Near-field Energy Transfer Research Articles

Ultrafast intraband Auger process in self-doped colloidal quantum dots

Summary Investigating the separate dynamics of electrons and holes has been challenging, although it is critical for the fundamental understanding of semiconducting nanomaterials. n-Type self-doped colloidal quantum dots (CQDs) with excess electrons occupying the low-lying state in the conduction band (CB) have attracted a great deal of attention because of not only their potential applications to infrared optoelectronics but also their intrinsic system that offers a platform for investigating electron dynamics without elusive contributions from holes in the valence band. Here, we show an unprecedented ultrafast intraband Auger process, electron relaxation between spin-orbit coupling states, and exciton-to-ligand vibrational energy transfer process that all occur exclusively in the CB of the self-doped β-HgS CQDs. The electron dynamics obtained by femtosecond mid-infrared spectroscopy will pave the way for further understanding of the blinking phenomenon, disproportionate charging in light-emitting diodes, and hot electron dynamics in higher quantum states coupled to surface states of CQDs.

Light-Controlled Near-Field Energy Transfer in Plasmonic Metasurface Coupled MoS2 Monolayer.

The energy transfer from plasmonic nanostructures to semiconductors has been extensively studied to enhance light-harvesting and tailor light-matter interactions. In this study, the efficient energy transfer from an Au metasurface to monolayered MoS2 within a near-field coupling regime is reported. The metasurface is designed and fabricated to demonstrate strong photoluminescence (PL) and cathodoluminescence (CL) emission spectra. In the coupled heterostructure of MoS2 with a metasurface, both the Raman shift and absorption spectral intensities of monolayered MoS2 are affected. The spectral profile and PL peak position can be tailored owing to the energy transfer between plasmonic nanostructures and semiconductors. This is confirmed by ultrafast lifetime measurement. A theoretical model of two coupled oscillators is proposed, where the expanded general solutions (EGS) of such a model result in a series of eigenvalues that correspond to the renormalization of energy levels in modulated MoS2. The model can predict the peak shift up to tens of nanometers in hybrid structures and hence provides an alternative method to describe energy transfer between metallic structures and two-dimensional (2D) semiconductors. A viable approach for studying light-matter interactions in 2D semiconductors via near-field energy transfer is presented, which may stimulate the applications of functional nanophotonic devices.

Nanoscale control of single molecule Förster resonance energy transfer by a scanning photonic nanoantenna

Abstract Förster Resonance Energy Transfer (FRET) is a widely applied technique in biology to accurately measure intra- and inter-molecular interactions at the nanometre scale. FRET is based on near-field energy transfer from an excited donor to a ground state acceptor emitter. Photonic nanoantennas have been shown to modify the rate, efficiency and extent of FRET, a process that is highly dependent on the near-field gradient of the antenna field as felt by the emitters, and thus, on their relative distance. However, most of the experiments reported to date focus on fixed antennas where the emitters are either immobilized or diffusing in solution, so that the distance between the antenna and the emitters cannot be manipulated. Here, we use scanning photonic nanoantenna probes to directly modulate the FRET efficiency between individual FRET pairs with an unprecedented nanometric lateral precision of 2 nm on the antenna position. We find that the antenna acts as an independent acceptor element, competing with the FRET pair acceptor. We directly map the competition between FRET and donor-antenna transfer as a function of the relative position between the antenna and the FRET donor-acceptor pair. The experimental data are well-described by FDTD simulations, confirming that the modulation of FRET efficiency is due to the spatially dependent coupling of the single FRET pair to the photonic antenna.

Screening of the quantum dot Förster coupling at small distances.

We study the near-field energy transfer rates between two finite size quantum dot disks, generalizing the result of Förster coupling between two point dipoles. In particular, we derive analytical results for the envelope of the electronic wave function for model potentials at the boundaries of quantum dot disks and demonstrate how the Förster interaction is screened as the size of the dots becomes comparable to the dot-dot separation.

