Highly Sensitive Thin-Film Field-Effect Transistor Sensor for Ammonia with the DPP-Bithiophene Conjugated Polymer Entailing Thermally Cleavable <i>tert</i>-Butoxy Groups in the Side Chains

The sensing and detection of ammonia have received increasing attention in recent years because of the growing emphasis on environmental and health issues. In this paper, we report a thin-film field-effect transistor (FET)-based sensor for ammonia and other amines with remarkable high sensitivity and satisfactory selectivity by employing the DPP-bithiophene conjugated polymer pDPPBu-BT in which <i>tert</i>-butoxycarboxyl groups are incorporated in the side chains. This polymer thin film shows <i>p</i>-type semiconducting property. On the basis of TGA and FT-IR analysis, <i>tert</i>-butoxycarboxyl groups can be transformed into the −COOH ones by eliminating gaseous isobutylene after thermal annealing of pDPPBu-BT thin film at 240 °C. The FET with the thermally treated thin film of pDPPBu-BT displays remarkably sensitive and selective response toward ammonia and volatile amines. This can be attributed to the fact that the elimination of gaseous isobutylene accompanies the formation of nanopores with the thin film, which will facilitate the diffusion and interaction of ammonia and other amines with the semiconducting layer, leading to high sensitivity and fast response for this FET sensor. This FET sensor can detect ammonia down to 10 ppb and the interferences from other volatile analytes except amines can be negligible

Alternating Conjugated Electron Donor–Acceptor Polymers Entailing Pechmann Dye Framework as the Electron Acceptor Moieties for High Performance Organic Semiconductors with Tunable Characteristics

In this paper, we report the design, synthesis and semiconducting behavior of two conjugated D–A polymers <b>P-BPDTT</b> and <b>P-BPDBT</b> which entail <b>BPD</b>, a Pechmann dye framework, as electron accepting moieties, and thieno­[3,2-<i>b</i>]­thiophene and 2,2′-bithiophene as electron donating moieties. Their HOMO/LUMO energies and bandgaps were estimated based on the respective cyclic voltammgrams and absorption spectra of thin films. <b>P-BPDTT</b> possesses lower LUMO level and narrower bandgap than <b>P-BPDBT</b>. On the basis of the characterization of the field-effect transistors, a thin film of <b>P-BPDTT</b> exhibits ambipolar semiconducting properties with hole and electron mobilities reaching 1.24 cm² V^–1 s^–1 and 0.82 cm² V^–1 s^–1, respectively, after thermal annealing. In comparison, thin film of <b>P-BPDBT</b> only shows <i>p</i>-type semiconducting behavior with hole mobility up to 1.37 cm² V^–1 s^–1. AFM and XRD studies were presented to understand the interchain arrangements on the substrates and the variation of carrier mobilities

Improving Ambipolar Semiconducting Properties of Thiazole-Flanked Diketopyrrolopyrrole-Based Terpolymers by Incorporating Urea Groups in the Side-Chains

Two new ambipolar thiazole-flanked diketopyrrolopyrrole-based polymers pDPPTz2T-1 and pDPPTz2T-2 with urea-containing linear side-chains were prepared. The formation of hydrogen bonding enhanced the ambipolar semiconducting properties, including mobilities and on/off ratios. The average mobilities (hole and electron) of pDPPTz2T-2 were 25 and 3 times higher than those of pDPPTz2T without urea groups, whereas the average on/off ratios (<i>I</i>_on/<i>I</i>_off) for hole and electron were 100 and 4 times higher than those obtained for pDPPTz2T. Thin-film microstructure studies reveal that incorporating urea groups into polymer side-chains can enhance interchain packings, including the alkyl chain lamellar and π–π stackings. Our results clearly show how incorporating urea groups in side-chains significantly influence semiconducting properties, which could be extended to other conjugated systems toward ambipolar and even n-type FETs

Conjugated Random Donor–Acceptor Copolymers of [1]Benzothieno[3,2‑<i>b</i>]benzothiophene and Diketopyrrolopyrrole Units for High Performance Polymeric Semiconductor Applications

