Nanjing Tech University

MXenes, a new family of 2D materials, combine hydrophilic surfaces with metallic conductivity. Delamination of MXene produces single-layer nanosheets with thickness of about a nanometer and lateral size of the order of micrometers. The high aspect ratio of delaminated MXene renders it promising nanofiller in multifunctional polymer nanocomposites. Herein, Ti3C2T(x) MXene was mixed with either a charged polydiallyldimethylammonium chloride (PDDA) or an electrically neutral polyvinyl alcohol (PVA) to produce Ti3C2T(x)/polymer composites. The as-fabricated composites are flexible and have electrical conductivities as high as 2.2 × 10(4) S/m in the case of the Ti3C2T(x)/PVA composite film and 2.4 × 10(5) S/m for pure Ti3C2T(x) films. The tensile strength of the Ti3C2T(x)/PVA composites was significantly enhanced compared with pure Ti3C2T(x) or PVA films. The intercalation and confinement of the polymer between the MXene flakes not only increased flexibility but also enhanced cationic intercalation, offering an impressive volumetric capacitance of ∼530 F/cm(3) for MXene/PVA-KOH composite film at 2 mV/s. To our knowledge, this study is a first, but crucial, step in exploring the potential of using MXenes in polymer-based multifunctional nanocomposites for a host of applications, such as structural components, energy storage devices, wearable electronics, electrochemical actuators, and radiofrequency shielding, to name a few.

The design and characterization of thermally activated delayed fluorescence (TADF) materials for optoelectronic applications represents an active area of recent research in organoelectronics. Noble metal-free TADF molecules offer unique optical and electronic properties arising from the efficient transition and interconversion between the lowest singlet (S1 ) and triplet (T1 ) excited states. Their ability to harvest triplet excitons for fluorescence through facilitated reverse intersystem crossing (T1 →S1 ) could directly impact their properties and performances, which is attractive for a wide variety of low-cost optoelectronic devices. TADF-based organic light-emitting diodes, oxygen, and temperature sensors show significantly upgraded device performances that are comparable to the ones of traditional rare-metal complexes. Here we present an overview of the quick development in TADF mechanisms, materials, and applications. Fundamental principles on design strategies of TADF materials and the common relationship between the molecular structures and optoelectronic properties for diverse research topics and a survey of recent progress in the development of TADF materials, with a particular emphasis on their different types of metal-organic complexes, D-A molecules, and fullerenes, are highlighted. The success in the breakthrough of the theoretical and technical challenges that arise in developing high-performance TADF materials may pave the way to shape the future of organoelectronics.

ADVERTISEMENT RETURN TO ISSUEPREVReviewNEXTFluorescent Chemosensors Based on Spiroring-Opening of Xanthenes and Related DerivativesXiaoqiang Chen†‡, Tuhin Pradhan§, Fang Wang†, Jong Seung Kim*§, and Juyoung Yoon*†View Author Information† Departments of Chemistry and Nano Science and of Bioinspired Science (WCU), Ewha Womans University, Seoul 120-750, Korea‡ State Key Laboratory of Materials-Oriented Chemical Engineering, College of Chemistry and Chemical Engineering, Nanjing University of Technology, Nanjing 210009, China§ Department of Chemistry, Korea University, Seoul 136-701, Korea*Phone: 82-2-3277-2400 (J.Y.); 82-2-3290-3143 (J.S.K.). Fax: 82-2-3277-2384 (J.Y.); 82-2-3290-3121 (J.S.K.). E-mail: [email protected] (J.Y.); [email protected] (J.S.K.).Cite this: Chem. Rev. 2012, 112, 3, 1910–1956Publication Date (Web):October 31, 2011Publication History Received5 June 2011Published online31 October 2011Published inissue 14 March 2012https://pubs.acs.org/doi/10.1021/cr200201zhttps://doi.org/10.1021/cr200201zreview-articleACS PublicationsCopyright © 2011 American Chemical SocietyRequest reuse permissionsArticle Views23539Altmetric-Citations1780LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access optionsGet e-Alertsclose SUBJECTS:Fluorescence,Heterocyclic compounds,Ions,Mercury,Sensors Get e-Alerts

/graphite. Thirdly, the device innovations for the next generation of supercapacitors are provided successively, mainly emphasizing flow supercapacitors, alternating current (AC) line-filtering supercapacitors, redox electrolyte enhanced supercapacitors, metal ion hybrid supercapacitors, micro-supercapacitors (fiber, plane and three-dimensional) and multifunctional supercapacitors including electrochromic supercapacitors, self-healing supercapacitors, piezoelectric supercapacitors, shape-memory supercapacitors, thermal self-protective supercapacitors, thermal self-charging supercapacitors, and photo self-charging supercapacitors. Finally, the future developments and key technical challenges are highlighted regarding further research in this thriving field.

