Suppression of damping in a diamagnetically levitated dielectric sphere via eddy currents and static charge reduction.

Diamagnetically levitated micro-nano oscillators play a crucial role in fundamental physics research and the advancement of high-precision sensors. Achieving high sensitivity in acceleration or force sensing is a fundamental requirement within these research domains. The primary limitation in achieving such sensitivity is thermal noise, which is directly proportional to the motion damping of the oscillator. Theoretical modeling suggests the presence of significant damping mechanisms induced by eddy currents. In this study, we validated the theoretical model by optimizing the structure of the magnet trap, confirming the impact of eddy currents on the damping of the oscillators. Additionally, we observed another type of damping caused by static charge in moving levitated dielectrics. Subsequently, we proposed an innovative theoretical model to explain this phenomenon and verified its validity during the charge neutralization process. Through these efforts, we successfully reduced the total damping from 1.6 mHz to 0.15 mHz, resulting in an order of magnitude improvement in performance. Our sensing system achieved the highest sensitivity of acceleration sensing in diamagnetically levitated submillimeter-scale dielectric to date, measuring 7.6±0.8)×10-10g/Hz. The exploration conducted in this study regarding the analysis and suppression of electromagnetic damping, along with associated thermal noise, holds significant promise for frontier research involving sensing with levitating dielectrics.

Stannate-Based Materials as Anodes in Lithium-Ion and Sodium-Ion Batteries: A Review.

Binary metal oxide stannate (M2SnO4; M = Zn, Mn, Co, etc.) structures, with their high theoretical capacity, superior lithium storage mechanism and suitable operating voltage, as well as their dual suitability for lithium-ion batteries (LIBs) and sodium-ion batteries (SIBs), are strong candidates for next-generation anode materials. However, the capacity deterioration caused by the severe volume expansion problem during the insertion/extraction of lithium or sodium ions during cycling of M2SnO4-based anode materials is difficult to avoid, which greatly affects their practical applications. Strategies often employed by researchers to address this problem include nanosizing the material size, designing suitable structures, doping with carbon materials and heteroatoms, metal-organic framework (MOF) derivation and constructing heterostructures. In this paper, the advantages and issues of M2SnO4-based materials are analyzed, and the strategies to solve the issues are discussed in order to promote the theoretical work and practical application of M2SnO4-based anode materials.

Corrigendum: Application of optical tweezers in cardiovascular research: More than just a measuring tool.

[This corrects the article DOI: 10.3389/fbioe.2022.947918.].

Application of optical tweezers in cardiovascular research: More than just a measuring tool.

Recent advances in the field of optical tweezer technology have shown intriguing potential for applications in cardiovascular medicine, bringing this laboratory nanomechanical instrument into the spotlight of translational medicine. This article summarizes cardiovascular system findings generated using optical tweezers, including not only rigorous nanomechanical measurements but also multifunctional manipulation of biologically active molecules such as myosin and actin, of cells such as red blood cells and cardiomyocytes, of subcellular organelles, and of microvessels in vivo. The implications of these findings in the diagnosis and treatment of diseases, as well as potential perspectives that could also benefit from this tool, are also discussed.

Fast size estimation of single-levitated nanoparticles in a vacuum optomechanical system.

Optical trapping of single nanoparticles in vacuum has various applications in both precise measurements and fundamental physics. However, to date, the number and size of randomly loaded nanoparticles in an optical trap is difficult to determine unless in vacuum. In this Letter, an efficient method for nanoparticle size estimation in an optical tweezer system before the evacuation of air was proposed and demonstrated experimentally, using scattering light from levitated particles. The particle radii deduced from the scattering light power in our proposal and from the kinetic theory of particles in gas match well (with the differences of less than 10%). For sample particles with radii ranging within 50-100 nm, we also provide a preselection rule based on this method, where over half of the trapped particles are verified as single particles. Such a particle analysis method is applicable also for the size estimation of levitated diamond particles, gold particles, and other plasmonic particles and can be applied to discovering novel scattering effects.

Study on synthesis and fluorescence property of rhodamine-naphthalene conjugate.

In this study, a novel ligand (HL) consisting of 2-methyl quinoline-4-carboxylic acid, rhodamine and naphthalene moiety, was designed and synthesized, it could be developed a ratiometric fluorescent sensor for selective detection of Al3+ via fluorescence resonance energy transfer (FRET) from naphthalimide moiety to rhodamine moiety. The addition of Al3+ trigger the significant fluorescence enhancement of HL at 550 nm at the expense of the fluorescent emission of HL centered at 524 nm.

Dynamic analysis and rotation experiment of an optical-trapped microsphere in air.

A dual-fiber optical trap system to trap and rotate a borosilicate microsphere has been proposed and experimentally demonstrated. The trapping system can be used as a probe to measure environmental parameters, such as torque, force, and viscosity of the surrounding medium. Under various conditions with different fiber misalignments, optical power, and fiber separation, the trapped sphere will exhibit three motion profiles including random oscillation, round rotation, and abnormal rotation. The power spectrum analysis method is used to measure rotation rates up to 385 Hz, which can be further increased by increasing laser power. In addition, simulation and experiment show consistent results in rotation rates and motion trajectory, which verifies the validity and accuracy of dynamic analysis.

Two fluorescein-based chemosensors for the fast detection of 2,4,6-trinitrophenol (TNP) in water.

Two fluorescein-based chemosensors have been developed. They exhibited rapid and selective detection of 2,4,6-trinitrophenol (TNP) via fluorescence quenching both in ethanol and water solution when excited by visible light.

A fluorescein-based chemosensor for relay fluorescence recognition of Cu(ii) ions and biothiols in water and its applications to a molecular logic gate and living cell imaging.

Relay recognition of copper(ii) ions and biothiols via a fluorescence "on-off-on" cascade was designed and realized as a new sequential combination of cations and small molecules. Probe 1 bearing a fluorescein skeleton was thus synthesized, which performed well in 100% HEPES buffer (pH = 7.0) solution, as a highly sensitive, selective fluorescence sensor for Cu2+. The limit of detection (LOD, 0.017 ppm) was obtained, and this value is much lower than 1.3 ppm, allowed by US EPA. The 1 : 1 complex generated from fast sensing of Cu2+ when excited at 491 nm, showed good relay recognition for biothiols (i.e., Cys, Hcy and GSH with low detection limits of 0.12 µM, 0.036 µM and 0.024 µM, respectively) via remarkable fluorescence enhancement. The origin of this relay process was disclosed through ESI-MS and corresponding density functional theory (DFT) computations. Notably, probe 1 can be utilized for the construction of a molecular logic gate with the IMPLICATION function by using the above fluorescence changes. Moreover, this relay recognition was also applied to HepG2 cell imaging successfully.

Fluorescein-Based Chromogenic and Ratiometric Fluorescence Probe for Highly Selective Detection of Cysteine and Its Application in Bioimaging.

A dual mode fluorescent probe, which is based on an integration of fluorescein and coumarin fluorophores, was developed for the discrimination of Cys from Hcy and GSH. This probe (2) shows the advantage of quick reaction (5 min) with Cys, resulting in a strong fluorescence turn-on response when excited at 450 nm. Notably, it also demonstrates the ratiometric fluorescence property while excited by a shorter wavelength (332 nm). All of results suggest probe 2 has a high selectivity toward Cys even in the presence of other amino acids, cations and anions. The detection limit of Cys was calculated as 0.084 µM, which was much lower than the intracellular concentration. 1H NMR, MS and DFT calculation were used to reveal the detection mechanism further. Finally, this low cytotoxic probe was successfully applied in bioimaging within HepG2 cells.