Your browser doesn't support javascript.
loading
Show: 20 | 50 | 100
Results 1 - 20 de 60
Filter
1.
Nature ; 618(7967): 951-958, 2023 Jun.
Article in English | MEDLINE | ID: mdl-37258675

ABSTRACT

Materials whose luminescence can be switched by optical stimulation drive technologies ranging from superresolution imaging1-4, nanophotonics5, and optical data storage6,7, to targeted pharmacology, optogenetics, and chemical reactivity8. These photoswitchable probes, including organic fluorophores and proteins, can be prone to photodegradation and often operate in the ultraviolet or visible spectral regions. Colloidal inorganic nanoparticles6,9 can offer improved stability, but the ability to switch emission bidirectionally, particularly with near-infrared (NIR) light, has not, to our knowledge, been reported in such systems. Here, we present two-way, NIR photoswitching of avalanching nanoparticles (ANPs), showing full optical control of upconverted emission using phototriggers in the NIR-I and NIR-II spectral regions useful for subsurface imaging. Employing single-step photodarkening10-13 and photobrightening12,14-16, we demonstrate indefinite photoswitching of individual nanoparticles (more than 1,000 cycles over 7 h) in ambient or aqueous conditions without measurable photodegradation. Critical steps of the photoswitching mechanism are elucidated by modelling and by measuring the photon avalanche properties of single ANPs in both bright and dark states. Unlimited, reversible photoswitching of ANPs enables indefinitely rewritable two-dimensional and three-dimensional multilevel optical patterning of ANPs, as well as optical nanoscopy with sub-ƅ localization superresolution that allows us to distinguish individual ANPs within tightly packed clusters.

2.
Nature ; 589(7841): 230-235, 2021 01.
Article in English | MEDLINE | ID: mdl-33442042

ABSTRACT

Avalanche phenomena use steeply nonlinear dynamics to generate disproportionately large responses from small perturbations, and are found in a multitude of events and materials1. Photon avalanching enables technologies such as optical phase-conjugate imaging2, infrared quantum counting3 and efficient upconverted lasing4-6. However, the photon-avalanching mechanism underlying these optical applications has been observed only in bulk materials and aggregates6,7, limiting its utility and impact. Here we report the realization of photon avalanching at room temperature in single nanostructures-small, Tm3+-doped upconverting nanocrystals-and demonstrate their use in super-resolution imaging in near-infrared spectral windows of maximal biological transparency. Avalanching nanoparticles (ANPs) can be pumped by continuous-wave lasers, and exhibit all of the defining features of photon avalanching, including clear excitation-power thresholds, exceptionally long rise time at threshold, and a dominant excited-state absorption that is more than 10,000 times larger than ground-state absorption. Beyond the avalanching threshold, ANP emission scales nonlinearly with the 26th power of the pump intensity, owing to induced positive optical feedback in each nanocrystal. This enables the experimental realization of photon-avalanche single-beam super-resolution imaging7 with sub-70-nanometre spatial resolution, achieved by using only simple scanning confocal microscopy and without any computational analysis. Pairing their steep nonlinearity with existing super-resolution techniques and computational methods8-10, ANPs enable imaging with higher resolution and at excitation intensities about 100 times lower than other probes. The low photon-avalanching threshold and excellent photostability of ANPs also suggest their utility in a diverse array of applications, including sub-wavelength imaging7,11,12 and optical and environmental sensing13-15.

3.
Nano Lett ; 24(1): 279-286, 2024 Jan 10.
Article in English | MEDLINE | ID: mdl-38117534

ABSTRACT

Emerging light-matter interactions in metal-semiconductor hybrid platforms have attracted considerable attention due to their potential applications in optoelectronic devices. Here, we demonstrate plasmon-induced near-field manipulation of trionic responses in a MoSe2 monolayer using tip-enhanced cavity-spectroscopy (TECS). The surface plasmon-polariton mode on the Au nanowire can locally manipulate the exciton (X0) and trion (X-) populations of MoSe2. Furthermore, we reveal that surface charges significantly influence the emission and interconversion processes of X0 and X-. In the TECS configuration, the localized plasmon significantly affects the distributions of X0 and X- due to the modified radiative decay rate. Additionally, within the TECS cavity, the electric doping effect and hot electron generation enable dynamic interconversion between X0 and X- at the nanoscale. This work advances our understanding of plasmon-exciton-hot electron interactions in metal-semiconductor-metal hybrid structures, providing a foundation for an optimal trion-based nano-optoelectronic platform.

