Luminescence Response Research Articles

Upconversion Luminescence Imaging of Tumors with EGFR-Affibody Conjugated Nanophosphors

ABSTRACTNear infrared (NIR) optical imaging has demonstrated significant potential as an effective modality for cancer molecular imaging. Among various NIR probes currently under investigation, upconversion nanophosphors (UCNPs) possess great promise due to their anti-Stokes emission and sequential photon absorption which result in superior detection sensitivity and a simple imaging setup, respectively. Here we investigated the utility of this imaging modality to detect tumor cells expressing the epidermal growth factor receptor (EGFR) using affibody functionalized nanophosphors and a custom built imaging system. Initially, aqueous dispersible NaYF4: Tm+3, Yb+3 UCNPs were synthesized and their photophysical properties were characterized. Then, their luminescence response as a function of concentration and their depth resolving capability in a tissue-simulating phantom were examined. Finally, we demonstrated the use of bioconjugated UCNPs for imaging EGFR-expressing tumors both in vitro and in vivo. Our data suggests that NIR imaging with UCNPs may be useful for noninvasive imaging of tumors.

Polymorph-Dependent Luminescence Response to Acid Vapors and Its Application in Safety Protection of File Information.

A Schiff base, (E)-1-(phenylimino)methyl-2-hydroxylnaphthalene (PIHN), was found to form both nonluminescent and luminescent polymorphs. A unique luminescence "turn on" behavior was observed when the nonluminescent polymorph was fumed with the vapor of aliphatic acids with two or three carbons in the main chain, while the luminescent polymorphs almost did not change the emission color under the same condition. As we know, this is the first report on polymorph-dependent acid response which discloses the influence of crystalline phase on acid-responsive behavior. The formation of hydrogen bonds between PIHN and aliphatic acid is proposed to be the reason for the responsive behavior of the nonemissive polymorph, and such a mechanism is different from the common protonation mechanism. A novel safety protection method of file information has been developed based on the polymorph-dependent luminescence response of PIHN. In addition, we disclose that a crystalline form could show multiple responsive behaviors toward different acids, which benefits the further design of novel acid sensors, such as the sensors that can qualitatively analyze the species of the acid source in an acidic environment.

Accurate Control of Core–Shell Upconversion Nanoparticles through Anisotropic Strain Engineering

AbstractThe effect of anisotropic interfacial strain on epitaxial growth and optical emission of sodium rare‐earth fluoride core–shell nanoparticles is investigated. A variety of sodium rare‐earth fluoride shells are grown on hexagonal‐phase NaYF4:Yb/Er core for providing anisotropic tuning of interfacial strains. Using high‐resolution transmission electron microscopy and X‐ray diffraction characterizations, the correlations between the epitaxial habits and the interfacial strains are quantitatively addressed. Furthermore, the growth affinity is tuned by controlling precursor concentration in conjunction with Ca2+ doping, which results in accurate regulation of the anisotropic growth. The lattice strain resulting from mismatched epitaxy is found to enhance luminescence response of the nanoparticles to temperature change.

Noticeable size dispersity and optical stability of sodium dodecyl sulphate (SDS)-coated MnSe quantum dots in extreme natural environment

The pH of the dispersing media has an influential role on the optical and radiative features of quantum particles/dots (QDs). Herein, we report size dispersity and luminescence response of sodium dodecyl sulphate (SDS)-coated MnSe QDs dispersed in extreme natural extracts. The hydrothermally processed QDs exhibited wutzite phase and numerous Raman active modes as revealed through the X-ray diffraction and Raman spectroscopy studies; respectively. Of varied pH (typically, from 2.5 to 9), distinctly different extracts were derived from starfruit, sugarcane, chilli, and neem leaves available locally. The hydrodynamic size of the QDs experiences a declining trend with increasing pH, with dispersing media being a buffer solution or a natural extract. Zeta potential makes a clear transition from the positive to the negative values, as one moves from a low (acidic) to high (basic) pH of the natural extracts, and subsequently, the isoelectric point (IEP) of the QDs in a medium has been predicted at pH 6.3. Whereas a more acidic medium offered a relatively lowered luminescence profile, the extracts of high pH ensured an intense blue–violet emission of the QDs located at ~ 428 nm along with defect-mediated peaks, expected at relatively higher wavelengths. Furthermore, the acidic environment tends to suppress both near band edge and defect-mediated emissions substantially. The optical stability of surfactant-coated QDs would find immense value in the areas of nano-bio interface applications, such as nano-bioconjugation, bio-imaging, and drug formulation in nano-medicine.

