Ze Yin

Local Field Modulation Induced Three‐Order Upconversion Enhancement: Combining Surface Plasmon Effect and Photonic Crystal Effect

A 2D surface plasmon photonic crystal (SPPC) is achieved by implanting gold nanorods onto the periodic surface apertures of the poly(methyl methacrylate) (PMMA) opal photonic crystals. On the surface of the SPPC, the overall upconversion luminescence intensity of NaYF4 :Yb(3+) , Er(3+) under 980 nm excitation is improved more than 10(3) fold. The device is easily shifted to a transparent flexible substrate, applied to flexible displays.

Remarkable enhancement of upconversion fluorescence and confocal imaging of PMMA Opal/NaYF4:Yb3+, Tm3+/Er3+ nanocrystals

Novel PMMA opal photonic crystal/NaYF(4):Yb(3+), Tm(3+)/Er(3+) nanocrystal composites were fabricated and tremendous improvement in upconversion luminescence (UCL) was observed under infrared 980 nm excitation. They were also explored to improve brightness of cell images.

Observation of Considerable Upconversion Enhancement Induced by Cu2–xS Plasmon Nanoparticles

Localized surface plasmon resonances (LSPRs) are achieved in heavily doped semiconductor nanoparticles (NPs) with appreciable free carrier concentrations. In this paper, we present the photonic, electric, and photoelectric properties of plasmonic Cu2-xS NPs/films and the utilization of LSPRs generated from semiconductor NPs as near-infrared antennas to enhance the upconversion luminescence (UCL) of NaYF4:Yb(3+),Er(3+) NPs. Our results suggest that the LSPRs in Cu2-xS NPs originate from ligand-confined carriers and that a heat treatment resulted in the decomposition of ligands and oxidation of Cu2-xS NPs; these effects led to a decrease of the Cu(2+)/Cu(+) ratio, which in turn resulted in the broadening, decrease in intensity, and red-shift of the LSPRs. In the presence of a MoO3 spacer, the UCL intensity of NaYF4:Yb(3+),Er(3+) NPs was substantially improved and exhibited extraordinary power-dependent behavior because of the energy band structure of the Cu2-xS semiconductor. These findings provide insights into the nature of LSPR in semiconductors and their interaction with nearby emitters and highlight the possible application of LSPR in photonic and photoelectric devices.

Self-assembly, highly modified spontaneous emission and energy transfer properties of LaPO4:Ce3+, Tb3+ inverse opals

The modification of photonic crystals (PCs) on photoluminescence of rare earth (RE) ions has attracted considerable interest, however, the modification of PCs on energy transfer (ET) processes of two separate RE centers has not been investigated yet. In this paper, three-dimensional Ce(3+), Tb(3+)-codoped LaPO4 inverse opal PCs (IOPCs) were fabricated by the PMMA colloidal template method. The modification of the photonic stop band (PSB) on emission spectra and the dynamics of the 5d-4f transition of Ce(3+) and the 4f-4f transition of Tb(3+) ions were systematically studied. It is interesting to observe that the spontaneous decay rates (SDR) of (5)D4-(7)F5 in the IOPCs were suppressed as highly as 173% in contrast to the reference ground powder samples (REF) due to the modification of the effective refractive index (n(eff)). The energy transfer (ET) rate of Ce(3+) to Tb(3+) did not change in the IOPCs, however, the energy migration rate among Tb(3+) ions was largely restrained. It is also significant to observe that, in the IOPCs, the temperature quenching and radiation trapping of photoluminescence were greatly suppressed due to the periodic empty cavity structure of IOPCs, which is significant for high-power light sources and laser devices.

Paper-based upconversion fluorescence resonance energy transfer biosensor for sensitive detection of multiple cancer biomarkers.

A paper-based upconversion fluorescence resonance energy transfer assay device is proposed for sensitive detection of CEA. The device is fabricated on a normal filter paper with simple nano-printing method. Upconversion nanoparticles tagged with specific antibodies are printed to the test zones on the test paper, followed by the introduction of assay antigen. Upconversion fluorescence measurements are directly conducted on the test zones after the antigen-to-antibody reactions. Furthermore, a multi-channel test paper for simultaneous detection of multiple cancer biomarkers was established by the same method and obtained positive results. The device showed high anti-interfere, stability, reproducible and low detection limit (0.89 ng/mL), moreover it is very easy to fabricate and operate, which is a promising prospect for a clinical point-of-care test.

Plasmon-Enhanced Upconversion Luminescence on Vertically Aligned Gold Nanorod Monolayer Supercrystals.

Upconversion nanophosphor is attracting worldwide interests owing to its unique optical properties and great application potentials. However, it is still a great challenge to effectively improve the efficiency/strength of upconversion nanophosphor. Plasmonic modulation is a promising way to solve this bottleneck. In this work, we present a simple yet versatile concept on magnifying upconversion luminescence of NaYF4:Yb(3+), Er(3+) nanocrystals through local field manipulation of surface plasmon. Gold nanorods were directionally assembled into a vertically aligned monolayer supercrystals over large areas. The FDTD simulation indicates that the electromagnetic field strength |E|(2) can be improved about 113 folds at the hot spots of monolayer supercrystals. After optimization, on the surface of the vertically aligned monolayer supercrystals, the overall upconversion luminescence intensity of NaYF4:Yb(3+), Er(3+) under 980 nm excitation was improved more than 35 fold.