4.
Nano Lett ; 24(12): 3777-3784, 2024 Mar 27.
Article in English | MEDLINE | ID: mdl-38497654

ABSTRACT

Gap plasmon (GP) resonance in static surface-enhanced Raman spectroscopy (SERS) structures is generally too narrow and not tunable. Here, we present an adaptive gap-tunable SERS device to selectively enhance and modulate different vibrational modes via active flexible Au nanogaps, with adaptive optical control. The tunability of GP resonance is up to Ć¢ĀˆĀ¼1200 cm-1 by engineering gap width, facilitated by mechanical bending of a polyethylene terephthalate substrate. We confirm that the tuned GP resonance selectively enhances different Raman spectral regions of the molecules. Additionally, we dynamically control the SERS intensity through the wavefront shaping of excitation beams. Furthermore, we demonstrate simulation results, exhibiting the mechanical and optical properties of a one-dimensional flexible nanogap and their advantage in high-speed biomedical sensing. Our work provides a unique approach for observing and controlling the enhanced chemical responses with dynamic tunability.

5.
Angew Chem Int Ed Engl ; : e202413672, 2024 Oct 29.
Article in English | MEDLINE | ID: mdl-39470130

ABSTRACT

Developing efficient scintillators with environmentally friendly compositions, adaptable bandgaps, and robust chemical stability is crucial for modern X-ray radiography. While copper(I)-iodide cluster crystals show promise, the vast design space of inorganic cores and organic ligands poses challenges for conventional approaches. In this study, we present machine learning-guided discovery of copper(I)-iodide cluster scintillators for efficient X-ray luminescence imaging. Our findings reveal that combining base learning models with fused features enhances model generalization, achieving an impressive determination coefficient of 0.88. By leveraging this approach, we obtain a high-performance Cu(I)-I cluster scintillator, named copper iodide-(1-Butyl-1,4-diazabicyclo[2.2.2]octan-1-ium)2, which exhibit radioluminescence 56 times stronger than that of PbWO4, and enables a detection limit for X-rays of 19.6 nGyair s-1. Furthermore, we demonstrate the versatility of these scintillators by incorporating them as microfillers in the fabrication of flexible composite scintillators for X-ray imaging, achieving a static resolution of 20 lp mm-1 and demonstrating promising performance for dynamic X-ray imaging.

6.
Acc Chem Res ; 49(12): 2746-2755, 2016 12 20.
Article in English | MEDLINE | ID: mdl-27993009

ABSTRACT

Plasmonic coupling-based electromagnetic field localization and enhancement are becoming increasingly important in chemistry, nanoscience, materials science, physics, and engineering over the past decade, generating a number of new concepts and applications. Among the plasmonically coupled nanostructures, metal nanostructures with nanogaps have been of special interest due to their ultrastrong electromagnetic fields and controllable optical properties that can be useful for a variety of signal enhancements such as surface-enhanced Raman scattering (SERS). The Raman scattering process is highly inefficient, with a very small cross-section, and Raman signals are often poorly reproducible, meaning that very strong, controllable SERS is needed to obtain reliable Raman signals with metallic nanostructures and thus open up new avenues for a variety of Raman-based applications. More specifically, plasmonically coupled metallic nanostructures with ultrasmall (Ć¢ĀˆĀ¼1 nm or smaller) nanogaps can generate very strong and tunable electromagnetic fields that can generate strong SERS signals from Raman dyes in the gap, and plasmonic nanogap-enhanced Raman scattering can be defined as Raman signal enhancement from plasmonic nanogap particles with Ć¢ĀˆĀ¼1 nm gaps. However, these promising nanostructures with extraordinarily strong optical signals have shown limited use for practical applications, largely due to the lack of design principles, high-yield synthetic strategies with nanometer-level structural control and reproducibility, and systematic, reliable single-molecule/single-particle-level studies on their optical properties. All these are extremely important challenges because even small changes (<1 nm) in the structure of the coupled plasmonic nanogaps can significantly affect the plasmon mode and signal intensity. In this Account, we examine and summarize recent breakthroughs and advances in plasmonic nanogap-enhanced Raman scattering with metal nanogap particles with respect to the design and synthesis of plasmonic nanogap structures, as well as ultrasensitive and quantitative Raman signal detection using these structures. The applications and prospects of plasmonic nanogap particle-based SERS are also discussed. In particular, reliable synthetic and measurement strategies for plasmonically coupled nanostructures with Ć¢ĀˆĀ¼1 nm gap, in which both the nanogap size and the position of a Raman-active molecule in the gap can be controlled with nanometer/sub-nanometer-level precision, can address important issues regarding the synthesis and optical properties of plasmonic nanostructures, including structural and signal reproducibility. Further, single-molecule/single-particle-level studies on the plasmonic properties of these nanogap structures revealed that these particles can generate ultrastrong, quantifiable Raman signals in a highly reproducible manner.

