Organic dyes emitting in the second near‐infrared (NIR‐II, 900–1700 nm) window, with high molar extinction coefficients (MEC) and quantum yields (QY) in aqueous, are essential for in vivo bioimaging ...and biosensing. In this work, we developed a dibodipy‐based aggregation‐induced emission (AIE) fluorescent probe, THPP, to meet this aim. THPP exhibits a high MEC and has intensified absorption and emission in J‐aggregated state, which significantly enhance the fluorescence intensity (≈55 folds) and extend the maximal absorption/emission wavelengths to 970/1010 nm in NIR‐II region. Based on the bright THPP, imaging with a high frame rate (34 frames per second) at a deep “valid penetration depth” up to 6 mm can be achieved. This enabled simultaneous and dynamic imaging of vasculatures and deep tissues. Besides, we succeeded in monitoring the respiratory rate of acute‐lung‐injury mice and tracing the collateral circulation process with a high frame rate.
A J‐aggregated AIE dibodipy‐based fluorescent probe, THPP, was synthesized. The probe exhibits enhanced fluorescence intensity in the NIR‐II window for dynamic in vivo imaging.
Over the past decade, high-quality lanthanide doped upconverting nanoparticles (UCNPs) have been successfully synthesized with the rapid development of nanotechnology. Due to the unique electron ...configuration of lanthanide ions, there are rich energy level structures in the near-infrared, visible and ultraviolet spectral range. However, for UCNPs, only a limited number of efficient upconversion excitation and emission have been generated due to the limited number of sensitizer (Yb
3+
) and activator (Tm
3+
, Er
3+
, and Ho
3+
) ions, and the application is mainly focused on the bio-imaging by using the upconversion luminescence of UCNPs. Recently, more and more researchers have started to focus on tuning of upconversion optical properties and developing of multi-functional UCNPs by using the combination of sub-lattice mediated energy migration, core@shell structural engineering and UCNPs based nanocomposites which greatly expands the range of applications for lanthanide-doped UCNPs. Therefore, a "nanolab" can be created on UCNPs, where the property modulation can be realized
via
the designed host-dopants combinations, core@shell nanostructure, energy exchange with "alien species" (organic dyes, quantum dots,
etc.
), and so on. In this paper, we provide a comprehensive survey of the latest advances made in developing lanthanide-doped UCNPs, which include excitation and emission energy levels guided designing of the UCNP nanostructure, the synthesis techniques to fabricate the nanostructure with optimum energy level structure and optical properties, the fabrication of UCNPs-based nanocomposites to extend the applications by introducing the additional functional components, or integrating the functional moiety into one nanocomposite.
This review aims to summarize recent progress in optical properties and applications engineering of upconversion nanoparticles
via
the designed nanostructure.
A small‐molecule fluorophore FD‐1080 with both excitation and emission in the NIR‐II region has been successfully synthesized for in vivo imaging. A heptamethine structure is designed to shift the ...absorption and emission into NIR‐II region. Sulphonic and cyclohexene groups are introduced to enhance its water solubility and stability. The quantum yield of FD‐1080 is 0.31 %, and can be increased to 5.94 % after combining with fetal bovine serum (FBS). Significantly, 1064 nm NIR‐II excitation was demonstrated with the high tissue penetration depth and superior imaging resolution compared to previously reported NIR excitation from 650 nm to 980 nm. FD‐1080 is not only capable of realizing non‐invasive high‐resolution deep‐tissue hindlimb vasculature and brain vessel bioimaging, but also quantifying the respiratory rate based on the dynamic imaging of respiratory craniocaudal motion of the liver for the awake and anaesthetized mouse.
A small‐molecule fluorophore, FD‐1080, with both excitation and emission in the NIR‐II region has been synthesized for in vivo imaging. It exhibits high quantum yield, deep tissue penetration depth, superior spatial resolution, prominent signal‐to‐background ratio, and dynamic imaging capability.
The concept of valley pseudospin, labelling quantum states of energy extrema in momentum space, is attracting attention1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13 because of its potential as a new type ...of information carrier. Compared with the non-topological bulk valley transport, realized soon after predictions1, 2, 3, 4, 5, topological valley transport in domain walls6, 7, 8, 9, 10, 11, 12, 13 is extremely challenging owing to the inter-valley scattering inevitably induced by atomic-scale imperfections--but an electronic signature was recently observed in bilayer graphene12, 13. Here, we report the experimental observation of topological valley transport of sound in sonic crystals. The macroscopic nature of sonic crystals permits a flexible and accurate design of domain walls. In addition to a direct visualization of the valley-selective edge modes through spatial scanning of the sound field, reflection immunity is observed in sharply curved interfaces. The topologically protected interface transport of sound, strikingly different from that in traditional sound waveguides14, 15, may serve as the basis for designing devices with unconventional functions.
