Surfaces and heterojunction interfaces, where defects and energy levels dictate charge‐carrier dynamics in optoelectronic devices, are critical for unlocking the full potential of perovskite ...semiconductors. In this progress report, chemical structures of perovskite surfaces are discussed and basic physical rules for the band alignment are summarized at various perovskite interfaces. Common perovskite surfaces are typically decorated by various compositional and structural defects such as residual surface reactants, discrete nanoclusters, reactions by products, vacancies, interstitials, antisites, etc. Some of these surface species induce deep‐level defect states in the forbidden band forming very harmful charge‐carrier traps and affect negatively the interface band alignments for achieving optimal device performance. Herein, an overview of research progresses on surface and interface engineering is provided to minimize deep‐level defect states. The reviewed subjects include selection of interface and substrate buffer layers for growing better crystals, materials and processing methods for surface passivation, the surface catalyst for microstructure transformations, organic semiconductors for charge extraction or injection, heterojunctions with wide bandgap perovskites or nanocrystals for mitigating defects, and electrode interlayer for preventing interdiffusion and reactions. These surface and interface engineering strategies are shown to be critical in boosting device performance for both solar cells and light‐emitting diodes.
Recent progress on perovskite surface and interface science of perovskite optoelectronic devices is summarized. The impact of various surface and interface defects on heterojunction energy barriers and carrier dynamics in devices is reviewed and discussed. Practical engineering methods to mitigate these defects at various interfaces in devices are also considered.
Magnetic resonance imaging (MRI) is a clinical imaging modality effective for anatomical and functional imaging of diseased soft tissues, including solid tumors. MRI contrast agents (CA) have been ...routinely used for detecting tumor at an early stage. Gadolinium‐based CA are the most commonly used CA in clinical MRI. There have been significant efforts to design and develop novel Gd(III) CA with high relaxivity, low toxicity, and specific tumor binding. The relaxivity of the Gd(III) CA can be increased by proper chemical modification. The toxicity of Gd(III) CA can be reduced by increasing the agents' thermodynamic and kinetic stability, as well as optimizing their pharmacokinetic properties. The increasing knowledge in the field of cancer genomics and biology provides an opportunity for designing tumor‐specific CA. Various new Gd(III) chelates have been designed and evaluated in animal models for more effective cancer MRI. This review outlines the design and development, physicochemical properties, and in vivo properties of several classes of Gd(III)‐based MR CA tumor imaging. WIREs Nanomed Nanobiotechnol 2013, 5:1–18. doi: 10.1002/wnan.1198
This article is categorized under:
Diagnostic Tools > Biosensing
Diagnostic Tools > In Vivo Nanodiagnostics and Imaging
The tumor microenvironment plays a critical role in tumor initiation, progression, metastasis, and resistance to therapy. It is different from normal tissue in the extracellular matrix, vascular and ...lymphatic networks, as well as physiologic conditions. Molecular imaging of the tumor microenvironment provides a better understanding of its function in cancer biology, and thus allowing for the design of new diagnostics and therapeutics for early cancer diagnosis and treatment. The clinical translation of cancer molecular imaging is often hampered by the high cost of commercialization of targeted imaging agents as well as the limited clinical applications and small market size of some of the agents. Because many different cancer types share similar tumor microenvironment features, the ability to target these biomarkers has the potential to provide clinically translatable molecular imaging technologies for a spectrum of cancers and broad clinical applications. There has been significant progress in targeting the tumor microenvironment for cancer molecular imaging. In this review, we summarize the principles and strategies of recent advances made in molecular imaging of the tumor microenvironment, using various imaging modalities for early detection and diagnosis of cancer.
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An electroactive room‐temperature phosphorescence (RTP) polymer has been demonstrated based on a characteristic donor‐oxygen‐acceptor geometry. Compared with the donor–acceptor reference, the ...inserted oxygen atom between donor and acceptor can not only decrease hole‐electron orbital overlap to suppress the charge transfer fluorescence, but also strengthen spin‐orbital coupling effect to facilitate the intersystem crossing and subsequent phosphorescence channels. As a result, a significant RTP is observed in solid states under photo excitation. Most noticeably, the corresponding polymer light‐emitting diodes (PLEDs) reveal a dominant electrophosphorescence with a record‐high external quantum efficiency of 9.7 %. The performance goes well beyond the 5 % theoretical limit for typical fluors, opening a new door to the development of pure organic RTP polymers towards efficient PLEDs.
A donor‐oxygen‐acceptor geometry has been demonstrated for the design of electroactive pure organic room‐temperature phosphorescence polymers, whose PLEDs achieve a promising EQE of 9.7 %.
Transition metal oxides are capable of a wide range of work functions. This quality allows them to be used in many applications that involve charge transfer with adsorbed molecules, for example as ...heterogeneous catalysts, as charge‐injection layers in organic electronics, and as electrodes in fuel cells. Chemical and structural factors can alter transition‐metal oxide work functions, often making their work functions difficult to control. Little is known about the effects of the cation oxidation state and point defects on the oxide work function. It is necessary to understand how such chemical and structural factors affect work functions in order to controllably tune transition metal oxides for desired applications. Here, a correlation between the oxide work function and cation oxidation state is demonstrated. This correlation is attributed to the change in cation electronegativity with oxidation state. A model is presented that relates the work function to the oxygen deficiency for d0 oxides in the limit of dilute oxygen vacancies. It is proposed that the rapid initial decrease in work function, observed for d0 oxides, is caused by an increase in the density of donor‐like defect states. It is also shown that oxides tend to have decreased work functions near a metal/metal‐oxide interface as a consequence of the relationship between defects and work function. These insights provide guidelines for tuning transition metal oxide work functions.
