The recent breakthrough of organometal halide perovskites as the light harvesting layer in photovoltaic devices has led to power conversion efficiencies of over 16%. To date, most perovskite solar ...cells have adopted a structure in which the perovskite light absorber is placed between carrier-selective electron- and hole-transport layers (ETLs and HTLs). Here we report a new type of compact layer free bilayer perovskite solar cell and conclusively demonstrate that the ETL is not a prerequisite for obtaining excellent device efficiencies. We obtained power conversion efficiencies of up to 11.6% and 13.5% when using poly(3-hexylthiophene) and 2,2′,7,7′-tetrakis(N,N-di(4-methoxyphenyl)amino)-9,9′-spirobifluorene, respectively, as the hole-transport material. This performance is very comparable to that obtained with the use of a ZnO ETL. Impedance spectroscopy suggests that while eliminating the ZnO leads to an increase in contact resistance, this is offset by a substantial decrease in surface recombination.
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IJS, KILJ, NUK, PNG, UL, UM
Metal-organic frameworks (MOFs) are constructed from metal ions/clusters coordinated by organic linkers (or bridging-ligands). The hallmark of MOFs is their permanent porosity, which is frequently ...found in MOFs constructed from metal-clusters. These clusters are often formed
in situ
, whereas the linkers are generally pre-formed. The geometry and connectivity of a linker dictate the structure of the resulting MOF. Adjustments of linker geometry, length, ratio, and functional-group can tune the size, shape, and internal surface property of a MOF for a targeted application. In this critical review, we highlight advances in MOF synthesis focusing on linker design. Examples of building MOFs to reach unique properties, such as unprecedented surface area, pore aperture, molecular recognition, stability, and catalysis, through linker design are described. Further search for application-oriented MOFs through judicious selection of metal clusters and organic linkers is desirable. In this review, linkers are categorized as ditopic (Section 1), tritopic (Section 2), tetratopic (Section 3), hexatopic (Section 4), octatopic (Section 5), mixed (Section 6), desymmetrized (Section 7), metallo (Section 8), and N-heterocyclic linkers (Section 9).
Advances in metal-organic frameworks are highlighted with an emphasis on tuning the structure and function
via
linker design.
Over the past few decades, the design and development of advanced electrocatalysts for efficient energy conversion technologies have been subjects of extensive study. With the discovery of graphene, ...two-dimensional (2D) nanomaterials have emerged as some of the most promising candidates for heterogeneous electrocatalysts due to their unique physical, chemical, and electronic properties. Here, we review 2D-nanomaterial-based electrocatalysts for selected electrocatalytic processes. We first discuss the unique advances in 2D electrocatalysts based on different compositions and functions followed by specific design principles. Following this overview, we discuss various 2D electrocatalysts for electrocatalytic processes involved in the water cycle, carbon cycle, and nitrogen cycle from their fundamental conception to their functional application. We place a significant emphasis on different engineering strategies for 2D nanomaterials and the influence these strategies have on intrinsic material performance, such as electronic properties and adsorption energetics. Finally, we feature the opportunities and challenges ahead for 2D nanomaterials as efficient electrocatalysts. By considering theoretical calculations, surface characterization, and electrochemical tests, we describe the fundamental relationships between electronic structure, adsorption energy, and apparent activity for a wide variety of 2D electrocatalysts with the goal of providing a better understanding of these emerging nanomaterials at the atomic level.
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Conventional cancer chemotherapy is often associated with toxicity issues. Thus, new drug delivery systems (DDSs) are developed as alternatives owing to their potential to selectively target affected ...cells while sparing normal tissues. Among them, noninvasive and biocompatible mesoporous silica nanoparticle (MSN)-based targeted DDSs have developed rapidly. In particular, controlled gatekeepers capping the pore entrances of MSNs play prominent and crucial roles in achieving specific drug release and avoiding premature leakage in the delivery process before the target is reached, and perfect gatekeepers can only be removed under specific internal or external stimuli, such as pH, redox potential, temperature, biomolecules, light, magnetic field and ultrasound, or a combination of these stimuli, which is significant for precise therapeutic treatments and potential applications in human bodies. Thus, the main focus of this review is to highlight the most recent progress on the design of various controlled MSN gatekeepers to achieve 'zero premature release' drug delivery. The diverse gatekeepers are categorised into the following kinds according to their types and characteristics: (1) polymers; (2) inorganic nanomaterials; (3) host-guest assemblies; and (4) biomacromolecules. This review will offer a broad palette of opportunities for researchers with interests including nanomaterial fabrication and modification, targeted drug delivery and stimuli-responsive drug release.
Progress on the design of diverse gatekeepers for mesoporous silica nanoparticle based drug delivery systems is summarized.
Foodborne pathogens like Listeria monocytogenes can cause various illnesses and pose a serious threat to public health. They produce species-specific microbial volatile organic compounds, i.e., the ...biomarkers, making it possible to indirectly measure microbial contamination in foodstuff. Herein, highly ordered mesoporous tungsten oxides with high surface areas and tunable pores have been synthesized and used as sensing materials to achieve an exceptionally sensitive and selective detection of trace Listeria monocytogenes. The mesoporous WO3-based chemiresistive sensors exhibit a rapid response, superior sensitivity, and highly selective detection of 3-hydroxy-2-butanone. The chemical mechanism study reveals that acetic acid is the main product generated by the surface catalytic reaction of the biomarker molecule over mesoporous WO3. Furthermore, by using the mesoporous WO3-based sensors, a rapid bacteria detection was achieved, with a high sensitivity, a linear relationship in a broad range, and a high specificity for Listeria monocytogenes. Such a good gas sensing performance foresees the great potential application of mesoporous WO3-based sensors for fast and effective detection of microbial contamination for the safety of food, water safety and public health.
