Aqueous, dispersible, luminescent YPO4:Eu3+-K+ and hybrid magnetic-luminescent Fe3O4@YPO4:Eu3+-K+ nanoparticles are prepared at an optimum temperature with a simple synthesis route. The shape of ...YPO4:Eu3+-K+ nanoparticles is found to be nanorods. Photoluminescence spectrum of a sample upon excitation at 395 nm shows the characteristic peaks of Eu3+ such as magnetic–dipole transition (5D0 → 7F1) at 592 nm, the electric–dipole transition (5D0 → 7F2) at 615 nm, and electric–dipole transition (5D0 → 7F4) at 695 nm. Luminescence intensity increases with K+ doping. Interestingly, their luminescence intensities are almost the same. This could be explained by the polarizability effect of the PO4 3– group and K+ upon emission of Eu3+. This high intensity at 695 nm will be useful in bioimaging since this wavelength falls in biological window I. This hybrid material shows a hyperthermia temperature under an AC magnetic field, making this material a potential candidate for cancer therapy.
Nanocrystals having single-band red emission under near-infrared (NIR) excitation through the upconversion process offer great advantages in terms of enhanced cellular imaging in
and
experiments in ...the biological window (600-900 nm), as a security ink, in photothermal therapy (PTT), in photodynamic therapy (PDT), and so forth but are challenging for materials scientists. In this work, we report for the first time the preparation of a super bright red emitter at 655 nm from monodispersed NaErF
:0.5%Tm@NaYF
:20%Yb nanocrystals (core@active shell). This phosphor exhibits 35 times stronger photoluminescence as compared to NaErF
:0.5%Tm@NaYF
(core@inactive shell). Here, an Er
-enriched host matrix works simultaneously as an activator and a sensitizer under NIR excitation. Upconversion red emission at 655 nm arises due to the electronic transition of Er
via the involvement of a three-photon absorption (expected to be a two-photon absorption), which has been confirmed via a power-dependent luminescence study. Tm
ions incorporated into the core with the active shell act as trapping centers, which promote the red band emission via the back-energy transfer process. Moreover, the active shell containing Yb
ions efficiently transfers the energy to the Er
-enriched core, which suppresses the nonradiative channel rate, and Tm
ions act as trapping centers, which reduce the luminescence quenching via reduction of energy migration to the surface of the host lattice. Also, we have shown the potential applications of these nanocrystals: cellular imaging through downconversion and upconversion processes and security ink.
Eu3+ (2, 5, 7 and 10 at.%) activated SrWO4 phosphors were prepared via a polyol synthesis route at low temperature ( similar to 150 degree C) under urea hydrolysis. X-ray diffraction studies of all ...Eu3+ doped samples corroborate good crystallinity with a tetragonal scheelite-type structure of the SrWO4 phase. The value of strain was obtained in the range similar to 0.003 to 0.004 for as-prepared (ASP) and samples annealed at 900 degree C. Vibrational modes were studied using IR and Raman Spectroscopy. Photoluminescence studies of Eu3+ doped SrWO4 samples were carried out under 266, 394 and 464 nm excitations. An intense red emission was observed with a strong peak at similar to 613 nm due to 5D0 arrow right 7F2 transition under 266 nm. Effect of annealing at 900 degree C on the photoluminescence properties of samples has been studied and it was found that luminescence intensity increases up to similar to 9 times (for 10 at.% Eu3+-doped SrWO4) on annealing as compared to the corresponding as-prepared sample. High asymmetric ratios (A21) similar to 6-13 were observed demonstrating it to be a red emitter. Calculated CIE co-ordinates of these Eu3+ doped samples under 266 nm excitation for ASP and annealed at 900 degree C are x = 0.65 & y = 0.34, which are closer to the standard of NTSC (x = 0.67 & y = 0.33). These studies reveal that SrWO4:Eu3+ nano-phosphors can be used as potential red emitting phosphors for the development of white LEDs.
Cancer is among the leading causes of mortality and morbidity in the world. Metallic nanoparticles, especially gold nanoparticles (AuNPs) have emerged to be attractive systems to circumvent the ...associated adverse effects. By the virtue of their unique properties of tunable size, shape, composition, optical properties, biocompatibility, minimal toxicity, multivalency, fluorescence-luminescence property and surface plasmon resonance; AuNPs have the potential to be used as drug delivery systems. It is vital to ensure that the drug reaches the target site of action for selective kill of cancer cells without harm to healthy cells. These AuNPs can be easily functionalized with a wide array of ligands like peptides, oligonucleotides, polymers, carbohydrates for active targeting to ensure site specific delivery and reduced systemic effects. AuNPs have been in-vestigated as carriers for gene delivery, drug delivery with or without photothermal therapy, in diagnosis based on radiation or spectroscopy. They have emerged as attractive theranostic approach in the overall management of cancer with superior benefit to risk features. In this review, we have discussed synthesis of different AuNPs (nanorods, spherical nanoparticles, and hollow AuNPs), their functionalization strategies and their applications in biomedical domain. Various research studies and clinical trials on application of AuNPs in diagnosis and therapeutics are highlighted.