7.
Small ; 12(34): 4726-34, 2016 Sep.
Article in English | MEDLINE | ID: mdl-27028989

ABSTRACT

Plasmonic nanostructures are widely studied and used because of their useful size, shape, composition and assembled structure-based plasmonic properties. It is, however, highly challenging to precisely design, reproducibly synthesize and reliably utilize plasmonic nanostructures with enhanced optical properties. Here, we devise a facile synthetic method to generate Au surface roughness-controlled nanobridged nanogap particles (Au-RNNPs) with ultrasmall (≈1 nm) interior gap and tunable surface roughness in a highly controllable manner. Importantly, we found that particle surface roughness can be associated with and enhance the electromagnetic field inside the interior gap, and stronger nanogap-enhanced Raman scattering (NERS) signals can be generated from particles by increasing particle surface roughness. The finite-element method-based calculation results support and are matched well with the experimental results and suggest one needs to consider particle shape, nanogap and nanobridges simultaneously to understand and control the optical properties of this type of nanostructures. Finally, the potential of multiplexed Raman detection and imaging with RNNPs and the high-speed, high-resolution Raman bio-imaging of Au-RNNPs inside cells with a wide-field Raman imaging setup with liquid crystal tunable filter are demonstrated. Our results provide strategies and principles in designing and synthesizing plasmonically enhanced nanostructures and show potential for detecting and imaging Raman nanoprobes in a highly specific, sensitive and multiplexed manner.


Subject(s)
Imaging, Three-Dimensional , Metal Nanoparticles/chemistry , Optical Phenomena , Spectrum Analysis, Raman/methods , Cell Line, Tumor , DNA/chemistry , Electromagnetic Fields , Gold/chemistry , Humans , Hydroxylamine/chemistry , Metal Nanoparticles/ultrastructure , Surface Properties
8.
Chem Soc Rev ; 44(6): 1302-17, 2015 Mar 21.
Article in English | MEDLINE | ID: mdl-25042637

ABSTRACT

Lanthanide-doped upconverting nanoparticles (UCNPs) have recently attracted enormous attention in the field of biological imaging owing to their unique optical properties: (1) efficient upconversion photoluminescence, which is intense enough to be detected at the single-particle level with a (nonscanning) wide-field microscope setup equipped with a continuous wave (CW) near-infrared (NIR) laser (980 nm), and (2) resistance to photoblinking and photobleaching. Moreover, the use of NIR excitation minimizes adverse photoinduced effects such as cellular photodamage and the autofluorescence background. Finally, the cytotoxicity of UCNPs is much lower than that of other nanoparticle systems. All these advantages can be exploited simultaneously without any conflicts, which enables the establishment of a novel UCNP-based platform for wide-field two-photon microscopy. UCNPs are also useful for multimodal in vivo imaging because simple variations in the composition of the lattice atoms and dopant ions integrated into the particles can be easily implemented, yielding various distinct biomedical activities relevant to magnetic resonance imaging (MRI), computed tomography (CT), and positron emission tomography (PET). These multiple functions embedded in a single type of UCNPs play a crucial role in precise disease diagnosis. The application of UCNPs is extended to therapeutic fields such as photodynamic and photothermal cancer therapies through advanced surface conjugation schemes.


