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PEGylation prolongs the blood circulation time of drugs; however, it simultaneously reduces the tumor penetration of drugs due to the nonfouling function and bulky hydrodynamic volume of PEG, leading to unsatisfactory outcomes in the treatment of solid tumors. Herein, we report the in situ growth of a bioreducible polymer of poly( N -oxide) from an important protein drug of interferon alpha (IFN) to generate site-specific IFN-poly( N -oxide) conjugates with higher bioactivity than a clinically used PEGylated IFN of PEGASYS. An IFN-poly( N -oxide) conjugate is screened out to have a circulating half-life as long as 51 h, which is similar to that of PEGASYS but 96-fold greater than that of IFN. However, the conjugate greatly outperforms PEGASYS and IFN in tumor penetration and antitumor efficacy in mice bearing melanoma. This enhanced tumor penetration is ascribed to the adsorption-mediated transcytosis of the conjugate whose poly( N -oxide) is biologically reduced into poly(tertiary amine), under hypoxia, which can be further protonated in the acidic tumor microenvironment. These novel findings demonstrate that poly( N -oxide)s are not only long-circulating but also bioreducible under hypoxia and are of great promise as next-generation carriers to deliver drugs into the interior of solid tumors to enhance their antitumor efficacy.

Gastrointestinal diseases affect many people in the world and significantly impair life quality and burden the healthcare system. The functional parameters of the gastrointestinal tract such as motility and pH can effectively reflect the changes of gastrointestinal activity in physiological and pathological conditions. Thus, a noninvasive method for real-time and quantitative measurement of gastrointestinal functional parameters in vivo is highly desired. At present, there are many strategies widely used for the diagnosis of gastrointestinal diseases in clinic, including X-ray barium meal examination, ultrasound imaging, radionuclide examination, endoscopy, etc . However, these methods are limited in determining the gastrointestinal status and cannot provide comprehensive quantitative information. Photoacoustic imaging (PAI) is a rapid noninvasive real-time imaging technique in which multiple types of functional and quantitative information can be simultaneously obtained. Unfortunately, very few ratiometric PAI contrast agents have been reported for quantification of gastrointestinal functional parameters in vivo . In this work, a broad, pH-responsive ratiometric sensor based on polyaniline and Au triangular nanoplates was developed. Utilizing the sensor as a contrast agent, PAI served as an all-in-one technique, accurately measuring the gastrointestinal functional parameters in a single test. Notably, this sensor was examined to be ultrasensitive with pH responses as fast as 0.6 s and durability as long as 24 h, and was repeatable and reversible for longitudinal monitoring. The quantitative results demonstrated a significant disorder in motility and decrease in pH for gastric and duodenal ulcers. Collectively, the combination of PAI and this broad pH-responsive sensor might be a promising candidate for quantitative diagnosis of gastrointestinal diseases.

Organic-inorganic hybrid lead halide perovskites have been widely investigated in optoelectronics both experimentally and theoretically. The present work incorporates chemically modified graphene into nanocrystal SnO 2 as the electron transporting layer (ETL) for highly efficient planar perovskite solar cells. The modification of SnO 2 with highly conductive two-dimensional naphthalene diimide-graphene can increase surface hydrophobicity and form van der Waals interaction between the surfactant and the organic-inorganic hybrid lead halide perovskite compounds. As a result, highly efficient perovskite solar cells with power conversion efficiency of 20.2% can be achieved with an improved fill factor of 82%, which could be mainly attributed to the augmented charge extraction and transport.

In planar n-i-p heterojunction perovskite solar cells, the electron transport layer (ETL) plays important roles in charge extraction and determine the morphology of the perovskite film. Here, we report a solution-processed carbon quantum dots (CQDs)/TiO 2 composite that has negligible absorption in the visible spectral range, a very attractive feature for perovskite solar cells. Using this novel CQDs/TiO 2 ETL in conjunction with a planar n-i-p heterojunction, we achieved an unprecedented efficiency of ∼19% under standard illumination test conditions. It was found that a CQDs/TiO 2 combination increases both the open circuit voltage and short-circuits current density as compared to using TiO 2 alone. Various advanced spectroscopic characterizations including ultrafast spectroscopy, ultraviolet photoelectron spectroscopy, and electronic impedance spectroscopy elucidate that the CQDs increases the electronic coupling between the CH 3 NH 3 PbI 3-x Cl x and TiO 2 ETL interface as well as energy levers that contribute to electron extraction.

