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Lab Chip, 2017, Accepted Manuscript
DOI: 10.1039/C7LC01187C, PaperThomas Litschel, Michael Meredith Norton, Vardges Tserunyan, Seth Fraden
We present an experimental system of networks of coupled non-linear chemical reactors, which we theoretically model within a reaction-diffusion framework. The networks consist of patterned arrays of diffusively coupled nanoliter-scale...
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Lab Chip, 2018, Advance Article
DOI: 10.1039/C7LC01088E, PaperEric Y. Liu, Sukwon Jung, David A. Weitz, Hyunmin Yi, Chang-Hyung Choi
Capillary microfluidic fabrication of monodisperse and chemically functional hydrogel microspheres with selective conjugation schemes yields improved protein conjugation.
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Reduction of the FeII complex [(PhPP2Cy)FeCl2] (2) generates an electron rich and unsaturated Fe0 which is reacted with white phosphorus. The new complex obtained, [(PhPP2Cy)Fe(η4-P4)] (3), is the first iron cyclo-P4 complex and the only known stable end deck cyclo-P4 complex outside of group V. Complex 3 bears a FeII center as shown by Mössbauer spectroscopy, associated to a P42- fragment. Analysis of the molecular orbitals rationalizes the distinct reactivity of complex 3. Reaction of complex 3 with H+ affords the unstable complex [(PhPP2Cy)Fe(η4-P4)(H)]+ (4), whereas with CuCl and BCF the complexes [(PhPP2Cy)Fe(η4:η1-P4)(μ-CuCl)]2 (5) and [(PhPP2Cy)Fe(η4:η1-P4)B(C6F5)3] (6) are formed.

Science chats with the filmmaker who brought Ötzi the mummy back to life
Abstract

Direct cellular imaging of the localization and dynamics of biomolecules helps to understand their function and reveals novel mechanisms at the single-cell resolution. In contrast to routine fluorescent-protein-based protein imaging, technology for RNA imaging remains less well explored because of the lack of enabling technology. Herein, we report the development of an aptamer-initiated fluorescence complementation (AiFC) method for RNA imaging by engineering a green fluorescence protein (GFP)-mimicking turn-on RNA aptamer, Broccoli, into two split fragments that could tandemly bind to target mRNA. When genetically encoded in cells, endogenous mRNA molecules recruited Split-Broccoli and brought the two fragments into spatial proximity, which formed a fluorophore-binding site in situ and turned on fluorescence. Significantly, we demonstrated the use of AiFC for high-contrast and real-time imaging of endogenous RNA molecules in living mammalian cells. We envision wide application and practical utility of this enabling technology to in vivo single-cell visualization and mechanistic analysis of macromolecular interactions.

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Let's split! An aptamer-initiated fluorescence complementation (AiFC) method was developed for RNA imaging by engineering a green fluorescence protein (GFP)-mimicking turn-on RNA aptamer into two split fragments that could tandemly bind to target mRNA. The use of AiFC enables the non-invasive, high-contrast real-time imaging of endogenous RNA molecules in living mammalian cells.

Abstract

A tricyclic phosphine has been generated that has a rigid molecular backbone with the P atoms exclusively bound to C(sp2) atoms as well as a very large Tolman angle and buried volume. It is an interesting new ligand in coordination chemistry (Au, Pd complexes) and shows unusual insertion reactions into its endocyclic P−C bonds facilitated by its inherent molecular strain.

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Give it a tri: A trilithium compound reacted with PCl3 to afford a new tricyclic and sterically highly shielded phosphine that has a large Tolman angle, and ligand basicity comparable to that of PPh3. Ring strain results in a promising reactivity, as demonstrated by the insertion of S or Se atoms into the P−C bonds.

