Upconversion photoluminescence of CdS nanocrystals in polymeric film

He, Jun; Scholes, Gregory D.; Qu, Yingli; Ji, Wei

doi:10.1063/1.2960536

Cited by 10 publications

(10 citation statements)

References 28 publications

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“…Figure 6 f shows that the profi les of the TPF spectra of QF1 composite fi lms are similar at different excitation intensities without any red/blue shift, indicating that the re-absorption effect or high-intensity induced bandgap renormalizations are not involved in the nonlinear adsorption process. [ 20 ] Furthermore, the results of other composite fi lms are the same ( Figure S7, Supporting Information), which is in agreement with the general two-photon absorption theory. [ 28 ] …”

Section: Materials Assembly Of Nano Functional Materialssupporting

confidence: 88%

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Engineering of Fluorescent Emission of Silk Fibroin Composite Materials by Material Assembly

Lin

Meng

Toh

et al. 2014

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This novel materials assembly technology endows the designated materials with additional/enhanced performance by fixing "functional components" into the materials. Such functional components are molecularly recognized and accommodated by the designated materials. In this regard, two-photon fluorescence (TPF) organic molecules and CdTe quantum dots (QDs) are adopted as functional components to functionalize silk fibers and films. TPF organic molecules, such as, 2,7-bis[2-(4-nitrophenyl) ethenyl]-9,9-dibutylfluorene (NM), exhibit TPF emission quenching because of the molecular stacking that leads to aggregation in the solid form. The specific recognition between -NO2 in the annealed fluorescent molecules and the -NH groups in the silk fibroin molecules decouples the aggregated molecules. This gives rise to a significant increase in the TPF quantum yields of the silk fibers. Similarly, as another type of functional components, CdTe quantum dots (QDs) with different sizes were also adopted in the silk functionalization method. Compared to QDs in solution the fluorescence properties of functionalized silk materials display a long stability at room temperature. As the functional materials are well dispersed at high quantum yields in the biocompatible silk a TPF microscope can be used to pursue 3D high-resolution imaging in real time of the TPF-silk scaffold.

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Section: Materials Assembly Of Nano Functional Materialssupporting

confidence: 88%

“…It is well known that the transition probability for TPF depends on the square of the incident light intensity. [ 20 ] It can be seen in Figure S3 (Supporting Information) that all emission signals of NM silk are proportional to the excitation intensity, confi rming the presence of the TPF process.…”

Section: Materials Assembly Of Organic Functional Materialsmentioning

confidence: 85%

Engineering of Fluorescent Emission of Silk Fibroin Composite Materials by Material Assembly

Lin

Meng

Toh

et al. 2014

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“…Surface states have been proposed to play an important role in the upconversion in nanoparticles such as CdS and CdSe 175. For semiconductor QDs with three‐dimensional (3D) quantum confinement, upconversion has recently been reported for CdS,176 InP,177 CdSe,175 InAs/GaAs,178 InGaN/GaN multiple quantum wells,179 ZnSe,180 CdSeS,172 Er‐doped CdS181 and lanthanide‐doped NaYF 4 182…”

Section: Optical Propertiesmentioning

confidence: 99%

Exciton Dynamics in Semiconductor Nanocrystals

2013

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This review article provides an overview of recent advances in the study and understanding of dynamics of excitons in semiconductor nanocrystals (NCs) or quantum dots (QDs). Emphasis is placed on the relationship between exciton dynamics and optical properties, both linear and nonlinear. We also focus on the unique aspects of exciton dynamics in semiconductor NCs as compared to those in bulk crystals. Various experimental techniques for probing exciton dynamics, particularly time-resolved laser methods, are reviewed. Relevant models and computational studies are also briefly presented. By comparing different materials systems, a unifying picture is proposed to account for the major dynamic features of excitons in semiconductor QDs. While the specific dynamic processes involved are material-dependent, key processes can be identified for all the materials that include electronic dephasing, intraband relaxation, trapping, and interband recombination of free and trapped charge carriers (electron and hole). Exciton dynamics play a critical role in the fundamental properties and functionalities of nanomaterials of interest for a variety of applications including optical detectors, solar energy conversion, lasers, and sensors. A better understanding of exciton dynamics in nanomaterials is thus important both fundamentally and technologically.

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“…The nanoparticle radius is comparable to the Bohr exciton radius in the corresponding bulk material, leading to splitting of continuum of electronic energy levels into discrete states with the effective band gap energy blue shifted from that of the bulk. II-VI semiconductor nanostructures have been investigated widely and demonstrated potential application in solar cells [1], light emitting diodes [2], IR photodetectors [3], electrically driven lasers [4], optical limiters [5] biological fluorescent labels [6] and upconversion luminescent materials [7]. Semiconductor nanocrystals have been prepared either as powder or stable self standing nanocrystals by using different organic stabilizers to prevent them from aggregation by capping their surfaces.…”

Section: Introductionmentioning

confidence: 99%

“…Semiconductor nanoparticles or quantum dots (QDs) with typical dimensions of 1-100 nm have generated enormous attention in the past decades because their optical and electronic properties are dramatically different from those of the corresponding bulk crystals and also because of their wide applications in the fields of optoelectronic and biological technology [1][2][3][4][5][6][7]. Chalcogenide semiconductors such as cadmium sulfide is a well characterized II-VI group inorganic semiconductor with a wide direct band gap of 2.42 eV (bulk CdS) and a small exciton Bohr radius of 2.5 nm.…”

Section: Introductionmentioning

confidence: 99%