydride in the presence of anhydrous sodium acetate. The absorption and fluorescence characteristics of 4‐(2,5‐dimethoxy‐phenylmethelene)‐2‐phenyl‐5‐oxazolone (DMPO) were investigated in different solvents. DMPO dye exhibits red shift in both absorption and emission spectra as solvent polarity increases, indicating change in the dipole moment of molecules upon excitation due to an intramolecular charge transfer interaction. The fluorescence quantum yield depends strongly on the properties of the solvents, which was attributed to positive and negative solvatokinetic effects. A crystalline solid of DMPO gave strong excimer like emission at 630 nm due to the excitation of molecular aggregates. This is expected from the idealized crystal structure of the dye that belongs to the B‐type class of Steven's Classification. DMPO displayed fluorescence quenching by triethylamine via nonemissive exciplex formation.     

Systematic Investigation of Molecular Arrangements and Solid‐State Fluorescence Properties on Salts of Anthracene‐2,6‐disulfonic Acid with Aliphatic Primary Amines

Organic salts of anthracene‐2,6‐disulfonic acid (ADS) with a wide variety of primary amines have been fabricated, and their arrangements of anthracene molecules and solid‐state fluorescence properties investigated. Single‐crystal X‐ray studies reveal that the salts show seven types of crystal forms and corresponding molecular arrangements of anthracene moieties depending on the amine, while anthracene shows only one form and arrangement in the solid state. Depending on the molecular arrangements, the ADS salts exhibit various solid‐state fluorescence properties: spectral shift (30 nm) and suppression and enhancement of the fluorescence intensity. Especially the ADS salt with n‐heptylamine (nHepA), which shows discrete anthracene moieties in the crystal, exhibits the highest quantum yield (Φ_F=46.1±0.2 %) in the series of ADS salts, which exceeds that of anthracene crystal (Φ_F=42.9±0.2 %). From these systematic investigations on the arrangements and the solid‐state properties, the following factors are essential for high fluorescence quantum yield in the solid state: prevention of contact between π planes of anthracene moieties and immobilization of anthracene rings. In addition, such organic salts have potential as a system for modulating the molecular arrangements of fluorophores and the concomitant solid‐state properties. Thus, systematic investigation of this system constructs a library of arrangements and properties, and the library leads to remarkable strategies for the development of organic solid materials.     

In Situ Solid‐State Generation of (BN)2‐Pyrenes and Electroluminescent Devices

New BN‐heterocyclic compounds have been found to undergo double arene photoelimination, forming rare yellow fluorescent BN‐pyrenes that contain two B? N units. Most significant is the discovery that the double arene elimination can also be driven by excitons generated electrically within electroluminescent (EL) devices, enabling the in situ solid‐state conversion of BN‐heterocycles to BN‐pyrenes and the use of BN‐pyrenes as emitters for EL devices. The in situ exciton‐driven elimination (EDE) phenomenon has also been observed for other BN‐heterocycles.     

Synthesis and Solid‐state Reaction of 1‐[3′‐(Benzotriazol‐2″‐yl)‐4′ ‐hydroxybenzoyl]‐3‐methyl‐5‐pyrazolones

A new kind of UV stabilizers, 1‐(3′‐(benzotriazol‐2″‐yl)‐4′‐hydroxy‐benzoyl)‐3‐methyl‐5‐pyrazolones (1a‐d), was synthesized with the aim to bind them chemically to certain polymers. The reaction of 1d with substituted benzaldehydes 4 in the molten state at 150°C and in the solid state at room temperature produced the condensation products l‐(3′‐(5″‐chlorobenzotriazol‐2″‐yl)‐4′‐hydroxyl‐5′‐chlorobenzoyl)‐3‐methyl‐4‐arylmethylene‐5‐pyrazolones (2) and 4,4′‐arylmethylene‐bis [1‐(3′‐(5″‐chloro‐benzotriazol‐2″‐yl)‐4′‐hydroxy‐5′‐chloro‐benzoyl)‐3‐methyl‐5‐pyrazolone] s (3), respectively, as the major product. On the other hand, the reaction of 1d with 4 at 50°C in chloroform solution proceeded non‐selectively to give a mixture of 2 and 3.     