Abstract

The cyanobacterial prenyltransferase AmbP3 catalyzes the reverse prenylation of the tetracyclic indole alkaloid hapalindole U at its C-2 position. Interestingly, AmbP3 also accepts hapalindole A, a halogenated C-10 epimer of hapalindole U, and catalyzes normal prenylation at its C-2 position. The comparison of the two ternary crystal structures, AmbP3-DMSPP/hapalindole U and AmbP3-DMSPP/hapalindole A, at 1.65–2.00 Å resolution revealed two distinct orientations for the substrate binding that define reverse or normal prenylation. The tolerance of the enzyme for these altered orientations is attributed to the hydrophobicity of the substrate binding pocket and the plasticity of the amino acids surrounding the allyl group of the prenyl donor. This is the first study to provide the intimate structural basis for the normal and reverse prenylations catalyzed by a single enzyme, and it offers novel insight into the engineered biosynthesis of prenylated natural products.

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One Way or Another: AmbP3 is a prenyltransferase that catalyzes both reverse and regular prenylation depending on the substrate. X-ray crystal structure analysis of AmbP3 in complex with reverse and regular prenylation substrates elucidates the structural basis of its surprising plasticity in catalyzing two types of prenylation.

Abstract

Photoacoustics is a powerful biomedical imaging and detection technique, because it is a noninvasive, nonionizing, and low-cost method facilitating deep tissue penetration. However, suitable contrast agents need to be developed to increase the contrast for in vivo imaging. Gold nanoparticles are often discussed as potential sonophores due to their large absorption cross-section and their tunable plasmon resonance. However, disadvantages such as toxicity and low photoacoustic efficiency in the tissue transparency window prevail, preventing their clinical application. As a result, there remains a strong need to develop colloidal photoacoustic contrast agents which absorb in the tissue transparency window, exhibit high photoacoustic signal, and are biocompatible. Here, a facile synthetic approach is presented to produce melanin shells around various gold nanoparticle geometries, from spheres to stars and rods. These hybrid particles show excellent dispersability, better biocompatibility, and augmented photoacoustic responses over the pure melanin or pristine gold particles, with a rod-shape geometry leading to the highest performance. These experimental results are corroborated using numerical calculations and explain the improved photoacoustic performance with a thermal confinement effect. The applicability of melanin coated gold nanorods as gastrointestinal imaging probes in mouse intestine is showcased.

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Here, the preparation of melanin coated gold particles is presented. The melanin coating provides enhanced colloidal stability, improved biocompatibility, and augmented photoacoustic contrast. The reasons for these improvements are analyzed experimentally and theoretically and it is found that a thermal confinement effect leads to enhanced photothermal efficiency, which is exploited for intestinal photoacoustic imaging.

Abstract

Multicolor tunable and multistate switchable organogel is reported, which consists of a cyanostilbene organogelator showing aggregation-induced enhanced emission and a turn-on type photochromic diarylethene dye. The mixed organogel can be reversibly switched among four different states (blue-emitting gel, nonemissive sol, green-emitting gel, and green-emitting sol) modulated by a combination of orthogonal stimuli of heat and light. It is interestingly noted that this four-state switching constitutes a combinational logic circuit consisting of two stimuli inputs and three outputs. Reversible fluorescence writing, switching, erasing, and image patterning processes on this mixture gel system are demonstrated.

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Multistate addressable fluorescent organogel is constructed by mixing the aggregation-induced enhanced emission organogelator and fluorescent turn-on diarylethene. Through its reversible and orthogonal stimuli-responsiveness, an integrated logic circuit, where thermal- and optical-inputs can be translated into four different outputs (blue-emitting gel, nonemissive sol, green-emitting gel, and green-emitting sol), is demonstrated.

Abstract

The biomimetic principle of harnessing topographical structures to determine liquid motion behavior represents a cutting-edge direction in constructing green transportation systems without external energy input. Here, inspired by natural Nepenthes peristome, a novel anisotropic wettability surface with characteristic structural features of periodically aligned and overlapped arch-shaped microcavities, formed by employing ferrofluid assemblies as dynamic templates, is presented. The magnetic strength and orientation are precisely adjustable during the generation process, and thus the size and inclination angle of the ferrofluid droplet templates could be tailored to make the surface morphology of the resultant polymer replica achieve a high degree of similarity to the natural peristome. The resultant anisotropic wettability surface enables autonomous unidirectional water transportation in a fast and continuous way. In addition, it could be tailored into arbitrary shapes to induce water flow along a specific curved path. More importantly, based on the anisotropic wettability surface, novel pump-free microfluidic devices are constructed to implement multiphase flow reactions, which offer a promising solution to building low-cost, portable platform for lab-on-a-chip applications.

