CaWO4 Nanoparticles Research Articles

Preparation and Characterization of Red, Green, Blue (RGB) and White Luminescent Inorganic/Organic Polymers Through In Situ Polymerization.

YVO4:Eu3+/PMMA, LaPO4:Ce3+,Tb3+/PMMA and CaWO4/PMMA nanocomposites were prepared by in situ polymerization method with hydrophobic YVO4:Eu3+, LaPO4:Ce3+,Tb3+ and CaWO4 nanoparticles as the filler and poly (methyl methacrylate) (PMMA) as the host material. All the nanoparticles and composites have been well characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscope (TEM), the thermogravimetric analysis (TGA), photoluminescence excitation, and emission spectra and luminescence decays. YVO4:Eu3+/PMMA, LaPO4:Ce3+,Tb3+/PMMA, CaWO4/PMMA nanocomposites exhibit strong red, green and blue photoluminescence upon 254nm UV excitation, respectively. The yellow and white LED nanocomposites with CIE coordinates of (0.411, 0.498) and (0.334, 0.359) were obtained by triply integrating the red, green and blue nanoparticles into PMMA. Thanks to the abundant luminescent colors from RGB to yellow and white in these polymer composites under UV excitation, they can be potentially used in various optoelectronic fields.

The Influence of High-Energy Milling on the Phase Formation, Structural, and Photoluminescent Properties of CaWO4 Nanoparticles.

CaWO4 nanoparticles were obtained by facile mechanochemical synthesis at room temperature, applying two different milling speeds. Additionally, a solid-state reaction was employed to assess the phase composition, structural, and optical characteristics of CaWO4. The samples were analyzed by X-ray diffraction (XRD), transition electron microscopy (TEM), and Raman, infrared (IR), ultraviolet-visible (UV-Vis) reflectance, and photoluminescence (PL) spectroscopies. The phase formation of CaWO4 was achieved after 1 and 5 h of applied milling speeds of 850 and 500 rpm, respectively. CaWO4 was also obtained after heat treatment at 900 °C for 12 h. TEM and X-ray analyses were used to calculate the average crystallite and grain size. The Raman and infrared spectroscopies revealed the main vibrations of the WO4 groups and indicated that more distorted structural units were formed when the compound was synthesized by the solid-state method. The calculated value of the optical band gap of CaWO4 significantly increased from 2.67 eV to 4.53 eV at lower and higher milling speeds, respectively. The determined optical band gap of CaWO4, prepared by a solid-state reaction, was 5.36 eV. Blue emission at 425 (422) nm was observed for all samples under an excitation wavelength of 230 nm. CaWO4 synthesized by the solid-state method had the highest emission intensity. It was established that the intensity of the PL peak depended on two factors: the morphology of the particles and the crystallite sizes. The calculated color coordinates of the CaWO4 samples were located in the blue region of the CIE diagram. This work demonstrates that materials with optical properties can be obtained simply and affordably using the mechanochemical method.

Facile synthesis of CaWO4 nanoparticles incorporated on porous carbons with improved photocatalytic degradation of tetracycline

The construction of an efficient and recyclable photocatalyst for the degradation of antibiotics is still a challenge. In this work, we successfully synthesized porous carbon-supported CaWO4 nanoparticles (CaWO4 @C) by solidifying sodium alginate (SA) mixed with Na2WO4 by Ca2+ ions and subsequent high-temperature carbonization. The introduction of porous carbon significantly reduced the size of CaWO4 particles, increased the specific surface area for mass transport, and improved visible light utilization. The influence factors of photocatalytic activity were extensively explored through photocatalytic degradation of tetracycline (TC). As a result, the optimized CaWO4 @C exhibited excellent photocatalytic performance with the TC degradation rate of 94.56% after 60-min visible light irradiation. The TC photodegradation rate constant was calculated to be 0.051 min−1, which was 30.19-time higher than the pristine CaWO4. Besides, the photocatalytic reaction mechanism for degradation of TC was revealed in terms of free radical trapping experiments and electron spin resonance (ESR) techniques.

Effect of Paclitaxel Stereochemistry on X-ray-Triggered Release of Paclitaxel from CaWO4/Paclitaxel-Coloaded PEG-PLA Nanoparticles.

