Rare-earth based tetrapyrrolic sandwiches: chemistry, materials and applications

This review summarises advances in chemistry of tetrapyrrole sandwiches with rare earth elements and highlights the current state of their use in single-molecule magnetism, organic field-effect transistors, conducting materials and nonlinear optics.

A highly selective electron affinity facilitated H2S sensor: the marriage of tris(keto-hydrazone) and an organic field-effect transistor

Conjugated polymers (CPs) are emerging as part of a promising future for gas-sensing applications. However, some of their limitations, such as poor specificity, humidity sensitivity and poor ambient stability, remain persistent. Herein, a novel combination of a polymer-monomer heterostructure, derived from a CP (PDVT-10) and a newly reported monomer [tris(keto-hydrazone)] has been integrated in an organic field-effect transistor (OFET) platform to sense H₂S selectively. The hybrid heterostructure shows an unprecedented sensitivity (525% ppm^-1) and high selectivity toward H₂S gas. In addition, we demonstrated that the PDVT-10/tris(keto-hydrazone) OFET sensor has the lowest limit of detection (1 ppb), excellent ambient stability (∼5% current degradation after 150 days), good response-recovery behavior, and exceptional electrical behavior and gas response reproducibility. This work can help pave the way to incorporate futuristic gas sensors in a multitude of applications.

Cobweb-like, Ultrathin Porous Polymer Films for Ultrasensitive NO2 Detection

Gas sensors based on polymer field-effect transistors (FETs) have drawn much attention owing to the inherent merits of specific selectivity, low cost, and room temperature operation. Ultrathin (<10 nm) and porous polymer semiconductor films offer a golden opportunity for achieving high-performance gas sensors. However, wafer-scale fabrication of such high-quality polymer films is of great challenge and has rarely been realized before. Herein, the first demonstration of 4 in. wafer-scale, cobweb-like, and ultrathin porous polymer films is reported via a one-step phase-inversion process. This approach is extremely simple and universal for constructing various ultrathin porous polymer semiconductor films. Thanks to the abundant pores, ultrathin size, and high charge-transfer efficiency of the prepared polymer films, our gas sensors exhibit many superior advantages, including ultrahigh response (2.46 × 10⁶%), low limit of detection (LOD) (<1 ppm), and excellent selectivity. Thus, the proposed fabrication strategy is exceptionally promising for mass manufacturing of low-cost high-performance polymer FET-based gas sensors.

Gate-tunable gas sensing behaviors in air-stable ambipolar organic thin-film transistors

Chemiresistive gas sensors, which exploit their electrical resistance in response to changes in nearby gas environments, usually achieve selective gas detection using multi-element sensor arrays. As large numbers of sensors are required, they often suffer from complex and high-cost fabrication. Here, we demonstrate an ambipolar organic thin-film transistor as a potential multi-gas sensing device utilizing gate-tunable gas sensing behaviors. Combining behaviors of both electron and hole carriers in a single device, the proposed device showed dynamic changes depending on gate biases and properties of target gases. As a result, the gas response as a function of gate biases exhibits a unique pattern towards a specific gas as well as its concentrations, which is very different from conventional unipolar organic thin-film transistors. In addition, our device showed an excellent air-stable characteristic compared to typical ambipolar transistors, providing great potential for practical use in the future.

Ambipolar organic field effect transistor shows a great potential to be used for multi-gas sensing device utilizing gate-tunable gas sensing behaviors.

A phthalocyanine sensor array based on sensitivity and current changes for highly sensitive identification of three toxic gases at ppb levels

The first phthalocyanine-based sensor array by the combination of two parameters, namely current change direction and sensitivity, for accurate discrimination and wide range of detection of three toxic gases at ppb levels.

Ultrathin Phthalocyanine-Conjugated Polymer Nanosheet-Based Electrochemical Platform for Accurately Detecting H2O2 in Real Time

As a vital biological mediator and a widely used industrial oxidant, the accurate detection of hydrogen peroxide (H₂O₂) is of significance for both academic purpose and practical applications. Herein, we report a novel approach for the development of a high-performance electrochemical H₂O₂ sensor constructed by iron phthalocyanine (FePc)-based diyne-linked conjugated polymeric nanosheets (NSs), FePc-CP NSs. The FePc-CP NSs were delaminated from the bulk material via a defect- and disorder-induced synthetic strategy. By the quasi-Langmuir-Shäfer method, the prepared FePc-CP NSs were self-assembled into multilayer films with controllable thickness on electrodes. Owing to the highly exposed active centers on the surfaces, the FePc-CP NS film-modified electrodes exhibited excellent H₂O₂ determination performance with a wide linear detection range (0.1-1000 μM), a short response time (the response current approached the maximum value within 0.1 s), a low limit of detection (0.017 μM), and excellent sensitivity (97 μA cm^-2 mM^-1), which are comparable to the best results reported so far for electrochemical H₂O₂ sensors. In addition, the fabricated electrochemical H₂O₂ sensor also displayed satisfactory stability, reproducibility, and selectivity. Furthermore, the obtained FePc-CP NS film sensor can be applied in real-time monitoring of H₂O₂ in commercial orange juice and beer as well as H₂O₂ secreted from A549 live cells, revealing its application potential toward the accurate detection of H₂O₂ in real-sample analysis.

High mobility at the interface of the cocrystallized sandwich-type tetrapyrrole metal compound and fullerene layers

Organic field effect transistor (OFET) devices fabricated based on mixed-(phthalocyaninato)(porphyrinato) yttrium(iii) and fullerene cocrystals represent one of the most excellent cocrystal ambipolar OFET devices reported thus far.

A sandwich-type tetrakis(phthalocyaninato) europium–cadmium quadruple-decker complex: structural, spectroscopic, OFET, and gas sensing properties

A new tetrakis(phthalocyaninato) europium(iii)–cadmium(ii) quadruple-decker complex {[Pc(SC₆H₁₃)₈]Eu[Pc(SC₆H₁₃)₈]Cd[Pc(SC₆H₁₃)₈]Eu[Pc(SC₆H₁₃)₈]} (1) has been designed, synthesized, and characterized.

Hemiporphyrazine-Involved Sandwich Dysprosium Double-Decker Single-Ion Magnets

Both heteroleptic (phthalocyaninato)(hemiporphyrazinato) and homoleptic bis(hemiporphyrazinato) dysprosium double-decker complexes, Dy[H(Hp)₂] (1) and Dy[H(Pc)(Hp)] (2) (H₂Pc = metal-free phthalocyanine; H₂Hp = metal-free hemiporphyrazine), were designed, synthesized, and structurally characterized. The dysprosium center in both double-deckers are octa-coordinated with a nearly ideal square-antiprismatic coordination geometry, which provides an increased molecular anisotropy for the dysprosium ion and ensures the strengthened magnetic properties of both single-ion magnets (SIMs) in terms of coordination geometry. Magnetic studies reveal that both double-deckers exhibit typical SIM behavior with a spin reversal energy barrier of 80.1 ± 6.3 K for 1 and 57.3 ± 3.8 K for 2 as well as the hysteresis loops emerging at 3 K. In particular, introduction of two Hp ligands with four pyridine nitrogen atoms coordinated with the dysprosium spin center endows Dy[H(Hp)₂] (1) with the thus far highest energy barrier among the sandwich-type dysprosium SIMs with N₄-macrocyclic ligands, revealing the potential applications of sandwich-type lanthanide complexes with Hp ligands in molecular-based information storage.