White-Light Emission of Amine-Functionalized Organic/Inorganic Hybrids: Emitting Centers and Recombination Mechanisms

Magnesium cations as templates for the self-assembly of supramolecular luminescent {Mg@[B18φ34-35]}-clusters

Solvothermal reaction of magnesium nitrate and boron oxide in N,N-dimethylformamide produced a number of particularly complex supramolecular magnesium borates. Five topologically different types of negatively charged {Mg@[B18φ34-35]}-clusters, φ = O, OH, were observed with the magnesium cation as a core and octadecaborate anions as shells. The clusters assemble via common borate polyhedra forming 1D chains, a 2D mesoporous layer, and 3D mesoporous frameworks with an effective channel width of up to 16 Å. Topological analysis of the clusters in combination with the modular crystallography approach indicates that numerous new functional materials can be obtained by varying their assembly mode. At least one compound containing such clusters exhibits a very strong luminescence.

Ultra-Small Air-Stable Triplet-Triplet Annihilation Upconversion Nanoparticles for Anti-Stokes Time-Resolved Imaging

Image contrast is often limited by background autofluorescence in steady-state bioimaging microscopy. Upconversion bioimaging can overcome this by shifting the emission lifetime and wavelength beyond the autofluorescence window. Here we demonstrate the first example of triplet-triplet annihilation upconversion (TTA-UC) based lifetime imaging microscopy. A new class of ultra-small nanoparticle (NP) probes based on TTA-UC chromophores encapsulated in an organic-inorganic host has been synthesised. The NPs exhibit bright UC emission (400-500 nm) in aerated aqueous media with a UC lifetime of ≈1 μs, excellent colloidal stability and little cytotoxicity. Proof-of-concept demonstration of TTA-UC lifetime imaging using these NPs shows that the long-lived anti-Stokes emission is easily discriminable from typical autofluorescence. Moreover, fluctuations in the UC lifetime can be used to map local oxygen diffusion across the subcellular structure. Our TTA-UC NPs are highly promising stains for lifetime imaging microscopy, affording excellent image contrast and potential for oxygen mapping that is ripe for further exploitation.

Enhanced Photoluminescence Detection of Immunocomplex Formation by Antibody-Functionalized, Ge-Doped Biosilica from the Diatom Cyclotella sp

Diatoms are single-celled algae that biosynthesize cell walls of biogenic silica called "frustules" that are intricately patterned at the submicron- and nanoscale. In this study, we amplified the intrinsic luminescent properties of antibody-functionalized diatom biosilica frustules for enhanced, label-free, photoluminescence (PL) detection of immunocomplex formation. It was hypothesized that metabolically doped GeO centers in antibody-functionalized diatom biosilica would enhance PL emission associated with nucleophilic immunocomplex formation. Germanium (Ge) was metabolically inserted into the frustule biosilica by two-stage cell cultivation of the centric diatom Cyclotella sp. The biosilica frustules were isolated by hydrogen peroxide treatment and thermally annealed to convert Ge oxides in the biosilica (0.4 wt% Ge) to luminescent GeO centers. The Ge-doped biosilica frustules were then functionalized with Rabbit Immunoglobulin G (IgG). Upon immunocomplex formation with its complimentary antigen goat anti-Rabbit IgG, the Ge-oxide doped, antibody-functionalized frustule biosilica increased the intensity of PL emission by a factor of 2.6 relative to immunocomplex formation by antibody-functionalized frustule biosilica without Ge. It is proposed that the luminescent GeO centers in the Ge-oxide doped frustule biosilica were more sensitive to radiative recombination than luminescent silanol groups in frustule biosilica without Ge, resulting in a higher PL emission upon immunocomplex formation.

