We employed commercially available chip-calorimeter Flash DSC1 to investigate the low-temperature crystallization behaviors of random copolymer P(VDF-TrFE-CFE) ...(poly(vinylidenefluoride-trifluoroethylene-chlorofluoroethylene)), and compared them to the parallel results of P(VDF-TrFE). The resulted ferroelectric crystalline phases were identified by WAXD and FTIR. We found that, although our P(VDF-TrFE-CFE) contains higher content of VDF sequences than our P(VDF-TrFE), it performs crystallization of the ferroelectric phase at low temperatures much slower, and even exhibits cold crystallization upon heating back from fast cooling. We attributed the slowness to the effect of chemical confinement of large CFE comonomers. Our results facilitate better understanding of structural optimization for the electroactive applications of PVDF-based random copolymers.
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•We first-time observed cold crystallization in fast-cooled P(VDF-TrFE-CFE).•Ferroelectric crystalline phase of VDF-TrFE sequences is generated at low temperatures.•Room-temperature transition of ferroelectric domains is vital for electrocaloric refrigerators.
Nanoscale materials are now attracting a great deal of attention for biomedical applications. Conjugated polymer nanoparticles have remarkable photophysical properties that make them highly ...advantageous for biological fluorescence imaging. We report on conjugated polymer nanoparticles with phenylboronic acid tags on the surface for fluorescence detection of neurotransmitter dopamine in both living PC12 cells and brain of zebrafish larvae. The selective enrichment of dopamine and fluorescence signal amplification characteristics of the nanoparticles show rapid and high-sensitive probing such neurotransmitter with the detection limit of 38.8 nM, and minimum interference from other endogenous molecules. It demonstrates the potential of nanomaterials as a multifunctional nanoplatform for targeting, diagnosis, and therapy of dopamine-relative disease.
High-capacity or high-power-density capacitors are being actively investigated for portable electronics, electric vehicles, and electric power systems. We describe the filler system in dielectric ...nanocomposites with a small loading of Au nanorods NRs to elucidate the mechanism of interfacial crystallization behavior including the crystallization kinetics, and crystalline morphology and structure, and to investigate the intrinsic causes for concurrent great improvements in the dielectric constant and energy density in the nanocomposite system. Remarkly, at high crystallization temperature, the addition of Au NRs, which are used as heterogeneous nucleators, can reduce the nucleation barrier, resulting in accelerating the crystallization rate. However, the crystallization rate slows down at low temperatures because the addition of Au NRs limited the mobility of poly(vinylidene fluoride-chlorotrifluoroethylene) P(VDF-CTFE) chains, and thus enhanced the diffusion barrier. Furthermore, the addition of NRs has a huge impact on the crystalline morphology and structure which changes from large paraelectric α-phase spherulites with TGTG' conformations into minor ferroelectric γ-phase spherulites with T3GT3G' conformations, and also produces more exogenous interfaces between the lamellar crystals and amorphous regions, resulting in a higher dielectric constant and higher electric energy density in P(VDF-CTFE)/Au NRs nanocomposites. Our approach provides a facile and straightforward way to design or understand PVDF-based polymers for their practical applications in high-energy-density capacitors.
Nanoscale design of nanofillers and interfacial architecture are vital to achieve high-capacity and high-energy-conversion efficiency poly(vinylidene fluoride) (PVDF)-based nanocomposite materials ...for vast potential applications in modern electronic devices and electric power systems. Using traditional methods, the addition of ceramic nanoparticles can only produce one type of interface between the nanoparticles and this matrix, achieving an enhanced dielectric constant and energy density at the expense of the charge-discharge efficiency. Herein, we demonstrate a novel class of cross-linking nanofiller system, poly(vinylidene fluoride-chlorotrifluoroethylene)/γ-methacryloylpropyl trimethoxysilane@BaTiO
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P(VDF-CTFE)/MPS@BT. This novel approach can not only provide the interfaces between the nanoparticle and the matrix, but also scale down the size of crystalline domains, which results in producing more additional interfaces between the crystalline and amorphous phases to achieve an improved discharged energy density. Remarkably, the smaller crystalline domains, which were characterized by XRD and FTIR spectroscopy, could be beneficial for improving the dipole switchability from the polar phases to non-polar phases during the charge-discharge cycles, leading to unprecedented charge-discharge efficiency. Furthermore, the addition of MPS@BT NPs can regulate two stages of the discharge rate. The early discharge process can be accelerated, while the following stage is obviously delayed. The simplicity of the hierarchical interfacial engineering method provides a promising path to design ferroelectric polymer nanocomposites for dielectric capacitor applications.
Hierarchical interfaces were successfully established in ferroelectric nanocomposite networks, resulting in high energy density and low loss for capacitor applications.
