Nonradiative Decay Rate Research Articles

Enhanced Photothermal Therapy under Low‐Power Near‐Infrared Irradiation Enabled by a Si‐Cyclopentadithiophene‐Based Organic Molecule

AbstractDue to the inadequate photothermal conversion efficiency (PCE), most photothermal agents (PTAs) have to be used under high‐power near‐infrared (NIR) irradiation, which significantly exceeds medical safety standards, for achieving effective photothermal therapy (PTT) in antitumor treatment. This significantly hinders practical PTT application. Herein, three acceptor‐donor‐acceptor(A‐D‐A)‐type molecules are synthesized based on cyclopentadithiophene unit to develop effective PTAs. By incorporating the large‐size Si atom in the A‐D‐A molecules, the photosensitizer displays an increased packing distance in the aggregate state, leading to a blue‐shifted absorption spectrum that better matches the medial laser wavelength. Also, the Si incorporation strategy elevates the nonradiative decay rate constants (knr) of the A‐D‐A photosensitizer, and thereby a further enhancement in PCE is achieved for the PTA. Consequently, the SiO‐4F‐based nanoparticles exhibited 64.23% PCE, with excellent biosafety and photothermal stability. Under NIR irradiation with medical safety (808 nm, 0.33 W cm−2), SiO‐4F nanoparticles with 100 µg mL−1 yield a death rate of over 91% for diverse tumor cells. Moreover, in vivo experiments, SiO‐4F‐based PTT effectively inhibited and eliminated tumors. These findings suggest that the Si‐incorporated CDPT is promising for constructing effective A‐D‐A photosensitizers, enabling the PTT under NIR irradiation that meets medical safety standards.

Microwave Synthesis and Luminescence Efficiencies in Mixed-Ligand Europium Complexes.

The microwave-assisted methodology is now extended and fine-tuned for the synthesis of mixed-ligand europium complexes with an average reaction time of 12 min. Overall, 14 different complexes were synthesized to improve luminescence using our previously proposed strategy to boost luminescence through ligand diversification, specifically by applying it to quaternary europium complexes with at least one DBM (1,3-diphenylpropane-1,3-dionate) ligand. DBM is a strong absorbant of UV radiation that can dissipate energy through nonradiative channels; thus, it is a useful molecular scaffold for sunblockers and cosmetics. Accordingly, the following luminescent tetrakis and quaternary complexes were prepared: K[Eu(DBM)4], K[Eu(β)4], K[Eu(DBM)3(β)], K[Eu(DBM)2(β)2], K[Eu(DBM)2(β)(β')], and the fully mixed complex K[Eu(DBM)(BTFA)(TTA)(HFAC)], where β can be either BTFA (4,4,4-trifluoro-1-phenylbutane-1,3-dionate), TTA (4,4,4-trifluoro-1-(2-thienyl)butane-1,3-dionate), or HFAC (1,1,1,5,5,5-hexafluoropentane-2,4-dionate). For all the complexes, luminescence experiments were performed in chloroform and acetone solutions. Our findings confirm that mixed-ligand complexes exhibit superior quantum efficiencies compared to the average of their homoleptic counterparts. The presence of DBM in the complexes tends to dramatically increase the nonradiative decay rates of the solutions. Finally, we present formulae that provide a detailed understanding of the distinctive roles of each ligand and their relevant interactions in luminescence.

Multiple Resonance Quasi-fluorescence from BN-Doped Aromatic Compounds Modified with "Naphthalene" Units Approaches the BT.2020 Green Light Standard.

Developing fluorophores that conform to the Broadcast Service Television 2020 (BT.2020) standard presents a formidable challenge. Here, we propose an innovative approach that integrates two and three-boron/nitrogen (BN2)-embedded [4]helicene subunits with naphthalene, resulting in the synthesis of two novel narrowband bright green quasi-fluorescent emitters, NT-2B and NT-3B for ultra-high-definition displays. These emitters exhibit minimal reorganization energy and Huang-Rhys factor, emitting at 510 and 511 nm in dilute toluene solution with exceptionally narrow full width at half maximum values of 15 and 14 nm, respectively. Notably, NT-2B demonstrates an impressive photoluminescence quantum yield of 92.5 %, rapid radiative decay rate, and slow non-radiative decay rate. Owing to their narrowband emission characteristics and outstanding optoelectronic properties, corresponding OLEDs based on NT-2B demonstrate a high external quantum efficiency of 30.6 %, with an FWHM value of 21.5 nm and a CIEy of 0.74, positioning it as one of the leading narrow-band green emitters.