A Fluorescent Unnatural Mannosamine Derivative with Enhanced Emission Upon Complexation with Cucurbit[7]uril

Metabolic incorporation of unnatural functionality on glycans has allowed chemical biologists to observe and affect cellular processes. Recent work has resulted in glycan-fluorophore structures that allow for direct visualization of glycan-mediated processes, shining light on their role in living systems. This work describes the serendipitous discovery of a small chemical reporter-fluorophore. Investigations into the mechanism of fluorescence arising from (trimethylsilyl)methylglycine appended on mannosamine suggest rigidity and restriction of lone pair geometry contribute to the fluorescent behaviour. In fact, in situ cyclization and encapsulation in cucurbit[7]uril enhance fluorescence to levels that can be observed in live cells. While the reported unnatural mannosamine does not traverse the sialic acid biosynthetic pathway, this discovery may lead to small, "turn-on" chemical reporters for incorporation in living systems.

Förster Resonance Energy Transfer in Luminescent Solar Concentrators

Luminescent solar concentrators (LSCs) are an emerging technology to collect and channel light from a large absorption area into a smaller one. They are a complementary technology for traditional solar photovoltaics (PV), particularly suitable for application in urban or indoor environments where their custom colors and form factors, and performance under diffuse light conditions may be advantageous. Förster resonance energy transfer (FRET) has emerged as a valuable approach to overcome some of the intrinsic limitations of conventional single lumophore LSCs, such as reabsorption or reduced quantum efficiency. This review outlines the potential of FRET to boost LSC performance, using highlights from the literature to illustrate the key criteria that must be considered when designing an FRET-LSC, including both the photophysical requirements of the FRET lumophores and their interaction with the host material. Based on these criteria, a list of design guidelines intended to aid researchers when they approach the design of a new FRET-LSC system is presented. By highlighting the unanswered questions in this field, the authors aim to demonstrate the potential of FRET-LSCs for both conventional solar-harvesting and emerging LSC-inspired technologies and hope to encourage participation from a diverse researcher base to address this exciting challenge.

Aggregation-induced emission from silole-based lumophores embedded in organic-inorganic hybrid hosts

Aggregation-induced emitters - or AIEgens - are often symbolised by their photoluminescence enhancement as a result of aggregation in a poor solvent. However, for some applications, it is preferable for the AIE response to be induced in the solid-state. Here, the ability of an organic-inorganic hybrid polymer host to induce the AIE response from embedded silole-based lumophores has been explored. We have focussed on understanding how the incorporation method controls the extent of lumophore aggregation and thus the associated photophysical properties. To achieve this, two sample concentration series have been prepared, based on either the parent AIEgen 1,1-dimethyl-2,3,4,5-tetraphenylsilole (DMTPS) or the silylated analogue (DMTPS-Sil), which were physically doped or covalently grafted, respectively, to dU(600) - a member of the ureasil family of poly(oxyalkylene)/siloxane hybrids. Steady-state and time-resolved photoluminescence measurements, coupled with confocal microscopy studies, revealed that covalent grafting leads to improved dispersibility of the AIEgen, reduced scattering losses, increased photoluminescence quantum yields (up to ca. 40%) and improved chemical stability. Moreover, the ureasil also functions as a photoactive host that undergoes excitation energy transfer to the embedded DMTPS-Sil with an efficiency of almost 70%. This study highlights the potential for designing complex photoluminescent hybrid polymers exhibiting an ehanced AIE response for solid-state optical applications.

Synthesis, Optical and Electrical Characterization of Amino-alcohol Based Sol-gel Hybrid Materials

This manuscript describes the synthesis and characterization of five new organic–inorganic hybrid (OIH) sol-gel materials that were obtained from a functionalized siloxane 3-glycidoxypropyltrimethoxysilane (GPTMS) by the reaction with the new Jeffamine^®, namely three different diamines, i.e., EDR-148, RFD-270, and THF-170, a secondary diamine, i.e., SD-2001, and a triamine, i.e., T-403. The OIH sol-gel materials were characterized by UV-visible absorption spectrophotometry, steady-state photoluminescence spectroscopy, and electrochemical impedance spectroscopy. The reported OIH sol-gel materials showed that, with the exception of the samples prepared with Jeffamine^® SD-2001, the transmittance values ranged between 61% and 79%. Regarding the capacitance data, the values reported changed between 0.008 and 0.013 nF cm⁻². Due to their optical and electrical properties these new OIH materials show promising properties for applications as support films in an optical sensor area such as fiber sensor devices. Studies to assess the chemical stability of the OIH materials in contact with cement pastes after 7, 14, and 28 days were also performed. The samples prepared with THF–170 and GPTMS, when compared to the samples prepared with RFD-270 and T-403, exhibited improved behavior in the cement paste (alkaline environment), showing promising properties for application as support film in optical fiber sensors in the civil engineering field.