We have witnessed the flourish of bioelectronics, brain–computer interface, and brain science programme in recent decades. In this review, the up‐to‐date advances of dielectric, piezoelectric, and ...ferroelectric nanomaterials in the biomedical applications are summarised. Biomolecular detection methods have been developed, including dielectric‐gated field‐effect transistor, dielectrophoresis, non‐linear dielectric response, and optical tweezer. Endogenous bioelectricity is a crucial in cell proliferation, migration, differentiation, intracellular communication, neuronal activity, tissue growth. Piezoelectric and ferroelectric materials can be utilised as energy transducer to monitor physiological signal, such as blood pressure or respiration, and directly stimulate cell differentiation, neuronal regeneration, tissue repairment etc. They can also catalyse the electrochemical reaction of organisms through piezoelectricity. The intrinsic relevance between neuronal and ferroelectric polarisation signals inspires the application of the ferroelectrics in the modern intelligent bioelectronics like the artificial retina.
In this review, we summarise the latest advances of dielectric, piezoelectric, and ferroelectric nanomaterials in the biomedical applications. These materials can be utilised as energy transducer to monitor physiological signal, directly stimulate cell differentiation, neuronal regeneration, and tissue repairment.
Rapid growth in biological applications of nanomaterials brings about pressing needs for exploring nanomaterial-cell interactions. Cationic blue-emissive and anionic green-emissive conjugated ...polymers are applied as dual-color fluorescence probes to the surface of negatively charged magnetic nanoparticles through sequentially electrostatic adsorption. These conjugated polymers have large extinction coefficients and high fluorescence quantum yield (82% for PFN and 62% for ThPFS). Thereby, one can visualize trace amount (2.7 μg/mL) of fluorescence-labeled nanoparticles within cancer cells by confocal laser scanning microscopy. Fluorescence labeling by the conjugated polymers is also validated for quantitative determination of the internalized nanoparticles in each individual cell by flow cytometry analysis. Extensive overlap of blue and green fluorescence signals in the cytoplasm indicates that both conjugated polymer probes tightly bind to the surface of the nanoparticles during cellular internalization. The highly charged and fluorescence-labeled nanoparticles non-specifically bind to the cell membranes, followed by cellular uptake through endocytosis. The nanoparticles form aggregates inside endosomes, which yields a punctuated staining pattern. Cellular internalization of the nanoparticles is dependent on the dosage and time. Uptake efficiency can be enhanced three-fold by application of an external magnetic field. The nanoparticles are low cytotoxicity and suitable for simultaneously noninvasive fluorescence and magnetic resonance imaging application.
Ferroelectric poly(vinylidene fluoride) (PVDF) based polymers are attracting tremendous interest because of their potential applications in flexible non-volatile memories. Current research suggests ...that the existence of a large hysteresis loop results in high-voltage operation and low writing/erasing speed, which is originated from uniform chain packing and coherent ferroelectric sequences in the crystalline regions. Here, we demonstrate the novel approach to understand the defect-mediated switching mechanisms in ferroelectric polymers by PFM-probe based technology. The single-point and linear polarization reversal is well controlled by defect-mediated ferroelectric phases that determine activation energy, switching rate, and the thermal stability. By the regulation of VDF/TrFE ratio and varying processing conditions, the coherent ferroelectric phase with all-trans sequence in the P(VDF-TrFE) has been disrupted by defects. Specially, the crystallites formed at high temperature in the copolymer P(VDF-TrFE) 50:50 mol% exhibit less ordered ferroelectric crystalline sequences, thus attaining the excellent features of the low operation voltage of about 4 V with a switching time of 100 ms, ultra-high memory density of 43.9 Gbit∙in−2 (by a 7 V, 1 ms pulse) and a high usage temperature of 60 °C. Compared with P(VDF-TrFE) 68:32 mol%, normal ferroelectric, it saves approximate 50% ratio of energy cost, and realizes four times higher resolution. Understanding and controlling defect functionality in ferroelectric materials is as critical for realizing their reliable applications in ferroelectric memories.
Low-power-consuming, fast switching rate, and high usage temperature were attained in the defect-mediated P(VDF-TrFE) ultrathin films by using PFM testing. The excellent features in PVDF-based polymers can be potentially applied to many consumer electronics products, such as U-disk, CD-ROM, and digital versatile disks (DVD). Display omitted
•Low operation voltage, fast switching, ultra-high memory density and high usage temperature are attained in P(VDF-TrFE) 50:50 mol%.•The crystallites formed at high temperature in the copolymer P(VDF-TrFE) 50:50 mol% exhibit less ordered ferroelectric crystalline sequences.
