Manipulation Of Nanoparticles Research Articles

Optical Manipulation of Lanthanide-Doped Nanoparticles: How to Overcome Their Limitations.

Since Ashkin's pioneering work, optical tweezers have become an essential tool to immobilize and manipulate microscale and nanoscale objects. The use of optical tweezers is key for a variety of applications, including single-molecule spectroscopy, colloidal dynamics, tailored particle assembly, protein isolation, high-resolution surface studies, controlled investigation of biological processes, and surface-enhanced spectroscopy. In recent years, optical trapping of individual sub-100-nm objects has got the attention of the scientific community. In particular, the three-dimensional manipulation of single lanthanide-doped luminescent nanoparticles is of great interest due to the sensitivity of their luminescent properties to environmental conditions. Nevertheless, it is really challenging to trap and manipulate single lanthanide-doped nanoparticles due to the weak optical forces achieved with conventional optical trapping strategies. This limitation is caused, firstly, by the diffraction limit in the focusing of the trapping light and, secondly, by the Brownian motion of the trapped object. In this work, we summarize recent experimental approaches to increase the optical forces in the manipulation of lanthanide-doped nanoparticles, focusing our attention on their surface modification and providing a critical review of the state of the art and future prospects.

Studying and simulation of ellipsoidal contact models for application in AFM nano manipulation

Four contact models including Hertz, Jamari, Jeng-Wang and Weng-Tang-Zhou-Zhu were considered. To verify the results of contact mechanics, the indentation depth has been compared with spherical geometry. According to the obtained results, by comparing the spherical and elliptical geometries, the indentation depth for spherical geometry is higher than for the ellipsoidal geometry, due to the existence of eccentricity in elliptical contact models which does not exist in spherical geometry. Among the models, the Jeng-Wang and Weng-Tang-Zhou-Zhu are models that are based on the contact of a particle with the substrate. Based on the existing experimental work, Jeng-Wang is the most suitable model for being applied in particle-substrate contact point. The Hertz model has been developed from crowned cylinder equations in order to be implemented for ellipsoidal geometry, moreover the Jamari model investigates two ellipses in contact with each other. By comparing Jeng-Wang and Weng-Tang-Zhou-Zhu models it is obvious that Jeng-Wang has the highest indentation depth while for the Weng-Tang-Zhou-Zhu model it is the lowest. These trends happen for two contact points. Also four materials are compared, among which graphite and chromium have the highest and the lowest indentation depths, respectively. Finally based on the obtained results Jeng-Wang and Jamari are the most suitable contact models that can be implemented in the manipulation of ellipsoidal nanoparticles.

Tailored optical propulsion forces for controlled transport of resonant gold nanoparticles and associated thermal convective fluid flows.

Noble metal nanoparticles illuminated at their plasmonic resonance wavelength turn into heat nanosources. This phenomenon has prompted the development of numerous applications in science and technology. Simultaneous optical manipulation of such resonant nanoparticles could certainly extend the functionality and potential applications of optothermal tools. In this article, we experimentally demonstrate optical transport of single and multiple resonant nanoparticles (colloidal gold spheres of radius 200 nm) directed by tailored transverse phase-gradient forces propelling them around a 2D optical trap. We show how the phase-gradient force can be designed to efficiently change the speed of the nanoparticles. We have found that multiple hot nanoparticles assemble in the form of a quasi-stable group whose motion around the laser trap is also controlled by such optical propulsion forces. This assembly experiences a significant increase in the local temperature, which creates an optothermal convective fluid flow dragging tracer particles into the assembly. Thus, the created assembly is a moving heat source controlled by the propulsion force, enabling indirect control of fluid flows as a micro-optofluidic tool. The existence of these flows, probably caused by the temperature-induced Marangoni effect at the liquid water/superheated water interface, is confirmed by tracking free tracer particles migrating towards the assembly. We propose a straightforward method to control the assembly size, and therefore its temperature, by using a nonuniform optical propelling force that induces the splitting or merging of the group of nanoparticles. We envision further development of microscale optofluidic tools based on these achievements.

Helicity maximization below the diffraction limit

Optimally-chiral electromagnetic fields with maximized helicity density, recently introduced in [1], enable chirality characterization of optically small nanoparticles. Here, we demonstrate a technique to obtain optimally-chiral nearfields that leads to the maximization of helicity density, under the constraint of constant energy density, beyond the diffraction limit. We show how optimally-chiral illumination induces balanced electric and magnetic dipole moments in an achiral dielectric nanoantenna which leads to generating optimally-chiral scattered and total nearfield. In particular, we explore helicity and energy densities in nearfield of a spherical dielectric nanoantenna illuminated by an optimally-chiral combination of azimuthally and radially polarized beams that generates parallel induced electric and magnetic dipole moments that in turn also generate optimally-chiral scattered field with the same handedness of the incident field. The application of helicity maximization to nearfields results in helicity enhancement at nanoscale which is of great advantage in the detection of nanoscale chiral samples, microscopy, and optical manipulation of chiral nanoparticles.