Luminescent Solar Concentrators Based on Energy Transfer from an Aggregation-Induced Emitter Conjugated Polymer

Luminescent solar concentrators (LSCs) are solar-harvesting devices fabricated from a transparent waveguide that is doped or coated with lumophores. Despite their potential for architectural integration, the optical efficiency of LSCs is often limited by incomplete harvesting of solar radiation and aggregation-caused quenching (ACQ) of lumophores in the solid state. Here, we demonstrate a multilumophore LSC design that circumvents these challenges through a combination of nonradiative Förster resonance energy transfer (FRET) and aggregation-induced emission (AIE). The LSC incorporates a green-emitting poly(tetraphenylethylene), p-O-TPE, as an energy donor and a red-emitting perylene bisimide molecular dye (PDI-Sil) as the energy acceptor, within an organic-inorganic hybrid diureasil waveguide. Steady-state photoluminescence studies demonstrate the diureasil host induced AIE from the p-O-PTE donor polymer, leading to a high photoluminescence quantum yield (PLQY) of ∼45% and a large Stokes shift of ∼150 nm. Covalent grafting of the PDI-Sil acceptor to the siliceous domains of the diureasil waveguide also inhibits nonradiative losses by preventing molecular aggregation. Due to the excellent spectral overlap, FRET was shown to occur from p-O-TPE to PDI-Sil, which increased with acceptor concentration. As a result, the final LSC (4.5 cm × 4.5 cm × 0.3 cm) with an optimized donor-acceptor ratio (1:1 by wt %) exhibited an internal photon efficiency of 20%, demonstrating a viable design for LSCs utilizing an AIE-based FRET approach to improve the solar-harvesting performance.

White-light emission based on a single component Sm(iii) complex and enhanced optical properties by doping methods

Six lanthanide complexes with enhanced tunable photoluminescence were designed and synthesized using codoping methods and single component white-light emission was achieved.

Luminescent Electrochromic Devices for Smart Windows of Energy-Efficient Buildings

To address the challenges of the next generation of smart windows for energy-efficient buildings, new electrochromic devices (ECDs) are introduced. These include indium molybdenum oxide (IMO), a conducting oxide transparent in the near-infrared (NIR) region, and a NIR-emitting electrolyte. The novel electrolytes are based on a sol-gel-derived di-urethane cross-linked siloxane-based host structure, including short chains of poly (ε-caprolactone) (PCL(530) (where 530 represents the average molecular weight in g mol−1). This hybrid framework was doped with a combination of either, lithium triflate (LiTrif) and erbium triflate (ErTrif3), or LiTrif and bisaquatris (thenoyltrifluoroacetonate) erbium (III) ([Er(tta)3(H2O)2]). The ECD@LiTrif-[Er(tta)3(H2O)2] device presents a typical Er3+ NIR emission around 1550 nm. The figures of merit of these devices are high cycling stability, good reversibility, and unusually high coloration efficiency (CE = ΔOD/ΔQ, where Q is the inserted/de-inserted charge density). CE values of −8824/+6569 cm2 C−1 and −8243/+5200 cm2 C−1 were achieved at 555 nm on the 400th cycle, for ECD@LiTrif-ErTrif3 and ECD@LiTrif-[Er(tta)3(H2O)2], respectively.

