Koray Aydin

Although tremendous advances have been made in preparing porous crystals from molecular precursors, there are no general ways of designing and making topologically diversified porous colloidal crystals over the 10–1,000 nm length scale. Control over porosity in this size range would enable the tailoring of molecular absorption and storage, separation, chemical sensing, catalytic and optical properties of such materials. Here, a universal approach for synthesizing metallic open-channel… Show more

Although tremendous advances have been made in preparing porous crystals from molecular precursors, there are no general ways of designing and making topologically diversified porous colloidal crystals over the 10–1,000 nm length scale. Control over porosity in this size range would enable the tailoring of molecular absorption and storage, separation, chemical sensing, catalytic and optical properties of such materials. Here, a universal approach for synthesizing metallic open-channel superlattices with pores of 10 to 1,000 nm from DNA-modified hollow colloidal nanoparticles (NPs) is reported. By tuning hollow NP geometry and DNA design, one can adjust crystal pore geometry (pore size and shape) and channel topology (the way in which pores are interconnected). The assembly of hollow NPs is driven by edge-to-edge rather than face-to-face DNA–DNA interactions. Two new design rules describing this assembly regime emerge from these studies and are then used to synthesize 12 open-channel superlattices with control over crystal symmetry, channel geometry and topology. The open channels can be selectively occupied by guests of the appropriate size and that are modified with complementary DNA (for example, Au NPs). Show less

Reconfigurable, mechanically responsive crystalline materials are central components in many sensing, soft robotic, and energy conversion and storage devices. Crystalline materials can readily deform under various stimuli and the extent of recoverable deformation is highly dependent upon bond type. Indeed, for structures held together via simple electrostatic interactions, minimal deformations are tolerated. By contrast, structures held together by molecular bonds can, in principle, sustain… Show more

Reconfigurable, mechanically responsive crystalline materials are central components in many sensing, soft robotic, and energy conversion and storage devices. Crystalline materials can readily deform under various stimuli and the extent of recoverable deformation is highly dependent upon bond type. Indeed, for structures held together via simple electrostatic interactions, minimal deformations are tolerated. By contrast, structures held together by molecular bonds can, in principle, sustain much larger deformations and more easily recover their original configurations. Here we study the deformation properties of well-faceted colloidal crystals engineered with DNA. These crystals are large in size (greater than 100 µm) and have a body-centred cubic (bcc) structure with a high viscoelastic volume fraction (of more than 97%). Therefore, they can be compressed into irregular shapes with wrinkles and creases, and, notably, these deformed crystals, upon rehydration, assume their initial well-formed crystalline morphology and internal nanoscale order within seconds. For most crystals, such compression and deformation would lead to permanent, irreversible damage. The substantial structural changes to the colloidal crystals are accompanied by notable and reversible optical property changes. For example, whereas the original and structurally recovered crystals exhibit near-perfect (over 98%) broadband absorption in the ultraviolet–visible region, the deformed crystals exhibit significantly increased reflection (up to 50% of incident light at certain wavelengths), mainly because of increases in their refractive index and inhomogeneity. Show less

DNA programmable assembly has been combined with top-down lithography to construct superlattices of discrete, reconfigurable nanoparticle architectures on a gold surface over large areas. Specifically, the assembly of individual colloidal plasmonic nanoparticles with different shapes and sizes is controlled by oligonucleotides containing “locked” nucleic acids and confined environments provided by polymer pores to yield oriented architectures that feature tunable arrangements and independently… Show more

DNA programmable assembly has been combined with top-down lithography to construct superlattices of discrete, reconfigurable nanoparticle architectures on a gold surface over large areas. Specifically, the assembly of individual colloidal plasmonic nanoparticles with different shapes and sizes is controlled by oligonucleotides containing “locked” nucleic acids and confined environments provided by polymer pores to yield oriented architectures that feature tunable arrangements and independently controllable distances at both nanometer and micrometer length scales. These structures, which would be difficult to construct via other common assembly methods, provide a platform to systematically study and control light-matter interactions in nanoparticle-based optical materials. The generality and potential of this approach are explored by identifying a broadband absorber with a solvent polarity response that allows dynamic tuning of visible light absorption. Show less

Plasmonic materials provide electric-field localization and light confinement at subwavelength scales due to strong light-matter interaction around resonance frequencies. Graphene has been recently studied as an atomically thin plasmonic material for infrared and terahertz wavelengths. Here, we theoretically investigate localized surface plasmon resonances (LSPR) in a monolayer, nanostructured black phosphorus (BP). Using finite-difference time-domain simulations, we demonstrate LSPRs at… Show more

Plasmonic materials provide electric-field localization and light confinement at subwavelength scales due to strong light-matter interaction around resonance frequencies. Graphene has been recently studied as an atomically thin plasmonic material for infrared and terahertz wavelengths. Here, we theoretically investigate localized surface plasmon resonances (LSPR) in a monolayer, nanostructured black phosphorus (BP). Using finite-difference time-domain simulations, we demonstrate LSPRs at mid-infrared and far-infrared wavelength regime in BP nanoribbon and nanopatch arrays. Because of strong anisotropic in-plane properties of black phosphorus emerging from its puckered crystal structure, black phosphorus nanostructures provide polarization dependent, anisotropic plasmonic response. Electromagnetic simulations reveal that monolayer black phosphorus nanostructures can strongly confine infrared radiation in an atomically thin material. Black phosphorus can find use as a highly anisotropic plasmonic devices.

