Dynamic Trapping and Manipulation of Self-Assembled Ag Nanoplates as Efficient Plasmonic Tweezers.

Plasmonic tweezers based on periodic nanostructures have been used to manipulate particles through multiple and uniform local surface plasmon (LSP) fields. However, the coverage area of periodic nanostructures is limited, which restricts the range of trapping and manipulation. In this paper, we present a novel approach to achieve large-scale manipulation and trapping of microspheres by uniformly coupled LSP fields on a short-range disordered self-assembled Ag nanoplates (DSNP) film. The DSNP film is prepared by simple and low-cost methods─chemical growth and self-assembly technique, which overcome the challenges of preparing periodic nanostructures with a large coverage area. The uniform and coupled plasmon fields generated by this film provide enhanced electrodynamic interactions with particles, enabling the non-invasive and repeatable trapping of particles in solution. Utilizing sensitive LSPRs, dynamic manipulating particles was achieved by controlling the laser position. This large-scale platform of stable manipulation enabled by the DSNP film opens up new possibilities for the trapping and manipulation of nanoparticles in a variety of applications.

Theoretical and Experimental Investigations of Diffraction Characteristics Influenced by Holographic Reciprocity Effect in PQ/PMMA Polymers.

We propose the holographic reciprocity effect (HRE) to describe the relationship between the exposure duration (ED) and the growth rate of diffraction efficiency (GRoDE) in volume holographic storage. The HRE process is investigated experimentally and theoretically in order to avoid the diffraction attenuation. Herein, introducing the medium absorption, we present a comprehensive probabilistic model to describe the HRE. PQ/PMMA polymers are fabricated and investigated to reveal the influence of HRE on the diffraction characteristics through two recording approaches: pulsed exposure with nanosecond (ns) level and continuous wave (CW) exposure at the millisecond (ms) level. We obtain the holographic reciprocity matching (HRM) range of ED in PQ/PMMA polymers with 10-6~102 s level and improve the response time to microsecond (µs) order with no diffraction deficiency. This work can promote the application of volume holographic storage in high-speed transient information accessing technology.

Holographic Grating Enhancement Induced by a Dual-Photo-Initiator System in PMMA Substrate Polymers.

Polymer systems induced by the reaction between monomers and photo-initiators play a crucial role in the formation of volume-phase gratings. In this paper, we fabricated a dual-photo-initiator photopolymer by doping EY (Eosin Yellow) molecules into a TI (Titanocene, Irgacure 784@BASF) dispersed PMMA (poly-[methyl methacrylate]) substrate system, with the aim of promoting the diffusion and polymerization processes in volume holographic storage. The two-wave interference system is adopted to record a permanent grating structure in our materials. The temporal diffraction variations of photopolymerization (during the interference exposure) and dark diffusion (after the interference exposure) processes have been investigated and analyzed. Aiming to analyze the influence of EY doping ratios on holographic performances, some key parameters were examined in the experiment. We first measured the temporal evolution of diffraction efficiency, then an exponential fitting was adopted to obtain the response time. Finally, the angular selectivity was evaluated by the Bragg condition after holographic recording. Also, the temporal evolution of each component is described by the nonlocal polymerization-driven diffusion model with a dual-photo-initiator composition, theoretically. Furthermore, we experimentally achieved the holographic grating enhancement in both the dark diffusion and photopolymerization processes by doping appropriate EY concentrations, respectively. This work provides a foundation for the acceptability of TI&EY/PMMA polymers in further holographic storage research.

Enhanced trapping properties induced by strong LSPR-exciton coupling in plasmonic tweezers.

Plasmonic tweezers break the diffraction limit and enable trap the deep-subwavelength particles. However, the innate scattering properties and the photothermal effect of metal nanoparticles pose challenges to their effective trapping and the non-damaging trapping of biomolecules. In this study, we investigate the enhanced trapping properties induced by strong coupling between localized surface plasmon resonances (LSPR) and excitons in plasmonic tweezers. The LSPR-exciton strong coupling exhibits an anticrossing behavior in dispersion curves with a markable Rabi splitting of 196 meV. Plasmonic trapping forces on excitons experience a significant increase within this strong coupling system due to higher longitudinal enhancement of electric field enhancement, which enables efficient particle trapping using lower laser power and minimizes ohmic heat generation. Moreover, leveraging strong coupling effects allows the successful trapping of a 50 nm Au particle coated with J-aggregates, overcoming previous limitations associated with scattering characteristics and smaller size that hindered effective metal nanoparticle manipulation. These findings open up new possibilities for the nondestructive trapping of biomolecules and metal nanoparticles across various applications.

