RESUMEN

Despite having exceptional optical and photoelectric properties, the application of organometal halide perovskites (OHP) is restricted due to the limited penetration depth of the UV excitation light and poor stability. Attempts have been made to make composite materials by mixing other materials such as upconversion nanoparticles (UCNP) with OHP. In contrast to linear absorption and emission of OHP, the nonlinear upconversion of UCNP offers numerous advantages such as deep penetration depth of the near-infrared (NIR) excitation light, minimal photodamage to biological tissues, and negligible background interference, which offer great potential in various applications such as multiplexed optical encoding, three-dimensional displays, super-resolution bioimaging, and effective solar spectrum conversion. However, it is challenging to synthesize hybrid OHP-UCNP nanocrystals due to the inherent difference in crystal structures of hexagonal phase UCNP and cubic phase OHP. In this work, we report OHP-UCNP heterostructured nanocrystals synthesized via growing cubic phase NaGdF4 UCNP over cubic phase CsPbBr3 OHP in a seed-mediated process based on a very small lattice mismatch and then converting cubic phase UCNP to hexagonal phase through heating. The juxtaposition of UCNP over OHP in a single nanocrystal facilitates efficient energy transfer from UCNP to OHP under NIR excitation and acts as a protective layer improving the stability. The stability is further enhanced by coating an inert UCNP shell on the OHP-UCNP nano-heterostructures with the same UCNP material earlier used in the heterostructures. The coating demonstrated greater stability under continuous UV exposure and in harsh environments such as high temperatures and polar solvents. These NIR excitable perovskite-UCNP nano-heterostructures with improved stability have great potential for use in new optoelectronic and biological applications.

Asunto(s)

Nanopartículas , Compuestos de Calcio , Nanopartículas/química , Óxidos , Solventes , Titanio

RESUMEN

One-dimensional (1D) fibers have been widely used in composites reinforcement for microwave attenuation due to their outstanding mechanical and electromagnetic properties, especially in the axial direction. However, the precise control of fiber alignment in a polymer matrix remains a challenge. In this work, we successfully demonstrated the well-controlled alignment of silicon carbide nanowires (SiCNW) in a silicone matrix by using direct ink writing (DIW)-based 3D printing. It is proven that the printed multilayer material with fiber alignment could show a dramatic improvement in both reflection loss (RL) and effective attenuation bandwidth (EAB, RL < -10 dB). In particular, a uniaxial in-plane orientation is found to be the optimal alignment among other planar and also out-of-plane orientations. Benefiting from the optimized alignment, the 3D-printed SiC composite could show an EAB (∼6.4 GHz)1.6 times broader than that of the randomly mixed composite at the same thickness without alignment, associated with a minimum RL of -48 dB at 14.3 GHz. In addition, it is demonstrated that DIW could print different materials, such as SiCNW and multiwall carbon nanotube (MWCNT), in alternating layers for multiple-frequency-band attenuation benefiting from the distinct property of each material. Considering the one-step control of fiber alignment and material selectivity, DIW could play an important role in materials design for high-efficiency microwave attenuation.

RESUMEN

Owing to the problems associated with conventional cancer treatment methods, magnetic hyperthermia-based cancer therapy has gained importance recently. Achieving the desired heating effect at the site of the tumor with a minimal concentration of iron oxide nanoparticles (IONPs) and a safer field is necessary to explore the advantages of hyperthermia. For one to address this challenge, biocompatible IONPs with a desirable magnetic response at a tolerable field are necessary. In this work, magnetic shape anisotropy of iron oxide nanorods (NR) of different lengths (70, 115, 170, and 210 nm) with different aspect ratios ranging from 1.55 to 3.2 was explored to achieve higher hysteresis loss, in turn leading to better hyperthermia efficiency. The magnetic properties of the NRs with respect to the applied field were studied using micromagnetic simulation. Even though the nanorods with high aspect ratio showed a higher hysteresis loss of 69485 J/m3 at 2000 Oe, the field required to attain it was high and well beyond the safety limit. From nanorods of various aspect ratios, the nanorod with a lower aspect ratio of 1.55 and a length of 70 nm exhibited a better hysteresis loss and specific absorption rate (SAR) value of 4214 W g-1 was achieved at a frequency and alternating magnetic field of 400 kHz and 800 Oe, respectively. The PEGylated GO-Nanorod of 70 nm exhibited excellent antitumor efficacy in 4T1 tumor model mice by obstructing the tumor progression within a safer dosage and field.