Two bifunctional photoluminescent Zn (II) coordination polymers for detection of Fe3+ ion and nitrobenzene

Two new luminescent metal–organic coordination polymers (MOCPs) of {[Zn6(L)2(H2O)7]·(DMF)2}n (1) and {[Zn(H4L)(bpy)0.5(H2O)2]·H2O}n (2) were solvothermally constructed using zinc salts and ligands (H6L = 5,5′-(propane-2,2-diyl)bis(2-hydroxyisophthalic acid), bpy = 4,4′-bipyridine). The resulted MOCPs were characterized by elemental analysis, powder X-ray diffraction, and single-crystal X-ray diffraction. Single-crystal X-ray study results reveal that compounds 1 and 2 belong to P1¯ and P 21/n space group and show a two- and one-dimensional structure, respectively. Their photoluminescence (PL) properties and thermal properties were also studied. Interestingly, the luminescent responses of compounds 1 and 2 show highly sensitive detection of Fe3+ via an obvious fluorescence quenching. The detection limits of compounds 1 and 2 are 0.25 μM and 0.19 μM toward Fe3+. Compound 2 possesses a ring structure, which is big enough to allow small molecules to easily move into the crystal skeleton and interact with each other. Thus, the luminescence responses of compound 2 were investigated for various organic solvents. These results show that compound 2 has great potential to be developed as the favorable sensor for highly selective detection of nitrobenzene.

A Gold Quartet Framework with Reversible Anisotropic Structural Transformation Accompanied by Luminescence Response

Summary Hierarchy and chirality are the fundamental characteristics of biomolecules. Chemistry on hierarchical self-assembly and spontaneous symmetry breaking helps to uncover the mechanism of living activities and the origin of chirality in nature. Herein, we describe a chiral gold quartet framework (GQF) with C4-symmetric structure hierarchically aggregated from an achiral anionic [Au10(dpptrz)4S4]2− (dpptrz-Au10), which was acquired via click-reaction-induced and Au(I)⋅⋅⋅Au(I)-interaction-directed cluster-to-cluster transformation (CCT) from the rationally designed [(dppa)6Au18S8]2+ (dppa-Au18). Inter-cluster hydrogen bonding and alkali ion coordination were observed to assist the hierarchical self-assembly and chiral self-organization of the GQF. Upon exposing the crystal to vacuum, the bottom-up constructed GQF showed an anisotropic structural transformation accompanied by a visual luminescence change in a single-crystal-to-single-crystal (SCSC) manner that became reversible upon removal of vacuum. This research largely advances the potential of polynuclear gold(I)-sulfido clusters in hierarchical self-assembly and luminescent materials.

Thermochromic luminescence and dielectric response of copper(I) iodide based MOFs as luminescent thermometer

A copper(I) iodide based MOFs crystal with the formula [Cu4I4(Pz)2]n (Pz = [1,4-bis(4-pyridylmethyl)piperazine]) (1) was synthesized using a solvothermal method. The compound 1 crystallized in the monoclinic space group C2/c at room temperature and consisted of Cu4I4 clusters. Along the b-axis, an irregular window with a size of 7.8 × 31.6 Å was formed. The neighboring rotators (piperazine ring) had a long distance of 12.3 Å between their rotational axes (CH2-), making it easy to rotate. From the view of the crystal structure, 1 can serve as an ideal amphidynamic model, and an in-plane oscillatory fluctuation of the piperazine ring results from the dielectric relaxation. In addition, this compound also showed luminescence thermochromic properties, and a good linear relationship between the luminescence intensity ration of the three emission bands and the temperature was observed. Thus, this compound can be excellent as a luminescent thermometer. These findings provide a new strategy for constructing electrical and optical properties of amphidynamic MOFs.