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An anisotropic wettability surface with Nepenthes peristome inspired structures is fabricated through dynamic ferrofluid assembly. It enables autonomous unidirectional water transportation and could be tailored into arbitrary shapes to induce water flow along a specific curved path. Novel pump-free microfluidic devices are constructed for multiphase flow reactions, which offer a promising solution in building low-cost, portable platform for lab-on-a-chip applications.

Abstract

Magnetic semiconductors are highly sought in spintronics, which allow not only the control of charge carriers like in traditional electronics, but also the control of spin states. However, almost all known magnetic semiconductors are featured with bandgaps larger than 1 eV, which limits their applications in long-wavelength regimes. In this work, the discovery of orthorhombic-structured Ti2O3 films is reported as a unique narrow-bandgap (≈0.1 eV) ferromagnetic oxide semiconductor. In contrast, the well-known corundum-structured Ti2O3 polymorph has an antiferromagnetic ground state. This comprehensive study on epitaxial Ti2O3 thin films reveals strong correlations between structure, electrical, and magnetic properties. The new orthorhombic Ti2O3 polymorph is found to be n-type with a very high electron concentration, while the bulk-type trigonal-structured Ti2O3 is p-type. More interestingly, in contrast to the antiferromagnetic ground state of trigonal bulk Ti2O3, unexpected ferromagnetism with a transition temperature well above room temperature is observed in the orthorhombic Ti2O3, which is confirmed by X-ray magnetic circular dichroism measurements. Using first-principles calculations, the ferromagnetism is attributed to a particular type of oxygen vacancies in the orthorhombic Ti2O3. The room-temperature ferromagnetism observed in orthorhombic-structured Ti2O3, demonstrates a new route toward controlling magnetism in epitaxial oxide films through selective stabilization of polymorph phases.

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Epitaxial Ti2O3 (Ti3+: 3d1) thin films on Sapphire are systematically investigated, and, more interestingly, a new stabilized orthorhombic phase is fabricated. Depending on extensive physical and optical properties measurements, the new orthorhombic Ti2O3 is confirmed to be a narrow band-gap (≈0.11 eV) n-type semiconductor with emergent ferromagnetism, while the corundum Ti2O3 is a p-type antiferromagnetic semiconductor with a trigonal structure.

Abstract

Ionic soft actuators, which exhibit large mechanical deformations under low electrical stimuli, are attracting attention in recent years with the advent of soft and wearable electronics. However, a key challenge for making high-performance ionic soft actuators with large bending deformation and fast actuation speed is to develop a stretchable and flexible electrode having high electrical conductivity and electrochemical capacitance. Here, a functionally antagonistic hybrid electrode with hollow tubular graphene meshes and nitrogen-doped crumpled graphene is newly reported for superior ionic soft actuators. Three-dimensional network of hollow tubular graphene mesh provides high electrical conductivity and mechanically resilient functionality on whole electrode domain. On the contrary, nitrogen-doped wrinkled graphene supplies ultrahigh capacitance and stretchability, which are indispensably required for improving electrochemical activity in ionic soft actuators. Present results show that the functionally antagonistic hybrid electrode greatly enhances the actuation performances of ionic soft actuators, resulting in much larger bending deformation up to 620%, ten times faster rise time and much lower phase delay in a broad range of input frequencies. This outstanding enhancement mostly attributes to exceptional properties and synergistic effects between hollow tubular graphene mesh and nitrogen-doped crumpled graphene, which have functionally antagonistic roles in charge transfer and charge injection, respectively.