Three-component random copolymers having different ratios of [1]­benzothieno­[3,2-<i>b</i>]­benzothiophene (BTBT) and diketopyrrolopyrrole (DPP) units were synthesized, and their application in organic field effect transistors (OFET) has been discussed. These low band gap polymers exhibit p-type semiconducting properties, and it has been observed that increase in the percentage composition of the fused chalcogenophene (BTBT) in the polymer backbone significantly improves the charge carrier mobility (μ_h) up to 2.47 cm² V^–1 s^–1. The GIXRD technique and AFM have been used to explain the influence of BTBT on the nature of molecular packing in the polymer thin films. These results unveil the role of the effective conjugation length as well as the intermolecular ordering of the polymer chains on the charge carrier transport in OFET

Spin Radical Enhanced Magnetocapacitance Effect in Intermolecular Excited States

This article reports the magnetocapacitance effect (MFC) based on both pristine polymer MEH-PPV and its composite system doped with spin radicals (6R-BDTSCSB). We observed that a photoexcitation leads to a significant positive MFC in the pristine MEH-PPV. Moreover, we found that a low doping of spin radicals in polymer MEH-PPV causes a significant change on the MFC signal: an amplitude increase and a line-shape narrowing under light illumination at room temperature. However, no MFC signal was observed under dark conditions in either the pristine MEH-PPV or the radical-doped MEH-PPV. Furthermore, the magnitude increase and line-shape narrowing caused by the doped spin radicals are very similar to the phenomena induced by increasing the photoexcitation intensity. Our studies suggest that the MFC is essentially originated from the intermolecular excited states, namely, intermolecular electron–hole pairs, generated by a photoexcitation in the MEH-PPV. More importantly, by comparing the effects of spin radicals and electrically polar molecules on the MFC magnitude and line shape, we concluded that the doped spin radicals can have the spin interaction with intermolecular excited states and consequently affect the internal spin-exchange interaction within intermolecular excited states in the development of MFC. Clearly, our experimental results indicate that dispersing spin radicals forms a convenient method to enhance the magnetocapacitance effect in organic semiconducting materials

New Donor–Acceptor–Donor Molecules with Pechmann Dye as the Core Moiety for Solution-Processed Good-Performance Organic Field-Effect Transistors

In this paper, we report the synthesis and characterization of two new D-A-D molecules (<i>E</i>)-5,5′-bis­(5-(benzo­[<i>b</i>]­thiophen-2-yl)­thiophen-2-yl)-1,1′-bis­(2-ethyl- hexyl)-[3,3′-bipyrrolylidene]-2,2′(1<i>H</i>,1′<i>H</i>)-dione (<b>BTBPD</b>) and (<i>E</i>)-5,5′-bis- (5-(benzo­[<i>b</i>]­furan-2-yl)­thiophen-2-yl)-1,1′-bis­(2-ethylhexyl)-[3,3′-bipyrrolylidene]-2,2′(1<i>H</i>,1′<i>H</i>)-dione (<b>BFBPD</b>). They entail bipyrrolylidene-2,2′(1<i>H</i>,1′<i>H</i>)-dione (<b>BPD</b>, known as Pechmann dye) as the electron-accepting core that is flanked by two benzo­[<i>b</i>]­thiophene moieties and two benzo­[<i>b</i>]­furan moieties, respectively. Crystal structures of <b>BTBPD</b> and <b>BFBPD</b> provide solid evidence for the intermolecular donor–acceptor (D-A) interactions, which are favorable for improving charge transport performance. Organic field-effect transistors (OFETs) were prepared based on thin films of <b>BTBPD</b> and <b>BFBPD</b> through solution-processed technique. OFETs of <b>BTBPD</b> exhibit relatively high hole mobility up to 1.4 cm² V^–1 s^–1 with high on/off ratio up to 10⁶. In comparison, the hole mobility of OFETs with <b>BFBPD</b> (0.14 cm² V^–1 s^–1) is relatively low, because of the poor thin-film morphology and low molecular ordering, even after annealing. Thin-film morphological and XRD studies were carried out to understand the variation of hole mobilities after annealing at different temperatures. The present studies clearly demonstrate the potentials of <b>BPD</b> that is planar and polar as the electron-acceptor moiety to build D-A molecules for organic semiconductors with good performance