For many locally advanced tumors, the chemotherapy-radiotherapy (CT-RT) combination ("chemoradiation") is currently the standard of care. Intratumoral (IT) CT-based chemoradiation has the potential to overcome the limitations of conventional systemic CT-RT (side effects). For maximizing the benefits of IT CT-RT, our laboratory has previously developed a radiation-controlled drug release formulation, in which anticancer drug paclitaxel (PTX) and radioluminescent CaWO4 (CWO) nanoparticles (NPs) are co-encapsulated with poly(ethylene glycol)-poly(lactic acid) (PEG-PLA) block copolymers ("PEG-PLA/CWO/PTX NPs"). These PEG-PLA/CWO/PTX NPs enable radiation-controlled release of PTX and are capable of producing sustained therapeutic effects lasting for at least one month following a single IT injection. The present article focuses on discussing our recent finding about the effect of the stereochemical structure of PTX on the efficacy of this PEG-PLA/CWO/PTX NP formulation. Stereochemical differences in two different PTX compounds ("PTX-S" from Samyang Biopharmaceuticals and "PTX-B" from Biotang) were characterized by 2D heteronuclear/homonuclear NMR, Raman spectroscopy, and circular dichroism measurements. The difference in PTX stereochemistry was found to significantly influence their water solubility (WS); PTX-S (WS ≈ 4.69 μg/mL) is about 19 times more water soluble than PTX-B (WS ≈ 0.25 μg/mL). The two PTX compounds showed similar cancer cell-killing performances in vitro when used as free drugs. However, the subtle stereochemical difference significantly influenced their X-ray-triggered release kinetics from the PEG-PLA/CWO/PTX NPs; the more water-soluble PTX-S was released faster than the less water-soluble PTX-B. This difference was manifested in the IT pharmacokinetics and eventually in the survival percentages of test animals (mice) treated with PEG-PLA/CWO/PTX NPs + X-rays in an in vivo human tumor xenograft study; at short times (<1 month), concurrent PEG-PLA/CWO/PTX-S NPs produced a greater tumor-suppression effect, whereas PEG-PLA/CWO/PTX-B NPs had a longer-lasting radio-sensitizing effect. This study demonstrates the importance of the stereochemistry of a drug in a therapy based on a controlled release formulation.

Abstract 304: Effect of paclitaxel stereochemistry on x-ray-triggered release of paclitaxel from CaWO4/paclitaxel-coloaded PEG-PLA nanoparticles

Abstract Head and neck squamous cell carcinoma (HNSCC) is the 8th most common cancer in the United States predominantly affecting people over 65 years of age with an increasing rate of incidence across the world. Current therapies for HNSCC include surgical resection, chemotherapy (CT), and radiotherapy (RT). For locally advanced/unresectable HNSCC, the CT-RT combination (“chemoradiation”) has been shown to be more effective than CT or RT alone, and is currently the standard of care. Intratumoral (IT) chemotherapy-based chemoradiation has the potential to overcome the limitations of conventional systemic CT-RT that severely affects a patient’s quality of life. For realization of maximum benefits from IT CT-RT, our team has developed a radiation-controlled drug release nanoparticle formulation (paclitaxel (PTX) and CaWO4 nanoparticles (CWO NPs) co-encapsulated within a capsule formed by poly(ethylene glycol)-poly (lactic acid) (PEG-PLA), named “PEG-PLA/CWO/PTX NPs”). This unique formulation releases PTX only when it is exposed to X-ray irradiation. We have previously reported that IT-administered PEG-PLA/CWO/PTX NPs stay within the tumor for at least a month, producing significant therapeutic effects in terms of tumor suppression and survival in mouse models of HNSCC. This work demonstrates the effect of PTX stereochemistry on radiation-controlled release of the drug from a nano polymer matrix system (PEG-PLA/CWO/PTX NPs). The stereoisomertic characteristics of PTX products from two different manufacturers (“PTX-S”, and “PTX-B”) were analyzed by Raman spectroscopy, circular dichroism and 2D HMQC/NOESY NMR measurements. In their unencapsulated (free) state, PTX-S and PTX-B were comparable in their ability to kill cancer cells in vitro. However, they were found to be significantly different in water solubility; PTX-S (water solubility ≈ 4.69 μg/mL) is about 19 times more water soluble than PTX-B (water solubility ≈ 0.25 μg/mL). This difference in water solubility was found to cause a large difference in X-ray-triggered release kinetics of the PTX loaded within the PEG-PLA/CWO/PTX NPs in both in vitro and in vivo environments; PTX-S is released from PEG-PLA/CWO NPs significantly faster upon X-ray irradiation than PTX-B. This difference in release kinetics produced an interesting difference in their time-dependent therapeutic effects; at short times (&amp;lt; 1 month), concurrent PEG-PLA/CWO/PTX-S NPs produced a greater tumor suppression effect; on the other hand, PEG-PLA/CWO/PTX-B NPs had a longer lasting radio-sensitizing effect. In summary, the stereoisomers of PTX exhibit significantly different PK characteristics when used with controlled release carriers, even though they are pharmacologically indistinguishable in their unformulated form. Citation Format: Kaustabh Sarkar, Sandra Torresgrossa-Allen, Mark P. Langer, Gregory Durm, Sanjeev Narayanan, Bennett D. Elzey, You-Yeon Won. Effect of paclitaxel stereochemistry on x-ray-triggered release of paclitaxel from CaWO4/paclitaxel-coloaded PEG-PLA nanoparticles [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 304.

