Way Of Energy Transfer Research Articles

The potential of hyperbolic films for radiative heat transfer in micro/nanoscale

Thin films exhibit substantial potential in energy management and utilization as the development of micro- and nanofabrication technologies. It is well known that thermal radiation is one of the fundamental ways of energy transfer. However, the potential of hyperbolic films for radiative heat transfer is always ignored. Whether the radiative heat flux between hyperbolic films surpasses that of the bulk materials remains insufficiently explored. In this work, we theoretically investigate the radiative heat transfer between hexagonal boron nitride (hBN) at a separation from 20 ​nm to 2 ​μm. The results show that when the optical axis of hBN is oriented in-plane, the near-field radiative heat flux of hBN with a thickness of 10 ​nm exceeds that of hBN bulk by 47% and exceeds the blackbody limit by two orders of magnitude at a gap distance of 20 ​nm. The physical mechanism is attributed to the volume-confined hyperbolic polaritons can be excited in a higher wavevector space. Conversely, when the gap distance is 600 ​nm, the heat flux between films is considerably lower than that of bulk material. This work opens up potential avenues for developing hyperbolic film-dependent thermal devices and strategies for thermal management.

Broadband near-infrared emission in Bi-Er co-doped germanosilicate glasses

Broadband gain materials have garnered considerable attention on account of their practical utilization in optical amplifiers. Among them, Bi-doped glasses depict tremendous potential due to their unique broadband emission. In this paper, we report a series of Bi-Er co-doped germanosilicate glasses exhibiting broadband and tunable near-infrared (NIR) emission. By the strategy of Bi-Er co-doping, the luminescence bandwidth is effectively expanded in two ways: co-excitation and energy transfer between two active centers. Importantly, broadband luminescence covering O-E-S-C-L bands with full width at half maximum (FWHM) more than 320 nm is realized via the way of energy transfer. In addition, ultrabroadband emission covering C-L-U bands with FWHM of ∼370 nm and relatively flat emission of ∼170 nm is achieved via the way of co-excitation. Furthermore, the mechanism of energy transfer is discussed. These results indicate that Bi-Er co-doped germanosilicate glasses are the promising candidates in the field of optical fiber amplifiers.

Plasma activation mechanisms governed by specific energy input: Potential and perspectives

AbstractIn a low‐temperature plasma, the electrons pick up energy from the electric field in collisions with atoms and molecules, gaining high kinetic energy that must be sufficient for ionizing reactions to sustain the plasma. For molecular gases, an average energy per heavy gas particle is thus available in the plasma, the specific energy input, yielding plasma activation by inelastic collisions. Following a distribution law, the probability for the activation mechanism can be described by an Arrhenius‐like equation. The potential of this approach is demonstrated on the basis of plasma polymerization and plasma CO2conversion. For perspective, energy efficiencies are discussed as a function of conversion indicating the optimum that can be achieved by electron impact activation compared with additional ways of energy transfer, probably depending on certain constraints.

Energy Transfer Processes in NASICON-Type Phosphates under Synchrotron Radiation Excitation

The luminescence properties of NASICON-type Na3.6M1.8(PO4)3 (M = Y, Lu) and Na3Sc2(PO4)3 phosphates, undoped and rare earth-doped (RE = Tb3+, Dy3+, Eu3+, Ce3+), were studied using synchrotron radiation in a wide energy region of 4.5–45 eV. Intrinsic emission originating from self-trapped excitons with electron component localized at the 3d Sc states was detected in both doped and undoped Na3Sc2(PO4)3 while only defect-related emission was registered in Na3.6M1.8(PO4)3. Emission of RE ions substituting three-valent cations in low-symmetry sites was detected in all doped phosphates. The efficiency and pass ways of energy transfer from the host to emission centres were analysed based on luminescence excitation spectra. It is shown that the most efficient energy transfer is realized in Tb3+-doped phosphors, while it was poor for other RE ions. The differences in energy transfer efficiencies are explained by different position of RE f states in the crystal electronic band structure influencing the efficiency of charge carrier trapping in the substance. Based on excitation spectra analysis, the bandgap values were estimated to ~8 eV for all studied phosphates.

