Near-infrared Localized Surface Plasmon Resonance Research Articles

Tunable near-infrared localized surface plasmon resonances of djurleite nanocrystals: effects of size, shape, surface-ligands and oxygen exposure time

The effects of size, shape, surface ligands and oxygen exposure time on the localized surface plasmon resonance absorption in monoclinic djurleite nanocrystals have been demonstrated.

Phase conversion from hexagonal CuS(y)Se(1-y) to cubic Cu(2-x)S(y)Se(1-y): composition variation, morphology evolution, optical tuning, and solar cell applications.

In this work, we report a simple and low-temperature approach for the controllable synthesis of ternary Cu-S-Se alloys featuring tunable crystal structures, compositions, morphologies, and optical properties. Hexagonal CuS(y)Se(1-y) nanoplates and face centered cubic (fcc) Cu(2-x)S(y)Se(1-y) single-crystal-like stacked nanoplate assemblies are synthesized, and their phase conversion mechanism is well investigated. It is found that both copper content and chalcogen composition (S/Se atomic ratio) of the Cu-S-Se alloys are tunable during the phase conversion process. Formation of the unique single-crystal-like stacked nanoplate assemblies is resulted from oriented stacking coupled with the Ostwald ripening effect. Remarkably, optical tuning for continuous red shifts of both the band-gap absorption and the near-infrared localized surface plasmon resonance are achieved. Furthermore, the novel Cu-S-Se alloys are utilized for the first time as highly efficient counter electrodes (CEs) in quantum dot sensitized solar cells (QDSSCs), showing outstanding electrocatalytic activity for polysulfide electrolyte regeneration and yielding a 135% enhancement in power conversion efficiency (PCE) as compared to the noble metal Pt counter electrode.

Expanding the spectral tunability of plasmonic resonances in doped metal-oxide nanocrystals through cooperative cation-anion codoping.

We present a generalized cation-anion codoping methodology for the synthesis of monodisperse, doped metal-oxide nanocrystals (NCs) that exhibit near-infrared localized surface plasmon resonance (LSPR) with the highest reported quality factors. We demonstrate that, in addition to the use of common cation dopants, the incorporation of fluorine into the lattice as an anion dopant can further increase the free-carrier concentration within individual NCs; this supports the cooperative effects of mixed cation-anion doping in shifting the LSPR to higher energies. As a result, this method allows the LSPR of doped metal-oxide NCs to become tunable across a significantly broader wavelength range (1.5-3.3 μm), circumventing the prior limitations on the highest possible LSPR energies associated with single-element doping for a given oxide host. The strategy of cation-anion codoping can offer new possibilities for the chemical design of doped semiconductor and metal-oxide NCs with tailored LSPR characteristics.

Seeded Growth of Metal-Doped Plasmonic Oxide Heterodimer Nanocrystals and Their Chemical Transformation

We have developed a generalized seeded-growth methodology for the synthesis of monodisperse metal-doped plasmonic oxide heterodimer nanocrystals (NCs) with a near-unity morphological yield. Using indium-doped cadmium oxide (ICO) as an example, we show that a wide variety of preformed metal NCs (Au, Pt, Pd, FePt, etc.) can serve as the seeds for the tailored synthesis of metal-ICO heterodimers with exquisite size, shape, and composition control, facilitated by the delayed nucleation mechanism of the CdO phase. The metal-ICO heterodimers exhibit broadly tunable near-infrared localized surface plasmon resonances, and dual plasmonic bands are observed for Au-ICO heterodimers. We further demonstrate that the oxide domain of the Au-ICO heterodimers can be selectively and controllably transformed into a series of partially and completely hollow cadmium chalcogenide nanoarchitectures with unprecedented structural complexity, leaving the metal domain intact. Our work not only represents an exciting addition to the rapidly expanding library of chemical reactions that produce colloidal hybrid NCs, but it also provides a general route for the bottom-up chemical design of multicomponent metal-oxide-semiconductor NCs in a rational and sequential manner.