Fluorescence Modulation through the Inverted Energy Gap Law in Triply N─B←N‐Containing Windmill‐Shaped Triazines

A series of windmill‐shape heterocyclic molecules containing three N─B←N units, TBN and its derivatives, with quasi‐planar C3 symmetric backbone, are synthesized. The parent TBN exhibits a strongly allowed, doubly degenerate lowest excited state but suffers from very low fluorescence, due to very fast nonradiative decay rate through a conical intersection (CI) as revealed by femtosecond transient absorption spectroscopy and quantum‐chemical calculations. Introducing peripheral phenyl‐ or thienyl‐groups (Ph‐TBN or Th‐TBN) induces pronounced bathochromic shifts and enhances fluorescence, which is beneficial from inhibited nonradiative pathway by the increased energy barriers to access the CI at excited state. The understanding of this rather uncommon behaviour may open routes for the design of novel fluorescence materials.

Fluorescence Modulation through the Inverted Energy Gap Law in Triply N─B←N-Containing Windmill-Shaped Triazines.

A series of windmill-shape heterocyclic molecules containing three N─B←N units, TBN and its derivatives, with quasi-planar C3 symmetric backbone, are synthesized. The parent TBN exhibits a strongly allowed, doubly degenerate lowest excited state but suffers from very low fluorescence, due to very fast nonradiative decay rate through a conical intersection (CI) as revealed by femtosecond transient absorption spectroscopy and quantum-chemical calculations. Introducing peripheral phenyl- or thienyl-groups (Ph-TBN or Th-TBN) induces pronounced bathochromic shifts and enhances fluorescence, which is beneficial from inhibited nonradiative pathway by the increased energy barriers to access the CI at excited state. The understanding of this rather uncommon behaviour may open routes for the design of novel fluorescence materials.

Molecular Engineering of Xanthene Dyes with 3D Multimodal-Imaging Ability to Guide Photothermal Therapy.

Phototheranostics integrates light-based diagnostic techniques with therapeutic interventions, offering a non-invasive, precise, and swift approach for both disease detection and treatment. The efficacy of this approach hinges on the multimodal imaging potential and photothermal conversion efficiency (PCE) of phototheranostic agents (PTAs). Despite the promise, crafting multifunctional phototheranostic organic small molecules brims with challenges. In this research, four innovative xanthene-derived PTAs are synthesized by fine-tuning the donor-π-acceptor (D-π-A) system to strike a balance between radiative and nonradiative decay. The inherent robust photostability and intense fluorescence of the traditional xanthene core are preserved, meanwhile the addition of highly electron-withdrawing groups boosts the non-radiative decay rate to enhance PCE and photoacoustic imaging capabilities. Remarkably, one of the PTAs, DMBA, demonstrates an exceptional absolute fluorescence quantum yield of 2.46% in PBS, and when encapsulated into nanoparticles, it achieves a high PCE of 79.5%. Consequently, DMBA nanoparticles (DMBA-NPs) are effectively employed in fluorescence, 3D photoacoustic, and photothermal imaging-guiding tumor photothermal therapy. This represents the first instance of a multimodal phototheranostic xanthene agent achieving synergistic fluorescence and photoacoustic imaging for diagnostic purposes. Furthermore, this work paves the way for leveraging xanthene fluorophores as versatile tools in the development of multifunctional reagents.

Organonickel complex J-aggregation on interfacial evaporator promotes broadband absorption and salt rejection for efficient solar-powered desalination