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A functionally antagonistic hybrid electrode is newly designed for an ionic soft actuator by combining tubular graphene mesh with nitrogen-doped crumpled graphene. The charges are swiftly transferred via highly conductive graphene mesh and stored on highly capacitive nitrogen-doped graphene flakes. Adding graphene mesh significantly enhances the electromechanical and electrochemical properties of the electrode and consequently improves the actuator performances.

Abstract

Self-standing electrodes are the key to realize flexible Li-ion batteries. However, fabrication of self-standing cathodes is still a major challenge. In this work, porous LiCoO2 nanosheet arrays are grown on Au-coated stainless steel (Au/SS) substrates via a facile “hydrothermal lithiation” method using Co3O4 nanosheet arrays as the template followed by quick annealing in air. The binder-free and self-standing LiCoO2 nanosheet arrays represent the 3D cathode and exhibit superior rate capability and cycling stability. In specific, the LiCoO2 nanosheet array electrode can deliver a high reversible capacity of 104.6 mA h g−1 at 10 C rate and achieve a capacity retention of 81.8% at 0.1 C rate after 1000 cycles. By coupling with Li4Ti5O12 nanosheet arrays as anode, an all-nanosheet array based LiCoO2//Li4Ti5O12 flexible Li-ion battery is constructed. Benefiting from the 3D nanoarchitectures for both cathode and anode, the flexible LiCoO2//Li4Ti5O12 battery can deliver large specific reversible capacities of 130.7 mA h g−1 at 0.1 C rate and 85.3 mA h g−1 at 10 C rate (based on the weight of cathode material). The full cell device also exhibits good cycling stability with 80.5% capacity retention after 1000 cycles at 0.1 C rate, making it promising for the application in flexible Li-ion batteries.

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This work gives a novel approach to fabricate porous LiCoO2 nanosheet arrays on Au-coated stainless steel substrates. The trivial transformation on crystal structure is the key to build 3D nanoarray electrode. The all-nanosheet array based LiCoO2//Li4Ti5O12 full cell exhibits outstanding performance and good flexibility.

Abstract

Semiconducting molybdenum ditelluride (2H-MoTe2), a fast-emerging 2D material with an appropriate band gap and decent carrier mobility, is configured as field-effect transistors and is the focus of substantial research interest, showing hole-dominated ambipolar characteristics. Here, carrier modulation of ambipolar few-layer MoTe2 transistors is demonstrated utilizing magnesium oxide (MgO) surface charge transfer doping. By carefully adjusting the thickness of MgO film and the number of MoTe2 layers, the carrier polarity of MoTe2 transistors from p-type to n-type can be reversely controlled. The electron mobility of MoTe2 is significantly enhanced from 0.1 to 20 cm2 V−1 s−1 after 37 nm MgO film doping, indicating a greatly improved electron transport. The effective carrier modulation enables to achieve high-performance complementary inverters with high DC gain of >25 and photodetectors based on few-layer MoTe2 flakes. The results present an important advance toward the realization of electronic and optoelectronic devices based on 2D transition-metal dichalcogenide semiconductors.

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The MoTe2 transistors are electron doped by magnesium oxide (MgO) surface charge transfer doping. The electron mobility of MoTe2 is significantly enhanced from 0.1 to 20 cm2 V−1 s−1 after 37 nm MgO doping. The effective carrier modulation enables to achieve high-performance complementary inverters with high DC gain of >25 and photodetectors based on few-layer MoTe2 flakes.