Subwavelength generation of nondiffracting structured light beams

Nondiffracting light beams have been attracting considerable attention for their various applications in both classical and quantum optics. Whereas substantial investigations on generation of the nondiffracting beams were made, their lateral dimension is much larger than optical wavelength. Here we present both theoretically and experimentally a study of the generation of nondiffracting light beams at deep-subwavelength scale. The highly localized light field is a result of in-phase interference of high-spatial-frequency waves generated by optical sharp-edge diffraction with a circular thin film. It is shown that the generated beam can maintain its spot size below the optical diffraction limit for a distance of up to considerable Rayleigh range. Moreover, the topological structure of both the phase and polarization of a light beam is found to be preserved when it passes through the diffractive configuration, which enables generating nondiffracting vortex beams as well as transversely polarized vector beams at deep-subwavelength scale. This work opens a new avenue to manipulate higher-order vector vortex beams at subwavelength scale and may find intriguing applications in subwavelength optics, e.g., in superresolution imaging and nanoparticle manipulation.

Carboxymethyl cellulose supported green synthetic features of gold nanoparticles: Antioxidant, cell viability, and antibacterial effectiveness

Gold nanoparticles (AuNPs) are widely used in the diagnosis and treatment of diseases owing to their environmental friendliness and controllability due to their compatibility and high potency in drug delivery. Here, AuNPs were prepared from carboxymethyl cellulose (CMC) and showed an extensive absorption peak at 528 nm owing to the characterized Plasmon Surface Resonance. TEM measurement affirms that the Au particles had spherical shapes accompanied by a uniform distribution and a size of approximately 12-20 nm. Otherwise, SEM images showed that the AuNPs were configured in agglomerated spherical shapes and the crystalline phase was evident from SAED images and spikes in the XRD model. Vigorous antioxidant was tested using the DPPH scavenger analysis and the produced maximum trapping capacity (241.1 ± 13.22 mg/g) was reached at an AuNPs content of 106.25 mg/mL. The ratio of viable cells for AuNPs by HEK 293 T cell lines was reduced to 75.1 ± 3.8% at an approximated concentration of 500 μg / mL. Besides, the antibacterial potency was examined after one day of exposure to (E. coli and P. aeruginosa) and (S. aureus and B. subtilis). AuNPs were toxic against all selected bacteria. P. aeruginosa was the most susceptible bacterium to AuNPs with maximum inhibition zones of 50% whereas B. subtilis at 2 mg/L concentration of AuNPs takes the lowest percentages of inhibition zone with 30% compared to 25% for antibiotic standard. These extraordinary behaviors of AuNPs exhibits the manipulation of nanoparticles is highly recommended for universal use in the treatment of skin and wounds.

All-screen-printed graphite sensors integrating permanent bonded magnets. Fabrication, characterization and analytical utility

Electrochemical magneto assays have been extremely popular thanks to the facile manipulation of magnetic nanoparticles (MNPs) by a magnetic field. To this end, various related accessories, such as magnetic electrode shafts, electrochemical cells integrating (electro)magnets, magnetic stickers etc. have been developed aiming to attract MNPs on the electrode surface. Herein, we introduce for the first time screen-printed electrodes (SPEs) coupled with screen-printed permanent bonded magnets as a compact, portable, cheap and disposable alternative to aforementioned products. The bonded magnet (3 mm ∅, 56 ± 6 μm thick) consists of micro sized NdFeB particles dispersed in a thixotropic ink, and it was printed on a 100 μm thick polyester film, aligned with the electroactive surface of the SPE, which is printed on the other side of the substrate. Various parameters, such as the composition of the NdFeB/ink blend, the thickness and the pattern (compact or hole-engraved) of the printed magnet, and the thickness of the substrate were investigated by both experimental and theoretical studies. After the magnetization of the bonded magnet with a vibrating sample magnetometer at 2 T, a sufficient magnetic field strength was obtained. The performance is enhanced if a void round area is created in the center of the magnet to introduce a further area of strong field gradient. This pattern allows the development of stronger attracting forces to MNPs, higher MNPs loading and a better distribution of them on the electrode surface. The effective electron transfer between Fe3O4 MNPs and the electrode surface is shown with the electrochemical conversion of surface confined Fe3O4 MNPs to Prussian blue electroactive moieties and the amperometric determination of hydrogen peroxide, while the ultrasensitive determination of riboflavin using Ag/Fe3O4 MNP modified magnet-SPEs is demonstrated.

