Search

A target-triggered strand displacement-assisted target recycling based on carbon dots-based fluorescent probe and mesoporous silica nanoparticles@polydopamine (MSNs@PDA) was established to detect miRNA. The surface of MSNs rich in mesopores was coated with a layer of PDA, which can adsorb and quench the fluorescence of single-stranded Fuel DNA with fluorescent carbon dots (CDs) modified at the end through fluorescence resonance energy transfer (FRET). After adding double-stranded DNA-gold nanoparticles (dsDNA-AuNPs) and target let-7a, it will trigger two toehold-mediated strand displacement reactions (TSDR), leading to the recovery of fluorescence and the recycling of target let-7a (excitation wavelength: 380 nm; emission wavelength: 458 nm). The recovery value of fluorescence is proportional to the logarithm of the target microRNA let-7a concentration, thus realizing the sensitivity amplification detection of disease markers. The MSNs@PDA@Fuel DNA-CDs/dsDNA-AuNPs nanoplatform based on the strategy of "on-off-on" and TSDR cyclic amplification may hold great potential as an effective and safe nanoprobe for accurate fluorescence imaging of diseases related to miRNA with low abundances., (© 2024. The Author(s), under exclusive licence to Springer-Verlag GmbH Austria, part of Springer Nature.)

In the realm of flexible optoelectronic devices, intrinsic flexible fully π‐conjugated polymers (FπCPs) assume a pivotal role owing to their concurrent intrinsic viscoelasticity and robust optoelectronic properties. As flexible devices are destined to encounter diverse stress environments, the selection of functional materials based on mechanical requirements becomes imperative. Here, VPERD assessment system is introduced to scrutinize the mechanical properties of side‐chain plasticizing FπCPs. The acronym VPERD encapsulates five key aspects of mechanical characteristics, namely viscidity (V), plasticity (P), elasticity (E), rigidity (R), and ductility (D). The mechanical characteristics of FπCPs are tuned through the control of flexible chain density (FCD). Enhancing FCD induces superior chain softness, favorable solubility, and heightened viscoplasticity. Through precise regulation of FCD and thoughtful structural design, freestanding FπCPs nano‐films exhibit a remarkable maximum fracture strain of ≈50%. Deep‐blue flexible polymer light‐emitting diodes (PLEDs) reveal that maintaining FCD at ≈50% achieves a balance between mechanical and optoelectronic properties. The stretched films after strain fatigue both show that mild strain is conducive to enhancing the efficiency of FπCPs films and devices. According to VPERD assessment system, the prerequisite for achieving intrinsically flexible FπCPs lies in controlling the degree of side‐chain internal plasticization through the tuning of FCD. [ABSTRACT FROM AUTHOR]

Conjugated polymers with p‐orbital overlap show intramolecular‐conformation‐dependent photophysical and electrical properties. Compared to the non‐planar segments, the planar conformation segments have a relatively long effective conjugated length and rigid backbone structure, which are beneficial for the enhancement of optoelectronic properties. Herein, the effect of film thickness on the formation capacity of planar (β) conformations in polyfluorene (poly[4‐(octyloxy)‐9,9‐diphenylfluorene‐2,7‐diyl]‐co‐[5‐(octyloxy)‐9,9‐diphenylfluorene‐2,7‐diyl], PODPF) for the fabrication of stable deep‐blue polymer light‐emitting diodes (PLEDs) is explored. Thickness‐tunable films with thicknesses ranging from 15 to 270 nm by controlling the concentration of precursor solution are prepared. The main observations are as follows. The PODPF chains in thin films are less likely to adopt the β conformations associated with the loose interchain packing in nano‐aggregates than those in thick films. Red‐shifted and well‐resolved emission spectra are observed for the annealed film with a high thickness, indicating the greater presence of β‐conformation segments. More interestingly, interchain aggregation is a necessary but not sufficient condition for the formation of β conformations. Finally, PLEDs based on β‐conformation segments have outstanding brightness, low turn‐on voltage, and stable deep‐blue electroluminescent behavior, confirming the unique advantage of planar conformation for optoelectronic applications. [ABSTRACT FROM AUTHOR]