Control of the Solid‐State Chiral Optical Properties of a Supramolecular Organic Fluorophore Containing 4‐(2‐Arylethynyl)‐Benzoic Acid

The solid‐state chiral optical properties of a 4‐(2‐arylethynyl)‐benzoic acid/amine supramolecular organic fluorophore can be controlled by changing the arylethynyl group of the achiral 4‐(2‐arylethynyl)‐benzoic acid component molecule rather than the chirality of the amine component molecule.     

All Solid State Nickel(II)‐Selective Potentiometric Sensor Based on an Upper Rim Substituted Calixarene

A new ionophore, i.e. p‐(2‐thiazolazo)calix[4]arene ( I ) has been explored for its selective behavior towards Ni(II) ions. A poly(vinyl chloride) based membrane containing ( I ) as an electroactive material along with sodiumtetraphenylborate (NaTPB), and nitrophenyloctyl ether in the ratio 10 : 100 : 3 : 150 (I:PVC:NaTPB:NPOE) (w/w) was used to fabricate an all solid state nickel(II)‐selective sensor. The developed sensor exhibited a working concentration range of 1.0×10^?6–1.0×10^?1 M, with a Nernstian slope of 28.9±1.0 mV/decade of activity and a response time of 10–15 s. This sensor shows a detection limit of 9.0×10^?7 M. Its potential response remains unaffected of pH in the range 3.0–7.6, and the cell assembly could be used successfully in partially nonaqueous medium (up to 10 % v/v) without any significant change in the slope value or the working concentration range. The sensor worked satisfactorily for about ten weeks and exhibited excellent selectivity over a number of mono‐, bi‐, and tri‐valent cations including alkali, alkaline earth metal, and transition metal ions. It could be used as an indicator electrode for the end point determination in the potentiometric titration of nickel ions against ethylenediaminetetraacetic acid (EDTA) as well as for the determination of nickel ion concentration in real samples.     

Synthesis of Stoichiometric and Bulk CrN through a Solid‐State Ion‐Exchange Reaction

Chromium mononitride (CrN) exhibits interesting magnetic, structural, and electronic properties for technological applications. Experimental reports on these properties are often inconsistent owing to differences in the degree of nonstoichiometry in CrN_x. To date, the preparation of bulk and stoichiometric CrN has been challenging; most products are in the form of a thin film produced by non‐equilibrium processes, and are often nonstoichiometric and poorly crystallized. In this work, we formulated a solid‐state ion‐exchange route for the synthesis of CrN under high pressure. The final CrN product is phase‐pure, stoichiometric, and well‐crystallized in the bulk form. Near‐stoichiometric and well‐crystallized CrN can be synthesized using the same route at atmospheric pressure, making massive and industrial‐scale production technologically feasible. The successful synthesis of stoichiometric and bulk CrN is expected to open new opportunities in diverse areas of fundamental research.     

Ultrahigh Energy Density Realized by a Single‐Layer β‐Co(OH)2 All‐Solid‐State Asymmetric Supercapacitor

A conceptually new all‐solid‐state asymmetric supercapacitor based on atomically thin sheets is presented which offers the opportunity to optimize supercapacitor properties on an atomic level. As a prototype, β‐Co(OH)₂ single layers with five‐atoms layer thickness were synthesized through an oriented‐attachment strategy. The increased density‐of‐states and 100 % exposed hydrogen atoms endow the β‐Co(OH)₂ single‐layers‐based electrode with a large capacitance of 2028 F g^?1. The corresponding all‐solid‐state asymmetric supercapacitor achieves a high cell voltage of 1.8 V and an exceptional energy density of 98.9 Wh kg^?1 at an ultrahigh power density of 17 981 W kg^?1. Also, this integrated nanodevice exhibits excellent cyclability with 93.2 % capacitance retention after 10 000 cycles, holding great promise for constructing high‐energy storage nanodevices.     