Near infrared light excited sensors NaYbF4@ NaYF4

The luminescence and temperature response characteristics of NaYF4 containing 15% NaYBF4 were investigated. NaYbF4@ NaYF4 has good thermal stability and excellent response characteristics in the temperature in the range from 300 to 500 K, which significantly increases the upper limit of temperature detection of ytterbium temperature sensor. A self-calibration relationship between the reciprocal of temperature and the natural logarithm ratio of luminescent intensity has been discovered. Compared with the values of ln(I1048/I967) or ln (I947/I967) in Yb3+ emission spectra, the relationship between ln (I990/I967) and 1/T is not linear, but exponential attenuation relationship with better temperature resolution near 400 K. Oxygen has no influence on these relations because of the ordered and dense crystal structure, which leading to the separation of Yb3+ and oxygen.

Structural Studies Reveal Enantiospecific Recognition of a DNA G-Quadruplex by a Ruthenium Polypyridyl Complex.

By using X-ray crystallography, we show that the complexes Λ/Δ-[Ru(TAP)2 (11-CN-dppz)]2+ (TAP=1,4,5,8-tetraazaphenanthrene, dppz=dipyridophenazine) bind DNA G-quadruplex in an enantiospecific manner that parallels the specificity of these complexes with duplex DNA. The Λ complex crystallises with the normally parallel stranded d(TAGGGTTA) tetraplex to give the first such antiparallel strand assembly in which syn-guanosine is adjacent to the complex at the 5' end of the quadruplex core. SRCD measurements confirm that the same conformational switch occurs in solution. The Δ enantiomer, by contrast, is present in the structure but stacked at the ends of the assembly. In addition, we report the structure of Λ-[Ru(phen)2 (11-CN-dppz)]2+ bound to d(TCGGCGCCGA), a duplex-forming sequence, and use both structural models to provide insight into the motif-specific luminescence response of the isostructural phen analogue enantiomers.

Structural Studies Reveal Enantiospecific Recognition of a DNA G‐Quadruplex by a Ruthenium Polypyridyl Complex

AbstractBy using X‐ray crystallography, we show that the complexes Λ/Δ‐[Ru(TAP)2(11‐CN‐dppz)]2+ (TAP=1,4,5,8‐tetraazaphenanthrene, dppz=dipyridophenazine) bind DNA G‐quadruplex in an enantiospecific manner that parallels the specificity of these complexes with duplex DNA. The Λ complex crystallises with the normally parallel stranded d(TAGGGTTA) tetraplex to give the first such antiparallel strand assembly in which syn‐guanosine is adjacent to the complex at the 5′ end of the quadruplex core. SRCD measurements confirm that the same conformational switch occurs in solution. The Δ enantiomer, by contrast, is present in the structure but stacked at the ends of the assembly. In addition, we report the structure of Λ‐[Ru(phen)2(11‐CN‐dppz)]2+ bound to d(TCGGCGCCGA), a duplex‐forming sequence, and use both structural models to provide insight into the motif‐specific luminescence response of the isostructural phen analogue enantiomers.

Self-Assembly of Luminescent Gold Nanoparticles with Sensitive pH-Stimulated Structure Transformation and Emission Response toward Lysosome Escape and Intracellular Imaging.

Ultrasmall luminescent gold nanoparticles (AuNPs, d < 3.0 nm) with distinct optical properties and good biocompatibilities hold enormous promise for advanced disease theranostics. However, ultrasmall AuNPs generally show low cellular interaction and are hardly ever transported into the specific subcellular compartments, hampering their further biomedical use in cellular delivery and intracellular tracking. Using a conventional cationic polymer chitosan (CS) with the isoelectric point of 6.5 as a template, ultrasmall luminescent AuNPs can be easily formed into self-assembled nanostructures (AuNPs@CS) with significantly enhanced cellular interaction capability and sensitive emission response toward subcellular location. The self-assembled AuNPs@CS become compacted nanostructures (∼23.5 nm) with high luminescence at low pH values (e.g., pH < 6.5) but reversibly transform to swelled structures with weak luminescence at high pH values (e.g., pH 7.4). The self-assembly of AuNPs not only improves the emission properties but also alters the surface charge and assembly size, resulting in both enhanced cellular internalization and effective endosomal escape capability. More importantly, the sensitive luminescence response of the AuNPs@CS from the acidic organelle lysosome to the neutral cytoplasm demonstrates the great potential in optical intracellular tracking.

