Light-Emitting Microfibers from Lotus Root for Eco-Friendly Optical Waveguides and Biosensing.

Optical biosensors based on micro/nanofibers are highly valuable for probing and monitoring liquid environments and bioactivity. Most current optical biosensors, however, are still based on glass, semiconductors, or metallic materials, which might not be fully suitable for biologically relevant environments. Here, we introduce biocompatible and flexible microfibers from lotus silk as microenvironmental monitors that exhibit waveguiding of intrinsic fluorescence as well as of coupled light. These features make single-filament monitors excellent building blocks for a variety of sensing functions, including pH probing and detection of bacterial activity. These results pave the way for the development of new and entirely eco-friendly, potentially multiplexed biosensing platforms.

Manipulation of Moiré Superlattice in Twisted Monolayer-multilayer Graphene by Moving Nanobubbles.

In the heterostructure of two-dimensional (2D) materials, many novel physics phenomena are strongly dependent on the Moiré superlattice. How to achieve the continuous manipulation of the Moiré superlattice in the same sample is very important to study the evolution of various physical properties. Here, in minimally twisted monolayer-multilayer graphene, we found that bubble-induced strain has a huge impact on the Moiré superlattice. By employing the AFM tip to dynamically and continuously move the nanobubble, we realized the modulation of the Moiré superlattice, like the evolution of regular triangular domains into long strip domain structures with single or double domain walls. We also achieved controllable modulation of the Moiré superlattice by moving multiple nanobubbles and establishing the coupling of nanobubbles. Our work presents a flexible method for continuous and controllable manipulation of Moiré superlattices, which will be widely used to study novel physical properties in 2D heterostructures.

Systematic Proteomics Study on the Embryonic Development of Danio rerio.

The early development of zebrafish (Danio rerio) is a complex and dynamic physiological process involving cell division, differentiation, and movement. Currently, the genome and transcriptome techniques have been widely used to study the embryonic development of zebrafish. However, the research of proteomics based on proteins that directly execute functions is relatively vacant. In this work, we apply label-free quantitative proteomics to explore protein profiling during zebrafish's embryogenesis, and a total of 5961 proteins were identified at 10 stages of zebrafish's early development. The identified proteins were divided into 11 modules according to weighted gene coexpression network analysis (WGCNA), and the characteristics between modules were significantly different. For example, mitochondria-related functions enriched the early development of zebrafish. Primordial germ cell-related proteins were identified at the 4-cell stage, while the eye development event is dominated at 5 days post fertilization (dpf). By combining with published transcriptomics data, we discovered some proteins that may be involved in activating zygotic genes. Meanwhile, 137 novel proteins were identified. This study comprehensively analyzed the dynamic processes in the embryonic development of zebrafish from the perspective of proteomics. It provided solid data support for further understanding of the molecular mechanism of its development.

Systematic Identification of Microproteins during the Development of Drosophila melanogaster.

Short open reading frame-encoded peptides (SEPs) are microproteins with less than 100 amino acids that play an essential role in the growth and development of organisms. There are plenty of short open reading frames in Drosophila melanogaster that potentially code polypeptides. We chose 11 time points during the life cycle of Drosophila to investigate microproteins, particularly those related to development. Finally, we identified a total of 410 microproteins, of which 27 were noncoding RNA-encoded proteins. Of the 410 microproteins, 74 were expressed in all stages from embryo to adults, whereas 300 microproteins were only found in one or two time points. Approximately, one-third of the microproteins were not reported previously and 44 were obtained from de novo sequencing, validated by synthetic peptides. These microproteins are related to the main bioprocesses of growth and development, such as multicellular organism reproduction, postmating behavior, and oviposition. Over half of the microproteins have predicted functional domains and are conserved across species, suggesting that these microproteins have critical functions in fly development. This work enriches the D. melanogaster proteome and provides a significant data resource for growth and development research.

Point-Source Geometric Metasurface Holography.

Geometric metasurfaces have shown great potential in holography due to their straightforward geometric nature of phase control. The incident angles, spins, and wavelengths of the light provide various degrees of freedom to multiplex metasurface holographic images, which, however, are usually interrelated and hence challenging to be fully decoupled. Here, we report a synergetic recipe to break such seemingly inevitable interrelation by incorporating an effective point source (a pinhole), with which the spin, wavelength, and coordinate of the point source can be fully decoupled in meta-holograms. We experimentally demonstrate spin-decoupled, full-colored metasurface holography and dynamic holography controlled with the position of the point source. The significance of this work is not merely to offer an alternative approach to break the interrelation limitations of the geometric metasurface, but more importantly, it provides a promising route for point sources in reality to realize advanced functionalities with meta-optics, such as single-photon holography, fluorescence holography, etc.

Direct-indirect bandgap transition in monolayer MoS2 induced by an individual Si nanoparticle.