Subject(s)
Nanoparticles/chemistry , Animals , Contrast Media/chemistry , Humans , Lanthanoid Series Elements/chemistry , Magnetic Resonance Imaging , Microscopy, Fluorescence , Neoplasms/diagnosis , Photons , Positron-Emission Tomography , Spectroscopy, Near-Infrared , Tomography, X-Ray Computed
9.
Nano Lett ; 15(7): 4628-36, 2015 Jul 08.
Article in English | MEDLINE | ID: mdl-26075353

ABSTRACT

Here, we quantitatively monitored and analyzed the spectral redistributions of the coupled plasmonic modes of trimeric Au nanostructures with two Ć¢ĀˆĀ¼1 nm interparticle gaps and single-dye-labeled DNA in each gap as a function of varying trimer symmetries. Our precise Mie scattering measurement with the laser-scanning-assisted dark-field microscopy allows for individual visualization of the orientations of the radiation fields of the coupled plasmon modes of the trimers and analyzing the magnitude and direction of the surface-enhanced Raman scattering (SERS) signals from the individual plasmonic trimers. We found that the geometric transition from acute-angled trimer to linear trimer induces the red shift of the longitudinally polarized mode and the blue shift of the axially polarized mode. The finite element method (FEM) calculation results show the distinct "on" and "off" of the plasmonic modes at the two gaps of the trimer. Importantly, the single-molecule-level systematic correlation studies among the near-field, far-field, and surface-enhanced Raman scattering reveal that the SERS signals from the trimers are determined by the largely excited coupled plasmon between the two competing plasmon modes, longitudinal and axial modes. Further, the FEM calculation revealed that even 0.5 nm or smaller discrepancy in the sizes of two gaps of the linear trimer led to >10-fold difference in the SERS signal. Granted that two gap sizes are not likely to be completely the same in actual experiments, one of two gaps plays a more significant role in generating the SERS signal. Overall, this work provides the knowledge and handles for the understanding and systematic control of the magnitude and polarization direction of the both plasmonic response and SERS signal from trimeric nanostructures and sets up the platform for the optical properties and the applications of plasmonically coupled trimers and higher multimeric nanostructures.

10.
Phys Chem Chem Phys ; 17(20): 13201-5, 2015 May 28.
Article in English | MEDLINE | ID: mdl-25929753

ABSTRACT

Lanthanide-doped upconverting nanoparticles (UCNPs, NaYF4:Yb(3+),Er(3+)) are well known for emitting visible photons upon absorption of two or more near-infrared (NIR) photons through energy transfer from the sensitizer (Yb(3+)) to the activator (Er(3+)). Of the visible emission bands (two green and one red band), it has been suggested that the red emission results from two competing upconversion pathways where the non-radiative relaxation occurs after the second energy transfer (pathway A, (4)I15/2 Ć¢Ā†Ā’ (4)I11/2 Ć¢Ā†Ā’ (4)F7/2 Ć¢Ā†Ā’ (2)H11/2 Ć¢Ā†Ā’ (4)S3/2 Ć¢Ā†Ā’ (4)F9/2 Ć¢Ā†Ā’ (4)I15/2) or between the first and the second energy transfer (pathway B, (4)I15/2 Ć¢Ā†Ā’ (4)I11/2 Ć¢Ā†Ā’ (4)I13/2 Ć¢Ā†Ā’ (4)F9/2 Ć¢Ā†Ā’ (4)I15/2). However, there has been no clear evidence or thorough analysis of the partitioning between the two pathways. We examined the spectra, power dependence, and time profiles of UCNP emission at either 980 nm or 488 nm excitation, to address which pathway is preferred. It turned out that the pathway B is predominant for the red emission over a wide range of excitation powers.