Solar steam generation (SSG) driven by environment-friendly and renewable energy is emerging as a promising technology for alleviating clean water scarcity. So far, developing solar-thermal conversion materials for solar interfacial absorbers to advance evaporation rate and efficiency is still a crucial challenge. Herein, the thienyl-substituted organonickel bis(dithiolene) complex (NiTh) with an intense second near-infrared (NIR-II) absorption of intervalence charge transfer transition was synthesized and systemically compared with the phenyl-based complex (NiPh). Based on the delocalization electron property of thiophene, NiTh behaves with low adiabatic and high reorganization energies, contributing to its nonradiative decay rate and photothermal conversion. Its J-aggregation on the foam fiber was fabricated as a solar-to-heating interfacial layer with broad absorption from visible to NIR-II regions and salt-resistance ability, resulting in excellent solar light-harvesting. Under one sun of irradiation, the NiTh-adsorbed foam with red-shifted absorption and higher photothermal conversion ability exhibits a faster solar energy-to-evaporation rate (1.99 ± 0.10 kg m−2 h−1) compared with the NiPh-adsorbed foam (1.83 ± 0.06 kg m−2 h−1), of which the blank foam is 0.48 ± 0.03 kg m−2 h−1. The evaporation rate of solar-driven seawater desalination based on NiTh@foam evaporator can reach up to 1.80 ± 0.05 kg m−2 h−1, and the efficiency is as high as 122.1 ± 3.1 % due to the additional energy harvesting in the side areas that absorb sunlight and the light-trapping effect inside the three-dimensional evaporator. For organic pollutant solution, clean condensed water with an evaporation rate of 2.03–2.17 kg m−2 h−1 can be obtained through the SSG operation based on NiTh@foam. This study promotes a strategy for designing small molecules with NIR-II absorption and further modification on porous foam surfaces to achieve high-efficitive solar-driven evaporation application.

Unveiling the ligand effects on Pt(Ⅱ) carbene complexes for rapid, efficient and narrow-spectra blue phosphorescence

Tetradentate Pt(II) complexes, comprising of benzoimidazolyl N-heterocyclic carbene (BI-NHC) coordination, have shown superior performance in blue phosphorescent organic light-emitting diodes (PhOLEDs). Here, four frame-structured complexes were synthesized to explore the intrinsic ligand effect for rapid, efficient and narrow-spectra blue phosphorescence through experimental analyses and theoretical calculations. We found carbazolylpridine (CzPy) chelating part in Pt(II) BI-NHC complexes dominates the phosphorescence with the suppression of metal-centered transition and electron-vibration coupling. Consequently, the CzPy chelated complexes (PtN-dip and PtN-dtb) achieved high luminescent efficiency, rapid radiative decay rate (kr) and narrow emission spectra. The peripheral substituent 2,6-di-iso-propylphenyl (dip) on NHC of PtN-dip constrains the molecule, significantly reducing the non-radiative decay rate (knr) and enhancing the efficiency. The 3,5-di-tert-butylphenyl (dtb) in PtN-dtb could enhances low-frequency vibration coupling that could expedite the excitons decay, resulting in higher kr and knr. This work unveils the intrinsic factors behind the ligand effects of Pt(II) BI-NHC based complexes, leading to a rapid, efficient and narrow-spectra phosphorescence.

Bimetallic complexation for significant fluorescence enhancement of faecal pigment towards water quality testing

Systematic spectroscopic investigations revealed bimetallic complexation of faecal pigments (FP) in waterthrough their multiple binding sites. FP-Zn(II)/Gd(III) complexes showed narrow emission (FWHM ∼ 26 nm) with maximum intensity compared to different bimetallic complexes in water. The fluorescence intensity of bimetallic Zn(II)/Gd(III) complexes of FP increased ∼3–5 fold in aqueous media compared to the FP-Zn(II) complexes, i.e. well-known as Schlesinger’s test. The optimum Zn(II): Gd(III) stoichiometry was observed at 3:2 for maximum FP fluorescence enhancement. The bimetallic FP-Zn(II)/Gd(III) complexes also exhibited higher fluorescence lifetimes and quantum yield than FP-Zn(II) complexes. The photophysical investigations demonstrated that bimetallic Zn(II)/Gd(III) complexation increased the rigidity of chromophores present in FP. Consequently, a decrease in non-radiative decay rate constants (knr) by ∼ 1.5 times was observed for bimetallic complexes compared to FP-Zn(II) in water. Hence, a detection limit of the nanomolar concentration range of FP could be achieved in the aqueous media. The effect of diverse interfering factors (humic acid, water hardness, pH) on the fluorescence behaviour of FP-Zn(II)/Gd(III) complexes was also investigated with an approach mimicking real water samples. Finally, a simple non-extraction analytical approach for sensitive detection of FP in water was demonstrated while also considering the fluorescence matrix interference problem.

Influence of Aliphatic versus Aromatic Ligand Passivation on Intersystem Crossing in Au25(SR)18.