Tribological and Lubrication Performances of Nano-WO3 and CaWO4 Contained in Water-Based Fluid for Steel Strip during Hot Forming

CaWO4 and WO3 nanoparticles were prepared by the sol-gel method and Pechini method. The morphology and structure of nano-CaWO4 and nano-WO3 were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). Tribological, hot forming, and hot rolling lubrication properties of nano-CaWO4, nano-WO3, and mixed nano-CaWO4-WO3 as antiwear additives in water-based fluid were investigated using a four-ball friction and wear testing machine, Gleeble tester, and two-high rolling mill, respectively. Results showed that 0.3 wt% mixed nano-CaWO4-WO3 has excellent tribological properties in water-based fluid. The average wear scar diameter values decreased from 0.62 to 0.37 mm (mixed WO3-CaWO4) and the coefficient of friction value reduced from 0.080 to 0.064. This was due to the formation of a tribofilm (∼30 nm) on the worn surface during the forming process, avoiding direct contact between the metals. During Gleeble hot forming, the lubrication effect of the mixed nano-CaWO4-WO3 was the best. The nano-WO3-CaWO4 particles were relatively dispersed and dis not bond together under high temperature and pressure conditions, which played a role in reducing friction resistance between friction pairs. With the addition of 0.3 wt% mixed WO3-CaWO4 nanofluid, the surface quality was improved and it had the lowest surface roughness in the hot rolling process.

Effect of annealing on the structural and optical properties of pristine and cerium doped calcium tungstate nanoparticles synthesized via hydrothermal method

The work is an investigation of the effect of annealing temperature on pristine and rare earth doped CaWO4 nanoparticles with hydrothermal route. The sample was annealed at two varied temperatures 800 ºC and 1200 ºC for 5 h. The structural analysis reveals the reduction in the broadening of the peaks as a result of annealing. Surface morphology shows the formation of agglomerated structures. In Ce3+:CaWO4 nanoparticles the morphology is modified to dumbbell like and flake like structures after annealing. Raman shift observed at 909 cm−1 Ag modes confirms the presence of CaWO4 nanoparticles with its own rotational and vibrationalmodes. Increase in the absorption peak intensity and a double absorption edge appears as an intermediate energy level state after the inclusion of Ce3+ ion as dopant.

Photoluminescence and Induction Heating Studies of Fe3O4@CaWO4:5Dy3+ Magnetic-Luminescent Nanocomposite for Hyperthermia Application

A 5 at.% Dy3+ ions doped CaWO4 nanoparticles (CaWO4:5Dy) were synthesized by hydrothermal method using polyethylene glycol (PEG) as solvent medium and capping agent. The phase purity and crystalline properties of the prepared nanoparticles were obtained from the XRD analysis. TEM images revealed that the CaWO4:Dy3+ have particles of size approximately in the range 30-50 nm. The prepared magnetic luminescence nanocomposite exhibits a high saturation magnetization. The prepared nanocomposite can achieve hyperthermia temperature (42 ºC) in a short period by applying the alternating magnetic field, externally. The nanocomposite also shows photoluminescence properties. Nanomaterials described in this work can be used for optical imaging as well as hyperthermia applications.

