14 research outputs found
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 thienoÂ[3,2-<i>b</i>]Âthiophene 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 cm<sup>2</sup> V<sup>–1</sup> s<sup>–1</sup> and 0.82 cm<sup>2</sup> V<sup>–1</sup> s<sup>–1</sup>, 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 cm<sup>2</sup> V<sup>–1</sup> s<sup>–1</sup>. 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><sub>on</sub>/<i>I</i><sub>off</sub>) 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]ÂbenzothienoÂ[3,2-<i>b</i>]Âbenzothiophene (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<sub>h</sub>) up to 2.47 cm<sup>2</sup> V<sup>–1</sup> s<sup>–1</sup>. 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′-bisÂ(5-(benzoÂ[<i>b</i>]Âthiophen-2-yl)Âthiophen-2-yl)-1,1′-bisÂ(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-(benzoÂ[<i>b</i>]Âfuran-2-yl)Âthiophen-2-yl)-1,1′-bisÂ(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 benzoÂ[<i>b</i>]Âthiophene moieties and two benzoÂ[<i>b</i>]Âfuran 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 cm<sup>2</sup> V<sup>–1</sup> s<sup>–1</sup> with high on/off ratio up to 10<sup>6</sup>. In comparison, the hole mobility of OFETs with <b>BFBPD</b> (0.14 cm<sup>2</sup> V<sup>–1</sup> s<sup>–1</sup>) 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′-bisÂ(5-(benzoÂ[<i>b</i>]Âthiophen-2-yl)Âthiophen-2-yl)-1,1′-bisÂ(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-(benzoÂ[<i>b</i>]Âfuran-2-yl)Âthiophen-2-yl)-1,1′-bisÂ(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 benzoÂ[<i>b</i>]Âthiophene moieties and two benzoÂ[<i>b</i>]Âfuran 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 cm<sup>2</sup> V<sup>–1</sup> s<sup>–1</sup> with high on/off ratio up to 10<sup>6</sup>. In comparison, the hole mobility of OFETs with <b>BFBPD</b> (0.14 cm<sup>2</sup> V<sup>–1</sup> s<sup>–1</sup>) 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 cm<sup>2</sup>V<sup>–1</sup>s<sup>–1</sup>. 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 cm<sup>2</sup>V<sup>–1</sup>s<sup>–1</sup>
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 cm<sup>2</sup> V<sup>–1</sup> s<sup>–1</sup>, whereas typical ambipolar behavior is found for thin film of <b>DPPA3</b> with hole and electron mobilities reaching 0.062 cm<sup>2</sup> V<sup>–1</sup> s<sup>–1</sup> and 0.021 cm<sup>2</sup> V<sup>–1</sup> s<sup>–1</sup>, 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
PC<sub>71</sub>BM
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