Most existing work on adaptive allocation of sub- carriers and power in multiuser orthogonal frequency division multiplexing (OFDM) systems has focused on homogeneous traffic consisting solely of ...either delay-constrained data (guaranteed service) or non-delay-constrained data (best-effort service). In this paper, we investigate the resource allocation problem in a heterogeneous multiuser OFDM system with both delay-constrained (DC) and non-delay-constrained (NDC) traffic. The objective is to maximize the sum-rate of all the users with NDC traffic while maintaining guaranteed rates for the users with DC traffic under a total transmit power constraint. Through our analysis we show that the optimal power allocation over subcarriers follows a multi-level water-filling principle; moreover, the valid candidates competing for each subcarrier include only one NDC user but all DC users. By converting this combinatorial problem with exponential complexity into a convex problem or showing that it can be solved in the dual domain, efficient iterative algorithms are proposed to find the optimal solutions. To further reduce the computational cost, a low-complexity suboptimal algorithm is also developed. Numerical studies are conducted to evaluate the performance of the proposed algorithms in terms of service outage probability, achievable transmission rate pairs for DC and NDC traffic, and multiuser diversity.
Small‐molecule organic fluorophores, spectrally active in the 900–1700 nm region, with tunable wavelength and sensing properties are sought‐after for in vivo optical imaging and biosensing. A panel ...of fluorescent dyes (CX) has been developed to meet this challenge. CX dyes exhibit the wavelength tunability of cyanine dyes and have a rigidified polymethine chain to guarantee their stability. They are chemo‐ and photo‐stable in an aqueous environment and have tunable optical properties with maximal absorbing/emitting wavelength at 1089/1140 nm. They show great potential in high‐contrast in vivo bioimaging and multicolor detection with negligible optical cross talk. Förster resonance energy transfer (FRET) between CX dyes was demonstrated in deep tissue, providing an approach for monitoring drug‐induced hepatotoxicity by detection of OONO−. This report presents a series of NIR‐II dyes with promising spectroscopic properties for high‐contrast bioimaging and multiplexed biosensing.
A series of NIR‐II dyes (CX) with promising spectroscopic properties has been developed and used for in vivo multicolor imaging at a tissue depth of up to 4 mm. These were used to develop a FRET‐based fluorescence probe, which was successfully applied to the in vivo detection of drug‐induced hepatotoxicity. The regulation of NIR‐II fluorescence via FRET could serve as a general strategy for future NIR‐II fluorescent sensor design.
Chemiluminescence (CL) sensing without external excitation by light and autofluorescence interference has been applied to high‐contrast in vitro immunoassays and in vivo inflammation and tumor ...microenvironment detection. However, conventional CL sensing usually operates in the range of 400–850 nm, which limits the performance of in vivo imaging due to serious light scattering effects and signal attenuation in tissue. To address this challenge, a new type of CL sensor is presented that functions in the second near‐infrared window (NIR‐II CLS) with a deep penetration depth (≈8 mm). Successive CL resonance energy transfer (CRET) and Förster resonance energy transfer (FRET) from the activated CL substrate to two rationally designed donor‐acceptor‐donor fluorophores BTD540 and BBTD700 occurs. NIR‐II CLS can be selectively activated by hydrogen peroxide over other reactive oxygen species (ROSs). Moreover, NIR‐II CLS is capable of detecting local inflammation in mice with a 4.5‐fold higher signal‐to‐noise ratio (SNR) than that under the NIR‐II fluorescence modality.
A novel near‐infrared (NIR‐II) chemiluminescence sensor was prepared by cascade chemiluminescence resonance energy transfer (CRET) and one‐step Förster resonance energy transfer (FRET). The sensor is capable of in vivo high‐contrast inflammation imaging. Key: chemiluminescence (CL), 1,2‐dioxetanedione intermediate (DOD), fluorescence (FL), region of interest (ROI).
