The use of lanthanide elements for applications in various industries such as the chemical industry and in biomedical engineering is examined. Topics discussed include lanthanide nanoparticles as MRI ...contrast agents, lanthanide upconversion nanoparticles for biosensing, bioimaging, and therapy and nanoceria for nanomedicine.
While quasi‐two‐dimensional (quasi‐2D) perovskites have emerged as promising semiconductors for light‐emitting diodes (LEDs), the broad‐width distribution of quantum wells hinders their efficient ...energy transfer and electroluminescence performance in blue emission. In particular, the underlying mechanism is closely related to the crystallization kinetics and has yet to be understood. Here for the first time, the influence of bifunctional zwitterions with different coordination affinity on the crystallization kinetics of quasi‐2D perovskites is systematically investigated. The zwitterions can coordinate with Pb2+ and also act as co‐spacer organic species in quasi‐2D perovskites, which collectively inhibit the aggregation of colloidal precursors and shorten the distance of quantum wells. Consequently, restricted nucleation of high‐n phases and promoted growth of low‐n phases are achieved with moderately coordinated zwitterions, leading to the final film with a more concentrated n distribution and improved energy transfer efficiency. It thus enables high‐efficiency blue LEDs with a recorded external quantum efficiency of 15.6% at 490 nm, and the operation stability has also been prolonged to 55.3 min. These results provide useful directions for tuning the crystallization kinetics of quasi‐2D perovskites, which is expected to lead to high‐performance perovskite LEDs.
In this work, a facile strategy base on bifunctional zwitterions is proposed that effectively modulates the crystallization kinetics of quantum wells—both suppressing the formation of low‐n phases and restricting the growth of high‐n phases—contributing to a narrow n distribution. Accordingly, high‐performance sky‐blue PeLEDs at 490 nm with a recorded EQE of 15.6% are realized.
Cesium lead halide (CsPbX3) perovskite has emerged as a promising low‐threshold multicolor laser material; however, realizing wavelength‐tunable lasing output from a single CsPbX3 nanostructure is ...still constrained by integrating different composition. Here, the direct synthesis of composition‐graded CsPbBrxI3−x nanowires (NWs) is reported through vapor‐phase epitaxial growth on mica. The graded composition along the NW, with an increased Br/I from the center to the ends, comes from desynchronized deposition of cesium lead halides and temperature‐controlled anion‐exchange reaction. The graded composition results in varied bandgaps along the NW, which induce a blueshifted emission from the center to the ends. As an efficient gain media, the nanowire exerts position‐dependent lasing performance, with a different color at the ends and center respectively above the threshold. Meanwhile, dual‐color lasing with a wavelength separation of 35 nm is activated simultaneously at a site with an intermediate composition. This position‐dependent dual‐color lasing from a single nanowire makes these metal halide perovskites promising for applications in nanoscale optical devices.
Composition‐graded CsPbBrxI3−x nanowires resulting from desynchronized deposition and anion exchange are efficiently synthesized via vapor‐phase growth. The graded Br/I along the nanowire endows it with tunable emission. Position‐dependent lasing with different colors from the ends and center is detected. Dual‐color lasing is activated simutaneously from the site with an intermediate composition to that of the ends and center.
Non-reciprocal devices, which allow non-reciprocal signal routing, serve as fundamental elements in photonic and microwave circuits and are crucial in both classical and quantum information ...processing. The radiation-pressure-induced coupling between light and mechanical motion in travelling-wave resonators has been exploited to break the Lorentz reciprocity, enabling non-reciprocal devices without magnetic materials. Here, we experimentally demonstrate a reconfigurable non-reciprocal device with alternative functions as either a circulator or a directional amplifier via optomechanically induced coherent photon-phonon conversion or gain. The demonstrated device exhibits considerable flexibility and offers exciting opportunities for combining reconfigurability, non-reciprocity and active properties in single photonic devices, which can also be generalized to microwave and acoustic circuits.
A redox road to recoveryDevice longevity is a key issue for organic-inorganic perovskite solar cells. Encapsulation can limit degradation arising from reactions with oxygen and water, but light, ...electric-field, and thermal stresses can lead to metastable elemental lead and halide atom defects. Wang et al. show that for the lead-iodine system, the introduction of the rare earth europium ion pair Eu3+-Eu2+ can shuttle electrons and recover lead and iodine ions (Pb2+ and I−). Devices incorporating this redox shuttle maintained more than 90% of their initial power conversion efficiencies under various aging conditions.Science, this issue p. 265The components with soft nature in the metal halide perovskite absorber usually generate lead (Pb)0 and iodine (I)0 defects during device fabrication and operation. These defects serve as not only recombination centers to deteriorate device efficiency but also degradation initiators to hamper device lifetimes. We show that the europium ion pair Eu3+-Eu2+ acts as the “redox shuttle” that selectively oxidized Pb0 and reduced I0 defects simultaneously in a cyclical transition. The resultant device achieves a power conversion efficiency (PCE) of 21.52% (certified 20.52%) with substantially improved long-term durability. The devices retained 92% and 89% of the peak PCE under 1-sun continuous illumination or heating at 85°C for 1500 hours and 91% of the original stable PCE after maximum power point tracking for 500 hours, respectively.