Transient dynamics in a common singly resonant optical parametric oscillator

The dynamics of a common optical parametric oscillator (OPO) is demonstrated for the first time with dispersive Fourier transform (DFT) technique. The singly resonant MgO:PPLN-based optical parametric oscillator is synchronously pumped with an Yb-doped fiber amplifier, and delivers a femtosecond signal wave with a spectrum tuned from 1284 to 1517 nm. Then a DFT device is built and the birth and extinction dynamics of the single- and dual-wavelength signal wave of the OPO is recorded. Compared with conventional mode-locked lasers, the dynamics evolution of the OPO is entirely attributed to the nonlinear effects in the nonlinear crystal different from the atomic transitions in the active media, which gives rise to novel features in the starting progress of the OPO. Furthermore, a new way of energy transfer is discovered for the first time during the evolution of dual-wavelength signal wave. The results are believed to provide a unique insight into evolution in OPOs and are instructive for in-depth understanding of OPO and other nonlinear devices and materials.

The Australian way of energy transfer

The Australian way of energy transfer

Competition between Photoinduced Electron Transfer and Resonance Energy Transfer in an Example of Substituted Cytochrome c-Quantum Dot Systems.

Colloidal quantum dots (QDs) are nanoparticles that are able to photoreduce redox proteins by electron transfer (ET). QDs are also able to transfer energy by resonance energy transfer (RET). Here, we address the question of the competition between these two routes of QDs’ excitation quenching, using cadmium telluride QDs and cytochrome c (CytC) or its metal-substituted derivatives. We used both oxidized and reduced versions of native CytC, as well as fluorescent, nonreducible Zn(II)CytC, Sn(II)CytC, and metal-free porphyrin CytC. We found that all of the CytC versions quench QD fluorescence, although the interaction may be described differently in terms of static and dynamic quenching. QDs may be quenchers of fluorescent CytC derivatives, with significant differences in effectiveness depending on QD size. SnCytC and porphyrin CytC increased the rate of Fe(III)CytC photoreduction, and Fe(II)CytC slightly decreased the rate and ZnCytC presence significantly decreased the rate and final level of reduced FeCytC. These might be partially explained by the tendency to form a stable complex between protein and QDs, which promoted RET and collisional quenching. Our findings show that there is a net preference for photoinduced ET over other ways of energy transfer, at least partially, due to a lack of donors, regenerating a hole at QDs and leading to irreversibility of ET events. There may also be a common part of pathways leading to photoinduced ET and RET. The nature of synergistic action observed in some cases allows the hypothesis that RET may be an additional way to power up the ET.

Beam generator of 4-channel with zeroth order suppressed by reflective T-type grating

Four-port beam splitter with good uniformity was proposed by T-type double-layer with different dielectric grating. The total efficiency of the beam splitter is over 90% with beam splitting uniformity better than 3%. At the same time, the simplified modal analysis is added to calculate the grating mode and effective refractive index of the grating area, which clearly describes the physical propagation mechanism inside the grating. The finite element method is used to investigate the normalized field of the grating, which more intuitively reflects the way of energy transfer inside the grating. Finally, the incident characteristics and manufacturing tolerance of the grating are analyzed. Properties of the T-type grating were analyzed in three methods, which more fully illustrates the applicability and stability of the grating in this paper.

Large-scale Dynamics of Ultra-lean Hydrogen-air Flame Kernels in Terrestrial Gravity Conditions

ABSTRACT The paper discusses the results of an experimental study on combustion development in a large volume filled with ultra-lean hydrogen-air mixture under terrestrial gravity conditions. For the first time, characteristicflame ball evolutionIn particular, ittheBesides, the lateral expansion of the flame ball plays an important role, defining the changes in curvature radius and stretching of the flame. Due to this, flame breaks up and secondary flame kernels arise. So, the developed structure of the ultra-lean flame occurs to be much more complex than earlier registered cap-shaped flames. Large-scale dynamics of the flame ball is of paramount interest for understanding the stability of near-limit flames and for estimation of hazards related to the development of flame balls under real conditions. Studied processes represent a possible way of energy transfer from the spatial areas filled with less reactive mixtures toward areas with high mixture reactivity. Such a phenomenon stages of the during its convective upward motion on large spatial scales are described. The physical mechanisms defining the particularities of ultra-lean flame evolution subjected to the natural convection are proposed. is shown that the key role in the process of flame propagation in the ultra-lean mixture belongs to the convective rise of the hot combustion products in the gravity field. Herewith, velocity of the flame upward motion occurs to be much higher than the laminar burning velocity in the considered ultra-lean hydrogen-air mixture. may become a reason for the development of emergencies and should be thoroughly investigated and taken into account while designing reliable fire and explosion safety systems. Experimental results are compared with previously obtained numerical data that allowed to demonstrate the correctness of the mathematical modeling and physical mechanisms identified on its basis.