Glass-ceramics LiB3O5 – a perspective material for dosimetry

The technology of preparation of polycrystalline lithium triborate LiB3O5 (LBO) is presented. The glass-ceramics was synthesized by solid-state reaction technique. The formation of crystallites in glass matrix is achieved through special annealing procedure that imply melting of the batch and fast cooling down of the glass followed by annealing at the crystallization temperature. The procedure allows preparing of sufficiently large number of big-sized samples. The procedure of LBO polycrystalline glass preparation is easier and much cheaper than that of LBO single crystals. The existence of the crystallites within the glass matrix was confirmed by scanning electron microscopy and X-ray diffraction studies. Comparative analysis of the X-ray diffraction patterns for both amorphous and polycrystalline LBO glass as well as for LiB3O4 single crystals indicates that the crystallites are of the micro- and nanoscale average size. The TL properties of LBO glass-ceramics were studied. It was found that polycrystalline glass LiB3O4 exhibits strong thermally stimulated luminescence after they were exposed to X-ray radiation. In particular, the samples submitted to X-ray radiation at the room temperature exhibit strong luminescence upon heating up the samples to the temperatures 376 K and 413 K. Those thermostimulated luminescence bands can be attributed to luminescent centers in boron oxide complex that forms crystal lattice of LBO. The thermostimulated dose response determined by the peak heights increases linearly with the increase of the irradiation dose. Exceptional mechanical properties of polycrystalline LBO, cheap preparation along with the linear dependence of thermostimulated luminescence response open wide perspectives for that material to be used as the detectors of any types of radiation. High abundance of 6Li and 10B isotopes also makes LBO glass-ceramics capable of neutron detection. It is important that polycrystalline lithium triborate can be exploited as tissue-equivalent material for measuring of X-ray radiation dose. Further studies will focus on improving of the thermoluminescent characteristics of LBO glass-ceramics by various dopants.

Metal cation sensing by a NIR luminescent high-nuclearity Zn–Yb schiff base nanocluster

Two long Schiff base ligands H2L1 and H2L2 that have flexible long-chain backbones were used to synthesize 8- and 12-metal Zn-Ln nanoclusters [Zn4Eu4(L1)2(OAc)10(NO3)2(OH)4] (1) and [Zn8Yb4(L2)8(OAc)8](OH)4 (2), respectively. The crystal structures of 1 and 2 show that their molecular sizes are about 9 × 10 × 11 Å and 9 × 19 × 28 Å, respectively. Both clusters display typical emission bands of lanthanide ions. Interestingly, the Zn–Yb cluster 2 exhibits NIR luminescent response to metal cations, especially to Co2+ and Cu2+ at the ppm level.

Fluorescent electrospun PMMA microfiber mats with embedded NaYF4: Yb/Er upconverting nanoparticles

Functional upconverting nanoparticles (UCNPs) can offer new possibilities in fluorescent applications as they exhibit desired characteristic properties like large shift between the fluorescent emission signal and the infrared excitation wavelength, multi- and narrow-band absorption and emission in visible and near infrared - Vis/NIR, together with excellent photostability and low toxicity as opposed to semiconducting quantum dots. The upconversion luminescence emission or quenching characteristics of UCNPs can be altered upon exposure to physical or chemical environmental factors providing thus a functionality that can be utilized for sensing or imaging. Furthermore their functionalization with suitable indicator dyes or recognition elements can extend the range of luminescence response and ratiometric sensing to specific analytes. Synergistically, electrospun nano- and microfibers offering large surface area can enhance the functionality of UCNPs by retaining the fluorescence efficiency and improving the overall responsivity due to dramatically increased surface. For the optimization of this hybrid material system the controllable incorporation of UCNPs is required especially at increased concentration conditions needed for high brightness. Herein, we report the fabrication, morphological and optical characterization of electrospun polymer-based nanocomposite fibers, consisting of poly(methyl methacrylate) (PMMA) and upconverting lanthanide doped nanoparticles of the type NaYF4 : 20% Yb3+/2% Er3+ @ NaYF4. Morphological studies regarding the uniformity and aggregation effects of the UCNP inclusion within the fibers have been implemented followed by upconversion emission characterization by pulsed near-infrared excitation. The study and optimization of such nanocomposite fibrous systems could provide useful insights for the development of efficient upconverting electrospun fiber mats for a number of imaging and sensing applications.