Correction to: Hydrothermal temperature dependence of CaWO4 nanoparticles: structural, optical, morphology and photocatalytic activity

Correction to: Hydrothermal temperature dependence of CaWO4 nanoparticles: structural, optical, morphology and photocatalytic activity

Investigating photoluminescence properties of Eu3+ doped CaWO4 nanoparticles via Bi3+ amalgamation for w-LEDs application

ABSTRACT Eu3+-doped CaWO4 nanophosphors were synthesised in series for different atomic wt% concentrations (0, 0.5, 1, 2, 5 and 10) of Bi3+ 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 Bi3+ to Eu3+ in CaWO4:Eu3+/Bi3+ nanophosphors were also investigated. The results revealed that red luminescence of CaWO4:2Eu3+/1Bi3+ nanophosphor is 5.4 times stronger than CaWO4:2Eu3+. It was observed that the forces exist between Bi3+ and Eu3+ are due to the interaction of electric dipole-dipole interactions. The chroma of CaWO4:2Eu3+/1Bi3+ nanophosphors was calculated to be 97.40%. The energy transfer process was studied by measuring the decay curves due to Bi3+ and Eu3+ dopants. Enhanced red emission, high thermal stability, stronger 5D0 → 7F2 absorption intensity, high colour purity and decay studies indicate that CaWO4:Eu3+/Bi3+ nanophosphors are potential candidates to be used in white light-emitting diode (wLEDs).

Hydrothermal temperature dependence of CaWO4 nanoparticles: structural, optical, morphology and photocatalytic activity

In this paper, CaWO4 nanoparticles were prepared by the hydrothermal method using the temperature of 100 (CaWO4-100), 120 (CaWO4-120), 140 (CaWO4-140), and 160 °C (CaWO4-160) for 1 h. These nanoparticles have a tetragonal structure (I41/a) exhibiting a high crystallinity degree and average crystallite size from 24.61(0.12) nm to 40.13(0.18) nm. The main active modes were found from vibrational Raman and FTIR spectroscopies, agreeing with the structural characterization obtained by Rietveld refinement and Williamson-Hall plot results. The optical bandgap for these materials ascertained by diffuse reflectance spectroscopy is 3.9(05) eV, 3.9(9) eV, 3.9(6) eV, and 4.01(02) eV for CaWO4-100, CaWO4-120, CaWO4-140, and CaWO4-160, respectively. Irregular polyhedral nanoparticles were observed from FE-SEM images for all synthesized samples, wherein their EDX spectrum shows all characteristic atomic peaks of calcium tungstate. Finally, these samples yield a remarkable photocatalytic reaction in Rhodamine B dye (RhB) solution. However, the CaWO4-100 nanoparticles exhibit a more effective performance than in the other synthesized samples, mainly associated with lower particle size and high dislocation density. Moreover, the pH effect yields the best performance for acid medium (pH = 1), promoted by direct oxidation of RhB dye molecules through both holes and superoxide radicals.

Effects of annealing temperature on structural and photoluminescence properties of Eu, Dy and Sm doped CaWO4 nanoparticles

Nanoparticles of xRe2O3 – (100-x)CaWO4 (Re = Eu, Dy, Sm; x = 0, 1, 3, 5, 7 and 10 mol%) were synthesized by solid-state sintering at two annealing temperatures of 800 °C and 1150 °C and characterized by neutron diffraction, Raman and photoluminescence (PL) spectroscopy. The samples are composite materials and contain tetragonal CaWO4 and cubic Re2O3 phases. The unit cell parameters, atomic position co-ordinates, crystallite size, mole-fraction of phases, bond-lengths, bond-angles and cation-oxygen co-ordination numbers were determined by Rietveld analysis of the neutron diffraction data. The short-range structure of CaWO4 consists of snub disphenoid deltahedral CaO8 and tetrahedral WO4 units and the structure of cubic Re2O3 consists of two types of ReO6 units. All the W–O bonds in WO4 units are of equal lengths (1.77–1.79 Å) whereas two kinds of slightly different Ca–O bond-lengths (2.41–2.45 Å and 2.45–2.47 Å) exist in CaO8 units. The neutron pair distribution function of the undoped CaWO4 samples shows the first peak in the range of 1.71–1.74 Å due to W–O bonds and the second peak at 2.84 Å due to O–O and Ca–O pair correlations. Raman studies of Eu-doped samples show only W–O vibration modes, however, Sm and Dy-doped CaWO4 show weak Raman peaks of Sm2O3 and Dy2O3, along with W–O bond vibrations. PL studies show highest orange-red emission at 1 mol% Sm2O3, green emission at 1 mol% Dy2O3 and red emission at 3 mol% Eu2O3. The light emission intensity in all the samples increases with the increase in annealing temperature from 800 °C to 1150 °C.