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A virtually flat metasurface is proposed and experimentally realized, which can split different visible-frequency light to completely different or even contrary directions with an ultrawide angular range (>90°). The phase gradients provided by the metasurface have been engineered to exhibit significant wavelength-selective features. The metasurface of mirror-symmetric arrays behaves as a convex, concave, and planar mirror for distinct light wavelengths.

An inverse-design approach yields ultra-compact, high-performance photonic components from patterns of complex, subwavelength voids etched into silicon.

Single-layer direct band gap semiconductors such as transition metal dichalcogenides are quite attractive for a wide range of electronics, photonics, and optoelectronics applications. Their monolayer thickness provides significant advantages in many applications such as field-effect transistors for high-performance electronics, sensor/detector applications, and flexible electronics. However, for optoelectronics and photonics applications, inherent monolayer thickness poses a significant… Show more

Single-layer direct band gap semiconductors such as transition metal dichalcogenides are quite attractive for a wide range of electronics, photonics, and optoelectronics applications. Their monolayer thickness provides significant advantages in many applications such as field-effect transistors for high-performance electronics, sensor/detector applications, and flexible electronics. However, for optoelectronics and photonics applications, inherent monolayer thickness poses a significant challenge for the interaction of light with the material, which therefore results in poor light emission and absorption behavior. Here, we demonstrate enhanced light emission from large-area monolayer MoS2 using plasmonic silver nanodisc arrays, where enhanced photoluminescence up to 12-times has been measured. Observed phenomena stem from the fact that plasmonic resonance couples to both excitation and emission fields and thus boosts the light–matter interaction at the nanoscale. Reported results allow us to engineer light–matter interactions in two-dimensional materials and could enable highly efficient photodetectors, sensors, and photovoltaic devices, where photon absorption and emission efficiency highly dictate the device performance. Show less

We show that a triple-layer metal-insulator-metal (MIM) structure has spectrally selective IR absorption, while an ultra-thin metal film has non-selective absorption in the near infrared wavelengths. Both sub-wavelength scale structures were implemented with an ultra-thin 6 nm Cr top layer. MIM structure was demonstrated to have near perfect absorption at λ = 1.2 μm and suppressed absorption at λ = 1.8 μm in which experimental and simulated absorptions of the thin Cr film are even higher than… Show more

We show that a triple-layer metal-insulator-metal (MIM) structure has spectrally selective IR absorption, while an ultra-thin metal film has non-selective absorption in the near infrared wavelengths. Both sub-wavelength scale structures were implemented with an ultra-thin 6 nm Cr top layer. MIM structure was demonstrated to have near perfect absorption at λ = 1.2 μm and suppressed absorption at λ = 1.8 μm in which experimental and simulated absorptions of the thin Cr film are even higher than the MIM. Occurrence of absorption peaks and dips in the MIM were explained with the electric field intensity localization as functions of both the wavelength and the position. It has been shown that the power absorption in the lossy material is a strong function of the electric field intensity i.e. the more the electric field intensity, the more the absorption and vice versa. Therefore, it is possible to engineer IR emissive properties of these ultra-thin nanocavities by controlling the electric field localization with proper designs. Show less

Resonant plasmonic and metamaterial structures allow for control of fundamental optical processes such as absorption, emission and refraction at the nanoscale. Considerable recent research has focused on energy absorption processes, and plasmonic nanostructures have been shown to enhance the performance of photovoltaic and thermophotovoltaic cells. Although reducing metallic losses is a widely sought goal in nanophotonics, the design of nanostructured 'black' super absorbers from materials… Show more

Resonant plasmonic and metamaterial structures allow for control of fundamental optical processes such as absorption, emission and refraction at the nanoscale. Considerable recent research has focused on energy absorption processes, and plasmonic nanostructures have been shown to enhance the performance of photovoltaic and thermophotovoltaic cells. Although reducing metallic losses is a widely sought goal in nanophotonics, the design of nanostructured 'black' super absorbers from materials comprising only lossless dielectric materials and highly reflective noble metals represents a new research direction. Here we demonstrate an ultrathin (260 nm) plasmonic super absorber consisting of a metal–insulator–metal stack with a nanostructured top silver film composed of crossed trapezoidal arrays. Our super absorber yields broadband and polarization-independent resonant light absorption over the entire visible spectrum (400–700 nm) with an average measured absorption of 0.71 and simulated absorption of 0.85. Proposed nanostructured absorbers open a path to realize ultrathin black metamaterials based on resonant absorption. Show less