Abstract

Due to the direct and sufficient contacting with the aqueous environment, the directional and continuous transport of gas bubbles on open surface without energy input will advance a variety of applications in heat transfer, selective aeration, water electrolysis, etc. Unfortunately, the behaviors of gas bubbles in aqueous environment are mainly dominated by the buoyancy moving gas bubbles upward, resulting in their difficult manipulation. Therefore, realizing the directional and continuous transport of gas bubbles on open surface still remains a great challenge. Herein, a novel strategy integrating the superaerophilic wettability with geometry-gradient structure is proposed, which can engender high driving force and low hysteresis resistance force acting on the gas bubbles. In experiment, these fabricated superaerophilic geometry-gradient polyethylene surfaces demonstrate distinguished performance of directionally and continuously transporting gas bubbles on open surfaces without energy input. In addition, the antibuoyancy bubble transportation device and the underwater bubble microreactor are successfully prepared in this manuscript, both of which illustrate the feasibility in the applications of complex environment and gas-related fields. It can be envisioned that this study will promote the understanding and development of underwater functional superwettability materials to achieve the directional and continuous transport of gas bubbles on the open surface.

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Superaerophilic geometry-gradient surfaces can be facilely fabricated by utilizing the techniques of laser cutting, sandpaper rubbing, and surface superhydrophobic coating. Benefiting from the superaerophilic wettability and geometry-gradient morphology, the prepared surfaces are facilitated with low hysteresis resistance force and high driving force, which can accomplish the directional and continuous transport of underwater gas bubbles.

Abstract

An effective approach to develop a novel macroscopic anisotropic bilayer hydrogel actuator with on–off switchable fluorescent color-changing function is reported. Through combining a collapsed thermoresponsive graphene oxide-poly(N-isopropylacrylamide) (GO-PNIPAM) hydrogel layer with a pH-responsive perylene bisimide-functionalized hyperbranched polyethylenimine (PBI-HPEI) hydrogel layer via macroscopic supramolecular assembly, a bilayer hydrogel is obtained that can be tailored and reswells to form a 3D hydrogel actuator. The actuator can undergo complex shape deformation caused by the PNIPAM outside layer, then the PBI-HPEI hydrogel inside layer can be unfolded to trigger the on–off switch of the pH-responsive fluorescence under the green light irradiation. This work will inspire the design and fabrication of novel biomimetic smart materials with synergistic functions.

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A macroscopic anisotropic bilayer hydrogel actuator integrating complex shape-changing and fluorescent color-changing functions is explored. The thermoresponsive shape deformation can trigger the on–off switch of the pH-responsive fluorescence change, which will inspire the design of novel biomimetic smart materials with synergistic functions.

Abstract

In this work, a method for the rapid synthesis of metallic microtracks on polyetherimide is presented. The method relies on the photosynthesis of silver nanoparticles on the surface of the polymer substrates from photosensitive silver chloride (AgCl), which is synthesized directly on the polyetherimide surface. The study reveals that the use of AgCl as a photosensitive intermediate accelerates the reactions leading to the formation of silver nanoparticles by up to two orders of magnitude faster than other photodecomposition schemes. The patterning can be conducted under blue light, with notable advantages over UV exposure. Polymers of significant interest to the microelectronics and 3D printing industries can be directly patterned by light using this photography-inspired technique at throughputs high enough to be commercially advantageous. Light exposures as short as a few seconds are sufficient to allow the direct metallization of the illuminated polyetherimide surface. The results show that the silver required for the seed layer is minimal, and the later copper electroless plating results in the selective growth of conductive tracks for circuitry on the light-patterned areas, both on flexible films and 3D printed surfaces.

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A rapid photopatterning method for the selective plating on polyetherimide is presented. The use of AgCl as photosensitive intermediate allows manufacturing with very short exposures. Conductive copper tracks are produced on both flexible substrates for microelectronics and 3D printed pieces.

Abstract

Nanocarbon–metal oxide hybrids are among the most promising functional materials in many cutting-edge environmental and energy applications where efficient charge separation and extraction are keys to success. The next level of hybrid structures will be achieved once one learns how to control and tune charge/energy transfer processes at the interfaces. However, little is yet known about the nature and extent of these interfacial dynamics in nanocarbon hybrids. Here a model is designed in which ultrathin dielectric layers (Al2O3, ZrO2) between the hybrid's components (ZnO, TiO2) and carbon nanotubes allow for evaluating and tuning of interfacial charge transfer over an unusually long distance of at least 50 nm. Surprisingly, the transfer efficiency correlates linearly with the barrier layer thickness, indicating that electron conduction through the barrier layer constitutes the rate-limiting step. It is also demonstrated that the charge transfer efficiency can be tuned by the type of interlayer and its degree of crystallinity, thus controlling the hybrid's performance in the photocatalytic production of hydrogen. It is believed that this model system will help to understand and decipher the fundamentals regarding interfacial charge and energy transfer in nanocarbon hybrids with the aim to further advance these hybrid structures for a wide range of energy applications.