Solid‐State Synthesis and Characterization of 2‐Thioxo‐4‐Imidazolidinone Derivatives

A new and efficient two‐step solid‐state synthesis method is described for 2‐thioxo‐4‐imidazolidinone from aryl isothiocyanate and free amino acid. This method requires only simple equipment and is easy to perform. The products reported were characterized on the basis of IR, MS, ¹H NMR, ¹³C NMR and elemental analysis.     

Automated Solid‐Phase Synthesis of a β‐(1,3)‐Glucan Dodecasaccharide

β‐Glucans are a group of structurally heterogeneous polysaccharides found in bacteria, fungi, algae and plants. β‐(1,3)‐D ‐Glucans have been studied in most detail due to their impact on the immune system of vertebrates. The studies into the immunomodulatory properties of these glucans are typically carried out with isolates that contain a heterogeneous mixture of polysaccharides of different chain lengths and varying degrees of branching. In order to determine the structure–activity relationship of β‐(1,3)‐glucans, access to homogeneous, structurally‐defined samples of these oligosaccharides that are only available through chemical synthesis is required. The syntheses of β‐glucans reported to date rely on the classical solution‐phase approach. We describe the first automated solid‐phase synthesis of a β‐glucan oligosaccharide that was made possible by innovating and optimizing the linker and glycosylating agent combination. A β‐(1,3)‐glucan dodecasaccharide was assembled in 56 h in a stereoselective fashion with an average yield of 88 % per step. This automated approach provides means for the fast and efficient assembly of linker‐functionalized mono‐ to dodecasaccharide β‐(1,3)‐glucans required for biological studies.     

Metal‐Ion‐Mediated Tuning of Duplex DNA Binding by Bis(2‐(2‐pyridyl)‐1H‐benzimidazole)

Studies of double‐stranded‐DNA binding have been performed with three isomeric bis(2‐(n‐pyridyl)‐1H‐benzimidazole)s (n=2, 3, 4). Like the well‐known Hoechst 33258, which is a bisbenzimidazole compound, these three isomers bind to the minor groove of duplex DNA. DNA binding by the three isomers was investigated in the presence of the divalent metal ions Mg²⁺, Co²⁺, Ni²⁺, Cu²⁺, and Zn²⁺. Ligand–DNA interactions were probed with fluorescence and circular dichroism spectroscopy. These studies revealed that the binding of the 2‐pyridyl derivative to DNA is dramatically reduced in the presence of Co²⁺, Ni²⁺, and Cu²⁺ ions and is abolished completely at a ligand/metal‐cation ratio of 1:1. Control experiments done with the isomeric 3‐ and 4‐pyridyl derivatives showed that their binding to DNA is unaffected by the aforementioned transition‐metal ions. The ability of 2‐(2‐pyridyl)benzimidazole to chelate metal ions and the conformational changes of the ligand associated with ion chelation probably led to such unusual binding results for the ortho isomer. The addition of ethylenediaminetetraacetic acid (EDTA) reversed the effects completely.     

113Cd Solid‐State NMR for Probing the Coordination Sphere in Metal–Organic Frameworks

Spectroscopic techniques are a powerful tool for structure determination, especially if single‐crystal material is unavailable. ¹¹³Cd solid‐state NMR is easy to measure and is a highly sensitive probe because the coordination number, the nature of coordinating groups, and the geometry around the metal ion is reflected by the isotropic chemical shift and the chemical‐shift anisotropy. Here, a detailed investigation of a series of 27 cadmium coordination polymers by ¹¹³Cd solid‐state NMR is reported. The results obtained demonstrate that ¹¹³Cd NMR is a very sensitive tool to characterize the cadmium environment, also in non‐single‐crystal materials. Furthermore, this method allows the observation of guest‐induced phase transitions supporting understanding of the structural flexibility of coordination frameworks.