Asunto(s)

Óxido Ferrosoférrico , Grafito , Hipertermia Inducida , Nanotubos , Polietilenglicoles , Animales , Línea Celular , Supervivencia Celular/efectos de los fármacos , Compuestos Férricos/química , Óxido Ferrosoférrico/administración & dosificación , Óxido Ferrosoférrico/química , Grafito/administración & dosificación , Grafito/química , Humanos , Campos Magnéticos , Ratones Endogámicos BALB C , Nanotubos/química , Neoplasias/terapia , Polietilenglicoles/administración & dosificación , Polietilenglicoles/química

RESUMEN

Because of their high magnetization and suitable biocompatibility, iron-oxide nanoparticles (IONPs) have been widely employed in various biomedical applications, including magnetic hyperthermia for cancer treatment. In many cases, the colloidal stability requirement will limit the usage of ferromagnetic particles that are usually associated with good magnetic response. To address this challenge, a stable carrier for better colloidal stability regardless of the size or shape of the IONPs while at the same time providing enhanced magnetic hyperthermia heating performance is required. In this work, IONPs of different sizes (4, 8, 20, 45, and 250 nm) were engineered to reside in the graphene oxide (GO) sheet carrier, which were stable in aqueous solution even in the presence of a strong magnetic field. Out of various IONPs sizes, highest specific absorption rate (SAR) value of 5020 W g-1 was obtained with 45 nm GO-IONPs nanocomposites at a frequency and alternating magnetic field of 400 kHz and 32.5 kA m-1, respectively. The calculated intrinsic loss power (ILP) was 12.21 nH m2 kg-1, which is one of the highest ILP values reported for synthesized IONPs to the best of our knowledge. To enhance the excellent colloidal stability in biological environment, the GO-IONPs nanocomposites can be further grafted with polyethylene glycol (PEG) because agglomeration of pristine GO sheets occurs because of adsorption of cations. High ILP values could be well maintained even after PEG coating. The PEGylated 45 nm GO-IONP showed excellent antitumor efficacy in 4T1-tumor model mice by inhibiting tumor progression within a safe dosage range. Overall, the novel nanocomposite in this work-PEG-GO-IONP-possesses high hyperthermia performance, excellent colloidal stability in biological environment, and availability of functional groups in GO and can be utilized for tagging in various biomedical applications.

RESUMEN

Wastewater contaminated with heavy metals is a worldwide concern due to the toxicity to human and animals. The current study presents an incorporation of adsorption and low-field dynamic magnetic separation technique for the treatment of heavy-metal-contaminated water. The key components are the eco-fabricated magnetic filter with mesh architectures (constituted of a soft magnetic material (Ni,Zn)Fe2O4) and poly(acrylic acid) (PAA)-coated quasi-superparamagnetic Fe3O4 nanoparticles (NPs). PAA-coated Fe3O4 NPs possess high adsorption capacity of heavy metal ions including Pb, Ni, Co, and Cu and can be easily regenerated after the adjustment of pH. Moreover, magnetic mesh filter has shown excellent collection ability of quasi-superparamagnetic particles under a magnetic field as low as 0.7 kOe (0.07 T) and can easily release these particles during ultrasonic washing when small magnets are removed. In the end, after one filtration process, the heavy metal concentration can be significantly decreased from 1.0 mg L-1 to below the drinking water standard recommended by the World Health Organization (e.g., less than 0.01 mg L-1 for Pb). Overall, a proof-of-concept adsorption and subsequent low-field dynamic separation technique is demonstrated as an economical and efficient route for heavy metal removal from wastewater.