The electronic relaxation dynamics of gold monolayer protected clusters (MPCs) are influenced by the hydrocarbon structure of thiolate protecting ligands. Here, we present ligand-dependent electronic relaxation for a series of Au25(SR)18- (SR = SC8H9, SC6H13, SC12H25) MPCs using femtosecond time-resolved transient absorption spectroscopy. Relaxation pathways included a ligand-independent femtosecond internal conversion and a competing ligand-dependent picosecond intersystem crossing process. Intersystem crossing was accelerated for the aliphatic (SC6H13, SC12H25) thiolate MPCs compared to the aromatic (SC8H9) thiolate MPCs. Additionally, a 1.2 THz quadrupolar acoustic mode and a 2.4 THz breathing acoustic mode was identified in each cluster, which indicated that differences in ligand structure did not result in significant structural changes to the metal core of the MPCs. Considering that the difference in relaxation rates did not result from ligand-induced core deformation, the accelerated intersystem crossing was attributed to greater electron-vibrational coupling to Au-S vibrational modes. The results suggested that the organometallic semiring was less rigid for the aliphatic thiolate MPCs due to reduced steric effects, and in turn, increases in nonradiative decay rates were observed. Overall, these results imply that the protecting ligand structure can be used to modify carrier relaxation in MPCs.

Predicting Nonradiative Decay Rate Constants of Cyclometalated Ir(III) Complexes.

The theoretical calculation of the temperature-dependent nonradiative decay rate constant is fundamental for predicting the usefulness of transition-metal complexes for technological applications. Such a computation implies the determination of the barriers separating the emitting triplet state from metal-centered states, which are key mediators of this type of radiationless relaxation. We here do so for the two green-emitting cyclometalated Ir(III) complexes, [Ir(ppy)2(pyim)]+ and [Ir(diFppy)2(dtb-bpy)]+, of general formula [Ir(C∧N)2(N∧N)]+, performing DFT calculations with both B3LYP and PBE0 functionals. On the basis of the obtained results and the comparison with the experimental nonradiative decay rate constants, we conclude that B3LYP provides too low energy barriers to the metal-centered states, while the PBE0 provides reasonable values. We consequently recommend to avoid the use of the commonly employed B3LYP functional for the evaluation of such an energy barrier for cyclometalated Ir(III) complexes.

Octocrylene carboxylate as an antenna in a luminescent Europium(III) complex: Experimental and theoretical insights

A new carboxylic acid, 2-cyano-3,3-diphenyl-2-propenoic acid, CLN, a chromophore ligand, was obtained by an alkaline hydrolysis reaction from the octocrylene, a commercial type B ultraviolet (UVB) radiation absorber. The CLN structure was elucidated by single-crystal X-ray diffraction (SCXRD) as being tetragonal with space group P4‾21/c and the presence of a carboxylic acid group was confirmed by mass, infrared (IR), and proton nuclear magnetic resonance (1H NMR) spectroscopy. In this way, coordination compounds were developed between CLN and Ln(III), Ln = being Gadolinium (Gd) and Europium (Eu), with a stoichiometry of 4:13 metal:ligand, confirmed by thermal and elemental analyses, corroborating with the metal cluster predicted by Sparkle/AM1 semi-empirical model. Photoluminescence data indicated that Eu(III) is efficiently sensitized by CLN due to its triplet excited state, determined using the emission spectrum of the Gd(III) mimic complex (T = 25,477 cm−1), being suitable for this purpose. Therefore, the emission spectrum of the Eu(III) complex exhibited a 5D0 → 7FJ transitions characteristic of the lanthanide ion. Furthermore, the Judd-Ofelt intensity parameters, the radiative and non-radiative decay rates, and the intrinsic quantum yield evaluated using the software LUMPAC software were in good agreement with the experimental values.

Probing energy transfer in luminescent CaMoO4:Tb3+ by steady state and decay dynamics

Polyvinylpyrrolidone functionalized CaMoO4:Tb3+ were synthesized hydrothermally. The formation of tetragonal phase CaMoO4:Tb3+ and morphology of nanoparticles are thoroughly studied with XRD, TEM and FT-IR spectroscopy. Nanophosphors show green emission of Tb3+ at 544 nm when excited at 290 nm due to MoO42− absorption. The energy transfer from the host MoO42− to the activator Tb3+ is occurred mainly through dipole-dipole interactions. The decay lifetime of MoO42− emission decreases from ∼13 to 1 μs with the increase in Tb3+ concentration indicating occurrence of energy transfer. This is further corroborated with the calculation of radiative and non-radiative decay rates. The quantum yield and CIE color chromaticity are also studied.