LSPR Tunable Ag@PDMS SERS Substrate for High Sensitivity and Uniformity Detection of Dye Molecules.

At present, the use of efficient and cost-effective methods to construct plasmonic surface-enhanced Raman scattering (SERS) substrates of high sensitivity, uniformity and reproducibility is still crucial to satisfy the practical application of SERS technology. In this paper, a localized surface plasmonic resonance (LSPR) tunable flexible Ag@PDMS substrate was successfully constructed by the low-cost bio-template-stripping method and magnetron sputtering technology. The theory proves that the local electromagnetic field enhancement and "hot spot" distribution is adjustable by modifying the size of the optical cavity unit in the periodicity nanocavity array structure. Experimentally, using rhodamine 6G (R6G) as the target analyte, the SERS performance of optimal Ag@PDMS substrate (Ag film thickness for 315 nm) was researched in detail, which the minimum detection limit was 10-11 M and the enhancement factor was calculated as 8.03 × 108, indicating its high sensitivity. The relative standard deviation (RSD) was calculated as 10.38%, showing that the prepared substrate had excellent electromagnetic field enhancement uniformity. At last, the trace detection of Crystal violet (CV, LOD = 10-9 M) and the simultaneous detection of three common dyes (R6G, CV and Methylene blue (MB) mixture) were also realized. This result suggests that the SERS substrate has a good application prospect in the quantitative and qualitative detection of dye molecules.

Genomic insights into the evolutionary history and diversification of bulb traits in garlic.

BACKGROUND: Garlic is an entirely sterile crop with important value as a vegetable, condiment, and medicine. However, the evolutionary history of garlic remains largely unknown. RESULTS: Here we report a comprehensive map of garlic genomic variation, consisting of amazingly 129.4 million variations. Evolutionary analysis indicates that the garlic population diverged at least 100,000 years ago, and the two groups cultivated in China were domesticated from two independent routes. Consequently, 15.0 and 17.5% of genes underwent an expression change in two cultivated groups, causing a reshaping of their transcriptomic architecture. Furthermore, we find independent domestication leads to few overlaps of deleterious substitutions in these two groups due to separate accumulation and selection-based removal. By analysis of selective sweeps, genome-wide trait associations and associated transcriptomic analysis, we uncover differential selections for the bulb traits in these two garlic groups during their domestication. CONCLUSIONS: This study provides valuable resources for garlic genomics-based breeding, and comprehensive insights into the evolutionary history of this clonal-propagated crop.

Enhancedd-wave pairing in the two-dimensional Hubbard model with periodically modulated hopping amplitudes.

Utilizing determinant quantum Monte Carlo algorithm, the evolution of thed-wave pairing in the Hubbard model on the square lattice tuned by the periodically modulated hopping amplitudes is studied. The hopping amplitudes are homogeneous in thexˆ-direction, while in theyˆ-direction the hopping amplitudes are modulated with periodP, wherety=t+dt,ty'=t-(P-1)dt, and the modulation periodPequals 2, 3 and 4 lattice spacings. The latter two modulation periods are motivated by the observation of period-3 and period-4 stripe order in cuprate superconductors. For all the periodsP, we find that the modulated hopping inhomogeneity enhances thed-wave pairing and an optimal inhomogeneity exists.

Numerical study on a random plasmonic laser in the metal-insulator-metal structure.

This Letter proposes a random plasmonic laser in the metal-insulator-metal (MIM) structure, in which the dielectric core with gain is dispersed with circular dielectric nanoscatterers. The numerical results from finite-difference time-domain simulation indicate that scattering by the randomly distributed dielectric nanoscatterers in the MIM waveguide provides feedback to the random laser with surface plasmon. The design bypasses the requirement of a distributed feedback structure for the plasmonic waveguide-based nanolasers, which is challenging and expensive in fabrication. Additionally, the MIM structure makes this type of random laser easily applicable to nanoscale integrated photonic devices and circuits.