Remote structuring of near-field landscapes.

The electromagnetic near field enables subwavelength applications such as near-field microscopy and nanoparticle manipulation. Present methods to structure the near field rely on optical antenna theory, involving nanostructures that locally convert propagating waves into confined near-field patterns. We developed a theory of remote rather than local near-field shaping, based on cascaded mode conversion and interference of counterpropagating guided waves with different propagation constants. We demonstrate how to structure at will the longitudinal and transverse variation of the near field, allowing for distributions beyond the conventional monotonic decay of the evanescent field. We provide an experimental realization that confirms our theory. Our method applies to fields with arbitrary polarization states and mode profiles, providing a path toward three-dimensional control of the near field.

Analogy between periodic patterns in thin smectic liquid crystal films and the intermediate state of superconductors

Spontaneous breaking of symmetry in liquid crystal (LC) films often reveals itself as a microscopic pattern of molecular alignment. In a smectic-A LC, the emergence of positional order at the transition from the nematic phase leads to periodic textures that can be used as optical microarrays, templates for soft lithography, and ordering matrices for the organization and manipulation of functional nanoparticles. While both 1d and 2d patterns have been obtained as a function of the LC film thickness and applied fields, the connection has not been made between pattern formation and the peculiar critical behavior of LCs at the nematic-smectic transition, still eluding a comprehensive theoretical explanation. In this article, we demonstrate that an intense bend distortion applied to the LC molecular director while cooling from the nematic phase produces a frustrated smectic phase with depressed transition temperature, and the characteristic 1d periodic texture previously observed in thin films and under applied electric fields. In light of De Gennes' analogy with the normal-superconductor transition of a metal, we identify the 1d texture as the equivalent of the intermediate state in type I superconductors. The bend distortion is analog to the magnetic field in metals and penetrates in the frustrated phase as an array of undercooled nematic domains, periodically intermixed with bend-free smectic-A domains. Our findings provide fundamental evidence for theories of the nematic-smectic transition, highlighting the deep connection between phase frustration and pattern formation, and perspectives on the design of functional smectic microarrays.

Manipulation Technique for Precise Transfer of Single Perovskite Nanoparticles.

In this article, we present the pick-and-place technique for the manipulation of single nanoparticles on non-conductive substrates using a tungsten tip irradiated by a focused electron beam from a scanning electron microscope. The developed technique allowed us to perform the precise transfer of single BaTiO3 nanoparticles from one substrate to another in order to carry out measurements of elastic light scattering as well as second harmonic generation. Also, we demonstrate a fabricated structure made by finely tuning the position of a BaTiO3 nanoparticle on top of a dielectric nanowaveguide deposited on a glass substrate. The presented technique is based on the electrostatic interaction between the sharp tungsten tip charged by the electron beam and the nanoscale object. A mechanism for nanoparticle transfer to a non-conductive substrate is proposed and the forces involved in the manipulation process are evaluated. The presented technique can be widely utilized for the fabrication of nanoscale structures on optically transparent non-conductive substrates, which presents a wide range of applications for nanophotonics.

Monolayer Conveyor for Stably Trapping and Transporting Sub‐1 nm Particles

AbstractEfficient manipulation of nanoparticles and single molecules has always been of great interest and potential in nanotechnology. However, many challenges still remain in effectively functionalizing structures for this purpose. In this work, taking advantage of graphene's Dirac plasmon for its extreme confinement and tunability, a monolayer conveyor along which the position of optical potential well can be dynamically controlled is theoretically proposed. It is shown that by tuning a single voltage, one can manipulate the resonance along the graphene nanoribbon by changing graphene's effective surface plasmons wavelength. A configuration of monolayer graphene conveyor is proposed and Langevin dynamics reveals that a prototypical nanoparticle (1 nm size) can be effectively confined and transported along the device with proper external bias voltage. Hence, this work successfully proposes a promising avenue toward reconfigurable nanomanipulation of sub‐1 nm nanoparticles, and goes beyond the current state‐of‐the‐art of optical micrometer/nanometer‐sized particles manipulation with optical tweezers and nanoplasmonic tweezers.