Diabetic retinopathy (DR) is a leading cause of irreversible vision loss in working-age populations. Fat mass and obesity-associated protein (FTO) is an N
6
-methyladenosine (m
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A) demethylase that ...demethylates RNAs involved in energy homeostasis, though its influence on DR is not well studied. Herein, we detected elevated FTO expression in vitreous fibrovascular membranes of patients with proliferative DR. FTO promoted cell cycle progression and tip cell formation of endothelial cells (ECs) to facilitate angiogenesis in vitro, in mice, and in zebrafish. FTO also regulated EC-pericyte crosstalk to trigger diabetic microvascular leakage, and mediated EC–microglia interactions to induce retinal inflammation and neurodegeneration in vivo and in vitro. Mechanistically, FTO affected EC features via modulating CDK2 mRNA stability in an m
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A-YTHDF2-dependent manner. FTO up-regulation under diabetic conditions was driven by lactate-mediated histone lactylation. FB23-2, an inhibitor to FTO’s m
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A demethylase activity, suppressed angiogenic phenotypes in vitro. To allow for systemic administration, we developed a nanoplatform encapsulating FB23-2 and confirmed its targeting and therapeutic efficiency in mice. Collectively, our study demonstrates that FTO is important for EC function and retinal homeostasis in DR, and warrants further investigation as a therapeutic target for DR patients.
Synopsis
The fat mass and obesity-associated (FTO) protein, an N
6
-methyladenosine (m
6
A) demethylase, influences endothelial cell (EC) function and retinal homeostasis in diabetic retinopathy (DR), thus providing a promising nanotherapeutic approach for DR.
FTO expression is elevated in diabetic mice retinas and vitreous fibrovascular membranes of patients with proliferative DR.
FTO triggers diabetes-induced microvascular dysfunction by facilitating neovascularization and regulating EC–pericyte/microglia crosstalk.
FTO regulates CDK2 mRNA stability with the YTHDF2 reader in an m
6
A-dependent manner.
Lactic acid regulates FTO expression via histone lactylation.
FB23-2 suppresses demethylation activity of FTO to inhibit diabetes-induced EC phenotypes, showing therapeutic potential in DR in mice.
The fat mass and obesity-associated (FTO) protein, an N
6
-methyladenosine (m
6
A) demethylase, influences endothelial cell (EC) function and retinal homeostasis in diabetic retinopathy (DR), thus providing a promising nanotherapeutic approach for DR.
Brain imaging techniques enable visualizing the activity of central nervous system without invasive neurosurgery. Dopamine is an important neurotransmitter. Its fluctuation in brain leads to a wide ...range of diseases and disorders, like drug addiction, depression, and Parkinson’s disease. We designed near-infrared fluorescence dopamine-responsive nanoprobes (DRNs) for brain activity imaging during drug abuse and addiction process. On the basis of light-induced electron transfer between DRNs and dopamine and molecular wire effect of the DRNs, we can track the dynamical change of the neurotransmitter level in the physiological environment and the releasing of the neurotransmitter in living dopaminergic neurons in response to nicotine stimulation. The functional near-infrared fluorescence imaging can dynamically track the dopamine level in the mice midbrain under normal or drug-activated condition and evaluate the long-term effect of addictive substances to the brain. This strategy has the potential for studying neural activity under physiological condition.
Conductive nanofibers are adopted to enhance the electric properties of ferroelectric polymers. Polyaniline (PANI) nanofibers doped by protonic acids have a high dispersion stability in vinylidene ...fluoride‐trifluoroethylene copolymers P(VDF‐TrFE) and lead to percolative nanocomposites with enhanced electric responses. About a 50‐fold rise in the dielectric constant of the ferroelectric polymer matrix has been achieved. Percolation thresholds of the nanocomposites are relevant to doping levels of PANI nanofibers and can be as low as 2.9 wt% for fully doped nanofibers. The interface between the conductive nanofiber and the polymer matrix plays a crucial role in the dielectric enhancement of the nanocomposites in the vicinity of the percolation threshold. Compared with other dopants, perfluorosulfonic acid resin is better at improving the performance of the nanofibers in that it serves as a surface passivation layer for the conductive fillers and suppresses leakage current at low frequency. The nanofibers drastically reduce the electric field strength required to switch spontaneous polarization of P(VDF‐TrFE). The nanocomposites can be utilized for potential applications as high energy density capacitors, thin‐film transistors, and non‐volatile ferroelectric memories.
A drastic enhancement of the dielectric constant of ferroelectric copolymers is demonstrated by addition of a low content of conductive polyaniline nanofibers. The high dispersion stability of the fibers in the vinylidene fluoride‐trifluoroethylene copolymers (P(VDF‐TrFE)) leads to a percolative composite with highly desirable properties for high‐performance electromechanical devices. A 50‐fold rise in the dielectric response of the polymer matrix is observed.
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