11.
J Am Chem Soc ; 136(40): 14052-9, 2014 Oct 08.
Article in English | MEDLINE | ID: mdl-25198151

ABSTRACT

The design, synthesis and control of plasmonic nanostructures, especially with ultrasmall plasmonically coupled nanogap (Ć¢ĀˆĀ¼1 nm or smaller), are of significant interest and importance in chemistry, nanoscience, materials science, optics and nanobiotechnology. Here, we studied and established the thiolated DNA-based synthetic principles and methods in forming and controlling Au core-nanogap-Au shell structures [Au-nanobridged nanogap particles (Au-NNPs)] with various interior nanogap and Au shell structures. We found that differences in the binding affinities and modes among four different bases to Au core, DNA sequence, DNA grafting density and chemical reagents alter Au shell growth mechanism and interior nanogap-forming process on thiolated DNA-modified Au core. Importantly, poly A or poly C sequence creates a wider interior nanogap with a smoother Au shell, while poly T sequence results in a narrower interstitial interior gap with rougher Au shell, and on the basis of the electromagnetic field calculation and experimental results, we unraveled the relationships between the width of the interior plasmonic nanogap, Au shell structure, electromagnetic field and surface-enhanced Raman scattering. These principles and findings shown in this paper offer the fundamental basis for the thiolated DNA-based chemistry in forming and controlling metal nanostructures with Ć¢ĀˆĀ¼1 nm plasmonic gap and insight in the optical properties of the plasmonic NNPs, and these plasmonic nanogap structures are useful as strong and controllable optical signal-generating nanoprobes.

12.
Phys Chem Chem Phys ; 16(11): 5312-8, 2014 Mar 21.
Article in English | MEDLINE | ID: mdl-24496293

ABSTRACT

We present time-gated femtosecond stimulated Raman spectroscopy (fSRS) under the pre-resonance Raman conditions of diethylthiatricarbocyanine (DTTC) iodide. A 'pseudo emission-free' condition is achieved by delivering the probe beam ahead of the pump beam. Regeneratively amplified pulse trains are employed to create an angle-geometry (non-collimated) mixing between the pump and probe beams, leading to highly sensitive measurement of the stimulated Raman gain. Time-integrated spectroscopy allows for a more quantitative distinction between the contributions of stimulated Raman scattering and stimulated emission. We successfully obtain a highly sensitive (signal-to-noise ratio >100) stimulated Raman spectrum under the optimized conditions, which compares favourably to results obtained using two-dimensional correlation spectroscopy (2DCOS). Given the optical pre-resonance of Ć¢ĀˆĀ¼0.1 eV, the background signals mostly originate from the stimulated emission of excited electrons and are significantly reduced by partial overlapping of the pump and probe beams; a genuine fSRS spectral profile is obtained for a temporal delay of Ć¢ĀˆĀ¼0.2 ps between the two beams.


Subject(s)
Carbocyanines/chemistry , Spectrum Analysis, Raman/methods
13.
Nano Lett ; 13(12): 6113-21, 2013.
Article in English | MEDLINE | ID: mdl-24256433

ABSTRACT

Understanding the detailed electromagnetic field distribution inside a plasmonically coupled nanostructure, especially for structures with ~ 1 nm plasmonic gap, is the fundamental basis for the control and use of the strong optical properties of plasmonic nanostructures. Using a multistep AFM tip-matching strategy that enables us to gain the optical spectra with the optimal signal-to-noise ratio as well as high reliability in correlation measurement between localized surface plasmon (LSP) and surface-enhanced Raman scattering (SERS), the coupled longitudinal dipolar and high-order multipolar LSPs were detected within a dimeric structure, where a single Raman dye is located via a single-DNA hybridization between two differently sized Au-Ag core-shell particles. On the basis of the characterization of each LSP component, the distinct phase differences, attributed to different quantities of the excited quadrupolar LSPs, between the transverse and longitudinal regimes were observed for the first time. By assessing the relative ratio of dipolar and quadrupolar LSPs, we found that these LSPs of the dimer with ~ 1 nm gap were simultaneously excited, and large longitudinal bonding dipolar LSP/longitudinal bonding quadrupolar LSP value is required to generate high SERS signal intensity. Interestingly, a minor population of the examined dimers exhibited strong SERS intensities along not only the dimer axis but also the direction that arises from the interaction between the coupled transverse dipolar and longitudinal bonding quadrupolar LSPs. Overall, our high-precision correlation measurement strategy with a plasmonic heterodimer with ~ 1 nm gap allows for the observation of the characteristic spectral features with the optimal signal-to-noise ratio and the subpopulation of plasmonic dimers with a distinct SERS behavior, hidden by a majority of dimer population, and the method and results can be useful in understanding the whole distribution of SERS enhancement factor values and designing plasmonic nanoantenna structures.