Multi-component luminescence responsive Eu3+/Tb3+ hybrids based with metal-organic frameworks and zeolites A.

Both Zeolite A (ZA) and two kinds of 2,2'-bipyridine-5,5'-dicarboxylic acid (H2bpydc) linking meta-organic frameworks (MOFs) (MOF-253 (Al(OH)(bpydc)) and UiO-67 ([Zr6O4(OH)4(bpydc)6])) have been used to construct novel photofunctional multi-component lanthanide hybrid materials through covalent-coordination cooperative assembly. Microporous ZA is firstly functionalized by covalently grafting of the surface hydroxyl groups using special silane crosslinking reagent 3-methacryloxypropyltrimethoxysilane (MPTMS). Then the multi-component assembly are realized by coordination interaction between lanthanide ions (Eu3+/Tb3+), ZA through the carbonyl group of MPTMS unit and MOF-253 (or UiO-67) through the double nitrogen of bpydc linker. Subsequently, the obtained multicomponent hybrid materials (ZA-MPTMS-Eu/Tb-MOF-253(UiO-67)) are characterized by means of XRD, FT-IR, SEM and especially the photoluminescence properties are studied in details. These hybrids with both ZA and MOFs host show the main characteristic crystal framework morphology of ZA together with the composition of MOFs. They display the feature luminescence of Eu3+/Tb3+ ions for the energy transfer from bpydc linker of MOFs. Furthermore, ZA-MPTMS-Eu-UiO-67 hybrid material is selected to check the luminescence response to volatile substances, whose luminescence quenching is found for ammonia vapor.

Effect of charge transfer and structural rigidity on divergent luminescence response of a metal organic framework towards different metal ions: luminescence lifetime decay experiments and DFT calculations.

We have thoroughly studied the luminescence behaviour of a cadmium based MOF, [Cd(C12N2H8)(C7N1O4H3)] {C12N2H8 = 1,10-phenanthroline, C7N1O4H3 = 2,5-pyridine dicarboxylate}, 1. Both steady-state and time-resolved luminescence spectroscopic experiments were performed to understand the dissimilar responses of compound 1 towards different metal ions in aqueous medium. Upon excitation at 280 nm, compound 1 showed a luminescence spectrum centered at 365 nm, which exhibited a three-fold turn-on in the presence of a trace amount of Zn2+ in aqueous solution, whereas in the presence of Co2+, Hg2+, Ni2+, Fe2+ and Cu2+ the luminescence of compound 1 got largely quenched. Compound 1 did not show any response in the presence of other common metal ions such as K+, Mg2+, Na+, Mn2+, and Cr3+. By analysing all the experimental results, we successfully explained the versatile luminescence behaviour of compound 1. The turn-on of luminescence in the presence of Zn2+ ions was due to coordination bond formation and enhancement of the rigidity of compound 1 which resulted in the reduction of non-radiative decay processes to a large extent. The quenching of luminescence in the presence of transition metal ions was found to be static in nature, and was due to the possibility of ligand to metal charge transfer using the vacant d-orbital of the metal ions. In the case of Hg2+ which is a closed cell heavy metal ion, the quenching of luminescence was also static in nature and was due to a two-way charge transfer mechanism. We have also performed density functional theory calculations and obtained supportive results for the proposed mechanisms of luminescence turn-on and quenching. Moreover, compound 1 could be established as a selective and efficient sensor of Zn2+ in aqueous solution even in the presence of Cd2+ and other metal ions.