The work functions of transition‐metal oxides are correlated with the oxidation states of their metal cations. Due to the relationship between electronegativity and oxidation state, reduced oxides tend to have lower work functions. The trends revealed provide guidelines for tuning transition metal oxide work functions.
Hereditary genetic diseases, cancer, and infectious diseases are affecting global health and become major health issues, but the treatment development remains challenging. Gene therapies using DNA ...plasmid, RNAi, miRNA, mRNA, and gene editing hold great promise. Lipid nanoparticle (LNP) delivery technology has been a revolutionary development, which has been granted for clinical applications, including mRNA vaccines against SARS-CoV-2 infections. Due to the success of LNP systems, understanding the structure, formulation, and function relationship of the lipid components in LNP systems is crucial for design more effective LNP. Here, we highlight the key considerations for developing an LNP system. The evolution of structure and function of lipids as well as their LNP formulation from the early-stage simple formulations to multi-components LNP and multifunctional ionizable lipids have been discussed. The flexibility and platform nature of LNP enable efficient intracellular delivery of a variety of therapeutic nucleic acids and provide many novel treatment options for the diseases that are previously untreatable.
Eco‐innovation has gained currency as an effective means of addressing corporate environmental impacts. Yet the literature is inconclusive as to how different types of eco‐innovation influence ...different types of firm performance. This is problematic, as practitioners and policymakers will not embrace eco‐innovation unless there is clear evidence that through its implementation companies can achieve returns, not only on their environmental performance but also on their economic, social and operational performance. This paper aims to improve our understanding of this relationship by conducting a meta‐analysis and drawing on a much broader sample than previous meta‐analytic efforts in this field. The paper analyses 569 effects based on 160 studies and more than 124,000 firms (
N=124,077). Our results provide solid evidence of the positive impact eco‐innovation has on all types of firm performance but also highlight types of eco‐innovation that do not contribute to this relationship and the role moderators play in explaining discrepancies found in the literature.
Perovskite light-emitting diodes (PeLEDs) have shown excellent performance in the green and near-infrared spectral regions, with high color purity, efficiency, and brightness. In order to shift the ...emission wavelength to the blue, compositional engineering (anion mixing) and quantum-confinement engineering (reduced-dimensionality) have been employed. Unfortunately, LED emission profiles shift with increasing driving voltages due to either phase separation or the coexistence of multiple crystal domains. Here we report color-stable sky-blue PeLEDs achieved by enhancing the phase monodispersity of quasi-2D perovskite thin films. We selected cation combinations that modulate the crystallization and layer thickness distribution of the domains. The perovskite films show a record photoluminescence quantum yield of 88% at 477 nm. The corresponding PeLEDs exhibit stable sky-blue emission under high operation voltages. A maximum luminance of 2480 cd m
at 490 nm is achieved, fully one order of magnitude higher than the previous record for quasi-2D blue PeLEDs.
The all‐inorganic nature of CsPbI3 perovskites allows to enhance stability in perovskite devices. Research efforts have led to improved stability of the black phase in CsPbI3 films; however, these ...strategies—including strain and doping—are based on organic‐ligand‐capped perovskites, which prevent perovskites from forming the close‐packed quantum dot (QD) solids necessary to achieve high charge and thermal transport. We developed an inorganic ligand exchange that leads to CsPbI3 QD films with superior phase stability and increased thermal transport. The atomic‐ligand‐exchanged QD films, once mechanically coupled, exhibit improved phase stability, and we link this to distributing strain across the film. Operando measurements of the temperature of the LEDs indicate that KI‐exchanged QD films exhibit increased thermal transport compared to controls that rely on organic ligands. The LEDs exhibit a maximum EQE of 23 % with an electroluminescence emission centered at 640 nm (FWHM: ≈31 nm). These red LEDs provide an operating half‐lifetime of 10 h (luminance of 200 cd m−2) and an operating stability that is 6× higher than that of control devices.
Stable and efficient CsPbI3 perovskite light‐emitting diodes (PLEDs) are demonstrated by resurfacing perovskite with the aid of inorganic ligands (KI). The resurfaced perovskites show a 7× higher phase stability and higher thermal conductivity than in films with organic ligands. The PLEDs exhibit a record‐high external quantum efficiency (EQE) of ≈23 % and a 100‐fold improvement in the operating stability compared to previous EQE devices.
As one type of chromene, 2H-chromenes represent important oxygen heterocycles, which not only widely exist in natural products, pharmaceutical agents and biologically relevant molecules, but have ...also been used broadly in materials science and organic synthesis. Two major synthetic strategies have been developed towards such compounds. This review mainly focuses on the recent advances in this field, including benzopyran ring formation involving cyclization reactions and the late-stage functionalization of the parent 2H-chromenes.
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