Investigation of heat transfer modes in plasmonic nanoparticles

There has been much recent interest in understanding heat transfer in nanoparticle packings in nanotechnology such as emerging photonics applications. In this paper, we analyze heat transfer between two plasmonic nanoparticles in finite contact and suspended in air to delineate the dominant modes of heat transfer. We have previously investigated the heat transfer analysis of laser heating in a nanoparticle packing such that interfacial thermal conductance between the nanoparticle packings in contact and the predicted average nanoparticle packing temperature matches with the observations of laser sintering temperature well when GIC is about 20 (MW/m2K). When GIC is less than 20 (MW/m2K), the primary pathway for heat transfer is that across the particle-air-particle interface. Thermal transport in these assemblies is subject to electromagnetic field enhancements due to near-field energy transfer; however, we show that radiation heat transfer between the nanoparticles is not a significant heat transport mode. Sub-continuum thermal effects are found to strongly retard overall thermal transport between the particles through the air pathway.

Bisphosphonate Polymeric Ligands on Inorganic Nanoparticles

The design and synthesis of anchoring groups of bisphosphonate-amine (BP-NH2) are presented for the preparation of polymeric ligands on luminescent nanoparticles (NPs). Such ligands serve as overcoatings to impart colloidal stability and conjugation chemistries. These ligands were placed on quantum dots (QDs), gold nanoparticles (AuNPs), gold nanourchins (AuNUs), and iron oxide NPs (IONPs). The BP-NH2 anchoring groups were coupled to copolymers comprised of amine-terminated poly(ethylene glycol) (NH2-PEG) and poly(isobutylene-alt-maleic anhydride) (PIMA) units via aza-Michael coupling. In all cases, polymer synthesis was done as a one-pot reaction of amine-containing precursors with PIMA. The BP-NH2 anchoring groups provided similar colloidal stability as monophosphonate-amine (MP-NH2) anchoring groups on AuNPs. QDs were found to be more optically stable when coated with BP-NH2 vs MP-NH2 functionalized polymers in high-ionic-strength buffers, such as 5× phosphate-buffered saline (PBS). The versatility of BP–PIMA–PEG as universal NP overcoating chemistry was demonstrated through successful application onto IONPs and AuNUs of various sizes (50, 60, 80, and 100 nm in diameter) via simple ligand exchange reactions. Polymers that were functionalized with azide groups were prepared as substrates suitable for copper-free click chemistry addition of alkyne dyes. Successful coupling of dyes to the azide-copolymer-coated nanoparticles was verified by spectroscopic investigations of near-field resonance energy transfer (RET) interactions. Thus, a series of surface coordinating polymers with affinity to multiple materials were synthesized that yielded nanoparticles exhibiting good colloidal stability and that were amenable to subsequent conjugation reactions.

Analisa Desain, Konsep, dan Karakteristik Sistem Transfer Daya Nirkabel

<p>In the current era of the industrial revolution 4.0, the need for time, labor, and cost efficiency is a basic requirement for human life, especially regarding electrical energy sources. The supply of commercial electricity is still using electricity cables to deliver electricity to the load. Therefore, one of the ways of sending or transferring electrical power that continues to be developed today is wireless electricity transfer. The wireless transfer of electric power has several advantages compared to the use of cables, which can increase the convenience in the use of electrical equipment and can reduce the amount of electronic waste. This research will study the techniques or methods of near-field wireless energy transfer systems, namely the inductive coupling method, the magnetic resonance coupling method and the capacitive coupling method. The results of this study propose an optimal modeling of wireless power transfer so that results and quality are better, taking into account the distance between the sender and receiver because the work efficiency of wireless power transfer decreases with respect to distance. And the signal transmission frequency is low for inductive coupling, while the resulting frequency will be high on magnetic resonance coupling and capacitive coupling.</p>

Giant near-field radiative heat transfer between ultrathin metallic films.

Understanding energy transfer via near-field thermal radiation is essential for applications such as near-field imaging, thermophotovoltaics and thermal circuit devices. Evanescent waves and photon tunneling are responsible for the near-field energy transfer. In bulk noble metals, however, surface plasmons do not contribute efficiently to the near-field energy transfer because of the mismatch of wavelength. In this paper, a giant near-field radiative heat transfer rate that is orders-of-magnitude greater than the blackbody limit between two ultrathin metallic films is demonstrated at nanoscale separations. Moreover, different physical origins for near-field thermal radiation transfer for thick and thin metallic films are clarified, and the radiative heat transfer enhancement in ultrathin metallic films is proved to come from the excitation of surface plasmons. Meanwhile, because of the inevitable high sheet resistance of ultrathin metal films, the heat transfer coefficient is 4600 times greater than the Planckian limit for the separation of 10 nm in ultrathin metallic films, which is the same order or even greater than that in other 2D materials with low carrier density. Our work shows that ultrathin metallic films are excellent materials for radiative heat transfer, which may find promising applications in thermal nano-devices and thermal engineering.