New Donor–Acceptor–Donor Molecules with Pechmann Dye as the Core Moiety for Solution-Processed Good-Performance Organic Field-Effect Transistors

In this paper, we report the synthesis and characterization of two new D-A-D molecules (<i>E</i>)-5,5′-bis­(5-(benzo­[<i>b</i>]­thiophen-2-yl)­thiophen-2-yl)-1,1′-bis­(2-ethyl- hexyl)-[3,3′-bipyrrolylidene]-2,2′(1<i>H</i>,1′<i>H</i>)-dione (<b>BTBPD</b>) and (<i>E</i>)-5,5′-bis- (5-(benzo­[<i>b</i>]­furan-2-yl)­thiophen-2-yl)-1,1′-bis­(2-ethylhexyl)-[3,3′-bipyrrolylidene]-2,2′(1<i>H</i>,1′<i>H</i>)-dione (<b>BFBPD</b>). They entail bipyrrolylidene-2,2′(1<i>H</i>,1′<i>H</i>)-dione (<b>BPD</b>, known as Pechmann dye) as the electron-accepting core that is flanked by two benzo­[<i>b</i>]­thiophene moieties and two benzo­[<i>b</i>]­furan moieties, respectively. Crystal structures of <b>BTBPD</b> and <b>BFBPD</b> provide solid evidence for the intermolecular donor–acceptor (D-A) interactions, which are favorable for improving charge transport performance. Organic field-effect transistors (OFETs) were prepared based on thin films of <b>BTBPD</b> and <b>BFBPD</b> through solution-processed technique. OFETs of <b>BTBPD</b> exhibit relatively high hole mobility up to 1.4 cm² V^–1 s^–1 with high on/off ratio up to 10⁶. In comparison, the hole mobility of OFETs with <b>BFBPD</b> (0.14 cm² V^–1 s^–1) is relatively low, because of the poor thin-film morphology and low molecular ordering, even after annealing. Thin-film morphological and XRD studies were carried out to understand the variation of hole mobilities after annealing at different temperatures. The present studies clearly demonstrate the potentials of <b>BPD</b> that is planar and polar as the electron-acceptor moiety to build D-A molecules for organic semiconductors with good performance

1,6- and 2,7-<i>trans</i>-β-Styryl Substituted Pyrenes Exhibiting Both Emissive and Semiconducting Properties in the Solid State

Molecular materials that are both emissive and semiconducting are highly demanding for organic optoelectronics. In this article, we report the synthesis, emissive, and semiconducting properties of 1,6 and 2,7-<i>trans</i>-β-styryl substituted pyrenes (<b>16PyE</b> and <b>27PyE</b>). The results reveal that both <b>16PyE</b> and <b>27PyE</b> are emissive and semiconducting in the solid state. The fluorescence quantum yields of crystalline solids of <b>16PyE</b> and <b>27PyE</b> were determined to be 28.8% and 27.4%, respectively. Microrods of <b>16PyE</b> and microplates of <b>27PyE</b> were found to exhibit promising optical waveguilding behavior. Furthermore, on the basis of the transfer and output curves of the respective organic field effect transistors (OFETs), thin films of <b>16PyE</b> and <b>27PyE</b> were found to show <i>p</i>-type semiconducting properties with hole mobility up to 1.66 cm²V^–1s^–1. Such dual functions (emissive and semiconducting) of <b>16PyE</b> and <b>27PyE</b> can be ascribed to the unique intermolecular interactions and packing within crystals of <b>16PyE</b> and <b>27PyE</b>. Both 1,6 and 2,7-<i>trans</i>-β-styryl substituted pyrenes show relatively strong emissions in the solid state, and their microcrystalline samples exhibit promising optical waveguilding behavior. Moreover, their thin films exhibit <i>p</i>-type semiconducting property with hole mobilities up to 1.66 cm²V^–1s^–1