Smectic Defect Engineering Enabled by Programmable Photoalignment

AbstractTopological defects are vital for tailoring soft matter properties and inspiring remarkable applications. Arbitrary guiding and dynamic tuning of director distributions are highly pursued in defect engineering of liquid crystals. Till now, the orientation control of smectic defect walls remains a challenge. Here, photoalignment is adopted to preset the surface anchoring in order to guide smectic oily streaks. Flexible defect engineering such as deflecting, bending, and splaying is demonstrated. Based on their combination, more complicated defect arrays are realized in a predictable manner. After electric stimuli involved, new functions of tunability and rotatability are unlocked. This work brings new insights to soft matter architectures, and will upgrade the existing micromachines, nanoparticle manipulations and advanced photonic applications.

Dielectrophoretic borophene tweezer: Sub-10 mV nano-particle trapping

Impressive characteristics of the recently synthesized metallic borophene render it a promising two-dimensional (2D) material for a multitude of applications in nanotechnology. In this work, by employing a multiscale atom-to-tweezer methodology, the operation of borophene as electrode material in a dielectrophoretic (DEP) tweezer is carefully analyzed. According to the results, the proposed borophene-based DEP tweezer significantly enhances the electric field intensity gradient by at least 4 orders of magnitude, thereby surpassing the recently proposed graphene-based DEP tweezer in both short-range and long-range operating regimes. Furthermore, it is found that borophene pushes the limit of 2D-material-based DEP trapping to record-breakingly low voltages. The proposed borophene-based DEP tweezer is predicted to be capable of trapping sub-10-nm polystyrene beads by exerting voltages as low as 20 mV and capturing the herpes simplex virus type 1 (HSV-1) by applying a voltage of merely 2 mV, with nearly-100-percent spatial resolution. The results indicate that borophene-based DEP devices can realize ultimate control in the manipulation of nanoparticles.

Time evolution of photovoltaic fields generated by arbitrary light patterns in z-cut LiNbO3:Fe: application to optoelectronic nanoparticle manipulation.

The bulk photovoltaic effect is a phenomenon that generates high electric fields in certain ferroelectric crystals under illumination, as iron doped lithium niobate (LiNbO3:Fe). A variety of innovative applications of these electric fields require using of z-cut plates, in which the polar axis is normal to the larger crystal faces. However, the kinetics and distribution of the photovoltaic fields in this configuration have not been investigated in depth. In this work, the photovoltaic charge transport of z-cut configuration is studied through a complete finite element analysis. Light patterns commonly used for particle trapping applications are used to study the temporal evolution of the electric field developed by the crystal. Results show that photovoltaic currents perpendicular to the optical axis play a key role in the development of the final charge distribution. Moreover, there is a relevant, localized charge accumulation inside the crystal which is required to reach the saturation electric field in the whole illuminated volume. The role of crystal thickness and light absorption are analysed. It has been found that they are important to determine the time evolution of the process. The simulations are expected to be a key tool to analyse and improve photovoltaic optoelectronic tweezers.

Electromagnetic field of a relativistic electron vortex beam**Project supported by the National Natural Science Foundation of China (Grant Nos. 11574085, 91536218, and 11834003), the 111 Project, China (Grant No. B12024), the National Key Research and Development Program of China (Grant No. 2017YFA0304201), and the Innovation Program of Shanghai Municipal Education Commission, China (Grant No. 2019-01-07-00-05-E00079).

Electron vortex beams (EVBs) have potential applications in nanoscale magnetic probes of condensed matter and nanoparticle manipulation as well as radiation physics. Recently, a relativistic electron vortex beam (REVB) has been proposed [Phys. Rev. Lett. 107 174802 (2011)]. Compared with EVBs, except for orbital angular momentum, an REVB has intrinsic relativistic effect, i.e., spin angular momentum and spin–orbit coupling. We study the electromagnetic field of an REVB analytically. We show that the electromagnetic field can be separated into two parts, one is only related to orbital quantum number, and the other is related to spin–orbit coupling effect. Exploiting this separation property, the difference between the electromagnetic fields of the REVB in spin-up and spin-down states can be used as a demonstration of the relativistic quantum effect. The linear momentum and angular momentum of the generated electromagnetic field have been further studied and it is shown that the linear momentum is weakly dependent on the spin state; while the angular momentum is evidently dependent on the spin state and linearly increases with the topological charge of electron vortex beam. The electromagnetic and mechanical properties of the REVB could be useful for studying the interaction between REVBs and materials.

Dynamic polarization attractors of dissipative solitons from carbon nanotube mode-locked Er-doped laser

Abstract We report experimental observation of polarization attractors in the form of vector dissipative solitons from a carbon nanotube mode locked fiber laser. At a time scale of 14–14,000 roundtrips, the typical polarization locked vector solitons, and other appealing attractors are shown. In addition, we observe the vector dissipative solitons operated in dual-wavelength regime with central wavelength of 1533 and 1557 nm which can be related to a fixed point polarization attractor. The results unveiled complex oscillatory behavior of dissipative solitons in the polarization domain which may help understand laser physics, nonlinear optics. The demonstrated work may underpin a new type of high energy laser source leading to possible applications in nanoparticle manipulation, micromachining, spectroscopy etc.