Auger Suppression in n-Type HgSe Colloidal Quantum Dots.

Transient infrared photoluminescence upconversion is used to study the exciton dynamics in small-gap HgSe colloidal quantum dots in the 2000-6500 cm-1 (0.25-0.80 eV) range. The intraband mid-infrared photoluminescence decays show absent or greatly reduced Auger relaxation of biexcitons, proposed as a generic feature of weakly n-type quantum dots due to the sparse density of states in the conduction band. The nonradiative relaxation of the intraband carriers is instead consistent with near-field energy transfer to molecular vibrations of the surface ligands. In contrast, the interband near-infrared photoluminescence decays exhibit the typical distinct exciton and biexciton lifetimes with Auger coefficients comparable to other similarly sized quantum dots. Also observed are spectral and dynamical evidence of fine structure in the intraband transitions consistent with spin-orbit splitting of the electron P levels, and the emergence of plasmonic resonances in large particles.

Metadevices with Potential Practical Applications.

Metamaterials are “new materials” with different superior physical properties, which have generated great interest and become popular in scientific research. Various designs and functional devices using metamaterials have formed a new academic world. The application concept of metamaterial is based on designing diverse physical structures that can break through the limitations of traditional optical materials and composites to achieve extraordinary material functions. Therefore, metadevices have been widely studied by the academic community recently. Using the properties of metamaterials, many functional metadevices have been well investigated and further optimized. In this article, different metamaterial structures with varying functions are reviewed, and their working mechanisms and applications are summarized, which are near-field energy transfer devices, metamaterial mirrors, metamaterial biosensors, and quantum-cascade detectors. The development of metamaterials indicates that new materials will become an important breakthrough point and building blocks for new research domains, and therefore they will trigger more practical and wide applications in the future.

Near-field energy transfer between nanoparticles modulated by coupled multipolar modes

The near-field energy transfer between dielectric nanoparticles by considering the full coupling between all the thermal electric fields is studied theoretically for the case of a dimer and a trimer. We show that coupled modes between nanoparticles open channels through which energy may be transferred, increasing the power exchanged more than one order of magnitude as compared with existing models. We discuss how the contribution from coupled modes changes as parameters of the system are varied for the case of a two- and three-particle system. It is done by developing a spectral representation formalism for the near field, where fluctuating multipolar moments are fully incorporated, allowing identification of the contribution of energy transfer of each coupled mode. This information can be used to understand and control the energy flux among nanoparticles.

Effect of particle size distribution on near-field thermal energy transfer within the nanoparticle packings

Nanoscale size effects give rise to near-field thermal considerations when heating nanoparticles under high laser power. We solve Maxwell’s equations in the frequency domain to analyze near-field thermal energy effects for three nanoparticle assemblies with different variances in particle sizes and show that heat dissipation generally decreases as the spread in nanoparticle sizes increases within the nanoparticle packing. For this study, log-normally distributed copper nanoparticle packings with a mean radius of 116 nm and three different standard deviations (12, 48, and 84 nm) were created by using a discrete element model in which a specified number of particles is generated. The nanoparticle packings in the simulation are created by randomly placing each nanoparticle into the packing domain with a random initial velocity and a position. The nanoparticles are then allowed to interact with each other under gravitational and weak van der Waals forces until they settle to form a stable packing configuration. A finite-difference frequency-domain analysis, which yields the electromagnetic field distribution, is then applied to the packing by solving Maxwell’s equations to obtain absorption, scattering, and extinction coefficients. This analysis is used to calculate the surface plasmon effects due to the electromagnetic coupling between the nanoparticles and the dielectric medium under the different distributions and show that different particle distributions can create different plasmonic effects in the packing domain, which results in nonlocal heat transport. Overall, this analysis helps to reveal how sintering quality can be enhanced by creating stronger laser–particle interactions for specific groups of nanoparticles.