Heteroatom doping can endow graphene with various new or improved electromagnetic, physicochemical, optical, and structural properties. This greatly extends the arsenal of graphene materials and their potential for a spectrum of applications. Considering the latest developments, we comprehensively and critically discuss the syntheses, properties and emerging applications of the growing family of heteroatom-doped graphene materials. The advantages, disadvantages, and preferential doping features of current synthesis approaches are compared, aiming to provide clues for developing new and controllable synthetic routes. We emphasize the distinct properties resulting from various dopants, different doping levels and configurations, and synergistic effects from co-dopants, hoping to assist a better understanding of doped graphene materials. The mechanisms underlying their advantageous uses for energy storage, energy conversion, sensing, and gas storage are highlighted, aiming to stimulate more competent applications.

Photovoltaic (PV) technologies for solar energy conversion represent promising routes to green and renewable energy generation. Despite relevant PV technologies being available for more than half a century, the production of solar energy remains costly, largely owing to low power conversion efficiencies of solar cells. The main difficulty in improving the efficiency of PV energy conversion lies in the spectral mismatch between the energy distribution of photons in the incident solar spectrum and the bandgap of a semiconductor material. In recent years, luminescent materials, which are capable of converting a broad spectrum of light into photons of a particular wavelength, have been synthesized and used to minimize the losses in the solar-cell-based energy conversion process. In this review, we will survey recent progress in the development of spectral converters, with a particular emphasis on lanthanide-based upconversion, quantum-cutting and down-shifting materials, for PV applications. In addition, we will also present technical challenges that arise in developing cost-effective high-performance solar cells based on these luminescent materials.

Ferroptosis is a newly discovered form of regulated cell death that is the nexus between metabolism, redox biology, and human health. Emerging evidence shows the potential of triggering ferroptosis for cancer therapy, particularly for eradicating aggressive malignancies that are resistant to traditional therapies. Recently, there has been a great deal of effort to design and develop anticancer drugs based on ferroptosis induction. Recent advances of ferroptosis-inducing agents at the intersection of chemistry, materials science, and cancer biology are presented. The basis of ferroptosis is summarized first to highlight the feasibility and characteristics of triggering ferroptosis for cancer therapy. A literature review of ferroptosis inducers (including small molecules and nanomaterials) is then presented to delineate their design, action mechanisms, and anticancer applications. Finally, some considerations for research on ferroptosis inducers are spotlighted, followed by a discussion on the challenges and future development directions of this burgeoning field.

Great attention has been given to metal–organic frameworks (MOFs)-derived solid bases because of their attractive structure and catalytic performance in various organic reactions. The extraordinary skeleton structure of MOFs provides many possibilities for incorporation of diverse basic functionalities, which is unachievable for conventional solid bases. The past decade has witnessed remarkable advances in this vibrant research area; however, MOFs for heterogeneous basic catalysis have never been reviewed until now. Therefore, a review summarizing MOFs-derived base catalysts is highly expected. In this review, we present an overview of the recent progress in MOFs-derived solid bases covering preparation, characterization, and catalytic applications. In the preparation section, the solid bases are divided into two categories, namely, MOFs with intrinsic basicity and MOFs with modified basicity. The basicity can originate from either metal sites or organic ligands. Different approaches used for generation of basic sites are included, and each approach is described with representative examples. The fundamental principles for the design and fabrication of MOFs with basic functionalities are featured. In the characterization section, experimental techniques and theoretical calculations employed for characterization of basic MOFs are summarized. Some representive experimental techniques, such as temperature-programmed desorption of CO2 (CO2-TPD) and infrared (IR) spectra of different probing molecules, are covered. Following preparation and characterization, the catalytic applications of MOFs-derived solid bases are dealt with. These solid bases have potential to catalyze some well-known “base-catalyzed reactions” like Knoevenagel condensation, aldol condensation, and Michael addition. Meanwhile, in contrast to conventional solid bases, MOFs show some different catalytic properties due to their special structural and surface properties. Remarkably, characteristic features of MOFs-derived solid bases are described by comparing with conventional inorganic counterparts, keeping in mind the current opportunities and challenges in this field.

Humans rely increasingly on sensors to address grand challenges and to improve quality of life in the era of digitalization and big data. For ubiquitous sensing, flexible sensors are developed to overcome the limitations of conventional rigid counterparts. Despite rapid advancement in bench-side research over the last decade, the market adoption of flexible sensors remains limited. To ease and to expedite their deployment, here, we identify bottlenecks hindering the maturation of flexible sensors and propose promising solutions. We first analyze challenges in achieving satisfactory sensing performance for real-world applications and then summarize issues in compatible sensor-biology interfaces, followed by brief discussions on powering and connecting sensor networks. Issues en route to commercialization and for sustainable growth of the sector are also analyzed, highlighting environmental concerns and emphasizing nontechnical issues such as business, regulatory, and ethical considerations. Additionally, we look at future intelligent flexible sensors. In proposing a comprehensive roadmap, we hope to steer research efforts towards common goals and to guide coordinated development strategies from disparate communities. Through such collaborative efforts, scientific breakthroughs can be made sooner and capitalized for the betterment of humanity.