Tunable near-infrared localized surface plasmon resonances of heterostructured Cu_194S-ZnS nanocrystals

Strong near-infrared (NIR) localized surface plasmon resonances (LSPRs) have been observed in spherical Cu1.94S nanocrystals and matchstick-like Cu1.94S-ZnS heterostructured nanocrystals, which have been synthesized using a simple one-pot approach without any injection and pre-synthesis of metal precursors. The LSPRs peak of the Cu1.94S nanocrystals could be tuned from 1680 nm to 1375 nm by heterogrowth of ZnS onto the Cu1.94S nanocrystals due to the increase of free carriers (holes). The LSPRs absorbance can be optimized to 1322 nm by prolonging the growth time of the heterostructured nanocrystals, which may be used as a light absorbing agent for photothermal therapy.

Tuning of the near-infrared localized surface plasmon resonance of Cu2−xSe nanoparticles with lysozyme-induced selective aggregation

Poly(styrene sulfonic acid)sodium stabilized Cu2−xSe nanoparticles (PSS–Cu2−xSe NPs) with localized surface plasmon resonance (LSPR) absorption centered at 980 nm can be selectively aggregated by lysozyme (Lys) through the electrostatic attraction, giving rise to a red shift of the LSPR in the near-infrared (NIR) region.

Hydrophilic Cu2-xSe/reduced graphene oxide nanocomposites with tunable plasmonic properties and their applications in cellular dark-field microscopic imaging.

A facile aqueous chemical approach is developed for one-pot synthesis of the nanocomposites of heavily doped semiconductor nanoparticles (Cu2-xSe NPs) and reduced graphene oxide (rGO) at room temperature, wherein the reduction of GO and the in situ growth of Cu2-xSe NPs on rGO sheets occur simultaneously. The as-prepared Cu2-xSe/rGO nanocomposites exhibit a well-defined near-infrared (NIR) localized surface plasmon resonance (LSPR), which arises from free carriers (holes) and could be tuned from 1360 to 1050 nm by varying the reaction time, owing to the increase of the free carrier density in the valence band of Cu2-xSe NPs. This approach not only offers an efficient strategy to synthesize the self-doped Cu2-xSe/rGO nanocomposites with strong and tunable NIR absorption, but also develops new light scattering nanoprobes with good biocompatibility as well as unique optical properties for in vitro cellular dark-field microscopic imaging (iDFM).

Cu2–xS1–ySey Alloy Nanocrystals with Broadly Tunable Near-Infrared Localized Surface Plasmon Resonance

We report facile methods for synthesizing monodisperse Cu2–xS1–ySey alloy nanocrystals (NCs) with tunable composition and size. The near-infrared (NIR) localized surface plasmon resonance (LSPR) in these self-doped Cu2–xS1–ySey alloy NCs can be tuned over a broad range from 975 to 1650 nm. The LSPR shifted to longer wavelength with increasing sulfur content and with increased concentration of oleic acid used in the synthesis. This method provides new possibilities for broadly tuning LSPR wavelength by controlling the anion composition, cationic vacancy concentration, and surface ligands in heavily doped Cu2–xS1–ySey alloy NCs. This opens up access to LSPR absorbance across a broad portion of the near-IR using small colloidal quasi-isotropic NCs.

Designed Synthesis of Solid and Hollow Cu2–xTe Nanocrystals with Tunable Near-Infrared Localized Surface Plasmon Resonance

Solid and hollow structures of Cu2–xTe nanocrystals are synthesized by the injection of a Te–TOP solution at different reaction times. Both types of Cu2–xTe nanocrystals exhibit an intense absorption peak (localized surface plasmon resonance (LSPR)) in the near-infrared region, arising from excess holes in the valence band, and high molar extinction coefficients of 2.6 × 107 M–1 cm–1 at 1150 nm and 8.1 × 107 M–1 cm–1 at 1200 nm are demonstrated for the solid-type and hollow-type Cu2–xTe nanocrystals, respectively. The experimentally observed extinction spectra and calculated extinction spectra based on the electrostatic approximation are studied. The LSPR responses in the near-infrared (NIR) region for both solid and hollow Cu2–xTe nanocrystals are affected by the refractive index of the medium, whereas the NIR resonance shift is more obvious in the hollow-type Cu2–xTe nanocrystals. Furthermore, the localized surface plasmon band of the Cu2–xTe nanostructures can be tuned by post processing via oxidation ...