Printed Spiral Resonator for Displacement-Tolerant Near-Field Wireless Energy Transfer

Synthesis between the printed spiral coil and the planar interdigital capacitor for near-field wireless energy transfer (WET) is proposed. The proposed amalgamated design is intentionally positioned under several displacements, namely, planar offsets at the z-axis as well as lateral offsets at both the xand y-axes to investigate tolerance capability. This is particularly crucial in practical circumstances, whereby a perfect alignment between primary and secondary resonators is not usually achieved unless with the integration of magnet plates to aid seamless position latching, otherwise complex adaptive matching circuits are needed to compensate for displacements. At a fixed axial transfer distance of 25 mm, the corresponding maximum simulated and measured transfer efficiency is 73.01% and 71.84%, respectively, under perfect alignment. Sustainable power transfer efficiency (PTE) is demonstrated during a 360° planar clockwise rotation with the step size of 45° and the measured variation ratio is 0.02 while the feasibility of preserving PTE until 0.6 quotients of lateral displacement and axial distance is validated when up to 15-mm lateral offsets occur either from x or y reference planes. It can thus be concluded that the printed spiral resonator proposed appears to be a good candidate to rectify planar and lateral displacements featuring simplicity and space-saving robust structure that necessitates only a minimized footprint, thus paving the way for adaptation in WET applications, such as consumer electronics and implanted medical devices.

Multi-quantum-well quantum dots with stable dual emission.

Multi-quantum-well quantum dots (MQW-QDs) with multiple emission peaks have been evaluated as promising single source emitters in the fabrication of high performance white LEDs. However, they still face a critical issue of color shift in practical applications, which is mainly attributed to the redistribution of the excitons between the adjacent wells under different excitation powers. Herein, we report sandwich structural MQW-QDs that provide highly stable dual emission. The study on the optical properties and exciton dynamics reveals that the thickness of the inner-barrier plays a crucial role in balancing the exciton distribution through regulating near-field energy transfer and light absorption between the adjacent wells. Meanwhile, the wells and the outer-barrier mainly influence the luminescence efficiency and the wavelength control of the dual emission peaks. The MQW-QDs with a minimum color shift versus excitation power are finally achieved by optimizing the structure parameters. A white LED based on the developed MQW-QDs exhibits a stable white light spectrum with high tolerance to the change of the excitation power, ensuring the advancement of the performance of MQW-QDs in lighting and display applications.

Prospects and applications of plasmon-exciton interactions in the near-field regime

Abstract Plasmonics is a rapidly developing field at the boundary of fundamental sciences and device engineering, which exploits the ability of metal nanostructures to concentrate electromagnetic radiation. The principal challenge lies in achieving an efficient conversion of the plasmon-concentrated field into some form of useful energy. To date, a substantial progress has been made within the scientific community in identifying the major pathways of the plasmon energy conversion. Strategies based on the hot electron injection and the near-field energy transfer have already shown promise in a number of proof-of-principle plasmonic architectures. Nevertheless, there are several fundamental questions that need to be addressed in the future to facilitate the transition of plasmonics to a variety of applications in both light amplification and optical detection. Of particular interest is a plasmon-induced resonance energy transfer (PIRET) process that couples the plasmon evanescent field to a semiconductor absorber via dipole-dipole interaction. This relatively unexplored mechanism has emerged as a promising light conversion strategy in the areas of photovoltaics and photocatalysis and represents the main focus of the present minireview. Along these lines, we highlight the key advances in this area and review some of the challenges associated with applications of the PIRET mechanism in nanostructured systems.

Near-field refrigeration and tunable heat exchange through four-wave mixing

We modify and extend a recently proposed four-wave mixing scheme [C. Khandekar and A. Rodriguez, Opt. Express 25(19), 23164 (2017)] for achieving near-field thermal upconversion and energy transfer, to demonstrate efficient thermal refrigeration at low intensities ∼ 109W/m2 over a wide range of gap sizes (from tens to hundreds of nanometers) and operational temperatures (from tens to hundreds of Kelvins). We further exploit the scheme to achieve magnitude and directional tunability of near-field heat exchange between bodies held at different temperatures.

Precision Measurement of Phonon-Polaritonic Near-Field Energy Transfer between Macroscale Planar Structures Under Large Thermal Gradients.