Bilirubin-Coated Radioluminescent Particles for Radiation-Induced Photodynamic Therapy

Photodynamic therapy (PDT) has shown potential as a cancer treatment modality, but its clinical application is limited due to its visible-light activation since visible wavelengths of light cannot penetrate tissues well. Additionally, combination therapies utilizing PDT and radiotherapy have shown clinical promise in several cancers but are limited again by light penetration and the need for selective photosensitization of the treatment area. Herein, we report the development of bilirubin-photodynamic nanoparticles (PEGylated bilirubin-encapsulated CaWO4 nanoparticles or "PEG-BR/CWO NPs"). PEG-BR/CWO NPs are a formulation of PEGylated bilirubin micelles encapsulating CaWO4 nanoparticles. These particles are capable of activating PDT via X-ray irradiation within deep tissues due to the radioluminescence properties of their CaWO4 nanoparticle cores. PEG-BR/CWO NPs facilitate a combination of photodynamic and radiation therapy and represent a previously unexplored application of PEG-bilirubin conjugates as photosensitizing agents. When irradiated by X-rays, PEG-BR/CWO NPs emit UV-A and visible light from their CaWO4 cores, which excites bilirubin and leads to the production of singlet oxygen. PEG-BR/CWO NPs exhibit improvements over X-ray therapy alone in vitro and in murine xenograft models of head and neck cancer. The data presented in this study indicate that PEG-BR/CWO NPs are promising agents for facilitating combined radio-photodynamic therapy in deep tissue tumors.

Photoluminescent properties of Sm3+ and Tb3+ codoped CaWO4 nanoparticles obtained by a one-step sonochemical method

Luminescent materials with LED applications can have your emission color controlled by rare earth doping. In this work, Sm3+- and Tb3+-codoped CaWO4 nanoparticles were obtained by a one-step sonochemical method. The nanoparticles were characterized by X-ray diffractogram (XRD), Raman scattering (RS) spectroscopy, The Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and visible ultraviolet spectroscopy (UV–Vis). The photoluminescent measurements were taken at room and lower temperatures for analysis of doping in emission color. The diffractograms indicate the single-phase CaWO4 with the scheelite structure and it was observed a reduction in the crystallite size as the doping. SEM and TEM images indicate the formation of nanospheres for pure and samarium-doped samples, while terbium doping results in the formation of nanorods. Room temperature photoluminescence spectra indicate a blue emission for the bare and samarium-doped CaWO4, while terbium doping emits at the green color. The codoping mixes the colors blue, green, and orange, indicating a potential material with white color emission.

Barium tungstate nanoparticles to enhance radiation therapy against cancer

High-Z nanoparticles have emerged as a novel type of radiosensitizers due to their relatively large X-ray cross-section and ability to enhance radical production under irradiation. Recently, CaWO4 nanoparticles have been prepared and their potential as a radiosensitizer has been demonstrated. Herein, we investigated BaWO4 nanoparticles as a novel type of alkaline-earth metal tungstate radiosensitizer for radiotherapy (RT). We synthesized BaWO4 nanoparticles using hydrothermal reaction and coated them with polyvinylpyrrolidone (PVP). We found that BaWO4 nanoparticles could more efficiently enhance hydroxyl radical production under irradiation than CaWO4 nanoparticles. When tested in vitro, BaWO4 nanoparticles showed lower toxicity than CaWO4 nanoparticles in the absence of irradiation, but induced more significant oxidative stress under irradiation. When tested in vivo, BaWO4 nanoparticles led to more efficient tumor inhibition without causing systemic toxicity. Overall, our results suggest that BaWO4 nanoparticles can efficiently enhance RT and hold great potential as a novel type of radiosensitizing agent.