White-Light Emitting Di-Ureasil Hybrids

White-light emitting materials have emerged as important components for solid state lighting devices with high potential for the replacement of conventional light sources. Herein, amine-functionalized organic-inorganic di-ureasil hybrids consisting of a siliceous skeleton and oligopolyether chains codoped with lanthanide-based complexes, with Eu3+ and Tb3+ ions and 4,4'-oxybis(benzoic acid) and 1,10-phenanthroline ligands, and the coumarin 1 dye were synthesized by in situ sol⁻gel method. The resulting luminescent di-ureasils show red, green, and blue colors originated from the Eu3+, Tb3+, and C1 emissions, respectively. The emission colors can be modulated either by variation of the relative concentration between the emitting centers or by changing the excitation wavelength. White light emission is achieved under UV excitation with absolute quantum yields of 0.148 ± 0.015, 0.167 ± 0.017, and 0.202 ± 0.020 at 350, 332, and 305 nm excitation, respectively. The emission mechanism was investigated by photoluminescence and UV⁻visible absorption spectroscopy, revealing an efficient energy transfer from the organic ligands to the Ln3+ ions and the organic dye, whereas negligible interaction between the dopants is discerned. The obtained luminescent di-ureasils have potential for optoelectronic applications, such as in white-light emitting diodes.

Flexible Optical Amplifier for Visible-Light Communications Based on Organic-Inorganic Hybrids

Visible-light communications (VLCs) based on white light-emitting diodes (LEDs) are emerging as a low-cost and energy-efficient alternative solution to wireless communications. As white emitting LEDs use a combination of a long-lived yellow emission combined with the faster response of a blue emitting LED (∼460 nm), VLC technology requires amplification of the blue component to improve the signal-to-noise ratio. We report the fabrication and characterization of planar and channel waveguides based on a blue-emitting polyfluorene conjugated polyelectrolyte, namely, poly[9,9-bis(4-sulfonylbutoxyphenyl)fluorene-2,7-diyl-alt-1,4-phenylene] (PBS-PFP) incorporated into diureasil organic-inorganic hybrids for optical amplification in VLC. Taking advantage of the diureasil host as a UV self-patternable material, direct UV laser writing was used to pattern channel waveguides with a larger refractive index (Δn=0.09) compared to the nonexposed region, enabling confinement and guidance of the PBS-PFP emission with a maximum optical gain efficiency value of 1.62 ± 0.02 cm μJ^-1. This value is among the best figures of merit known for polymeric materials with additional advantages added by the diureasil hybrid host, namely, mechanical flexibility, thermal stability, and low insertion losses due to the nearly null refractive index contrast between the optical fiber and the amplification device, establishing the proposed approach as a promising cost-effective solution for optical amplification in VLCs.

Coupling Photoluminescence and Ionic Conduction Properties Using the Different Coordination Sites of Ureasil-Polyether Hybrid Materials

In this article, we demonstrate that each functional group of ureasil organic-inorganic hybrid (OIH) materials can act as a specific coordination site for a given active guest species, hence allowing the possibility of combining different functional properties. To illustrate this concept, the sol-gel process was used to produce diurea cross-linked siloxane-polyethylene oxide (U-PEO) and siloxane-polypropylene oxide (U-PPO) hybrid host frameworks with similar molecular weights (1900 and 2000 g mol^-1 for PEO and PPO, respectively), with Li⁺ and Eu³⁺ as active guest ions providing ionic conduction and photoluminescence (PL) properties, respectively. Comparison of Fourier transform infrared spectra and small-angle X-ray scattering results for single-doped (using Li⁺ or Eu³⁺) and co-doped (using Li⁺ and Eu³⁺) U-PEO and U-PPO hosts showed that in every case, there was specific coordination of Eu³⁺ by the carbonyl group of the urea bridge and of Li⁺ by ether-type oxygen of the PEO and PPO chains. Optical analyses demonstrated that loading with Li⁺ did not affect the luminescence properties of the Eu³⁺-loaded OIH. Although loading with Eu³⁺ had a small effect on ionic transport, co-doping with Li⁺ ions ensured macroscopic ion-conduction of the transparent and luminescent hybrid material. The results suggested that the combination of both properties in a transparent elastomeric material could be useful for the development of multifunctional devices. The results suggested that the combination of both properties in a transparent elastomeric material could be useful for the development of multifunctional polyelectrolytes applied in the field of dual luminescent devices such as photoelectrochromic smart windows.