The silicon vacancy centers in SiC: determination of intrinsic spin dynamics for integrated quantum photonics

The negatively charged silicon vacancy center (VSi−\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${{\\rm{V}}}_{{\\rm{Si}}}^{-}$$\\end{document}) in silicon carbide (SiC) is an emerging color center for quantum technology covering quantum sensing, communication, and computing. Yet, limited information currently available on the internal spin-optical dynamics of these color centers prevents us from achieving the optimal operation conditions and reaching the maximum performance especially when integrated within quantum photonics. Here, we establish all the relevant intrinsic spin dynamics of the VSi−\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${{\\rm{V}}}_{{\\rm{Si}}}^{-}$$\\end{document} center at cubic lattice site (V2) in 4H-SiC by an in-depth electronic fine structure modeling including the intersystem-crossing and deshelving mechanisms. With carefully designed spin-dependent measurements, we obtain all the previously unknown spin-selective radiative and non-radiative decay rates. To showcase the relevance of our work for integrated quantum photonics, we use the obtained rates to propose a realistic implementation of time-bin entangled multi-photon GHZ and cluster state generation. We find that up to three-photon GHZ or cluster states are readily within reach using the existing nanophotonic cavity technology.

Tension Induced Photoluminescence Enhancement in an Organic Single Crystal.

Organic single crystals possess distinct advantages due to their highly ordered molecular structures, resulting in improved stability, enhanced carrier mobility, and superior optical characteristics. However, their mechanical rigidity and brittleness impede the applications in flexible and wearable optoelectronic devices. Here, photoluminescence (PL) emission from 2,6-diphenylanthracene (DPA) single crystals is studied under tensile strain, which shows PL enhancement by more than two times with a strain of ≈1.42%. Such a tension induced PL enhancement is reversible, exhibiting no clear optical degradations during 100 cycles of bending and recovery processes. Theoretical calculations reveal that the deformation of molecular structure under strain induces a decrease of the dihedral between anthracene and benzene moieties in DPA molecules. Further, the increased molecular conjugation enhances the molecular oscillator strength, leading to the brightened PL emission. Meanwhile, with the decreased dihedral, the molecular vibrations in DPA crystals are suppressed, which can reduce the non-radiative decay rate. In contrast, no tension induced PL enhancement is observed in polycrystalline DPA thin films as the strain can be released via the grain boundaries. This study highlights the superior optical performance of DPA single crystals under strain field, which will provide new possibilities for DPA-based flexible devices.

Effect of tert‐Butylation on the Photophysics of Thermally Activated Delayed Fluorescence Emitters

Thermally activated delayed fluorescence (TADF) emitters potentially can provide organic light‐emitting diodes with 100% internal quantum efficiency by harvesting triplet excitons. Generally, TADF emitters are small molecules that are not applicable for solution processability. The addition of tert‐butyl groups to the periphery of TADF emitters has proven to improve their solubility in various organic solvents, reduce aggregation‐induced quenching, and enhance the photoluminescence quantum yield (PLQY). This article studies the photophysical influence of the tert‐butyl group attached to an emitter with a carbazole acceptor and a triazine donor. The resulting t3CzTrz‐F is a blue–green TADF emitter, in which the addition of a tert‐butyl group increases the rate of reverse intersystem crossing (rISC), while simultaneously decreasing the nonradiative decay rate substantially. In addition, dilution of t3CzTrz‐F in a host matrix in film results in an enhanced PLQY, which is associated with a decrease in the nonradiative decay constant, while there is no change in the rISC rate. Through a solid‐state NMR study, the change in rISC and nonradiative rate upon tert‐butylation by enlarged intermolecular spacing and reduced vibrational and rotational freedom is rationalized, resulting in improved photophysical performance.

Time-dependent Kohn-Sham electron dynamics coupled with nonequilibrium plasmonic response via atomistic electromagnetic model.