Defect engineering in metal-organic frameworks (MOFs) is an exciting concept for tailoring material properties, which opens up novel opportunities not only in sorption and catalysis, but also in controlling more challenging physical characteristics such as band gap as well as magnetic and electrical/conductive properties. It is challenging to structurally characterize the inherent or intentionally created defects of various types, and there have so far been few efforts to comprehensively discuss these issues. Based on selected reports spanning the last decades, this Review closes that gap by providing both a concise overview of defects in MOFs, or more broadly coordination network compounds (CNCs), including their classification and characterization, together with the (potential) applications of defective CNCs/MOFs. Moreover, we will highlight important aspects of "defect-engineering" concepts applied for CNCs, also in comparison with relevant solid materials such as zeolites or COFs. Finally, we discuss the future potential of defect-engineered CNCs.

Abstract Materials and structures with negative Poisson’s ratio exhibit a counter-intuitive behaviour. Under uniaxial compression (tension), these materials and structures contract (expand) transversely. The materials and structures that possess this feature are also termed as ‘auxetics’. Many desirable properties resulting from this uncommon behaviour are reported. These superior properties offer auxetics broad potential applications in the fields of smart filters, sensors, medical devices and protective equipment. However, there are still challenging problems which impede a wider application of auxetic materials. This review paper mainly focuses on the relationships among structures, materials, properties and applications of auxetic metamaterials and structures. The previous works of auxetics are extensively reviewed, including different auxetic cellular models, naturally observed auxetic behaviour, different desirable properties of auxetics, and potential applications. In particular, metallic auxetic materials and a methodology for generating 3D metallic auxetic materials are reviewed in details. Although most of the literature mentions that auxetic materials possess superior properties, very few types of auxetic materials have been fabricated and implemented for practical applications. Here, the challenges and future work on the topic of auxetics are also presented to inspire prospective research work. This review article covers the most recent progress of auxetic metamaterials and auxetic structures. More importantly, several drawbacks of auxetics are also presented to caution researchers in the future study.

Reactive oxygen (ROS) and nitrogen (RNS) species cause oxidative and nitrosative stresses, respectively. These stresses are implicated not only in diverse physiological processes but also in various pathological processes, including cancer and neurodegenerative disorders. In addition, some ROS and RNS in the environment are pollutants that threaten human health. As a consequence of these effects, sensitive methods, which can be employed to selectively monitor ROS and RNS in live cells, tissues and organisms as well as in environmental samples, are needed so that their biological roles can be understood and their concentrations in environmental samples can be determined. In this review, fluorescent, luminescent and colorimetric ROS and RNS probes, which have been developed since 2011, are comprehensively discussed.

The design and characterization of metal-organic complexes for optoelectronic applications is an active area of research. The metal-organic complex offers unique optical and electronic properties arising from the interplay between the inorganic metal and the organic ligand. The ability to modify chemical structure through control over metal-ligand interaction on a molecular level could directly impact the properties of the complex. When deposited in thin film form, this class of materials enable the fabrication of a wide variety of low-cost electronic and optoelectronic devices. These include light emitting diodes, solar cells, photodetectors, field-effect transistors as well as chemical and biological sensors. Here we present an overview of recent development in metal-organic complexes with controlled molecular structures and tunable properties. Advances in extending the control of molecular structures to solid materials for energy conversion and information technology applications will be highlighted.

Graphene is a well-known two-dimensional material that exhibits preeminent electrical, mechanical and thermal properties owing to its unique one-atom-thick structure. Graphene and its derivatives (e.g., graphene oxide) have become emerging nano-building blocks for separation membranes featuring distinct laminar structures and tunable physicochemical properties. Extraordinary molecular separation properties for purifying water and gases have been demonstrated by graphene-based membranes, which have attracted a huge surge of interest during the past few years. This tutorial review aims to present the latest groundbreaking advances in both the theoretical and experimental chemical science and engineering of graphene-based membranes, including their design, fabrication and application. Special attention will be given to the progresses in processing graphene and its derivatives into separation membranes with three distinct forms: a porous graphene layer, assembled graphene laminates and graphene-based composites. Moreover, critical views on separation mechanisms within graphene-based membranes will be provided based on discussing the effect of inter-layer nanochannels, defects/pores and functional groups on molecular transport. Furthermore, the separation performance of graphene-based membranes applied in pressure filtration, pervaporation and gas separation will be summarized. This article is expected to provide a compact source of relevant and timely information and will be of great interest to all chemists, physicists, materials scientists, engineers and students entering or already working in the field of graphene-based membranes and functional films.