Structural and optical characterization of Eu and Dy doped CaWO4 nanoparticles for white light emission

Abstract The structural and light emission properties of calcium tungstate (CaWO4) nanoparticles containing Eu3+ and Dy3+ are studied. CaWO4 nanoparticles were prepared by chemical routes followed by drying at 80°C, doping with 1, 3, 5, 7 and 10 mol% of Eu2O3 and/or Dy2O3 and final annealing at 800oC. The samples were characterized by field emission-scanning electron microscopy (FE-SEM), energy dispersive X-ray spectroscopy (EDS), synchrotron X-ray diffraction (XRD), Raman and photoluminescence (PL) spectroscopy. FE-SEM studies show that CaWO4 sample dried at 80°C contains spherical particles of diameter ∼5 μm, and upon annealing at 800°C, dense and irregular shaped structures are formed. EDS mapping found a uniform distribution of Eu and Dy ions and only a small segregation in the CaWO4 matrix is observed. XRD studies revealed the co-existence of the tetragonal CaWO4 and cubic Dy2O3 and/or Eu2O3 phases in the doped samples and rule out the replacement of Ca2+ by rare-earth ions. The structural parameters: crystallite size, lattice strain, unit cell dimensions, atomic position coordinates, bond-lengths, bond-angles and cation-oxygen coordination numbers were determined. The short-range structure of CaWO4 consists of interconnected CaO8 and WO4 units. All the W–O bonds in WO4 units have the same length whereas two types of Ca–O bond-lengths exist in CaO8 units. The undoped CaWO4 sample annealed at 800°C, has the smallest Ca–O bond-lengths and unit cell dimensions due to the compressive macrostrain induced by heat-treatment. On incorporating Eu3+ and Dy3+, the W–O and Ca–O bond-lengths increase slightly. Raman spectra of all the samples are similar and show W–O vibrational modes. PL studies found that the undoped CaWO4, Eu and Dy-doped CaWO4 samples emit blue, red and yellow light respectively. The co-doped sample: 2 mol% Eu2O3–5 mol% Dy2O3–CaWO4 was closest to the ideal white light emission properties.

Synthesis and optical properties of Mn-doped CaWO4 nanoparticles

Pure and Mn-doped calcium tungstate (Mn:CaWO4) nanoparticles (NPs) were synthesized by hydrothermal method which lead to the formation of high quality and narrow sized particles. The concentration of Mn in CaWO4 NPs was varied from 1% to 4% by weight. A distinct peak of Mn (d–d) transition was observed which is actually spin-forbidden but may be allowed due to crystal field effects. Electron spin resonance measurements revealed inclusion of Mn2+ at the substitutional site.. Room temperature photoluminescence emission (PL) and excitation (PLE) spectroscopies were carried out to understand the interactions of sp-d levels. PL spectra revealed the presence of both band-edge (∼450 nm) and Mn2+ related orange luminescence (∼530 nm). Time dependent photoluminescence (TDPL) studies were also carried out where the life time value of 4.3 ms obtained was in accordance with measurement for Mn in other systems. Thus TDPL further strengths the presence of Mn in 2+ state in CaWO4 NPs.

Synthesis and characterization of Ag+ and Zn2+ co-doped CaWO4 nanoparticles by a fast and facile sonochemical method

In this work, Ag+ and Zn2+ co-doped CaWO4 nanoparticles were obtained by fast and facile sonochemical method. The nanoparticles were characterized by X-ray diffraction (XRD), Fourier transformed infrared spectroscopy (FTIR), Raman spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), visible ultraviolet spectroscopy (UV–Vis) and photoluminescence property. The photocatalytic activity was studied against methylene blue (MB) dye under sunlight and CaWO4 powders were tested in 3 reuse cycles. The diffractograms indicate the non-formation of secondary phases and the Rietveld refinement estimated the crystallite sizes, being 27.38, 19.89, 18.70 and 16.39 nm for the pure, Ag, Zn and Ag:Zn samples, respectively. SEM and TEM images showed that the particles are agglomerated and have a mean diameter ranging from 16.76 (Ag:Zn) to 71.76 nm (pure). Defects generated by doping shift the gap band to higher energies and act to prevent electron/hole (e−/h+) pair recombination, reducing photoluminescence and favoring CaWO4 photocatalysis. Scavenger methodology indicated that h+ is the main mechanism acting in photocatalysis, and the reuse tests indicated that the silver-doped sample, even with the better initial response, loses efficiency over the course of the cycle, while the co-doped sample maintains efficiency, and is therefore indicated for reuse photocatalysis applications in methylene blue dye degradation.