Eu
3+
-doped CaWO
4
nanophosphors were synthesised in series for different atomic wt% concentrations (0, 0.5, 1, 2, 5 and 10) of Bi
3+
by polyol method. Their structure and morphology were ...characterised using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The photoluminescence properties and energy transfer from Bi
3+
to Eu
3+
in CaWO
4
:Eu
3+
/Bi
3+
nanophosphors were also investigated. The results revealed that red luminescence of CaWO
4
:2Eu
3+
/1Bi
3+
nanophosphor is 5.4 times stronger than CaWO
4
:2Eu
3+
. It was observed that the forces exist between Bi
3+
and Eu
3+
are due to the interaction of electric dipole-dipole interactions. The chroma of CaWO
4
:2Eu
3+
/1Bi
3+
nanophosphors was calculated to be 97.40%. The energy transfer process was studied by measuring the decay curves due to Bi
3+
and Eu
3+
dopants. Enhanced red emission, high thermal stability, stronger
5
D
0
→
7
F
2
absorption intensity, high colour purity and decay studies indicate that CaWO
4
:Eu
3+
/Bi
3+
nanophosphors are potential candidates to be used in white light-emitting diode (wLEDs).
We analyzed scaling behaviour of conductivity spectra of two fragile glass melts 2Ca(NO3)2.3KNO3 (CKN) and 2Ca(NO3)2.3RbNO3 (CRN) below and above their glass transition temperature (TG). Spectra were ...described in terms of power law. Conductivity isotherms of these systems were found to follow time temperature superposition principle (TTSP) below and above TG and can be scaled to a master curve using hopping frequency as scaling factor. However, for both the systems, a deviation from TTSP was discerned in the vicinity of TG. We also observed, for both CKN and CRN, a change in exponent factor of the power law and in number density of the mobile charge carriers around TG. The experimental data were also analyzed in terms of electric modulus mechanism. Both, conductivity and modulus formulism revealed the similar trend of TTSP behaviour. The deviation from TTSP near TG has been correlated with the changes observed in these two quantities. Further, it has been proposed that the magnitude of change in dispersion of conductivity spectra is directly related with the decoupling and fragility of the glass melt systems.
► A Change of dispersion in AC conductivity of fragile glass melts has been observed. ► The exponent factor of power law also reflects this change. ► Fragility and decoupling have been correlated to the magnitude of the change. ► The results were analyzed in terms of conductivity and modulus spectra.
Monodispersed upconversion nanoparticles NaYF4:Er3+/Yb3+ (UCNPs) have been synthesized via the thermolysis method. Förster or fluorescence resonance energy transfer (FRET) dynamics from ...NaYF4:Er3+/Yb3+ (UCNPs) to gold nanoparticles (AuNPs) are well understood. However, only FRET-based heating (negligible heating from fluorophore or gold) is not much known so far in such systems under near-infrared (NIR) photon excitation. NIR-to-visible upconversion (UC) has already proven its utility in bioassays. Ultrasensitive FRET responsible surface plasmon resonance (SPR) induced hyperthermia has been estimated through water-dispersible monodispersed hybrid UCNP@SiO2@AuNPs via 980 nm NIR laser excitation. The trivial amount of heating for UCNPs and AuNPs are tested under continuous wave (CW) laser excitation. At ∼600 mW laser input power, a temperature increase to ∼43 °C has been noted within 15 min upon CW 980 nm laser excitation. The time-dependent magnetic field study performed with Fe3O4 and hybrid UCNP@SiO2@AuNPs exhibits the usefulness toward the magnetic as well as surface plasmon resonance-based hyperthermia treatment. This hybrid has potential for use as a radio sensitizer in γ-ray irradiation because of the presence of AuNPs, a magnetic resonance imaging (MRI) agent because of the presence of Fe3O4, and a temperature sensor because of the presence of UCNP, and in photothermal heating because of the presence of UCNP@SiO2@AuNPs and AC magnetic-based hyperthermia because of the presence of Fe3O4.
