Deciphering the in situ phonon evolution of potassium sodium niobate under varying temperature and electric fields

The application of in situ Raman spectroscopy under multiple fields is widely recognized as an effective approach for investigating the physical mechanism of phase transitions in ferroelectrics, because it can directly provide the detailed information about the vibration evolution of various phonon modes within lattices, such as bond stretching and rotation. Based on this technique, our work aims to thoroughly probe the dynamics of phase transitions in traditional ferroelectric potassium sodium niobate [(K,Na)NbO3, KNN] under external fields, by analyzing the in situ dependence of wavenumber and intensity of phonon modes under the varying temperature and electric fields. The results indicate that different vibration modes respectively relating to the A-site ions and NbO6 octahedra in KNN exhibit distinct and abrupt distortion behavior during the orthorhombic-tetragonal and tetragonal-cubic transitions. Moreover, a certain degree of distortion can still be observed in the cubic phase above the Curie temperature. With an applied electric field, KNN presents quite different electrostriction in orthorhombic and tetragonal phases. Particularly, more than one kind of phonon mode undergoes non-linear variations under the varying electric fields, accompanied by the mutations at some fixed fields. These findings will be conducive to further understanding the phase transition mechanism in KNN from the perspective of phonon evolution. Simultaneously, it will also give crucial guidance for the design and development of KNN-based ferroelectrics as well as functional devices.

One-pot two-step synthesis of core-shell mesoporous silica-coated gold nanoparticles

Gold nanoparticles coated with mesoporous silica (Au@mSiO2) have been prepared by a facile one-pot two-step method. The resultant Au@mSiO2 exhibit an ideal core-shell structure with uniform mSiO2 coverage and without any interfacial adhesive layer on the Au surface. Some new explanations on the role that CTAB plays in the synthesis of Au@mSiO2 are discussed.

In vivo cancer targeting and fluorescence-CT dual-mode imaging with nanoprobes based on silver sulfide quantum dots and iodinated oil

In this article, a fluorescence-CT dual-mode nanoprobe is successfully synthesized by making use of distearoylphosphatidylethanolamine-poly(ethylene glycol)-folate (DSPE-PEG2000-FA) and other amphiphilic molecules to coat silver sulfide (Ag2S) quantum dots (QDs) and iodinated oil simultaneously. In vitro experiments show that the fluorescence wavelength of the nanoprobe is 1170 nm in the near infrared-II region. Its size is 139.6 nm, it has good dispersibility, and it has low cellular toxicity at concentrations up to 25 μg mL(-1) Ag. In vivo experiments revealed that the probe has a rather long circulation time (blood half-life of 5.7 hours), and the tissue histopathological tests show that it is not obviously harmful to major organs' normal function. Biochemical analysis (glutamic pyruvic transaminase and glutamic oxaloacetic transaminase levels) and blood analysis (white blood cell, red blood cell, hemoglobin and blood platelet counts) reveal that it has little influence on blood within 15 days of administration. When injected into HeLa xenograft nude mice by the tail vein, the probe elicited intensely enhanced fluorescence and X-ray computed tomography (CT) signals in the tumors after 24 hours, and the structure, size and position of tumor tissue were shown clearly. In a word, the probe has good tumor targeting capabilities, and it has significant value in fluorescence-CT dual-mode imaging in vivo.

Hybrid nanoprobes of bismuth sulfide nanoparticles and CdSe/ZnS quantum dots for mouse computed tomography/fluorescence dual mode imaging

Background

X-ray computed tomography (CT) imaging can be used to reveal the three-dimensional structure of deep tissue with high spatial resolution. However, it cannot reveal molecular or cellular changes, and has great limitations in terms of specificity and sensitivity. Fluorescence imaging technology is one of the main methods used for the study of molecular events in vivo and has important applications in life science research. Therefore, the combination of CT and fluorescence imaging is an ideal dual-modal molecular imaging method, which can provide data on both molecular function and tissue structure, and has important research value. In a previous study, Bi₂S₃ nanoparticles were wrapped with quantum dots in SiO₂ to generate CT and fluorescence imaging. However, this type of probe led to low survival and caused innegligible in vivo toxicity in mice. Therefore, it is necessary to develop new multifunctional probes that demonstrate biocompatibility and safety in vivo.