Multimodality Imaging of Silica and Silicon Materials In Vivo

Recent progress in the development of silica- and silicon-based multimodality imaging nanoprobes has advanced their use in image-guided drug delivery, and the development of novel systems for nanotheranostic and diagnostic applications. As biocompatible and flexibly tunable materials, silica and silicon provide excellent platforms with high clinical potential in nanotheranostic and diagnostic probes with well-defined morphology and surface chemistry, yielding multifunctional properties. In vivo imaging is of great value in the exploration of methods for improving site-specific nanotherapeutic delivery by silica- and silicon-based drug-delivery systems. Multimodality approaches are essential for understanding the biological interactions of nanotherapeutics in the physiological environment in vivo. The aim here is to describe recent advances in the development of in vivo imaging tools based on nanostructured silica and silicon, and their applications in single and multimodality imaging.

Novel Highly Luminescent Amine-Functionalized Bridged Silsesquioxanes

Amine-functionalized bridged silsesquioxanes (BSs) were synthesized from bis[(3-trimethoxysilyl)propyl] amine via a solvent-mediated route. BS-1 and BS-2 were obtained at neutral pH with sub- and stoichiometric amounts of water, respectively, and high tetrahydrofuran content. BS-3 was prepared with hyperstoichiometric water concentration, high tetrahydrofuran content, and hydrochloric acid. BS-4 was synthesized with hyperstoichiometric water concentration, high ethanol content, and sodium hydroxide. BS-1 and BS-2 were produced as transparent films, whereas BS-3 and BS-4 formed white powders. Face-to-face stacking of flat or folded lamellae yielded quasi-hydrophobic platelets with emission quantum yields of 0.05 ± 0.01 (BS-1 and BS-2) or superhydrophilic onion-like nanoparticles with exciting emission quantum yields of 0.38 ± 0.03 (BS-3) and 0.33 ± 0.04 (BS-4), respectively. The latter two values are the largest ever reported for amine-functionalized siloxane-based hybrids lacking aromatic groups. Fast Grotthus proton hopping between = NH2+/ = NH groups (BS-3) and = N⁻/ = NH groups (BS-4), promoted by H⁺ and OH⁻ ions, respectively, and aided by short amine-amine contacts provided by the onion-like morphology, account for this unique optical behavior.

Tunable White-Light Emission in Single-Cation-Templated Three-Layered 2D Perovskites (CH3CH2NH3)4Pb3Br10-xClx

Two-dimensional (2D) hybrid halide perovskites come as a family (B)₂(A)_n-1Pb_nX_3n+1 (B and A= cations; X= halide). These perovskites are promising semiconductors for solar cells and optoelectronic applications. Among the fascinating properties of these materials is white-light emission, which has been mostly observed in single-layered 2D lead bromide or chloride systems (n = 1), where the broad emission comes from the transient photoexcited states generated by self-trapped excitons (STEs) from structural distortion. Here we report a multilayered 2D perovskite (n = 3) exhibiting a tunable white-light emission. Ethylammonium (EA⁺) can stabilize the 2D perovskite structure in EA₄Pb₃Br_10-xCl_x (x = 0, 2, 4, 6, 8, 9.5, and 10) with EA⁺ being both the A and B cations in this system. Because of the larger size of EA, these materials show a high distortion level in their inorganic structures, with EA₄Pb₃Cl₁₀ having a much larger distortion than that of EA₄Pb₃Br₁₀, which results in broadband white-light emission of EA₄Pb₃Cl₁₀ in contrast to narrow blue emission of EA₄Pb₃Br₁₀. The average lifetime of the series decreases gradually from the Cl end to the Br end, indicating that the larger distortion also prolongs the lifetime (more STE states). The band gap of EA₄Pb₃Br_10-xCl_x ranges from 3.45 eV (x = 10) to 2.75 eV (x = 0), following Vegard's law. First-principles density functional theory calculations (DFT) show that both EA₄Pb₃Cl₁₀ and EA₄Pb₃Br₁₀ are direct band gap semiconductors. The color rendering index (CRI) of the series improves from 66 (EA₄Pb₃Cl₁₀) to 83 (EA₄Pb₃Br_0.5Cl_9.5), displaying high tunability and versatility of the title compounds.