Spontaneous n-Doping in Growing Monolayer MoS2 by Alkali Metal Compound-Promoted CVD.

Monolayer MoS2 has emerged as one of the most promising candidate materials for future semiconductor devices because of its fascinating physical properties and optoelectronic performance. Recently, the utilization of alkali metal compounds as promoters in CVD growth has been demonstrated to be a facile strategy for growing monolayer MoS2 and other 2D TMDs with large domain sizes. In this work, we systematically investigated the residues derived from alkali metal compounds and the spontaneous n-doping effect on monolayer MoS2 in alkali metal compound-promoted CVD growth. When using NaOH and other alkali metal compounds as promoters, it is found that the Raman peak of the A1g mode red shifted with a broadening width and the PL intensity of the A peak decreased with a red shift, which was attributed to the spontaneous n-doping effect during growth. Moreover, the growth using varying amounts of NaOH promoter suggests that the n-doping level could be controlled by the amount of promoter. X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary-ion mass spectroscopy (TOF-SIMS) showed the existence of cation-derived residues in the form of a Na-O cluster physiosorbed on top of monolayer MoS2, which was also confirmed by the transfer experiment. The NaOH treatment experiment and density functional theory (DFT) calculations demonstrate that sodium hydroxide clusters, which could be converted from a combination of Na-O clusters and water vapor, could produce an n-doping effect on monolayer MoS2. This study provides a facile route to controllably grow monolayer 2D materials with a desired doping level without further treatment.

Distinct ultrafast carrier dynamics of α-In2Se3 and ß-In2Se3: contributions from band filling and bandgap renormalization.

As an intrigued layered 2D semiconductor material, indium selenide (In2Se3) has attracted widespread attention due to its excellent properties. So far, the carrier dynamics of α-In2Se3 and ß-In2Se3 are still lacking a comprehensive understanding, which is essential to enhancing the performance of In2Se3-based optoelectronic devices. In this study, we explored the ultrafast carrier dynamics in thin α-In2Se3 and ß-In2Se3via transient absorption microscopy. For α-In2Se3 with a narrower bandgap, band filling and bandgap renormalization jointly governed the time evolution of the differential reflectivity signal, whose magnitude and sign at different delays were determined by the weights between the band filling and bandgap renormalization, depending on the carrier density. For ß-In2Se3, whose bandgap is close to the probe photon energy, only positive differential reflectivity was detected, which was attributed to strong band filling effect. In both materials, the lifetime decreased and the relative amplitude of the Auger process increased, when the pump fluence was increased. These findings could provide further insights into the optical and optoelectronic properties of In2Se3-based devices.

Reversible photoluminescence modulation of monolayer MoS2 on a ferroelectric substrate by light irradiation and thermal annealing.

Monolayer semiconducting two-dimensional (2D) materials are strongly emerging materials for exploring the spin-valley coupling effect and fabricating novel optoelectronic devices due to their unique structural symmetry and band structures. Due to their atomic thickness, their excitonic optical response is highly sensitive to the dielectric environment. In this work, we present a novel approach to reversibly modulate the optical properties of monolayer molybdenum disulfide (MoS2) via changing the dielectric properties of the substrate by laser irradiation and thermal annealing. We chose LiNbO3 as the substrate and recorded the PL spectra of monolayer MoS2 on LiNbO3 substrates with positive (P+) and negative (P-) ferroelectric polarities. A distinct PL intensity of the A peak was observed due to opposite doping by surface charges. Under light irradiation, the PL intensity of monolayer MoS2 on P+ Fe2O3-doped LiNbO3 gradually decreased with time due to the reduction of intrinsic p-doping, which originated from the drift of photo-excited electrons under a spontaneous polarization field and accumulation on the surface. The PL intensity was found to be restored by thermal annealing which could erase the charge redistribution. This study provides a strategy to reversibly modulate the optical properties of monolayer 2D materials on top of ferroelectric materials.

Holographic Grating Enhancement of TI/PMMA Polymers in the Dark Diffusion Process.