Methods

A polyethylene glycol-phospholipid bilayer structure was used to synthesize hybrid clusters containing hydrophobic Bi₂S₃ nanoparticles and quantum dots for combined CT/fluorescence imaging. Mean particle size, polydispersity index, and zeta potential were used to study the stability over an 8-week test period. In vivo CT and fluorescence imaging experiments were performed, and the in vivo safety of the probe was evaluated, using histopathological, biochemical, and blood analyses.

Results

The probe distinctly enhanced the CT contrast and had fluorescence imaging capability. In addition, the nanocomposite hybrid clusters showed a longer circulation time (>4 h) than iobitridol. The results also showed that the Bi₂S₃-QD@DSPE probe had good biocompatibility and safety, and did not affect normal organ functioning.

Conclusions

Bi₂S₃-QD@DSPE hybrid clusters exhibited remarkable performance in CT angiography and fluorescence imaging in vivo.

Multifunctional magnetic-hollow gold nanospheres for bimodal cancer cell imaging and photothermal therapy

Multifunctional nanocomposites combining imaging and therapeutic functions have great potential for cancer diagnosis and therapy. In this work, we developed a novel theranostic agent based on hollow gold nanospheres (HGNs) and superparamagnetic iron oxide nanoparticles (SPIO). Taking advantage of the excellent magnetic properties of SPIO and strong near-infrared (NIR) absorption property of HGNs, such nanocomposites were applied to targeted magnetic resonance imaging (MRI) and photoacoustic imaging (PAI) of cancer cells. In vitro results demonstrated they displayed significant contrast enhancement for T2-weighted MRI and strong PAI signal enhancement. Simultaneously, the nanocomposites exhibited a high photothermal effect under the irradiation of the near-infrared laser and can be used as efficient photothermal therapy (PTT) agents for selective killing of cancer cells. All these results indicated that such nanocomposites combined with MRI-PAI and PTT functionality can have great potential for effective cancer diagnosis and therapy.

Composite silica coated gold nanosphere and quantum dots nanoparticles for X-ray CT and fluorescence bimodal imaging

A composite nanoparticle containing QDs and Au was fabricated, and it was used for CT and fluorescence dual mode imaging simultaneously.

In vitro and in vivo CT imaging using bismuth sulfide modified with a highly biocompatible Pluronic F127

Probe bismuth sulfide modified with Pluronic F127 (Bi2S3-PF127), which has high biocompatibility and dispersibility, is synthesized using triblock copolymer Pluronic F127 to modify hydrophobic Bi2S3 nanoparticles that are prepared by a hot injection method. TEM results show that most of the probe has a length of about 14.85 ± 1.70 nm and a breadth of about 4.79 ± 0.63 nm. After injected into the tail vein of a mouse, the probe has obvious CT contrast enhancement capability from x-ray CT imaging results. Meanwhile, the probe's in vivo toxicity is also studied. It is found that hematoxylin and eosin stains of major organs have no change. A biochemical analysis (alanine aminotransferase and aspartate aminotransferase) prove the probe has no adverse effects. The results of a blood analysis (white blood cell count, red blood cell count, hemoglobin, and platelet count) are also normal. The biological distribution of Bi by ICP-AES shows that most of nanoparticles are cleaned out after injection 48 h, and the circulation half-life of the probe is 5.0 h, suggesting that Bi2S3-PF127 has a long circulation and indicating that the Bi2S3-PF127 probe has good biocompatibility and safety.

Folic acid-conjugated silica-coated gold nanorods and quantum dots for dual-modality CT and fluorescence imaging and photothermal therapy

Multifunctional nanoparticles (NPs) have great potential for multimodal cancer imaging and effective therapy. We have developed multifunctional NPs (GNR@SiO₂@QDs) by incorporating gold nanorods (GNRs) and CdSe/ZnS quantum dots (QDs) into silica. Folic acid (FA) as a targeting ligand was covalently conjugated on the surfaces of GNR@SiO₂@QDs with a silane coupling agent. Cell viability assay showed that these NPs had low cytotoxicity. And confocal fluorescence images illustrated that they could selectively target HeLa cells overexpressing folate receptors (FRs) rather than FR-deficient A549 cells. In vitro cell imaging experiments revealed that these NPs exhibited strong X-ray attenuation for X-ray computed tomography (CT) imaging and strong fluorescence for fluorescence imaging. They also showed an enhanced photothermal therapy (PTT) effect for cancer cells due to GNRs' high absorption coefficient in the near infrared (NIR) region and a better heat generation rate. All results show that they have great potential in theranostic applications such as for targeted tumor imaging and therapy.