Multifunctional Compact Hybrid Au Nanoshells: A New Generation of Nanoplasmonic Probes for Biosensing, Imaging, and Controlled Release

Gold nanoshells (AuNSs) with tunable localized surface plasmon resonance (LSPR) peaks in the near-infrared (NIR) region possess unique optical properties-particularly that soft tissues are "transparent" at these wavelengths-making them of great interest in cancer diagnosis and treatment. Since 1998 when Halas and co-workers invented the first generation of AuNS, with a silica core and Au shell, researchers have studied and designed AuNSs for theranostic-individualized, combination diagnosis and therapy-nanomedicine. As demand has increased for more powerful and practical theranostic applications, so has demand for the next generation of AuNSs-compact yet complex multifunctional AuNSs with finely integrated plasmonic and nonplasmonic inorganic components. For in vivo biomedical applications, such a hybrid AuNS offers the desirable optical properties of NIR LSPR. Size, however, has proved a more challenging parameter to control in hybrid AuNSs. The ideal size of therapeutic NPs is 10-100 nm. Larger particles have limited diffusion in the extracellular space, while particles less than 5 nm are rapidly cleared from the circulation through extravasation or renal clearance. Conventional methods of preparing AuNS have failed to obtain small-sized hybrid AuNSs with NIR LSPR responses. In this Account, we present a new class of multifunctional hybrid AuNSs with ultrathin AuNSs and varied, functional (nonplasmonic) core components ranging from "hard" semiconductor quantum dots (QDs), to superparamagnetic NPs, to "soft" liposomes made using poly-l-histidine as a template to direct Au deposition. The resultant hybrid AuNSs are uniform and compact (typically 15-60 nm) but also preserve the optical properties and shell-type NIR response necessary for biomedical use. We also demonstrate these particles' innovative plasmonic applications in biosensing, multimodal imaging and controlled release. More importantly, the magnetic-plasmonic Fe3O4/Au core-shell NP enables a new biological imaging method-magnetomotive photoacoustic (mmPA) imaging, which suppresses the nonmagnetomotive background and therefore offers remarkable contrast enhancement and improved specificity compared with photoacoustic images using conventional NP contrast agents. The advantages of our AuNSs are obvious: they are monodisperse, small (<100 nm), highly integrated, and have tunable visible-NIR plasmonic responses. All of these properties are crucial for in vitro or in vivo biological/biomedical studies and many applications, especially for studies of single cells or molecules which require particle monodispersity and tight size control. The plasmonic fluorescent QD/Au and the magnetic plasmonic Fe3O4/Au core-shell NPs may also reveal new physical phenomena that may lead to useful applications, owing to their well-defined core-shell nanoarchitectures and underlying nanoscale physical interactions.

Near-infrared optical response of thin film pH-sensitive hydrogel coated on a gold nanocrescent array

A hydrogel-based chemiresponsive sensor for monitoring H(+) (pH) has been developed by coating the surface of a gold nanocrescent array structure with a thin film of a poly(2-hydroxylethyl methacrylate)-based (poly-HEMA) hydrogel. The transmission measurement results of the close-packed gold nanocrescent array fabricated via electron beam lithography demonstrate near-infrared localized surface plasmon resonance peaks with sensitivities up to 332 nm/RIU in detecting refractive index change. Measurements of the hydrogel under solutions of increasing pH show the plasmon peak blueshifts by 17 nm and the integrated transmission increases by 1.8 in the operating range of 4.5 - 6.4 pH, which is ideal for biochemical sensor applications.