MoS2 is promising for the next generation of electronic and optoelectronic devices by virtue of its unique optical, electrical and mechanical properties. Bandgap engineering of it is an interesting topic. However, the reported factors including temperature, defect, strain and external electric field are difficult to handle precisely. Here, we demonstrated direct-indirect bandgap transition in monolayer MoS2 induced by an individual Si nanoparticle. We observed photoluminescence (PL) emission with obvious spectral redshift and broadening in the MoS2/Si heterostructures after depositing Si nanoparticles onto the surface of monolayer MoS2. Raman spectra of heterostructures show measurable shifts in contrast with the bare MoS2. Energy transfer between MoS2 and Si nanoparticles did not happen, which is demonstrated by scattering spectra of MoS2/Si heterostructures. In addition, the natural oxide layer presented on the surface of Si nanoparticles can effectively prevent the carrier transferring from Si nanoparticles to MoS2. Thus, we attribute the direct-indirect bandgap transition of monolayer MoS2 to the strain induced by Si nanoparticles controlled by their sizes. The PL intensity of MoS2/Si heterostructure depends on the size of Si nanoparticles, resulting from the enhanced optical absorption of monolayer MoS2 based on Mie resonances of Si nanoparticles. The MoS2/Si heterostructure is promising for photodetector and circuit integration.

Directional radiation and photothermal effect enhanced control of 2D excitonic emission based on germanium nanoparticles.

Dielectric nanostructures with Mie resonances have shown promising applications for building nanoantennas and metasurfaces. Coupling between Mie resonators and transition metal dichalcogenide (TMDC) monolayers is of great significance, because the existence of Mie resonances can modulate phases and radiation directions effectively. Recently, monolayer binary and ternary TDMCs have drawn more attention owing to the intriguing and tunable excitonic states from visible to near infrared. However, the coupling mechanism between monolayer TMDCs and Mie resonators has not been well studied. Moreover, it is still a great challenge to realize the control of excitonic emission wavelength and intensity simultaneously. Here, for the first time, we demonstrate that germanium nanoparticles (Ge NPs), a typical high refractive index dielectric Mie resonator, are capable of controlling both the intensity and direction of PL emissions in the near-infrared from monolayer WSe2(1-x)Te2x. Through putting Ge NPs below or above monolayers, we observed the obvious emission directivity because of the higher refractive index and higher loss of Ge than silicon. Besides, higher absorption in Ge NPs brings photothermal effects during the interaction with TMDCs. These findings indicate that Ge-based Mie resonators may guide the design of new type nanophotonics devices in the future.

Observation of the Kondo Effect in Multilayer Single-Crystalline VTe2 Nanoplates.

We report the chemical vapor deposition (CVD) growth, characterization, and low-temperature magnetotransport of 1T phase multilayer single-crystalline VTe2 nanoplates. The transport studies reveal that no sign of intrinsic long-range ferromagnetism but localized magnetic moments exist in the individual multilayer metallic VTe2 nanoplates. The localized moments give rise to the Kondo effect, evidenced by logarithmical increment of resistivity with decreasing temperature and negative magnetoresistance (NMR) regardless of the direction of magnetic field at temperatures below the resistivity minimum. The low-temperature resistivity upturn is well described by the Hamann equation, and the NMR at different temperatures, a manifestation of the magnetization of the localized spins, is well fitted to a Brillouin function for S = 1/2. Density functional theory calculations reveal that the localized magnetic moments mainly come from the interstitial vanadium ions in the VTe2 nanoplates. Our results will shed light on the study of magnetic properties, strong correlation, and many-body physics in two-dimensional metallic transition metal dichalcogenides.

Directional Fano Resonance in an Individual GaAs Nanospheroid.

Fano resonance has been observed in a wide variety of nanophotonic structures such as photonic crystals, plasmonic structures, and metamaterials. It arises from the interference of discrete resonance states with broadband continuum states. As an emerging nanophotonic material, high-index all-dielectric nanomaterials provide a new platform to achieve Fano resonance by virtue of the simultaneous excited electric and magnetic resonances. However, to date, Fano resonance in the visible region has not been observed in individual high-index all-dielectric nanoparticles. Here, for the first time, the experimental observation of the directional Fano resonance is reported in an individual GaAs nanospheroid. The special geometry enables GaAs nanospheroids to generate spectrally overlapped electric and magnetic dipole resonances, which enhances their spectral coupling, giving rise to asymmetric-shaped backward scattering spectrum. This directional Fano resonance can be tuned by the aspect ratio of nanospheroids as well as excitation polarization. In addition, efficient directional light scattering is realized at the total scattering peak of the GaAs nanospheroid. The forward-to-backward scattering ratio can be largely enhanced due to Fano dip in the backward scattering spectrum. These findings suggest that high-index all-dielectric nanospheroid is a promising candidate for directional sources and optical switches.

Ultrafast Control of Phase and Polarization of Light Expedited by Hot-Electron Transfer.

All-optical modulation is an entangled part of ultrafast nonlinear optics with promising impacts on tunable optical devices in the future. Current advancements in all-optical control predominantly offer modulation by means of altering light intensity, while the ultrafast manipulation of other attributes of light have yet to be further explored. Here, we demonstrate the active modulation of the phase, polarization, and amplitude of light through the nonlinear modification of the optical response of a plasmonic crystal that supports subradiant, high Q, and polarization-selective resonance modes. The designed mode is exclusively accessible via TM-polarized light, which enables significant phase modulation and polarization conversion within the visible spectrum. To tailor the device performance in the time domain, we exploit the ultrafast transport dynamics of hot electrons at the interface of plasmonic metals and charge acceptor materials to facilitate an ultrafast switching speed. In addition, the operating wavelength of the proposed device can be tuned through the control of the in-plane momentum of light. Our work reveals the viability of dynamic phase and polarization control in plasmonic systems for all-optical switching and data processing.