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Microplastics and nanoplastics have become emerging particulate anthropogenic pollutants and rapidly turned into a field of growing scientific and public interest. These tiny plastic particles are ...found in the environment all around the globe as well as in drinking water and food, raising concerns about their impacts on the environment and human health. To adequately address these issues, reliable information on the ambient concentrations of microplastics and nanoplastics is needed. However, micro- and nanoplastic particles are extremely complex and diverse in terms of their size, shape, density, polymer type, surface properties, etc. While the particle concentrations in different media can vary by up to 10 orders of magnitude, analysis of such complex samples may resemble searching for a needle in a haystack. This highlights the critical importance of appropriate methods for the chemical identification, quantification, and characterization of microplastics and nanoplastics. The present article reviews advanced methods for the representative mass-based and particle-based analysis of microplastics, with a focus on the sensitivity and lower-size limit for detection. The advantages and limitations of the methods, and their complementarity for the comprehensive characterization of microplastics are discussed. A special attention is paid to the approaches for reliable analysis of nanoplastics. Finally, an outlook for establishing harmonized and standardized methods to analyze these challenging contaminants is presented, and perspectives within and beyond this research field are discussed.
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The study of surface texturing has been a great interest to the researcher over the last years. Surface texturing improves the property of the surface of the material in the working area. It creates ...a pattern of micron dimensions over the surface to influence the surface property in its working area. Several techniques are used to fabricate these micro dimensions. Electrochemical micromachining (EMM) emerges as a new technique with several benefits. This review paper highlights the advantages of EMM over other processes and discusses different methods to develop the micro-features. EMM process is capable of fabricating micron-size features without changing any surface property at a low cost.
Heteroatom doping is an effective strategy to modify the surface properties of carbon electrode, thus boosting its electrochemical performance. In this work, phosphorus (P)-doped porous carbons with ...high specific surface are prepared by KOH pre-activation of ultrapure anthracite and further H3PO4 activation. H3PO4 post-activation not only generates more mesoporous for a rapid ion diffusion, but also provides potential P-source for the P-doping on carbon scaffold. The increase of P-doped content significantly restrains the formation of unstable quinone and carboxylic groups, and then enhances oxidation stability of P-doped porous carbon. When evaluated as electrodes in 1 m Et4NBF4/PC, the resultant material exhibits excellent rate capability of 75% retention at 30 A g−1, extraordinary stability of 90% capacitance retention after 20000 cycles and low leakage current of less than 1.2 μA. More importantly, due to the blockage of active oxidation sites by phosphate groups, the P-doped porous carbon can stably operate at higher voltage of 3.0 V in Et4NBF4/PC compared to that of undoped porous carbon, so as to deliver a high energy density of 38.65 Wh kg−1 at 1500 W kg−1. The study offers insightful material chemistry for industrial application of H3PO4 activated porous carbon in advanced electrochemical energy storage.
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•Phosphate groups on the carbon scaffold effectively block the active oxidation sites.•The optimized P-doped carbon demonstrates a mesoporous rate of even up to 87.48%.•P-doped carbon retains as high as 90.2% of initial capacitance over 20000 cycles.•High-voltage cycling stability and energy density are significantly improved.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Luminescence quenching at high dopant concentrations generally limits the dopant concentration to less than 1–5 mol% in lanthanide-doped materials, and this remains a major obstacle in designing ...materials with enhanced efficiency/brightness. In this work, we provide direct evidence that the major quenching process at high dopant concentrations is the energy migration to the surface (i.e., surface quenching) as opposed to the common misconception of cross-relaxation between dopant ions. We show that after an inert epitaxial shell growth, erbium (Er3+) concentrations as high as 100 mol% in NaY(Er)F4/NaLuF4 core/shell nanocrystals enhance the emission intensity of both upconversion and downshifted luminescence across different excitation wavelengths (980, 800, and 658 nm), with negligible concentration quenching effects. Our results highlight the strong coupling of concentration and surface quenching effects in colloidal lanthanide-doped nanocrystals, and that inert epitaxial shell growth can overcome concentration quenching. These fundamental insights into the photophysical processes in heavily doped nanocrystals will give rise to enhanced properties not previously thought possible with compositions optimized in bulk.
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Hydrogels are a unique class of polymeric materials that possess an interconnected porous network across various length scales from nano- to macroscopic dimensions and exhibit remarkable ...structure-derived properties, including high surface area, an accommodating matrix, inherent flexibility, controllable mechanical strength, and excellent biocompatibility. Strong and robust adhesion between hydrogels and substrates is highly desirable for their integration into and subsequent performance in biomedical devices and systems. However, the adhesive behavior of hydrogels is severely weakened by the large amount of water that interacts with the adhesive groups reducing the interfacial interactions. The challenges of developing tough hydrogel-solid interfaces and robust bonding in wet conditions are analogous to the adhesion problems solved by marine organisms. Inspired by mussel adhesion, a variety of catechol-functionalized adhesive hydrogels have been developed, opening a door for the design of multi-functional platforms. This review is structured to give a comprehensive overview of adhesive hydrogels starting with the fundamental challenges of underwater adhesion, followed by synthetic approaches and fabrication techniques, as well as characterization methods, and finally their practical applications in tissue repair and regeneration, antifouling and antimicrobial applications, drug delivery, and cell encapsulation and delivery. Insights on these topics will provide rational guidelines for using nature's blueprints to develop hydrogel materials with advanced functionalities and uncompromised adhesive properties.
This review presents insights into the fundamental challenges of wet adhesion, and the applications of catechol-functionalized hydrogels in diverse areas.
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