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A novel hybrid system enables monitoring and tuning of interfacial charge transfer and manipulation of photocatalytic properties in nanocarbon–inorganic hybrids through implementation of ultrathin dielectric barrier layers using atomic layer deposition. Distance-dependent quenching studies with solid-state photoluminescence reveal electron conduction through the barrier layer as the rate-limiting step.

Abstract

The exploring of catalysts with high-efficiency and low-cost for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is one of the key issues for many renewable energy systems including fuel cells, metal–air batteries, and water splitting. Despite several decades pursuing, bifunctional oxygen catalysts with high catalytic performance at low-cost, especially the one that could be easily scaled up for mass production are still missing and highly desired. Herein, a hybrid catalyst with NiCo alloy nanoparticles decorated on N-doped carbon nanofibers is synthesized by a facile electrospinning method and postcalcination treatment. The hybrid catalyst [email protected] 2 exhibits outstanding ORR and OER catalytic performances, which is even surprisingly superior to the commercial Pt/C and RuO2 catalysts, respectively. The synergetic effects between alloy nanoparticles and the N-doped carbon fiber are considered as the main contributions for the excellent catalytic activities, which include decreasing the intrinsic and charge transfer resistances, increasing C[DOUBLE BOND]C, graphitic-N/pyridinic-N contents in the hybrid catalyst. This work opens up a new way to fabricate high-efficient, low-cost oxygen catalysts with high production.

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NiCo alloy nanoparticles decorated on N-doped carbon nanofibers as a highly active and durable oxygen electrocatalyst at low-cost are synthesized and reported. The hybrid catalyst with suitable amount of NiCo alloy nanoparticles loading ([email protected] 2) gives the most outstanding oxygen reduction reaction and oxygen evolution reaction electrocatalytic performances, which is even surprisingly superior to the commercial Pt/C and RuO2 catalysts, respectively.

Abstract

A near-infrared (NIR) fluorescent donor/acceptor (D/A) nanoplatform based on Förster resonance energy transfer is important for applications such as deep-tissue bioimaging and sensing. However, previously reported D/A nanoparticles (NPs) often show limitations such as aggregation-induced fluorescence quenching and poor interfacial compatibility that reduces the efficiency of the energy transfer and also leads to leaching of the small molecular fluorophores from the NP matrix. Here highly NIR-fluorescent D/A NPs with a fluorescence quantum yield as high as 46% in the NIR region (700–850 nm) and robust optical stability are reported. The hydrophobic core of each NP is composed of donor and acceptor moieties both of which are tethered with polycaprolactone (PCL), while the hydrophilic corona is composed of poly[oligo(ethylene glycol) methyl ether methacrylate] to offer colloidal stability and “stealthy” effect in aqueous media. The PCL matrix in each colloidal NP not only offers biocompatibility and biodegradability but also minimizes the aggregation-caused fluorescence quenching of D/A chromophores and prevents the leakage of the NIR fluorophores from the NPs. In vivo imaging using these NIR NPs in live mice shows contrast-enhanced imaging capability and efficient tumor-targeting through enhanced permeability and retention effect.

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Near-infrared fluorescent colloidal nanoparticles composed of polycaprolactone-tethered donors/acceptors show efficient Förster resonance energy transfer and enhanced fluorescence quantum yield as high as 46% in the NIR region (700–850 nm) and a large Stokes shift of 233 nm. The good biocompatibility, robust structural integrity, and bright near-infrared fluorescence make them promising for bioimaging applications.

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