Subject(s)
Gold/chemistry , Metal Nanoparticles/chemistry , Nanostructures/chemistry , Nanotechnology , Polymers/chemistry , Spectrum Analysis, Raman , Surface Plasmon Resonance , Surface Properties
14.
Nat Commun ; 15(1): 8111, 2024 Sep 16.
Article in English | MEDLINE | ID: mdl-39285162

ABSTRACT

A deep understanding of how the host matrix influences the afterglow properties of molecule dopants is crucial for designing advanced afterglow materials. Despite its appeal, the impact of defects on the afterglow performance in molecule-doped SiO2 matrices has remained largely unexplored. Herein, we detail the synthesis of monodisperse SiO2 microparticles by hydrothermally doping molecules, such as 4-phenylpyridine, 4,4'-bipyridine, and 1,4-bis(pyrid-4-yl)benzene. Our results demonstrate that hydrothermal reactions induce not only the formation of emissive defects in the SiO2 matrix but also enable molecule doping through SiO2 pseudomorphic transformation. Optical analyses reveal a remarkable afterglow activation of doped molecules, driven by a synergistic interplay of hydrogen bonding and physical fixation. Specifically, 4-phenylpyridine doping leads to an impressive 227- and 271-fold enhancement in fluorescence and afterglow, respectively, and an extraordinary 3711-fold enhancement in the afterglow lifetime of the resulting SiO2 MPs. We also document hybrid states involving molecule dopants and SiO2 defects, explaining energy transfer from molecule dopants to defects in both singlet and triplet states. The robust achievement of molecule doping provides flexibility to tailor excitation-dependent afterglow attributes while preserving angle-dependent structural colors, facilitating the creation of diverse building blocks for multiscale optical platforms for afterglow modulation and information encoding.

15.
Analyst ; 138(19): 5588-93, 2013 Oct 07.
Article in English | MEDLINE | ID: mdl-23884074

ABSTRACT

We presented a scalable fabrication method for the preparation of multilayered nano-prism vertex (NV)-tips whose dimensions can be controlled for tip-enhanced Raman spectroscopy (TERS). The NV-tip had sharp vertices (diameter ~20 nm) originated from the chemical lift-off process after the angle-grinding process, enabling high resolution imaging. TERS measurements were performed on brilliant cresyl blue (BCB) molecules using a Ag/Au NV-tip, revealing the enhanced field localization at the vertices of the NV-tip. Furthermore, we could observe the polarization effect of the NV-tip. Our NV-tips should be a powerful tool for basic research on TERS experiments and SPM applications.


Subject(s)
Nanotechnology/instrumentation , Nanotechnology/methods , Spectrum Analysis, Raman/instrumentation , Spectrum Analysis, Raman/methods
16.
Phys Chem Chem Phys ; 15(15): 5276-87, 2013 Apr 21.
Article in English | MEDLINE | ID: mdl-23525118

ABSTRACT

This perspective presents an overview of single-molecule surface-enhanced Raman scattering (sm-SERS). Our overview is organized as a brief theoretical background, discussion of the factors that enhance SERS, various experimental preparations for inserting a single molecule in a hot spot, recent sm-SERS experiments, and a perspective. Although, there have been numerous review papers on sm-SERS, we mainly concentrated on the logical development of sm-SERS on the basis of the fundamental concepts and their physical significance, so that readers outside this field can understand the motivation and the underlying physics when describing current sm-SERS measurements. Indeed, understanding such current sm-SERS experiments conducted by representative groups would be very helpful for readers to answer for themselves the fundamental and practical questions surrounding sm-SERS: (1) what information can sm-SERS provide? (2) Which factors based on the SERS mechanism should be considered to significantly amplify the SERS signal? (3) What kinds of related microscopy techniques could be combined with sm-SERS to attain more meaningful results? (4) Which statistical approaches can be used and how they can be applied to properly analyze sm-SERS data? We hope that this review article can help readers answer these questions.