Fabrication of Au-Ag nanocage@NaYF4@NaYF4:Yb,Er core-shell hybrid and its tunable upconversion enhancement

Localized electric filed enhancement by surface plasmon resonance (SPR) of noble metal nanoparticles is an effective method to amplify the upconversion luminescence (UCL) strength of upconversion nanoparticles (UCNPs), whereas the highly effective UCL enhancement of UCNPs in colloids has not been realized until now. Here, we designed and fabricated the colloidal Au-Ag nanocage@NaYF4@NaYF4:Yb,Er core-shell hybrid with different intermediate thickness (NaYF4) and tunable SPR peaks from visible wavelength region to NIR region. After the optimization of the intermediate spacer thickness (~7.5 nm) of NaYF4 NPs and the SPR peak (~950 nm) of noble metal nanoparticles, an optimum enhancement as high as ~25 folds was obtained. Systematic investigation indicates that UCL enhancement mainly originates from the influence of the intermediate spacer and the coupling of Au-Ag nanocages with the excitation electromagnetic field of the UCNPs. Our findings may provide a new thinking on designing highly effective metal@UCNPs core-shell hybrid in colloids.

Semiconductor plasmon-sensitized broadband upconversion and its enhancement effect on the power conversion efficiency of perovskite solar cells

Photon upconversion (UC) is an attractive strategy to substantially enhance the power conversion efficiency (PCE) of solar cells via upconverting unavailable near-infrared sunlight to available visible light. However, to date, it is almost infeasible to achieve effective PCE improvement of solar cells with the assistance of UC materials, limited by their poor UC efficiency and extremely weak and narrowband near-infrared absorption. Here, we demonstrate the efficient photon energy UC in semiconductor plasmon mCu2−xS@SiO2@Er2O3 (mCSE) nanocomposites, where the broadband semiconductor plasmon (800–1600 nm) of mCu2−xS serves as an antenna to sensitize UC of Er2O3 nanoparticles. The overall upconversion luminescence (UCL) of the composites was dramatically enhanced by a factor of ∼1000, with a maximal inner quantum efficiency of 14.3%. The excitation range was expanded, ranging from 800 to 1600 nm. As a proof-of-concept, the highly efficient mCSE nanocomposites were utilized to improve the PCE of perovskite solar cells (PSCs). The expansion of the near-infrared response (800–1000 nm) and considerable improvement of the PCE were obtained, with an optimum PCE of 17.8%. The mCSE composites in PSCs enhanced the photocurrent via electron transfer from oxygen defects to the conduction band of TiO2 under irradiation of one sunlight. Under irradiation of 15 suns, the electron transfer and reabsorption of UCL both contributed to the enhancement of PCE. Our work can provide an insightful thought on boosting UC efficiency as well as broadening the PCE of PSCs.

Highly modified spontaneous emission in NaY(MoO4)2:Yb3+/Er3+ inverse opal photonic crystals

The up-conversion luminescence (UCL) of rare earth (RE) ion doped nanomaterials has attracted extensive interest because of its wide and great potential application. However, the lower UCL efficiency due to the local thermal effect among the ions is still an obstacle for real application. Photonic modulation is a novel way to suppress the local thermal effect and cross relaxation. In this work, NaY(MoO4)2:Yb3+/Er3+ inverse opal photonic crystals (IOPCs) were fabricated through the poly methylmethacrylate (PMMA) template and the modification of the IOPC structure on the emission spectra and dynamic of Er3+ ions was systemically studied. It is interesting to observe that in the IOPCs, the high-order UCL 2H9/2 → 4I15/2 was relatively enhanced. At the same time, the local thermal effect induced by laser irradiation was suppressed. The studies on UCL dynamics indicated that the nonradiative transition rate of Er3+ was considerably suppressed. The facts above indicated that in the IOPCs, the UCL efficiency of Er3+ was improved due to the periodic macroporous structure.

Highly sensitive and selective detection of mercury ions based on up-conversion FRET from NaYF4:Yb3+/Er3+ nanophosphors to CdTe quantum dots

The detection of Hg2+ has attracted considerable attention because of the serious health and environmental problems caused by it. There has been progress in the development of fluorescence biosensors based on quantum dots (QDs) for the detection of Hg2+. However, most of them are valid only in aqueous solution rather than in human serum due to the influence of protein autofluorescence in serum excited by ultraviolet or visible light. Herein, we designed and synthesized a novel NaYF4:Yb3+, Er3+ upconversion nanoparticle (UCNP)/CdTe QD composite probe for Hg2+ detection. The NaYF4:Yb3+, Er3+ UCNPs were synthesized via a solvothermal method. By grafting the CdTe QD probe onto the surface of the NaYF4:Yb3+, Er3+ UCNP, a fluorescence resonance energy transfer (FRET) biosensor for determination of Hg2+ ions was obtained under the pumping of 980 nm infrared light, which was capable of overcoming autoluminescence from serum. The spectral response towards Hg2+ suggested that the fluorescence intensity of the QDs reduced linearly with increasing Hg2+ concentration. The sensor showed high selectivity, a low detection limit of 15 nM and good linear Stern–Volmer characteristics, both in the buffer and serum. This biosensor has great potential for real applications of Hg2+ detection in biological and analytical fields.