The dark diffusion enhancement process (DDEP) caused by photopolymerization during the pre-exposure of TI/PMMA (titanocene dispersed methyl methacrylate matrix) polymers was theoretically analyzed and experimentally investigated, revealing the holographic grating enhancement of TI/PMMA polymers in the post-exposure process without additional operations. The diffusion of photo-initiators and photoproducts dominated the grating enhancement process after exposure. We adopted two pre-exposure methods, long-time (second level) and short-time (millisecond level) laser exposure, at 532 nm, to investigate the DDEP during the post-exposure process. A five-fold enhancement in grating strength was achieved in consecutive long-time pre-exposures, while a two-fold grating development was examined after short-time exposure. Additionally, the exposure durations and repetition rates influenced the grating increment of the DDEP. This study provided a basis for the feasibility of holographic application in TI/PMMA photopolymers via the dark diffusion effect.

Quantum Monte Carlo study of the Hubbard model with next-nearest-neighbor hopping t': pairing and magnetism.

Using the finite-temperature determinant quantum Monte Carlo (DQMC) algorithm, we study the pairing symmetries of the Hubbard Hamiltonian with next-nearest-neighbor (NNN) hopping t' on square lattices. By varying the value of t', we find that the d-wave pairing is suppressed by the onset of t', while the p + ip-wave pairing tends to emerge for low electron density and t' around -0.7. Together with the calculation of the anti-ferromagnetic and ferromagnetic spin correlation function, we explore the relationship between anti-ferromagnetic order and the d-wave pairing symmetry, and the relationship between ferromagnetic order and the p + ip-wave pairing symmetry. Our results may be useful for the exploration of the mechanism of the electron pairing symmetries, and for the realization of the exotic p + ip-wave superconductivity.

Electrically tunable polarization of random lasing from dye-doped nematic liquid crystals.

Tunable polarizing direction of random lasing emission by an applied electric field which radiated from the lateral end face of homogeneously aligned, dye-doped nematic liquid crystal (NLC) cell was demonstrated for the first time, to the best of our knowledge. The lasing emission was partially polarized in the direction along the director of the NLC without the applied electric field. By tuning the applied electric field, the NLC director could be rotated to arbitrary direction from homogeneous to homeotropic alignment, resulting in the polarizing direction of lasing emission to any direction from parallel to perpendicular to the substrate surface in the end face.

A Chromosome-Level Genome Assembly of Garlic (Allium sativum) Provides Insights into Genome Evolution and Allicin Biosynthesis.

Garlic, an economically important vegetable, spice, and medicinal crop, produces highly enlarged bulbs and unique organosulfur compounds. Here, we report a chromosome-level genome assembly for garlic, with a total size of approximately 16.24 Gb, as well as the annotation of 57 561 predicted protein-coding genes, making garlic the first Allium species with a sequenced genome. Analysis of this garlic genome assembly reveals a recent burst of transposable elements, explaining the substantial expansion of the garlic genome. We examined the evolution of certain genes associated with the biosynthesis of allicin and inulin neoseries-type fructans, and provided new insights into the biosynthesis of these two compounds. Furthermore, a large-scale transcriptome was produced to characterize the expression patterns of garlic genes in different tissues and at various growth stages of enlarged bulbs. The reference genome and large-scale transcriptome data generated in this study provide valuable new resources for research on garlic biology and breeding.

Impact of the pitch angle on the spin Hall effect of light weak measurement.

The spin Hall effect of light (SHEL), as a photonic analogue of the spin Hall effect, has been widely studied for manipulating spin-polarized photons and precision metrology. In this work, a physical model is established to reveal the impact of the interface pitch angle on the SHEL accompanied by the Imbert-Fedorov angular shift simultaneously. Then, a modified weak measurement technique is proposed in this case to amplify the spin shift experimentally, and the results agree well with the theoretical prediction. Interestingly, the amplified transverse shift is quite sensitive to the variation of the interface pitch angle, and the performance provides a simple and effective method for precise pitch angle sensing with a minimum observable angle of 6.6 × 10-5°.

Differential expression of microRNAs in tomato leaves treated with different light qualities.