Forced convection heat transfer and friction factor of water/bio-glycol mixture based TiO2-SiO2 nanofluids

The research on nanofluids as heat transfer fluid has been done for many years and the manipulation of nanoparticles kept evolving as time passes by. After an exceptional heat transfer performance enhancement was found in single nanofluids, combining two types of nanoparticles in a base fluid has garnered researcher’s attention all over the globe. The study on performance of heat transfer for a combination of two types of nanoparticle in a mixture of water and Bio-glycol has yet to be established; hence, the present study was conducted to investigate the heat transfer performance of TiO2-SiO2 nanofluids in 60:40 mixture of water and Bio-Glycol. The TiO2-SiO2 nanofluids was prepared by using the two-step method at three different particle concentration, namely 0.5%, 1.0% and 1.5%. Forced convection heat transfer experiment was carried out at bulk temperature 30°C and Reynolds number in the range of 1000 to 8000. A constant heat flux was supplied to the test section throughout the experiment. The Nusselt number of TiO2-SiO2 nanofluids was found at particle concentration 1.5%, 70.11% enhanced from the base fluid. The average enhancement of heat transfer coefficient for each particle concentration 0.5%, 1.0% and 1.5% are 40.3%, 63.4% and 70.3%, respectively. Heat transfer coefficient enhancement for 1.0% and 1.5% particle concentration almost similar at low concentration, however, as Reynolds number increase, the augmentation gap increases. The results of friction factor displayed a decrease trend with the increase of Reynolds number. While the friction factor of TiO2-SiO2 nanofluids insignificantly increased from the base fluid, the increment between particles concentration almost negligible.

Massively Multiplexed Submicron Particle Patterning in Acoustically Driven Oscillating Nanocavities.

Nanoacoustic fields are a promising method for particle actuation at the nanoscale, though THz frequencies are typically required to create nanoscale wavelengths. In this work, the generation of robust nanoscale force gradients is demonstrated using MHz driving frequencies via acoustic-structure interactions. A structured elastic layer at the interface between a microfluidic channel and a traveling surface acoustic wave (SAW) device results in submicron acoustic traps, each of which can trap individual submicron particles. The acoustically driven deformation of nanocavities gives rise to time-averaged acoustic fields which direct suspended particles toward, and trap them within, the nanocavities. The use of SAWs permits massively multiplexed particle manipulation with deterministic patterning at the single-particle level. In this work, 300 nm diameter particles are acoustically trapped in 500 nm diameter cavities using traveling SAWs with wavelengths in the range of 20-80 µm with one particle per cavity. On-demand generation of nanoscale acoustic force gradients has wide applications in nanoparticle manipulation, including bioparticle enrichment and enhanced catalytic reactions for industrial applications.

Method of optical manipulation of gold nanoparticles for surface-enhanced Raman scattering in a microcavity.

In this study, an optical manipulation and micro-surface-enhanced Raman scattering (microSERS) setup based on a microcavity was developed for efficient capture of gold nanoparticles using the photothermal effect. In addition, optical manipulation of gold nanoparticles and SERS signal detection were performed using only one laser. The results show that the SERS enhancement effect based on the microcavity was more than 20 times that based on a gold colloid solution. The laser power and velocity of nanoparticles exhibited a good linear relationship, and the velocity of nanoparticles decreased with decreasing radius r, which verifies the detriment of the radial thermophoresis in this study. This method can be used to quickly and efficiently drive metal nanoparticles and provides a promising approach for analysis of substances in the fields of chemistry and biology.

Complex Dynamics of Optical Solitons Interacting with Nanoparticles

In this Letter we further develop the proposed approach of optical manipulation based on the interactions of non-linear optical effects with nanoparticles. The interaction of the dissipative optical solitons with nanoparticles is studied numerically. It is shown that the attraction of the nanoparticles to the solitons can result in the formation of a stable bound state of the solitons and the nanoparticles. The collision of the solitons with different numbers of trapped particles is studied, and it is shown that the collision of the solitons can result in releasing or redistributing the nanoparticles between the solitons. It is demonstrated that the particle mediated interaction between the solitons can affect their dynamics significantly. The reported effects can be successfully used for optical manipulation of nanoparticles and pave a way for efficient control over their dynamics on nanoscale.