Achieving high energy transfer efficiency in Sr6Ca4(PO4)6F2:Ce3+, Mn2+ by regulating the occupation of activator

Series of color tunable Sr6Ca4(PO4)6F2:Ce3+, Mn2+ were achieved. In the way of energy transfer, the activator Mn2+ should get large energy from sensitizer Ce3+ and show high efficiency. However, with increasing Mn2+ concentration the emission intensity of Ce3+ decreases rapidly, the emission intensity of Mn2+ shows unapparent increase. It indicates that there are lots of energy losses in the process of energy transfer from Ce3+ to Mn2+. With the high concentration of Mn2+, the severe concentration quenching effect of Mn2+ occurs in Sr6Ca4(PO4)6F2:Ce3+, Mn2+. In order to reduce the energy loss owing to the concentration quenching effect, Mg2+ ions are introduced into Sr6Ca4(PO4)6F2:Ce3+, Mn2 to regulate the occupation of Mn2+. Consequently, the distance between Mn2+ increases and the energy loss between Mn2+ is effectively reduced. Therefore the emission intensity of Mn2+ increases greatly, and high energy transfer efficiency of Ce3+→Mn2+ is achieved.

Luminescence properties of Dy3+ or/and Sm3+ doped LiLa(WO4)2 phosphors and energy transfer from Dy3+ to Sm3+

The Dy3+ or/and Sm3+ doped LiLa(WO4)2 phosphors are synthesized by a facile solid state reaction method. The phase and luminescence properties of the phosphors are investigated. The powder X-ray diffraction (XRD) results show that the phosphor has a tetragonal phase crystal structure. The quenching concentration of single doped Dy3+ and Sm3+ in the LiLa(WO4)2 are determined to be 6% and 3%, respectively. Under the excitation of 404 nm, warm white light is obtained in the co-doped phosphors. With the concentration of Sm3+ increasing, the correlated color temperature (CCT) gradually decreases from 3090 to 2453 K. Two kinds of energy transfer may exist at the same time. The overlap between the emission spectrum of Dy3+ and the excitation spectrum of Sm3+ reveals that the energy of Dy3+ can transfer to Sm3+ via radiation. Another way of energy transfer, that is non-radiative energy transfer, is attributed to the excited state of Dy3+ (4F9/2) slightly higher than that of Sm3+ (4I19/2). The calculation results show that non-radiative energy transfer process from Dy3+ to Sm3+ ions is predominated by quadrupole–quadrupole interaction.

New methodology for the heat flow prediction for different construction materials

Among the ways of energy transfer by conduction is that of molecular interaction, in which the greater motion of a molecule at a higher energy level (temperature) imparts energy to adjacent molecules at lower energy levels. This type of transfer is present, to some degree, in all systems in which a temperature gradient exists and in which molecules of a solid, liquid, or gas are present. So, in heat transfer, the thermal conductivity of a substance is an intensive property that indicates its ability to conduct heat In particular in the building sector. The thermal flux is often measured with a mathematical analysis but for the same material, on the other hand the estimate will be disruptive and sometimes very difficult when the material changes. In this paper, a single equation for predicting heat flux of different materials is given.

Hybrid nanocomposites of a fluorescent block copolymer and quantum dots: An efficient way for energy transfer

Förster resonance energy transfer (FRET) phenomenon has great potential in several applications, whose efficiency is dependent on the energy transfer between a suitable pair of fluorophores. In this work, a new block copolymer, PS-b-PS(co-pyren-1-yl), with fluorescent properties, was synthetized and used as donor component in the fluorophores pair copolymer/cadmium telluride quantum dots (CdTe QDs). Thus, water-soluble CdTe QDs, previously transferred into organic phase, by replacing the stabilizer ligands, thioglycolic acid by 1-dodecanethiol (1-DDT), were used to prepare a new hybrid nanocomposite. FRET studies between the fluorescent copolymer and CdTe-DDT QDs revealed that this fluorophores pair can experience FRET with an efficiency of 48%, being an efficient antenna system for light harvesting applications.