Unexpected "Hammerlike Liquid" to Pulverize Silica Powders to Stable Sols and Its Application in the Preparation of Sub-10 nm SiO2 Hybrid Nanoparticles with Chirality

Silane coupling agents are well-known as surface modifiers for various kinds of silica (SiO2). However, in the present research, it has been found that they can also work as "hammerlike liquid" to pulverize different kinds of bulk amorphous SiO2 in aqueous systems. This new function was typically clarified by using 3-aminopropyltrimethoxysilane (APS) and bundles of chiral SiO2 nanofibers (with average diameter of ∼10 nm) as raw materials. By a simple reflux of the mixture of SiO2 nanofibers and excessive APS in pure H2O, the solid-containing mixture turned into a completely clear solution that contained sub-10 nm, amine-modified, and water-soluble hybrid SiO2 sols (HS-sols). Moreover, this solution showed blue luminescence under ultraviolet irradiation. Furthermore, the circular dichroism and vibrational circular dichroism spectra revealed that the HS-sols are optically active even though the pristine chiral SiO2 nanofibers were completely destroyed. It was considered that the chirality of SiO2 nanofibers was due to the asymmetric arrangement of Si and O atoms in chiral domains (<10 nm) on the Si-O-Si network of SiO2, and these domains are still preserved in chiral HS-sols. This green method has high potential for the recycling of rich SiO2 sources to obtain functional SiO2 nanomaterials with applications such as optical display, imaging, and chiral recognition. Also, it offers a tool for the analysis of the structural properties of SiO2 on the molecular scale.

In situ growth of fluorescent silicon nanocrystals in a monolithic microcapsule as a photostable, versatile platform

A facile, one-step method was developed for the in situ formation of fluorescent silicon nanocrystals (SiNC) in a microspherical encapsulating matrix. The obtained SiNC encapsulated polymeric microcapsules (SiPM) possess uniform size (0.1-2.0 μm), strong fluorescence, and nanoporous structure. A unique two stage, time dependent reaction was developed, as the growth of SiNC was slower than the formation of polymeric microcapsules. The resulting SiPM with increasing reaction time exhibited two levels of stability, and correspondingly, the release of SiNC in aqueous media showed different behavior. With reaction time <1 h, the obtained low-density SiPM (LD-SiPM) as matrix microcapsules, would release encapsulated SiNC on demand. With >1 h reaction time, resulting high-density SiPM (HD-SiPM) became stable SiNC reservoirs. SiPM exhibit stable photoluminescence. The porous structure and fluorescence quenching effects make SiPM suitable for bioimaging, drug loading and sorption of heavy metals (Hg(2+) as shown) as an intrinsic indicator. SiPM were able to reduce metal ions, forming SiPM/metal oxide and SiPM/metal hybrids, and their applications in bio-sensing and catalysis were also demonstrated.

Facile and Chemically Pure Preparation of YVO4:Eu(3+) Colloid with Novel Nanostructure via Laser Ablation in Water

A YVO₄:Eu³⁺ colloid with an interesting nanostructure was formed by pulsed laser ablation in deionized water without any additives or surfactants. Analyses of particle morphology, composition and optical properties were accomplished by SEM, TEM, EDS PL and UV-vis. Ovoid-like particles formed by the agglomeration of numerous nanocrystals were observed by SEM and TEM, while EDS with area-mode analysis revealed that the content of dopant ion was well retained within the nanoparticles. In addition, the formation mechanism is deduced and discussed for the first time in this research. The findings of this study could provide new insights into the understanding of laser-induced oxide materials and offer an opportunity for other research groups to pursue red emitting nanophosphors with outstandingly purity.