Computational modeling of plasmon-mediated molecular photophysical and photochemical behaviors can help us better understand and tune the bound molecular properties and reactivity and make better decisions to design and control nanostructures. However, computational investigations of coupled plasmon-molecule systems are challenging due to the lack of accurate and efficient protocols to simulate these systems. Here, we present a hybrid scheme by combining the real-time time-dependent density functional theory (RT-TDDFT) approach with the time-domain frequency dependent fluctuating charge (TD-ωFQ) model. At first, we transform ωFQ in the frequency-domain, an atomistic electromagnetic model for the plasmonic response of plasmonic metal nanoparticles (PMNPs), into the time-domain and derive its equation-of-motion formulation. The TD-ωFQ introduces the nonequilibrium plasmonic response of PMNPs and atomistic interactions to the electronic excitation of the quantum mechanical (QM) region. Then, we combine TD-ωFQ with RT-TDDFT. The derived RT-TDDFT/TD-ωFQ scheme allows us to effectively simulate the plasmon-mediated "real-time" electronic dynamics and even the coupled electron-nuclear dynamics by combining them with the nuclear dynamics approaches. As a first application of the RT-TDDFT/TD-ωFQ method, we study the nonradiative decay rate and plasmon-enhanced absorption spectra of two small molecules in the proximity of sodium MNPs. Thanks to the atomistic nature of the ωFQ model, the edge effect of MNP on absorption enhancement has also been investigated and unveiled.

A Thorough Examination of the Variables Affecting the Quantum Efficiency of Radiative Decay of Trichlorotriphenylmethyl Radicals.

Fluorescence quantum efficiency is determined by the competition between radiation and nonradiation processes of the excited states. Understanding the factors affecting the radiation and nonradiative decay rates is of great significance for the design of luminescent materials. The excitation state deactivation mechanisms of singlet and triplet states have been extensively studied, providing a comprehensive understanding of the processes involved in the relaxation of these states. However, research on free radical systems involving doublet states is relatively scarce. Therefore, in this study, radiation and nonradiative decay rates and the mechanism of a series of trichlorotriphenylmethyl-based radicals were investigated theoretically. The results indicate that the relative rotations of electron donor and acceptor, as well as the internal rotations of trichlorotriphenylmethyl moiety, play important roles in energy dissipation through nonradiative channels. The effect of a solid-state environment on the radiation and nonradiative decay rates of radicals was investigated using a combination of quantum mechanics and molecular mechanics methods. The results indicate that the solid-state environment restricts the expansion of the conjugated system in the excited state of radicals, leading to a slight decrease in radiative decay rate. In addition, the solid-state environment reduces the reorganization energy and also affects the adiabatic excitation energy of radicals. The reduction in reorganization energy results in a decrease in nonradiative rate, while the opposite effect is observed for adiabatic excitation energy. The nonradiative rate of radicals in a solid-state environment is thus inflected by a combination of molecular geometric structure relaxation and ground-excited state energy gap.

Dynamic control of spontaneous emission using magnetized InSb higher-order-mode antennas

We exploit InSb’s magnetic-induced optical properties to design THz sub-wavelength antennas that actively tune the radiative decay rates of dipole emitters at their proximity. The proposed designs include a spherical InSb antenna and a cylindrical Si-InSb hybrid antenna demonstrating distinct behaviors. The former dramatically enhances both radiative and non-radiative decay rates in the epsilon-near-zero region due to the dominant contribution of the Zeeman-splitting electric octupole mode. The latter realizes significant radiative decay rate enhancement via magnetic octupole mode, mitigating the quenching process and accelerating the photon production rate. A deep-learning-based optimization of emitter positioning further enhances the quantum efficiency of the proposed hybrid system. These novel mechanisms are promising for tunable THz single-photon sources in integrated quantum networks.

Brilliant quantum dots’ photoluminescence from a dual-resonance plasmonic grating

Semiconductor quantum dots (QDs) have recently caused a stir as a promising and powerful lighting material applied in real-time fluorescence detection, display, and imaging. Photonic nanostructures are well suited for enhancing photoluminescence (PL) due to their ability to tailor the electromagnetic field, which raises both radiative and nonradiative decay rate of QDs nearby. However, several proposed structures with a complicated manufacturing process or low PL enhancement hinder their application and commercialization. Here, we present two kinds of dual-resonance gratings to effectively improve PL enhancement and propose a facile fabrication method based on holographic lithography. A maximum of 220-fold PL enhancement from CdSe/CdS/ZnS QDs are realized on 1D Al-coated photoresist (PR) gratings, where dual resonance bands are excited to simultaneously overlap the absorption and emission bands of QDs, much larger than those of some reported structures. Giant PL enhancement realized by cost-effective method further suggests the potential of better developing the nanostructure to QD-based optical and optoelectronic devices.