The exorbitant level of hydrogen peroxide is closely related to many human diseases. The development of novel probes for H 2 O 2 detection will be beneficial to disease diagnosis. In this study, a novel Nd 3+ -sensitized upconversion nanoprobe based on Forster resonance energy transfer was first developed for sensing H 2 O 2 . This nanosystem was made of core−shell upconversion nanoparticles (emission at 540 and 660 nm), dicyanomethylene-4H-pyran (DCM)−H 2 O 2 , and poly acrylic acid (PAA)−octylamine. Obviously, upconversion nanoparticles (UCNPs) doped with Nd 3+ acted as an energy donor, and DCM−H 2 O 2 , transferring to DCM−OH with the reaction of H 2 O 2 , acted as an energy acceptor. The ratiometric upconversion luminescence (540 nm/660 nm) signal could be utilized to visualize the H 2 O 2 level, and the LOD of the nanoprobe for H 2 O 2 was quantified to be 0.168 μM. Meanwhile, owing to the dope of Nd 3+ , the nanoprobe would not induce the overheating effect in biological samples and could possess deeper tissue penetration depth, compared with the UCNPs excited by 980 nm light during bioimaging. The nanoprobe could also play an important role in detecting the exogenous and endogenous H 2 O 2 in living cells with ratiometric UCL (upconversion luminescence) imaging. Furthermore, our nanoprobe could function in detecting the H 2 O 2 in a tumor-bearing mouse model. Therefore, this novel nanoprobe along with the ratiometric method for responding and bioimaging H 2 O 2 could serve as a new model that promotes the emergence of novel probes for H 2 O 2 detection.
Singlet oxygen, as the main member of reactive oxygen species, plays a significant role in cancer photodynamic therapy. However, the in vivo real‐time detection of singlet oxygen remains challenging. In this work, a Förster resonance energy transfer (FRET)‐based upconversion nanoplatform for monitoring the singlet oxygen in living systems is developed, with the ability to evaluate the in vivo dose–effect relationship between singlet oxygen and photodynamic therapy (PDT) efficacy. In details, this nanoplatform is composed of core–shell upconversion nanoparticles (UCNPs), photosensitizer MC540, NIR dye IR‐820, and poly(acryl amine) PAA‐octylamine, where the UCNPs serve as an energy donor while IR‐820 serves as an energy acceptor. The nanoparticles are found to sensitively reflect the singlet oxygen levels generated in the tumor tissues during PDT, by luminescence intensity changes of UNCPs at 800 nm emission. Furthermore, it could also enable tumor treatment with satisfactory biocompatibility. To the best knowledge, this is the first report of a theranostic nanoplatform with the ability to formulate the in vivo dose–effect relationship between singlet oxygen and PDT efficacy and to achieve tumor treatment at the same time. This work might also provide an executable strategy to evaluate photodynamic therapeutic efficacy based on singlet oxygen pathway.
Single-crystal-like silicon (Si) thin films on bendable and scalable substrates via direct deposition are a promising material platform for high-performance and cost-effective devices of flexible electronics. However, due to the thick and unintentionally highly doped semiconductor layer, the operation of transistors has been hampered. We report the first demonstration of high-performance flexible thin-film transistors (TFTs) using single-crystal-like Si thin films with a field-effect mobility of ∼200 cm/V·s and saturation current, I/l > 50 μA/μm, which are orders-of-magnitude higher than the device characteristics of conventional flexible TFTs. The Si thin films with a (001) plane grown on a metal tape by a "seed and epitaxy" technique show nearly single-crystalline properties characterized by X-ray diffraction, Raman spectroscopy, reflection high-energy electron diffraction, and transmission electron microscopy. The realization of flexible and high-performance Si TFTs can establish a new pathway for extended applications of flexible electronics such as amplification and digital circuits, more than currently dominant display switches.
This study demonstrates the first flexible single‐junction III‐V photovoltaic solar cells (SCs) based on single‐crystal‐like gallium arsenide (GaAs) thin films on a low‐cost metal substrate by direct and continuous deposition, which can bypass expensive single crystal wafer fabrication. The two‐dimensional modeling of the GaAs SC is developed and used to study feasibility of single‐crystal‐like GaAs thin films for high performance SC devices. A promising SC device performance characteristic with an open‐circuit voltage of 560 mV and short circuit current of 19.4 mA/cm2, resulting in a conversion efficiency of ~7.6%, is demonstrated.
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