A non-traditional energy transfer process in CWPO heterogeneous reaction for wastewater treatment

A novel heat transfer pathway in the solid–liquid heterogeneous reaction was realized by a reactor integrated with a high frequency alternating magnetic field (inducting heating reactor, abbr. iHR). In this way, electrical energy converted into heat on the surface of catalyst particles and then heat was transferred from catalysts to liquid phase. That was opposite to traditional heat transfer process. For the novel thermal transfer pathway, temperature on the surface of catalysts was much higher than that of liquid phase. Based on the novel energy transmission style, the new way of energy transfer was used to improve efficiency of some energy-intensive heterogeneous reactions, e.g., catalytic degradation, catalysts regeneration and Fischer–Tropsch synthesis. As an experimental sample, we applied the technology to a typical wastewater treatment process, catalytic wet peroxide oxidation (CWPO). Further, we investigated the relationship between temperature and energy transfer process, the advantage of the reaction and the characteristics of the catalysts. The successful operation increased degradation efficiency of organic pollutant in aqueous solution and proved that the process was energy-saving.

The efficiency of non-photochemical fluorescence quenching of phycobilisomes by the orange carotenoid protein

We report on theoretical efficiency of non-photochemical fluorescense quenching of phycobilisomes by the orange carotenoid protein. The created 3D computer model of the three-cylindrical phycobilisomes core allowed us to determine the distances between centers of mass of all phycobilin chromophores of the core and calculate the time and an average number of energy migration steps for the resulting non-radiative excitation transfer from the phycobilisomes to photosystem II. The obtained kinetic scheme equations for a way of energy transfer confirm the incomplete interception of energy flow in the phycobilisomes core by the orange carotenoid protein. Theoretical estimation of the rate of phycobilisomes quenching is in good agreement with experimental data.

Strategy for Microwave Energy Harvesting From Ambient Field or a Feeding Source

Wireless energy transfer has been demonstrated using microwave electromagnetic support. Significant efficiencies are reported in the case of large dimension systems. Lots of embedded systems require a small power supply but with a large degree of integration where standard contactless energy transfer techniques suffer from poor efficiency. In such systems, RF input energy is rectified using rectenna circuits. The latter circuits are optimized for a given input RF power and cannot accommodate the two possible ways of energy transfer: the dedicated transfer (high power) or the harvesting of ambient energy (low power). This paper presents a novel rectenna architecture tunable for 900 MHz-2.45 GHz operation, able to process RF input power in the -30 to +30 dBm (dB miliwatt) range with a peak efficiency of 80%.

Hybrid system based on quantum dots and photosystem 2 core complex

We show that semiconductor nanocrystals (quantum dots, QD) can be used to increase the absorption capacity of pigment-protein complexes. In a mixture of photosystem 2 core complex (PS2) and QD, the fluorescence of the latter decreases several-fold due to the transfer of the absorbed energy to the PS2 core complex. We discuss Förster's inductive-resonance mechanism as a possible way of energy transfer in donor-acceptor pairs QD-PS2 core complex. Calculations based on the experimental data show that the enhancement of PS2 fluorescence and the rate of Q(A) reduction increase up to 60% due to efficient energy migration from QD to PS2.