Tuning the Semiconducting Behaviors of New Alternating Dithienyldiketopyrrolopyrrole–Azulene Conjugated Polymers by Varying the Linking Positions of Azulene

Three new conjugated polymers <b>DPPA1</b>, <b>DPPA2</b>, and <b>DPPA3</b> with dithienyldiketopyrrolopyrrole (DPP) and azulene moieties were synthesized and characterized. The five-membered rings of azulene are connected with DPP in <b>DPPA1</b> and <b>DPPA2</b>, whereas the seven-membered ring of azulene is incorporated into the backbone of <b>DPPA3</b>. The LUMO energy of <b>DPPA3</b>, which was determined on the basis of the respective cyclic voltammograms and absorption spectra, is lower than those of <b>DPPA1</b> and <b>DPPA2</b>. OFETs were successfully fabricated with thin films of <b>DPPA1</b>, <b>DPPA2</b>, and <b>DPPA3</b>. Thin films of <b>DPPA1</b> and <b>DPPA2</b> exhibit p-type semiconducting properties with hole mobilities up to 0.97 cm² V^–1 s^–1, whereas typical ambipolar behavior is found for thin film of <b>DPPA3</b> with hole and electron mobilities reaching 0.062 cm² V^–1 s^–1 and 0.021 cm² V^–1 s^–1, respectively. The results reveal that semiconducting properties of <b>DPPA1</b>, <b>DPPA2</b>, and <b>DPPA3</b> can be tuned by varying the linkage positions of azulene with DPP moieties. Furthermore, <b>DPPA1</b>, <b>DPPA2</b>, and <b>DPPA3</b> were tested preliminarily as photovoltaic materials. The power conversion efficiency (PCE) reaches 2.04% for the blending thin film <b>DPPA1</b> with PC₇₁BM

Video1_Clinical characteristics and proposed mechanism of pediatric spinal cord injury resulting from backbend practice.mp4

ObjectivePediatric spinal cord injury without radiographic abnormality (SCIWORA) caused by backbend practice is increasing. This study proposed an underlying ‘combined injury mechanism’ related to the spinal cord and femoral nerve overstretching.MethodsPediatric patients diagnosed with backbend-associated SCIWORA at the China Rehabilitation Research Center during 2017–2021 were recruited. Clinical and imaging data were collected, and each patient's clinical course and prognosis were determined. Healthy dancers were recruited to simulate the backbend, obtain images, and estimate the spinal cord and femoral nerve stretch ratio. A model for the ‘combined injury mechanism’ was established using 4-week-old SD rats.ResultsForty-two SCIWORA female patients with an average age of 6 (SD 1) years and an average hospitalization time of 91 (SD 43) days were assessed. The primary initial symptom was pain in the back and/or lower extremities (33, 79%). The average time from injury onset to severe paralysis was 2.0 (SD 0.6) hours. Most patients had complete paraplegia (32, 76%), and neurological levels were distributed mainly in thoracic segments (38, 91%). Patients with elicited tendon reflexes on admission tended to have an incomplete spinal cord injury (p = 0.001) and improved motor recovery (p = 0.018). After one year, the most common complications were scoliosis (31, 74%) and abnormal hips (14, 33%). Injury of the caudal spinal cord torn by nerve roots was confirmed by surgical exploration in a case. The thoracic spinal cord and femoral nerves were overstretched by 148.8 ± 3.6% and111.7 ± 4.0%, respectively, in a full backbend posture. The ‘combined injury mechanism’ was partially replicated in the animal model.ConclusionSpinal overstretch and transient dislocation are considered the primary mechanisms by which SCIWORA occurs in children. Overstretching the femoral nerve aggravates spinal cord injuries caused by backbend practice.</p