Subject(s)
Spectrum Analysis, Raman , Metal Nanoparticles/chemistry , Microscopy, Atomic Force , Nanotechnology , Silver/chemistry
17.
Phys Chem Chem Phys ; 15(12): 4243-9, 2013 Mar 28.
Article in English | MEDLINE | ID: mdl-23386278

ABSTRACT

We investigated the correlations among the structure, Rayleigh scattering, and single-molecule surface-enhanced Raman scattering (SERS) of DNA-tethered Au-Ag core-shell nanoparticles, especially in dimer and trimer forms. For the optimal correlation measurements, accurate information on the position of the nanoparticle is crucial for locating the nanoparticle at the center of the excitation source for the optical measurements. To achieve this, we developed a multistep correlation strategy that enables us to unambiguously correlate the AFM images with optical images within a few nanometers. We also newly defined the correlation accuracy in this paper as a useful concept for the correlation measurements. With this reliable correlation accuracy, we performed various statistical analyses to thoroughly elucidate the relationships between particle structure, Rayleigh scattering and SERS in terms of the incident polarization and scattering intensity ratio.

18.
Nano Lett ; 12(4): 1879-84, 2012 Apr 11.
Article in English | MEDLINE | ID: mdl-22443346

ABSTRACT

We report a simple but efficient method to synthesize carbon nanotube-bridged wires (NBWs) with gaps as small as 5 nm. In this method, we have combined a strategy for assembling carbon nanotubes (CNTs) inside anodized aluminum oxide pores and the on-wire lithography technique to fabricate CNT-bridged wires with gap sizes deliberately tailored over the 5-600 nm range. As a proof-of-concept demonstration of the utility of this architecture, we have prepared NBW-based chemical and biosensors which exhibit higher analyte sensitivity (lower limits of detection) than those based on planar CNT networks. This observation is attributed to a greater surface-to-volume ratio of CNTs in the NBWs than those in the planar CNT devices. Because of the ease of synthesis and high yield of NBWs, this technique may enable the further incorporation of CNT-based architectures into various nanoelectronic and sensor platforms.

19.
Adv Sci (Weinh) ; 10(5): e2205526, 2023 Feb.
Article in English | MEDLINE | ID: mdl-36461749

ABSTRACT

The search for color-tunable, efficient, and robust scintillators plays a vital role in the development of modern X-ray radiography. The radioluminescence tuning of copper iodide cluster scintillators in the entire visible region by bandgap engineering is herein reported. The bandgap engineering benefits from the fact that the conduction band minimum and valence band maximum of copper iodide cluster crystals are contributed by atomic orbitals from the inorganic core and organic ligand components, respectively. In addition to high scintillation performance, the as-prepared crystalline copper iodide cluster solids exhibit remarkable resistance toward both moisture and X-ray irradiation. These features allow copper iodide cluster scintillators to show particular attractiveness for low-dose X-ray radiography with a detection limit of 55 nGy s-1 , a value ≈100 times lower than a standard dosage for X-ray examinations. The results suggest that optimizing both inorganic core and organic ligand for the building blocks of metal halide cluster crystals may provide new opportunities for a new generation of high-performance scintillation materials.

20.
Adv Mater ; 35(48): e2307198, 2023 Nov.
Article in English | MEDLINE | ID: mdl-37821358

ABSTRACT

Synthesizing monodisperse afterglow microparticles (MPs) is crucial for creating photonic crystal (PC) platforms with multiple optical states for optoelectronics. However, achieving high uniformity in both size and morphology is challenging for inorganic afterglow MPs using conventional methods. In this contribution, a novel approach for the synthesis of carbon dot (CD)-doped SiO2 MPs with tunable afterglow properties and size distributions is reported. These mechanism studies suggest that the pseudomorphic transformation of SiO2 MPs enables CD doping, providing a hydrogen bond-enriched environment for triplet state stabilization, which generates green afterglow while retaining the uniformity in size and morphology of the parent SiO2 MPs. Furthermore, the utility of CD-doped SiO2 MPs in the fabrication of rationally designed PC patterns is shown using a combined consecutive dip-coating and laser-assisted etching strategy. The pattern displays multiple optical responses under different lighting conditions, including angle-dependent structural colors and blue luminescence under daylight and upon 365-nm irradiation, respectively, as well as time-dependent green afterglow after ceasing UV excitation. The findings pave the way for further controlling the dynamics of spontaneous emissions by PCs to enable complicated optical states for advanced photonics.

SELECTION OF CITATIONS
SEARCH DETAIL