We report on a new collective phenomenon in metamaterials: spectral line collapse with increasing number of the unit cell resonators (meta-molecules). Resembling the behaviour of exotic states of matter, such as Bose-Einstein condensates of excitons and magnons, this new effect is linked to the suppression of radiation losses in periodic arrays. We demonstrate experimentally spectral line collapse at microwave, terahertz and optical frequencies. It emerges as a universal and truly scalable effect underpinned by classical electromagnetic interactions between the excited meta-molecules.The burgeoning field of metamaterials provides unique opportunities to engineer the electromagnetic properties of artificial media and achieve exotic functionalities, such as negative refraction [1] and cloaking [2]. Similarly to natural crystals, which are created by arranging individual atoms and molecules in a regular grid, periodic ensembles of subwavelength electromagnetic resonators present an effective medium to an incident with properties not available in natural materials. Here, we study the dependence of the metamaterial properties on the number of meta-molecules in the microwave, THz and optical domain, and demonstrate a new collective phenomenon in metamaterials: in contrast to solid state crystals, where bulk arrangements result in broadening of the individual element spectral line, leading eventually to the formation of absorption bands, regular ensembles of meta-molecules can exhibit the opposite effect, i.e. spectral line collapse. The reported phenomenon is characteristic to a novel class of artificial media, which we call "coherent" metamaterials [3] and are characterized by very strong interactions between the electromagnetically excited metamolecules that provide for a low rate of energy loss due to scattering and lead to a high-quality resonant response. An example of a coherent metamaterial is an array of ASRs, where the meta-molecular excitation corresponds to an oscillating magnetic dipole perpendicular to the plane of the array that does not interact directly with the magnetic field of the incident wave, thus creating a nearly thermodynamically isolated ensemble of strongly interacting coherent "molecules" with interesting physical properties. To illustrate this behavior we present a comparison with an "incoherent" metamaterial: a twodimensional array formed by pairs of concentric conducting rings that also supports a high-quality resonant response. In this case, however, the response of the array is a sum of the individual meta-molecule responses, rather than a collective property.The coherent microwave metamaterial was manufactured as a regular planar array of asymmetric split rings (ASR) etched from a 35 µm thick copper layer on a 1.6 mm thick FR4 substrate. The diameter of the ASR was 6 mm with a line width of 0.4 mm and was split in two segments corresponding to 140 • and 160 • arcs. The unit cell of 7.5 × 7.5 mm 2 rendered the arrays nondiffracting at normal incidence for frequencies of up to 40 GHz. I...

We report the first experimental demonstration of compensating Joule losses in metallic photonic metamaterial using optically pumped PbS semiconductor quantum dots.Metallic Joule losses in nano-structured metamaterials are the main obstacle in achieving optical negative index media and narrow resonance frequency selective surfaces for photonic applications. Several schemes have been suggested to overcome these losses including using gain media and parametric processes. [1][2][3][4][5][6][7][8][9] In particular it has been shown theoretically that through the localfield amplification mechanism a very small amount of gain can strongly change absorption and transmission of certain metamaterials 10,11 to the extend of creating conditions for a metamaterial

Lipid nanodiscs are widely used platforms for studying membrane proteins in a near-native environment. Lipid nanodiscs made with membrane scaffold proteins (MSPs) in the linear form have been well studied. Recently, a new kind of nanodisc made with MSPs in the circular form, referred to as covalently circularized nanodiscs (cNDs), has been reported to have some possible advantages in various applications. Given the potential of nanodisc technology, researchers in the field are very interested in learning more about this new kind of nanodisc, such as its reproducibility, production yield, and the possible pros and cons of using it. However, research on these issues is lacking. Here, we report a new study on nanodiscs made with circular MSPs, which are produced from a method different from the previously reported method. We show that our novel production method, detergent-assisted sortase-mediated ligation, can effectively avoid high-molecular-weight byproducts and also significantly improve the yield of the target proteins up to around 80% for larger circular MSP constructs. In terms of the application of circular MSPs, we demonstrate that they can be used to assemble nanodiscs using both synthetic lipids and native lipid extract as the source of lipids. We also show that bacteriorhodopsin can be successfully incorporated into this new kind of cND. Moreover, we found that cNDs have improved stability against both heat and high-concentration-induced aggregations, making them more beneficial for related applications.

Metrics & MoreArticle Recommendations * sı Supporting Information ABSTRACT: "Spin" has been recently reported as an important degree of electronic freedom to improve the performance of electrocatalysts and photocatalysts. This work demonstrates the manipulations of spin-polarized electrons in CsPbBr 3 halide perovskite nanoplates (NPLs) to boost the photocatalytic CO 2 reduction reaction (CO 2 RR) efficiencies by doping manganese cations (Mn 2+ ) and applying an external magnetic field. Mn-doped CsPbBr 3 (Mn-CsPbBr 3 ) NPLs exhibit an outstanding photocatalytic CO 2 RR compared to pristine CsPbBr 3 NPLs due to creating spinpolarized electrons after Mn doping. Notably, the photocatalytic CO 2 RR of Mn-CsPbBr 3 NPLs is significantly enhanced by applying an external magnetic field. Mn-CsPbBr 3 NPLs exhibit 5.7 times improved performance of photocatalytic CO 2 RR under a magnetic field of 300 mT with a permanent magnet compared to pristine CsPbBr 3 NPLs. The corresponding mechanism is systematically investigated by magnetic circular dichroism spectroscopy, ultrafast transient absorption spectroscopy, and density functional theory simulation. The origin of enhanced photocatalytic CO 2 RR efficiencies of Mn-CsPbBr 3 NPLs is due to the increased number of spin-polarized photoexcited carriers by synergistic doping of the magnetic elements and applying a magnetic field, resulting in prolonged carrier lifetime and suppressed charge recombination. Our result shows that manipulating spin-polarized electrons in photocatalytic semiconductors provides an effective strategy to boost photocatalytic CO 2 RR efficiencies.

We have developed a two-step electron-beam lithography process to fabricate a tandem array of three pairs of tip-like gold nanoelectronic detectors with electrode gap size as small as 9 nm, embedded in a coplanar fashion to 60 nm deep, 100 nm wide, and up to 150 μm long nanochannels coupled to a world-micro-nanofluidic interface for easy sample introduction. Experimental tests with a sealed device using DNA-protein complexes demonstrate the coplanarity of the nanoelectrodes to the nanochannel surface. Further, this device could improve transverse current detection by correlated time-of-flight measurements of translocating samples, and serve as an autocalibrated velocimeter and nanoscale tandem Coulter counters for single molecule analysis of heterogeneous samples.