BACKGROUND: Light is the main source of energy and, as such, is one of the most important environmental factors for plant growth, morphogenesis, and other physiological responses. MicroRNAs (miRNAs) are endogenous non-coding RNAs that contain 21-24 nucleotides (nt) and play important roles in plant growth and development as well as stress responses. However, the role of miRNAs in the light response is less studied. We used tomato seedlings that were cultured in red light then transferred to blue light for 2 min to identify miRNAs related to light response by high-throughput sequencing. RESULTS: A total of 108 known miRNAs and 141 predicted novel miRNAs were identified in leaf samples from tomato leaves treated with the different light qualities. Among them, 15 known and 5 predicted novel miRNAs were differentially expressed after blue light treatment compared with the control (red light treatment). KEGG enrichment analysis showed that significantly enriched pathways included zeatin biosynthesis (ko00908), homologous recombination (ko03440), and plant hormone signal transduction (ko04075). Zeatin biosynthesis and plant hormone signal transduction are related to plant hormones, indicating that plant hormones play important roles in the light response. CONCLUSION: Our results provide a theoretical basis for further understanding the role of miRNAs in the light response of plants.

Holographic response characteristics influenced by an absorptive diffusion polymerization model in bulk TI/PMMAs.

Dynamic formation of a volume holographic grating is mainly caused by the diffusion polymerization of a photoinitiator in TI/poly-(methyl methacrylates) (PMMAs). Here, we consider the time-dependent absorption coefficient in this material to establish an absorption modulated diffusion polymerization model. An experimental and theoretical investigation in TI/PMMAs with different sample thicknesses (1-3 mm) is presented. It is indicated that the thickness can regulate the holographic sensitivity and constancy in TI/PMMAs. Furthermore, we also examined the dark diffusion process, multiplexed gratings recording, pre-exposure holographic enhancement, and long-term full exposure in TI/PMMAs with different thicknesses to analyze their holographic sensitivity and constancy. It is predicted that, in general, the absorption characteristics in TI/PMMA can be further affected by changing its thickness, thus it is able to satisfy different requirements in high-density holographic memories.

Porous Molybdenum Carbide Nanostructures Synthesized on Carbon Cloth by CVD for Efficient Hydrogen Production.

Molybdenum carbide (Mo2 C) is a promising noble-metal-free electrocatalyst for the hydrogen evolution reaction (HER), due to its structural and electronic merits, such as high conductivity, metallic band states and wide pH applicability. Here, a simple CVD process was developed for synthesis of a Mo2 C on carbon cloth (Mo2 C@CC) electrode with carbon cloth as carbon source and MoO3 as the Mo precursor. XRD, Raman, XPS and SEM results of Mo2 C@CC with different amounts of MoO3 and growth temperatures suggested a two-step synthetic mechanism, and porous Mo2 C nanostructures were obtained on carbon cloth with 50 mg MoO3 at 850 °C (Mo2 C-850(50)). With the merits of unique porous nanostructures, a low overpotential of 72 mV at current density of 10 mA cm-2 and a small Tafel slope of 52.8 mV dec-1 was achieved for Mo2 C-850(50) in 1.0 m KOH. The dual role of carbon cloth as electrode and carbon source resulted into intimate adhesion of Mo2 C on carbon cloth, offering fast electron transfer at the interface. Cyclic voltammetry measurements for 5000 cycles revealed that Mo2 C@CC had excellent electrochemical stability. This work provides a novel strategy for synthesizing Mo2 C and other efficient carbide electrocatalysts for HER and other applications, such as supercapacitors and lithium-ion batteries.

High efficiency active wavefront manipulation of spin photonics based on a graphene metasurface.

Metasurfaces have been widely studied for manipulating light fields. In this work, a novel metasurface element is achieved with a high circular polarization amplitude conversion efficiency of 88.5% that creates an opposite phase shift ranging from -180° to 180° between incidence and reflection for different spin components. By arranging the elements according to different requirements, spin-dependent reflection, focusing and scattering are demonstrated. It is also demonstrated that tuning of the Fermi energy is an viable way to active control the circular polarization conversion efficiency and expand the applicable bandwidth. The results open a new route for modifying and designing the wavefront of circular polarized light.