Luminescent and magnetic materials with a high content of Eu3+-EDTA complexes

Bifunctional optical magnetic materials with a high europium content have been prepared.

Easily processable multimodal spectral converters based on metal oxide/organic-inorganic hybrid nanocomposites

This manuscript reports the synthesis and characterization of the first organic-inorganic hybrid material exhibiting efficient multimodal spectral converting properties. The nanocomposite, made of Er(3+), Yb(3+) codoped zirconia nanoparticles (NPs) entrapped in a di-ureasil d-U(600) hybrid matrix, is prepared by an easy two-step sol-gel synthesis leading to homogeneous and transparent materials that can be very easily processed as monolith or film. Extensive structural characterization reveals that zirconia nanocrystals of 10-20 nm in size are efficiently dispersed into the hybrid matrix and that the local structure of the di-ureasil is not affected by the presence of the NPs. A significant enhancement in the refractive index of the di-ureasil matrix with the incorporation of the ZrO2 nanocrystals is observed. The optical study demonstrates that luminescent properties of both constituents are perfectly preserved in the final hybrid. Thus, the material displays a white-light photoluminescence from the di-ureasil component upon excitation at UV/visible radiation and also intense green and red emissions from the Er(3+)- and Yb(3+)-doped NPs after NIR excitation. The dynamics of the optical processes were also studied as a function of the lanthanide content and the thickness of the films. Our results indicate that these luminescent hybrids represent a low-cost, environmentally friendly, size-controlled, easily processed and chemically stable alternative material to be used in light harvesting devices such as luminescent solar concentrators, optical fibres and sensors. Furthermore, this synthetic approach can be extended to a wide variety of luminescent NPs entrapped in hybrid matrices, thus leading to multifunctional and versatile materials for efficient tuneable nonlinear optical nanodevices.

Synergistic photoluminescence enhancement in conjugated polymer-di-ureasil organic-inorganic composites

Energy transfer between a hybrid di-ureasil host and conjugated polymer dopants results in a dramatic enhancement in the photoluminescence quantum yield due to exciton isolation at long-lived trap sites.

Poly(fluorene) conjugated polyelectrolyte (CPE)-di-ureasil organic–inorganic composites have been prepared using a versatile sol–gel processing method, which enables selective localisation of the CPE within the di-ureasil matrix. Introduction of the CPE during the sol–gel reaction leads to a homogeneous distribution of the CPE throughout the di-ureasil, whereas a post-synthesis solvent permeation route leads to the formation of a confined layer of the CPE at the di-ureasil surface. The CPE and the di-ureasil both function as photoactive components, contributing directly to, and enhancing the optical properties of their composite material. The bright blue photoluminescence exhibited by CPE-di-ureasils is reminiscent of the parent CPE; however the distinct contribution of the di-ureasil to the steady-state emission profile is also apparent. This is accompanied by a dramatic increase in the photoluminescence quantum yield to >50%, which is a direct consequence of the synergy between the two components. Picosecond time-correlated single photon counting measurements reveal that the di-ureasil effectively isolates the CPE chains, leading to emissive trap sites which have a high radiative probability. Moreover, intimate mixing of the CPE and the di-ureasil, coupled with their strong spectral overlap, results in efficient excitation energy transfer from the di-ureasil to these emissive traps. Given the simple, solution-based fabrication method and the structural tunability of the two components, this approach presents an efficient route to highly desirable CPE-hybrid materials whose optoelectronic properties may be enhanced and tailored for a targeted application.