One-step hydrothermal synthesis of CaWO4/α-Ag2WO4 heterojunction: An efficient photocatalyst for removal of organic contaminants

A new class of CaWO4/α-Ag2WO4 heterojunction composites was synthesized by one-step hydrothermal method without adding any templates or surfactants. The XRD results indicate that the composite consists of CaWO4 and α-Ag2WO4 crystal phases. The FE-SEM and TEM studies confirm the CaWO4 nanoparticles are deposited on the rod-like α-Ag2WO4. The RAMAN and XPS analysis has used to analyze the vibrational properties, chemical composition and oxidation states of the prepared catalysts. The composite heterostructure holds the sufficient contact between the CaWO4 and α-Ag2WO4 nanoparticles which favor for adsorbed the organic molecules for photocatalytic process and also beneficial for the sediment of the catalyst particles. The CaWO4/α-Ag2WO4 (1CA) composite shows the highest photocatalytic activity (MB dye 85%, 105 min) and reaction rate constant compared to all other photocatalysts under the light irradiation. The highest degradation efficiency of 1CA composite ascribed to the effective separation of photogenerated e− and h+ pairs and lower recombination rate. The recycling results reveal that 1CA photocatalyst possess good degradation ability after four cycle tests. Moreover, the photocatalytic mechanism revealed that the h+ and OH are the key reactive species for the photodegradation of organic dyes over CaWO4/α-Ag2WO4 photocatalyst.

Radioluminescent nanoparticles for radiation-controlled release of drugs

The present work demonstrates a novel concept for intratumoral chemo-radio combination therapy for locally advanced solid tumors. For some locally advanced tumors, chemoradiation is currently standard of care. This combination treatment can cause acute and long term toxicity that can limit its use in older patients or those with multiple medical comorbidities. Intratumoral chemotherapy has the potential to address the problem of systemic toxicity that conventional chemotherapy suffers, and may, in our view, be a better strategy for treating certain locally advanced tumors. The present study proposes how intratumoral chemoradiation can be best implemented. The enabling concept is the use of a new chemotherapeutic formulation in which chemotherapy drugs (e.g., paclitaxel (PTX)) are co-encapsulated with radioluminecsnt nanoparticles (e.g., CaWO4 (CWO) nanoparticles (NPs)) within protective capsules formed by biocompatible/biodegradable polymers (e.g., poly(ethylene glycol)-poly(lactic acid) or PEG-PLA). This drug-loaded polymer-encapsulated radioluminescent nanoparticle system can be locally injected in solution form into the patient's tumor before the patient receives normal radiotherapy (e.g., 30–40 fractions of 2–3 Gy daily X-ray dose delivered over several weeks for locally advanced head and neck tumors). Under X-ray irradiation, the radioluminescent nanoparticles produce UV-A light that has a radio-sensitizing effect. These co-encapsulated radioluminescent nanoparticles also enable radiation-triggered release of chemo drugs from the polymer coating layer. The non-toxic nature (absence of dark toxicity) of this drug-loaded polymer-encapsulated radioluminescent nanoparticle (“PEG-PLA/CWO/PTX”) formulation was confirmed by the MTT assay in cancer cell cultures. A clonogenic cell survival assay confirmed that these drug-loaded polymer-encapsulated radioluminescent nanoparticles significantly enhance the cancer cell killing effect of radiation therapy. In vivo study validated the efficacy of PEG-PLA/CWO/PTX-based intratumoral chemo-radio therapy in mouse tumor xenografts (in terms of tumor response and mouse survival). Results of a small-scale NP biodistribution (BD) study demonstrate that PEG-PLA/CWO/PTX NPs remained at the tumor sites for a long period of time (> 1 month) following direct intratumoral administration. A multi-compartmental pharmacokinetic model (with rate constants estimated from in vitro experiments) predicts that this radiation-controlled drug release technology enables significant improvements in the level and duration of drug availability within the tumor (throughout the typical length of radiation treatment, i.e., > 1 month) over conventional delivery systems (e.g., PEG-PLA micelles with no co-encapsulated CaWO4, or an organic liquid, e.g., a 50:50 mixture of Cremophor EL and ethanol, as in Taxol), while it is capable of maintaining the systemic level of the chemo drug far below the toxic threshold limit over the entire treatment period. This technology thus has the potential to offer a new therapeutic option that has not previously been available for patients excluded from conventional chemoradiation protocols.