Here, a comprehensive study of the influence of polymer:fullerene mixing behavior on the performance, thin-film microstructure, photophysics, and device physics of polymer solar cells is presented. In particular, blends of the donor polymer PBDTTT-EFT with the acceptor PC 71 BM that exhibit power conversion efficiencies over 9% are investigated. Through tuning of the fullerene concentration in PBDTTT-EFT:PC 71 BM blends, the impact of fullerene mixing behavior is systematically investigated via a combination of synchrotron-based X-ray scattering and spectroscopy techniques. The impact of fullerene loading on photophysics and device physics is further explored with steady-state photoluminescence measurements, ultrafast transient absorption spectroscopy, and transient photovoltage measurements. In the low fullerene concentration regime (<50 wt %), most fullerene molecules are dispersed in the polymer matrix, resulting in severe geminate and nongeminate recombination due to a lack of pure fullerene aggregates and percolating pathways for charge separation and transport. In the high fullerene concentration regime (>70 wt %), large fullerene domains result in incomplete PC 71 BM exciton harvesting with the presence of fullerene molecules also disrupting the molecular packing of polymer crystallites. The optimum fullerene concentration of ∼60-67 wt % balances the requirements of charge generation and charge collection. These findings demonstrate that controlling the fullerene concentration in the mixed phase and optimizing the balance between pure and mixed phases are critical for maximizing the efficiency of highly mixed polymer/fullerene solar cells.

Surface-sensitive NEXAFS spectroscopy is used to probe the interaction between low work function metal electrodes and fullerene derivatives in organic solar cells. Evaporation of either Ca or Al electrodes onto films of the fullerene derivatives (6,6)-phenyl-C61-butyric acid methyl ester (PCBM) and indene-C60 bisadduct (ICBA) leads to a dramatic change in the observed NEXAFS spectrum. The observed changes cannot be explained only in terms of interfacial electronic doping or charge transfer, but rather point to the formation of new chemical bonds that destroy the extensive electron delocalization on the C60 cage. A combination of ex situ and in situ ultrahigh vacuum measurements indicates that metal evaporation results in a change in the electronic structure of PCBM that then facilitates chemical degradation and oxidation in the presence of oxygen. To investigate the effect of this chemical interaction on device performance, a unique transfer method to laminate the Al electrode to the top of polymer blend is used, in which case, the chemical degradation of the fullerene is not observed. Device performance of P3HT/PCBM blend solar cells in which the top metal electrode has either been thermally evaporated or transferred is then compared. These results highlight that chemical, as well as electronic, interactions between metals and organic semiconductors must be considered.

It is well-established that thermal annealing optimizes the morphology and improves the efficiency of P3HT-based organic solar cells, but the effects of different cooling rates after annealing are not well understood. In this paper, we use a model system based on poly(3-hexylthiophene) (P3HT) and phenyl-C61-butyric acid methyl ester (PCBM) to examine the relationship between morphology and device performance for annealing before (preannealing) and after (postannealing) the application of the electrode, with different cooling rates and in different device architectures. In the conventional structure, postannealing is confirmed to significantly enhance efficiency. The device prepared with a slow cooling rate (3.6%) shows a higher average power conversion efficiency than that prepared with a fast cooling rate (3.3%). The microstructural changes underlying this 10% increase in device performance and further effects of cooling rate, pre- and postannealing, and device architecture are comprehensively examined with a combination of synchrotron-based techniques, including grazing incidence wide-angle X-ray scattering, near-edge X-ray absorption fine structure spectroscopy, and X-ray photoelectron spectroscopy. The best device in the conventional architecture (postannealed with slow cooling rate) shows a more face-on orientation and narrower orientational distribution of P3HT crystallites. In addition, postannealing leads to PCBM diffusion toward the blend/top electrode interface. The enrichment of PCBM at the blend/top electrode interface plays a positive role in aiding electron collection at the electrode in the conventional structure, but it has a negative effect on the performance of the inverted structure, where hole collection at the top electrode instead is required. For this reason, in an inverted structure, preannealed films with slow cooling exhibit the best photovoltaic performance.