Despite its strong potentials in emerging energy applications, near-field thermal radiation between large planar structures has not been fully explored in experiments. Particularly, it is extremely challenging to control a subwavelength gap distance with good parallelism under large thermal gradients. This article reports the precision measurement of near-field radiative energy transfer between two macroscale single-crystalline quartz plates that support surface phonon polaritons. Our measurement scheme allows the precise control of a gap distance down to 200nm in a highly reproducible manner for a surface area of 5×5 mm^{2}. We have measured near-field thermal radiation as a function of the gap distance for a broad range of thermal gradients up to ∼156 K, observing more than 40 times enhancement of thermal radiation compared to the blackbody limit. By comparing with theoretical prediction based on fluctuational electrodynamics, we demonstrate that such remarkable enhancement is owing to phonon-polaritonic energy transfer across a nanoscale vacuum gap.

Rapid and universal detection of ovalbumin based on N,O,P-co-doped carbon dots-fluorescence resonance energy transfer technology

Fluorescence resonance energy transfer (FRET), a near-field energy transfer from a fluorescent donor to a fluorescent acceptor within close proximity, has been widely used in biosensing. In this study, a rapid and universal sensor for the detection of ovalbumin (OVA) using nitrogen, oxygen, phosphoric co-doped CDs (NOP-CDs) and graphene oxide (GO) was established based on the FRET technology. First, novel NOP-CDs peak at 443 nm were synthesized by a one-pot hydrothermal method using egg powder and phosphorus acid. Then, in the absence of OVA, the fluorescence of OVA-antibody modified NOP-CDs was quenched by GO via electrostatic attraction and π-π stacking interaction due to the FRET effect. The introduced OVA competed to displace the GO by special binding with the anti-OVA, resulting in the recovery of the fluorescence. This sensor displayed a linear response to OVA from 0.5 to 15 μg/mL with a detection limit of 153 ng/mL and was successfully applied to the detection of the OVA sample with recoveries ranging from 99.25 to 118.90%. In summary, the green and easy-to-synthesize nano-material was used in this method, the accurate detection results, and the simple process exhibited the great potential of this method for practical applications.

Plasmon-Resonance-Energy-Transfer-Based Spectroscopy on Single Nanoparticles: Biomolecular Recognition and Enzyme Kinetics.

The small absorption cross sections of most molecules led to the low sensitivity of traditional optical absorption spectroscopy. This obstacle might be overcome by applying the near-field plasmon resonance energy transfer (PRET) between plasmonic nanoparticle and surrounding molecules. In this work, we utilized PRET-based spectroscopy on single gold nanostars to study the specific biomolecule recognition and enzyme kinetics choosing biotin-SA pair and DNase I as models. By analyzing the changes of absorption spectra for black hole quencher 3 (BHQ3), derived from spectra difference, we explored the kinetics of specific biomolecule recognition and enzyme digestion in different physiological environment, and we found that the viscosities of media and the sizes of molecules play vital role in biomolecular recognition and enzyme digestion. Compared with the traditional optical absorption spectroscopy techniques, PRET-based spectroscopy offers a nanoscopic resolution owing to the small size of the probe, is more sensitive and achieves detection on the order of hundreds or even dozens of molecules, and can achieve high selectivity due to the specific biomolecular recognition. This method might be used in the fields of molecular diagnostics, drug discovery, cell systems, and clinical diagnostics.

Electrically Injected Hybrid Organic/Inorganic III-Nitride White Light-Emitting Diodes with Nonradiative Förster Resonance Energy Transfer

An electrically injected hybrid organic/inorganic III-nitride white light-emitting diode (LED) has been fabricated by using a two-dimensional (2D) microhole array structure. The hybrid LED geometry significantly enhances proximity between the inorganic active-region and the down-converting yellow organic light-emitting polymers (OLEPs), enabling the near-field nonradiative Forster resonance energy transfer (FRET) process with high efficiency while retaining excellent electrical characteristics of an unpatterned planar LED. A reduction in the recombination lifetime in the InGaN/GaN blue active region has been observed with the hybrid device, confirming the nonradiative FRET process occurring between the InGaN/GaN blue active region and the yellow organic polymer. This results in a typical FRET efficiency of 16.7%, where the FRET interaction area accounts for approximately 0.64% of the remaining blue-emitting inorganic LED, but enhancing total device efficiency. An optimized white-light EL emission is achie...