Bi‐Modal Nonlinear Optical Contrast from Si Nanoparticles for Cancer Theranostics

AbstractPresenting a safe alternative to conventional compound quantum dots and other functional nanostructures, nanosilicon can offer a series of breakthrough hyperthermia‐based therapies under near‐infrared, radiofrequency, ultrasound, etc., excitation, but the size range to sensitize these therapies is typically too large (&gt;10 nm) to enable efficient imaging functionality based on photoluminescence properties of quantum‐confined excitonic states. Here, it is shown that large Si nanoparticles (NPs) are capable of providing two‐photon excited luminescence (TPEL) and second harmonic generation (SHG) responses, much exceeding that of smaller Si NPs, which promises their use as probes for bi‐modal nonlinear optical bioimaging. It is finally demonstrated that the combination of TPEL and SHG channels makes possible efficient tracing of both separated Si NPs and their aggregations in different cell compartments, while the resolution of such an approach is enough to obtain 3D images. The obtained bi‐modal contrast provides lacking imaging functionality for large Si NPs and promises the development of novel cancer theranostic modalities on their basis.

Luminescence responses of CePO4: Tb monospheres toward vitamin C and permanganate

(Ce0.9Tb0.1)PO4 monospheres (˜1.39 ± 0.11 μm) of negligible aggregation and high geometric uniformity were synthesized via microwave assisted homogeneous precipitation, whose luminescence responses toward MnO4− oxidant and vitamin C reductant were studied in detail. Through exciting Ce3+ with 275 nm UV light, strong and broad UV emission centered at ˜350 nm (FWHM ˜40 nm) and sharp green emission at ˜544 nm (FWHM ˜10 nm) were obtained, and efficient Ce3+ → Tb3+ energy transfer, with an efficiency of ˜65%, was observed. Interacting the monospheres with MnO4− (0–50 μM) effectively quenched the luminescence via Ce3+ oxidation, and treating the luminescence-quenched monospheres with VC (0–250 μM) sufficiently recovered the luminescence via Ce4+ reduction. Numerical expressions were also established to correlate the emission intensity with VC and MnO4− concentrations. Besides, the colloidal monospheres exhibited the favorable response time of ˜18 and 50 s for 25 μM of MnO4− and 150 μM of VC, respectively.

Ionization quenching in scintillators used for dosimetry of mixed particle fields

Ionization quenching in ion beam dosimetry is often related to the fluence- or dose-averaged linear energy transfer (LET). Both quantities are however averaged over a wide LET range and a mixed field of primary and secondary ions. We propose a novel method to correct the quenched luminescence in scintillators exposed to ion beams. The method uses the energy spectrum of the primaries and accounts for the varying quenched luminescence in heavy, secondary ion tracks through amorphous track structure theory. The new method is assessed against more traditional approaches by correcting the quenched luminescence response from the BCF-12, BCF-60, and 81-0084 plastic scintillators exposed to a 100 MeV pristine proton beam in order to compare the effects of the averaged LET quantities and the secondary ions. Calculations and measurements show that primary protons constitute more than 92% of the energy deposition but account for more than 95% of the luminescence signal in the scintillators. The quenching corrected luminescence signal is in better agreement with the dose measurement when the secondary particles are taken into account. The Birks model provided the overall best quenching corrections, when the quenching corrected signal is adjusted for the number of free model parameters. The quenching parameter kB for the BCF-12 and BCF-60 scintillators is in agreement with literature values and was found to be m keV−1 for the 81-0084 scintillator. Finally, a fluence threshold for the 100 MeV proton beam was calculated to be of the order of 1010 cm−2, corresponding to 110 Gy, above which the quenching increases non-linearly and the Birks model no longer is applicable.

Multiple Luminescence Responses towards Mechanical Stimulus and Photo-Induction: The Key Role of the Stuck Packing Mode and Tunable Intermolecular Interactions.

Organic luminescence with different forms continues to be one of the most active research fields in science and technology. Herein, an ultra-simple organic molecule (TPA-B), which exhibits both mechanoluminescence (ML) and photo-induced room-temperature phosphorescence (RTP) in the crystalline state, provides an opportunity to reveal the internal mechanism of ML and the dynamic process of photo-induced RTP in the same molecule. Through the detailed investigation of photophysical properties together with crystal structures, the key role of molecular packing and intermolecular interactions was highlighted in the luminescence response by mechanical and light stimulus, affording efficient strategies to design potential smart functional materials with multiple luminescence properties.