Optical nanomaterials have been widely used in anticounterfeiting applications. There have been significant developments powered by recent advances in material science, printing technologies, and the ...availability of smartphone‐based decoding technology. Recent progress in this field is surveyed, including the availability of optical reflection, absorption, scattering, and luminescent nanoparticles. It is demonstrated that advances in the design and synthesis of lanthanide‐doped upconversion nanoparticles will lead to the next generation of anticounterfeiting technologies. Their tunable optical properties and optical responses to a range of external stimuli allow high‐security level information encoding. Challenges in the scale‐up synthesis of nanomaterials, engineering of assessorial devices for smart‐phone‐based decryption, and alignment to the potential markets which will lead to new directions for research, are discussed.
Recent advances in the development of anticounterfeiting technologies are surveyed. It is demonstrated that lanthanide‐doped upconversion nanoparticles hold significant potential for developing next‐generation high‐level anticounterfeiting technologies. This is a result of synthesis scale‐up, their multidimensional optical properties, and design strategies to encrypt information. Engineering compact smartphone‐based decryption devices is a future trend for next‐generation anticounterfeiting technologies.
Fluorescent nanothermometers can probe changes in local temperature in living cells and in vivo and reveal fundamental insights into biological properties. This field has attracted global efforts in ...developing both temperature-responsive materials and detection procedures to achieve sub-degree temperature resolution in biosystems. Recent generations of nanothermometers show superior performance to earlier ones and also offer multifunctionality, enabling state-of-the-art functional imaging with improved spatial, temporal and temperature resolutions for monitoring the metabolism of intracellular organelles and internal organs. Although progress in this field has been rapid, it has not been without controversy, as recent studies have shown possible biased sensing during fluorescence-based detection. Here, we introduce the design principles and advances in fluorescence nanothermometry, highlight application achievements, discuss scenarios that may lead to biased sensing, analyze the challenges ahead in terms of both fundamental issues and practical implementations, and point to new directions for improving this interdisciplinary field.
Morphology control in laboratory and industry setting remains as a major challenge for organic solar cells (OSCs) due to the difference in film-drying kinetics between spin coating and the printing ...process. A two-step sequential deposition method is developed to control the active layer morphology. A conjugated polymer that self-assembles into a well-defined fibril structure is used as the first layer, and then a non-fullerene acceptor is introduced into the fibril mesh as the second layer to form an optimal morphology. A benefit of the combined fibril network morphology and non-fullerene acceptor properties was that a high efficiency of 16.5% (certified as 16.1%) was achieved. The preformed fibril network layer and the sequentially deposited non-fullerene acceptor form a robust morphology that is insensitive to the polymer batches, solving a notorious issue in OSCs. Such progress demonstrates that the utilization of polymer fibril networks in a sequential deposition process is a promising approach towards the fabrication of high-efficiency OSCs.
Lanthanide-doped upconversion nanoparticles (UCNPs) are capable of converting near-infra-red excitation into visible and ultraviolet emission. Their unique optical properties have advanced a broad ...range of applications, such as fluorescent microscopy, deep-tissue bioimaging, nanomedicine, optogenetics, security labelling and volumetric display. However, the constraint of concentration quenching on upconversion luminescence has hampered the nanoscience community to develop bright UCNPs with a large number of dopants. This review surveys recent advances in developing highly doped UCNPs, highlights the strategies that bypass the concentration quenching effect, and discusses new optical properties as well as emerging applications enabled by these nanoparticles.
Abstract
Energy-dissipation elastomers relying on their viscoelastic behavior of chain segments in the glass transition region can effectively suppress vibrations and noises in various fields, yet ...the operating frequency of those elastomers is difficult to control precisely and its range is narrow. Here, we report a synergistic strategy for constructing polymer-fluid-gels that provide controllable ultrahigh energy dissipation over a broad frequency range, which is difficult by traditional means. This is realized by precisely tailoring the relaxation of confined polymer fluids in the elastic networks. The symbiosis of this combination involves: elastic networks forming an elastic matrix that displays reversible deformation and polymer fluids reptating back and forth to dissipate mechanical energy. Using prototypical poly (n-butyl acrylate) elastomers, we demonstrate that the polymer-fluid-gels exhibit a controllable ultrahigh energy-dissipation property (loss factor larger than 0.5) with a broad frequency range (10
−2
~ 10
8
Hz). Energy absorption of the polymer-fluid-gels is over 200 times higher than that of commercial damping materials under the same dynamic stress. Moreover, their modulus is quasi-stable in the operating frequency range.