Upconversion emissions from lanthanide-doped nanocrystals have sparked extensive research interests in nanophotonics, biomedicine, photovoltaics, photocatalysis, etc. Rational modulation of ...upconversion emissions is highly desirable to meet the requirements of specific applications. Among the diverse developed methods, local structure engineering is fundamentally feasible, through which the upconversion emission intensity, selectivity, wavelength shift, and lifetime can be tuned effectively. The underlying mechanism of the local-structure-dependent upconversion emissions lies in the degree of parity hybridization and energy level splitting of lanthanide ions as well as the interionic energy transfer efficiency. Over the past few years, there has been significant progress in local-structure-engineered upconversion emissions. In this Perspective, we first introduce the principles of upconversion emissions and typical characterization methods for local structure. Subsequently, we summarize recent achievements in tuning of upconversion emissions through local structure engineering, including host composition adjustment, external field regulation, and interfacial strain management. Finally, we propose a few perspectives that should tackle the current bottlenecks. This Perspective is expected to deepen the understanding of local-structure-dependent upconversion emissions and arouse adequate attention to the engineering of local structure for desired properties of inorganic nanocrystals.
Rare earth (RE) materials, which are excited in the ultraviolet and emit in the visible light spectrum, are widely used as phosphors for lamps and displays. In the 1960’s, researchers reported an ...abnormal emission phenomenon where photons emitted from a RE element carried more energy than those absorbed, owing to the sequential energy transfer between two RE ionsYb3+-sensitized Er3+ or Tm3+in the solid state. After further study, researchers named this abnormal emission phenomenon upconversion (UC) emission. More recent approaches take advantage of solution-based synthesis, which allows creation of homogenous RE nanoparticles (NPs) with controlled size and structure that are capable of UC emission. Such nanoparticles are useful for many applications, especially in biology. For these applications, researchers seek small NPs with high upconversion emission intensity. These UCNPs have the potential to have multicolor and tunable emissions via various activators. A vast potential for future development remains by developing molecular antennas and energy transfer within RE ions. We expect UCNPs with optimized spectra behavior to meet the increasing demand of potential applications in bioimaging, biological detection, and light conversion. This Account focuses on efforts to control the size and modulate the spectra of UCNPs. We first review efforts in size control. One method is careful control of the synthesis conditions to manipulate particle nucleation and growth, but more recently researchers have learned that the doping conditions can affect the size of UCNPs. In addition, constructing homogeneous core/shell structures can control nanoparticle size by adjusting the shell thickness. After reviewing size control, we consider how diverse applications impose different requirements on excitation and/or emission photons and review recent developments on tuning of UC spectral profiles, especially the extension of excitation/emission wavelengths and the adjustment and purification of emission colors. We describe strategies that employ various dopants and others that build rationally designed nanostructures and nanocomposites to meet these goals. As the understanding of the energy transfer in the UC process has improved, core/shell structures have been proved useful for simultaneous tuning of excitation and emission wavelengths. Finally, we present a number of typical examples to highlight the upconverted emission in various applications, including imaging, detection, and sensing. We believe that with deeper understanding of emission phenomena and the ability to tune spectral profiles, UCNPs could play an important role in light conversion studies and applications.
Graphitic carbon nitrides (g‐C3N4) are a class of 2D polymeric materials mainly composed of carbon and nitrogen atoms. g‐C3N4 are attracting dramatically increasing interest in the areas of sensing, ...imaging, and therapy, due to their unique optical and electronic properties. Here, the luminescent properties (mainly includes photoluminescence and electrochemiluminescence), and catalytic and photoelectronic properties related to sensing and therapy applications of g‐C3N4 materials are reviewed. Furthermore, the fabrication and advantages of sensing, imaging and therapy systems based on g‐C3N4 materials are summarized. Finally, the future perspectives for developing the sensing, imaging and therapy applications of the g‐C3N4 materials are discussed.
The sensing, imaging and therapy applications of g‐C3N4 materials are summarized. The luminescent, catalytic and photoelectronic properties and mechanisms of g‐C3N4 materials related to sensing and therapy applications are introduced and discussed. The principles and advantages of the sensing, imaging and therapy systems are concluded.
Optical encoding together with color multiplexing benefits on-site detection, and enriching the components with narrow emissions from lanthanide could greatly increase the coding density. Here, we ...show a typical example to combine emission color and lifetime that are simultaneously integrated in a single lanthanide nanoparticle. With the multicompartment core/shell structure, the nanoparticles can activate different emitting pathways under varied excitation. This enables the nanoparticles to generate versatile excitation orthogonalized upconversion luminescence in both emission colors and lifetimes. As a typical example, green emission of Er3+ and blue emission of Tm3+ can be triggered with 808 and 980 nm lasers, respectively. Moreover, with incorporation of Tb3+, not only is emission from Tb3+ introduced but also the lifetime difference of 0.13 ms (Er3+) and 3.6 ms (Tb3+) is yielded for the green emission, respectively. Multiplexed fingerprint imaging and time-gated luminescence imaging were achieved in wavelength and lifetime dimensions. The spectral and lifetime encoding ability from lanthanide luminescence greatly broadens the scope of luminescent materials for optical multiplexing studies.
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