The effect of colloidal nanoparticles on the phase changes of the amphiphilic AB linear diblock, A1A2B, and A2B heteroarm star copolymers confined between two polymer brush substrates was investigated by using a real-space self-consistent field theory. By changing the concentrations of nanoparticles and polymer brushes, the phase structure of the amphiphilic AB copolymer transforms from lamellar to core-shell hexagonal phase to cylinder phase. The pattern of A2B heteroarm star copolymer changes from core-shell hexagonal phases to lamellar phases and the layer decreases when increasing the density of the polymer brushes. The results showed that the phase behavior of the system is strongly influenced by the polymer brush architecture and the colloidal nanoparticle numbers. The colloidal nanoparticles and the soft confined surface of polymer brushes make amphiphilic AB copolymers easier to form ordered structures. The dispersion of the nanoparticles was also investigated in detail. The soft surfaces of polymer brushes and the conformation of the block copolymers work together to force the nanoparticles to disperse evenly. It will give helpful guidance for making some new functional materials by nano etching technology, nano photoresist, and nanoprinting. [ABSTRACT FROM AUTHOR]

Green‐processable printed large‐area light‐emitting diode (LED) is the crucial component of the high quality solid lighting and flat‐panel display. Accelerating the replacement from fossil‐based solvents to sustainable ecofriendly solvent is desirable for solution‐based printed organic electronics. Herein, by simple introducing methyl to the benzene groups of polydiarylfluorene‐based polymer, this work realizes the solution processing of blue polymer light‐emitting diodes (PLEDs) with a bio‐based solvent of limonene toward large‐area printed display. Film processed from this solvent exhibits satisfactory morphology and remarkable photophysical performances, even though the polymer chains show more serious aggregation in solution. What's more, devices fabricated with spin‐coated films present higher external quantum efficiency (EQE) and better spectra repeatability. Encouraged by the good film‐forming ability of this polymer in limonene, this work realizes the fabrication of printed large‐area films (5 × 5 cm2) with uniform emission and surface morphology by blade coating. Furthermore, this work develops passive matrix (PM) PLEDs arrays with 20 × 20 pixels that can dynamically display monochrome letters and numbers, demonstrating the potential application of cost‐effective printing techniques in large‐area display. [ABSTRACT FROM AUTHOR]

Large‐area polymer light‐emitting diodes (PLEDs) manufactured by printing are required for flat‐panel lighting and displays. Nevertheless, it remains challenging to fabricate large‐area and stable deep‐blue PLEDs with narrowband emission due to the difficulties in precisely tuning film uniformity and obtaining single‐exciton emission. Herein, efficient and stable large‐area deep‐blue PLEDs with narrowband emission are prepared from encapsulated polydiarylfluorene. Encapsulated polydiarylfluorenes presented an efficient and stable deep‐blue emission (peak: 439 nm; full width at half maximum (FWHM): 39 nm) in the solid state due to their single‐chain emission behavior without inter‐backbone chain aggregation. Large‐area uniform blade‐coated films (16 cm2) are also fabricated with excellent smoothness and morphology. Benefitting from efficient emission and excellent printed capacity, the blade‐coated PLEDs with a device area of 9 mm2 realized uniform deep‐blue emission (FWHM: 38 nm; CIE: 0.153, 0.067), with a corresponding maximum external quantum efficiency and the brightness comparable to those of devices based on spin‐coated films. Finally, considering the essential role of deep‐blue LEDs, a preliminary patterned PLED array with a pixel size of 800 × 1000 µm2 and a monochrome display is fabricated, highlighting potential full‐color display applications. [ABSTRACT FROM AUTHOR]

Control of the secondary conformational behavior of light‐emitting conjugated polymers (LCPs) is essential to obtain deep‐blue emission with a narrowband and stable color purity. Naturally π–π interactions induced by the planar aromatic segments may be easily observed in liner‐type LCPs, which lead to reduced emission efficiency, color purity, and energy bandgap. Herein, an alternating copolymerization strategy is proposed to obtain the singlet exciton behavior of a planar conformational segment from polydiarylfluorenes‐copolymers (P7‐6DPF, P7‐8DPF, and P7‐9DPF) toward deep‐blue polymer light‐emitting diodes (PLEDs). Compared to the highly crystalline capacity of P7DPF, P7‐8DPF, and P8DPF, alternative P7‐6DPF and P7‐9DPF present a feature and well‐resolved emission from a planar conformational segment of polyfluorene without obvious polaron features and charge transfer states. More interestingly, P7‐6DPF and P7‐9DPF show thickness‐independent electroluminescence (EL) behavior with a stable deep‐blue color purity, which is the precondition to fabricate large‐scale and high‐quality PLEDs. Finally, compared to control devices, PLEDs based on the P7‐6DPF and P7‐9DPF planar (β) conformational films present a well‐resolved and narrowband emission, stable EL spectra, high brightness (two‐ to threefold), and high current efficiency (1.3‐fold). Therefore, optimizing hierarchical structure via alternating copolymerization is an effective strategy to improve the performance and stability of deep‐blue PLEDs. [ABSTRACT FROM AUTHOR]