Bismuth is one of the most thoroughly investigated main group elements, which has been regarded as 'the wonder metal' because of its diverse oxidation states and profound propensities to form bismuth ...clusters, resulting from the easy involvement in chemical combinations for the electrons in the p orbital. This peculiarity allows them to behave as smart optically active centers in diverse host materials. Remarkable progress in the research of bismuth activated photonic materials has been seen over the last ten years owing to their unique properties and important applications in areas of telecommunication, biomedicine, white light illumination and lasers. The aim of this review is to present a critical overview of the current state of the art in bismuth activated photonic materials, their features, advantages and limitations as well as the future research trends. We first shortly introduce the fundamental properties of bismuth element including principles of bismuth-related luminescence and characterization techniques available. This is followed by a detailed discussion on the recent progress in the synthesis and characterization of bismuth-activated photonic materials, with an emphasis on material systems emitting in the near-infrared (NIR) spectral region. Furthermore, we describe the representative achievements regarding their prospective applications in broadband NIR optical amplifiers, fiber lasers, bioimaging, and white light-emitting diodes. Finally, we point out what key scientific questions remain to be answered, and present our perspectives on future research trends in this exciting field of sciences.
When a liquid film of a colloidal solution consisting of particles of different sizes is dried on a substrate, the colloids often stratify, where smaller colloids are laid upon larger colloids. This ...phenomenon is counterintuitive because larger colloids which have a smaller diffusion constant, are expected to remain near the surface during the drying process, leaving a layer of larger colloids on top of smaller colloids. Here we show that the phenomenon is caused by the interaction between the colloids, and can be explained by a diffusion model accounting for the interaction between the colloids. By studying the evolution equations both numerically and analytically, we derive the condition at which the stratified structures are obtained.
Abstract
Cross-relaxation among neighboring emitters normally causes self-quenching and limits the brightness of luminescence. However, in nanomaterials, cross-relaxation could be well-controlled and ...employed for increasing the luminescence efficiency at specific wavelengths. Here we report that cross-relaxation can modulate both the brightness of single upconversion nanoparticles and the threshold to reach population inversion, and both are critical factors in producing the ultra-low threshold lasing emissions in a micro cavity laser. By homogenously coating a 5-μm cavity with a single layer of nanoparticles, we demonstrate that doping Tm
3+
ions at 2% can facilitate the electron accumulation at the intermediate state of
3
H
4
level and efficiently decrease the lasing threshold by more than one order of magnitude. As a result, we demonstrate up-converted lasing emissions with an ultralow threshold of continuous-wave excitation of ~150 W/cm
2
achieved at room temperature. A single nanoparticle can lase with a full width at half-maximum as narrow as ~0.45 nm.
We propose a continuum theory of the liquid-liquid phase separation in an elastic network, where phase-separated microscopic droplets rich in one fluid component can form as an interplay of fluids ...mixing, droplet nucleation, network deformation, thermodynamic fluctuation, etc. We find that the size of the phase-separated droplets decreases with the shear modulus of the elastic network in the form of ∝modulus^{-1/3} and the number density of the droplet increases almost linearly with the shear modulus ∝modulus, which are verified by the experimental observations. Phase diagrams in the space of (fluid constitution, mixture interaction, network modulus) are provided, which can help to understand similar phase separations in biological cells and also to guide fabrications of synthetic cells with desired phase properties.
Solvent evaporation in soft‐matter solutions (solutions of colloidal particles, polymers, and their mixtures) is an important process in material making and in the printing and coating industries. ...The solvent‐evaporation process determines the structure of materials and strongly affects their performance. Solvent evaporation involves many physicochemical processes: flow, diffusion, crystallization, gelation, glass transition, etc. and is quite complex. Here, recent progress in this important process is reported, with a special focus on theoretical and simulation studies.
Understanding the solvent‐evaporation process, especially how to control the structural changes during evaporation, is an important subject in many applications. Solutes are kinetically mobile in solution; therefore, the dynamics are fast and the fabrication time can be reduced. The final structure can be controlled by external means such as evaporation rate and solution pH value.
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