Spark plasma sintering (SPS), also known as pulsed electric current sintering (PECS) or field-assisted sintering technique (FAST), belongs to a class of powder metallurgy techniques. In SPS, the ...sample is simultaneously subjected to a uniaxial pressure and electrical current in a vacuum or protective atmosphere. Although the fundamental principles of this procedure were first proposed over 50 years ago, SPS acquired major importance only within the last 20 years. Scholars come to realize that SPS technique enables control of the powder surface condition, atomic diffusion behavior, and phase stability and crystal growth behavior, as well as accelerating densification of hard-to-sinter materials. This review summarizes the latest research findings with respect to experimental procedures, densification behaviors, microstructural characteristics, and mechanical properties of various traditional and novel materials synthesized using SPS, mainly highlighting the heating mechanisms in SPS and the effects induced by multi-physical fields on materials. In addition, influences of operating parameters containing current, voltage, and uniaxial pressure on product characteristics are reviewed for a wide range of materialsincluding hard-to-sinter materials, carbon-containing materials, nanocrystalline materials, non-equilibrium materials, gradient materials, interconnect materials, complex shape materials, and advanced functional materials.
Display omitted
•Effects of current, electric fields and pressure on SPS processing and micro-mechanisms in materials are investigated.•The state-of-the-art concepts of SPS devices for R&D and industrial application are presented.•The common technological superiority and optimization mechanisms of applying SPS in every material system are illustrated.•Overview on the design, experiment and simulation of both structural and functional materials developed by SPS technique.
Persistent luminescence is not affected by background autofluorescence, and thus holds the promise of high-contrast bioimaging. However, at present, persistent luminescent materials for in vivo ...imaging are mainly bulk crystals characterized by a non-uniform size and morphology, inaccessible core-shell structures and short emission wavelengths. Here we report a series of X-ray-activated, lanthanide-doped nanoparticles with an extended emission lifetime in the second near-infrared window (NIR-II, 1,000-1,700 nm). Core-shell engineering enables a tunable NIR-II persistent luminescence, which outperforms NIR-II fluorescence in signal-to-noise ratios and the accuracy of in vivo multiplexed encoding and multilevel encryption, as well as in resolving mouse abdominal vessels, tumours and ureters in deep tissue (~2-4 mm), with up to fourfold higher signal-to-noise ratios and a threefold greater sharpness. These rationally designed nanoparticles also allow the high-contrast multiplexed imaging of viscera and multimodal NIR-II persistent luminescence-magnetic resonance-positron emission tomography imaging of murine tumours.
A series of zirconium polyphenolate‐decorated‐(metallo)porphyrin metal–organic frameworks (MOFs), ZrPP‐n (n = 1, 2), featuring infinite ZrIV‐oxo chains linked via polyphenolate groups on four ...peripheries of eclipse‐arranged porphyrin macrocycles, are successfully constructed through a top–down process from simulation to synthesis. These are the unusual examples of Zr‐MOFs (or MOFs in general) based on phenolic porphyrins, instead of commonly known carboxylate‐based types. Representative ZrPP‐1 not only exhibits strong acid resistance (pH = 1, HCl) but also remains intact even when immersed in saturated NaOH solution (≈20 m), an exceptionally large range of pH resistance among MOFs. The metallation at the porphyrin core gives rise to materials with enhanced sorption and catalytic properties. In particular, ZrPP‐1‐Co, with precise and uniform distribution of active centers, exhibits not only high CO2 trapping capability (≈90 cm3 g−1 at 1 atm, 273 K, among the highest in Zr‐MOFs) but also high photocatalytic activity for reduction of CO2 into CO (≈14 mmol g−1 h−1) and high selectivity over CH4 (>96.4%) without any cocatalyst under visible‐light irradiation (λ > 420 nm). Given the strong chemical resistance under extreme alkali conditions, these catalysts can be recycled without appreciable loss of activity. The possible mechanism for photocatalytic reduction of CO2‐to‐CO over ZrPP‐1‐Co is also proposed.
Top–down fabrication of robust and porous materials based on infinite ZrIV‐polyphenolate chains linked via eclipsed‐arranged porphyrin macrocycles is presented. Among them, ZrPP‐1 retains its framework integrity when immersed in saturated NaOH solution as long as 1 week. Moreover, metallation at the porphyrin core gives rise to materials with enhanced CO2 trapping capability and high visible‐light‐driven CO2‐to‐CO photoreduction activity.
PDF