Amine functionalized ZrO2 nanoparticles as biocompatible and luminescent probes for ligand specific cellular imaging

Surface functionalized ZrO₂ nanoparticles show strong photoluminescence and are a versatile tool for cellular targeting due to their chemical functionality.

Multicomponent hybrids of surfactant-capped lanthanide polyoxometalates and ZIF-8 with tuneable luminescence

Two kinds of surfactant-functionalized lanthanide polyoxometalates and ZIF-8 nanoparticles were diffused together in polymer hosts, whose luminescence colour can be tuned by adjusting the composing units to provide useful data for multicomponent hybrids.

LaB6 nanoparticles with carbon-doped silica coating for fluorescence imaging and near-IR photothermal therapy of cancer cells

In this study, LaB6 nanoparticles are used as a novel nanomaterial for near-infrared (NIR) photothermal therapy because they are cheaper than nanostructured gold, are easy to prepare and have an excellent NIR photothermal conversion property. Furthermore, the surface of LaB6 nanoparticles is coated with a carbon-doped silica (C-SiO2) shell to introduce a fluorescent property and improve stability and biocompatibility. The resulting LaB6@C-SiO2 nanoparticles retain the excellent NIR photothermal conversion property and exhibit a bright blue emission under UV irradiation or a green emission under visible irradiation. Using a HeLa cancer cell line, it is demonstrated that LaB6@C-SiO2 nanoparticles have no significant cytotoxicity, but their presence leads to remarkable cell death after NIR irradiation. In addition, from the observation of cellular uptake, the fluorescence labeling function of LaB6@SiO2 (LaB6 core/SiO2 shell) nanoparticles is also confirmed. These results suggest that LaB6@C-SiO2 nanoparticles may potentially serve as an efficient multifunctional nano-platform for simultaneous fluorescent imaging and NIR-triggered photothermal therapy of cancer cells.

A luminescent lanthanide complex-based anion sensor with electron-donating methoxy groups for monitoring multiple anions in environmental and biological processes

We designed a ternary europium (III) tris(2-thenoyltrifluoroacetonate) with 2-(3,4,5-trimethoxyphenyl)imidazo[4,5-f]-1,10-phenanthroline (1) ligands for the luminescent detection of various anions, such as fluoride, acetate and dihydrogen phosphate. Characterization of the sensor's photophysical properties and via NMR showed that the sensor exhibits striking emission changes to fluoride (purple), acetate (green) and dihydrogen phosphate (blue) anions, respectively. Its fluorescence lifetime was determined to be 1.10 ms for europium ions and the complex showed an overall quantum yield of 10% in DMSO. Furthermore, transparent hybrid thick films composed of the europium complex and poly-methyl methacrylate matrix were successfully prepared via copolymerization. The resulting film overall displayed intense red emissions associated with europium ions. Fluorescence microscopic evaluation showed a homogenous distribution of aggregates with average diameters of 30-50 μm throughout the film. The accordingly produced film could give rise to a luminescence change to purple in response to fluoride anions.

Metal-free highly luminescent silica nanoparticles

Stable, cost-effective, brightly luminescent, and metal-free organosilica nanoparticles (NPs) were prepared using the Stöber method without any thermal treatment above 318 K. The white-light photoluminescence results from a convolution of the emission originated in the NH(2) groups of the organosilane and oxygen defects in the silica network. The time-resolved emission spectra are red-shifted, relative to those acquired in the steady-state regime, pointing out that the NPs emission is governed by donor-acceptor (D-A) recombination mechanisms. Moreover, the increase of the corresponding lifetime values with the monitored wavelength further supports that the emission is governed by a recombination mechanism typical of a D-A pair attributed to an exceptionally broad inhomogeneous distribution of the emitting centers peculiar to silica-based NPs. These NPs exhibit the highest emission quantum yield value (0.15 ± 0.02) reported so far for organosilica biolabels without activator metals. Moreover, the emission spectra and the quantum yield values are quite stable over time showing no significant aging effects after exposure to the ambient environment for more than 1 year, stressing the potential of these NPs as metal-free biolabels.