A novel strategy for controllable emissions from Eu3+ or Sm3+ ions co-doped SrY2O4:Tb3+ phosphors

Trivalent rare-earth (RE) ions (Eu(3+), Tb(3+) and Sm(3+)) activated multicolor emitting SrY(2)O(4) phosphors were synthesized by a sol-gel process. The structural and morphological studies were performed by the measurements of X-ray diffraction profiles and scanning electron microscope (SEM) images. The pure phase of SrY(2)O(4) appeared after annealing at 1300 °C and the doping of RE ions did not show any effect on the structural properties. From the SEM images, the closely packed particles were observed due to the roughness of each particle tip. The photoluminescence (PL) analysis of individual RE ions activated SrY(2)O(4) phosphors exhibits excellent emission properties in their respective regions. The Eu(3+) co-activated SrY(2)O(4):Tb(3+) phosphor creates different emissions by controlling the energy transfer from Tb(3+) to Eu(3+) ions. Based on the excitation wavelengths, multiple (green, orange and white) emissions were obtained by Sm(3+) ions co-activated with SrY(2)O(4):Tb(3+) phosphors. The decay measurements were carried out for analyzing the energy transfer efficiency and the possible ways of energy transfer from donor to acceptor. The cathodoluminescence properties of these phosphors show similar behavior as PL properties except the energy transfer process. The obtained results indicated that the energy transfer process was quite opposite to the PL properties. The calculated CIE chromaticity coordinates of RE ions activated SrY(2)O(4) phosphors confirmed the red, green, orange and white emissions.

Optical emission characteristics of glow discharges in Ar-O2 and He-O2 gas mixtures

We have investigated optical emissions from low-pressure DC glow discharges in Ar-O2 and He-O2 gas mixtures in the 300 to 850 nm spectral range. The ionic species present in these discharges reveal interesting energy transfer pathways between different constituents of the gas mixtures. In the case of Ar-O2 mixture, we observed the presence of highly excited Ar and O atoms as well as Ar+, Ar2 + and O2 + ions. Apparently, charge-exchange collisions between Ar2 + and O2 yield O2 + ions. The path ways of energy transfer are different for He-O2 gas mixture where O2 + ions are formed directly through collisions with excited He atoms. The O2 + ions subsequently capture free electrons and dissociate into excited O atoms.

The paradox high zooplankton biomass–low vegetal particulate organic matter in high turbidity zones: What way for energy transfer?

Estuarine ecosystems are characterized by high zooplanktonic biomasses, essentially constituted by copepods and mysids whose nutritional requirements are mainly provided by phytoplankton, an easily available carbon form. The Gironde estuary is characterized by high turbidities which limit light penetration in the water column and therefore primary production. Consequently, primary production is low and its availability for higher trophic level is very limited. The main goal of this study was to characterize the total vegetal particulate organic matter (POM) in high turbidity zones of the Gironde estuary during summer (a critical period characterized by high heterotrophic bacterial degradation and high zooplanktonic biomasses) and to analyse its utilization by zooplankton, using prey/predator experiments and trophic biomarkers (fatty acids). The specific goals were to define (i) how vegetal POM was exploited by the different zooplanktonic groups (protozoa, copepods and mysids) and (ii) which alternative preys could be used when vegetal POM was not sufficient to ensure their nutritional requirements. Chlorophyll biomass was very low in the MTZ during summer 2002 (0.48 ± 0.03 mg m − 3 ). Total zooplankton grazing was low (19% d − 1 ) probably due to a large contribution of detritus originating from terrestrial plants in vegetal POM compared to phytoplankton. The highest grazing pressure was exercised by the mysid Mesopodopsis slabberi due to its high abundances and by its almost entirely herbivorous diet (phytoplankton and small terrestrial detritus). Grazing rates (19.7 ± 4.2 and 9.6 μgC cop − 1 d − 1 for juveniles and adults, respectively) seemed to be sufficient to satisfy their daily carbon requirement. Grazing rate of the copepod Eurytemora affinis (139 ngC cop − 1 d − 1 ) seemed to be insufficient to cover its nutritional requirements and the copepods probably needed to complete a great part of their diet from protozoa. Grazing rates of the mysid Neomysis integer (24.7 ± 0.01 and 20.89 ± 8.45 μgC cop − 1 d − 1 for juveniles and adults, respectively) were higher than those of M. slabberi when feeding only on phytoplankton. However, when other preys were introduced in its environment, N. integer only fed on the copepod E. affinis with a preference for nauplii. The study revealed the great importance of protozoa and bacteria in the trophic transfers between vegetal POM and zooplankton in the MTZ during summer, despite the low protozoa grazing pressure on vegetal POM (3.1%). The detritic food chain probably implies various trophic transfers with little direct relationships between vegetal POM and zooplankton.