N-Heterocyclic carbene (NHC) organocatalysis in the presence of transition metals is a challenge because of the high affinity of NHCs for metals. In their Communication on page 161, J. Mao, P. J. Walsh, and co-workers present a system for the conjugate addition of aryl iodides to enals through cooperative catalysis between an NHC and a Pd catalyst. The catalytic cycles intersect at Pd, where the two newly formed Pd−C bonds undergo reductive elimination to give a C−C bond.

The synthesis of lanthanide-activated phosphors is pertinent to many emerging applications, ranging from high-resolution luminescence imaging to next-generation volumetric full-color display. In particular, the optical processes governed by the 4f-5d transitions of divalent and trivalent lanthanides have been the key to enabling precisely tuned color emission. The fundamental importance of lanthanide-activated phosphors for the physical and biomedical sciences has led to rapid development of novel synthetic methodologies and relevant tools that allow for probing the dynamics of energy transfer processes. Here, we review recent progress in developing methods for preparing lanthanide-activated phosphors, especially those featuring 4f-5d optical transitions. Particular attention will be devoted to two widely studied dopants, Ce3+ and Eu2+. The nature of the 4f-5d transition is examined by combining phenomenological theories with quantum mechanical calculations. An emphasis is placed on the correlation of host crystal structures with the 5d-4f luminescence characteristics of lanthanides, including quantum yield, emission color, decay rate, and thermal quenching behavior. Several parameters, namely Debye temperature and dielectric constant of the host crystal, geometrical structure of coordination polyhedron around the luminescent center, and the accurate energies of 4f and 5d levels, as well as the position of 4f and 5d levels relative to the valence and conduction bands of the hosts, are addressed as basic criteria for high-throughput computational design of lanthanide-activated phosphors.

Oxidative and nitrosative stress induced by ROS/RNS play crucial roles in a wide range of physiological processes and are also implicated in various diseases, including cancer and neurodegenerative disorders. Sensitive and selective methods for the detection of ROS/RNS based on fluorescent and luminescent probes are of great use in monitoring the in vivo production of these species and elucidating their biological functions. This critical review highlights recent advances that have been made in the development of fluorescent and luminescent probes employed to monitor various ROS/RNS (132 references).

A passive turnoff Passive radiative cooling technology uses the infrared atmospheric window to allow outer space to be a cold sink for heat. However, this effect is one that is only helpful for energy savings in the warmer months. Wang et al . and Tang et al . used the metal-insulator transition in tungsten-doped vanadium dioxide to create window glass and a rooftop coating that circumvents this problem by turning off the radiative cooling at lower temperatures. Because the transition is simply temperature dependent, this effect also happens passively. Model simulations suggest that these materials would lead to energy savings year-round across most of the climate zones in the United States. —BG

Photodynamic therapy (PDT) kills cancer cells by converting tumour oxygen into reactive singlet oxygen ((1)O2) using a photosensitizer. However, pre-existing hypoxia in tumours and oxygen consumption during PDT can result in an inadequate oxygen supply, which in turn hampers photodynamic efficacy. Here to overcome this problem, we create oxygen self-enriching photodynamic therapy (Oxy-PDT) by loading a photosensitizer into perfluorocarbon nanodroplets. Because of the higher oxygen capacity and longer (1)O2 lifetime of perfluorocarbon, the photodynamic effect of the loaded photosensitizer is significantly enhanced, as demonstrated by the accelerated generation of (1)O2 and elevated cytotoxicity. Following direct injection into tumours, in vivo studies reveal tumour growth inhibition in the Oxy-PDT-treated mice. In addition, a single-dose intravenous injection of Oxy-PDT into tumour-bearing mice significantly inhibits tumour growth, whereas traditional PDT has no effect. Oxy-PDT may enable the enhancement of existing clinical PDT and future PDT design.

The recent advances in the development of nonstoichiometric oxides, ranging from simple oxide, perovskite, layered perovskite, and pyrochlore, for oxygen reduction Reaction (ORR) and oxygen evolution reaction (OER) in metal-air batteries (MABs) and low-temperature fuel cells (LTFCs) are reviewed. These catalysts are characterized to be low cost and earth-abundant, as well as possess relatively high activity and stability under operation conditions. It is expected that these catalysts will be essential to the future development of multiple technologies. It is expected that the development of nonstoichiometric oxides, with the mutual development of system components, will lead to highly stable and efficient MABs and LTFCs in practical applications in the near future. The electrochemical strain microscopy technique may provide a direct visualization of the ORR/OER activation process on the scale of several nanometers and provide nanoscale understanding into local kinetics. An efficient approach to discover new materials with high intrinsic activities is to tune the electronic structure of existing materials.