Controlling the semiconductor nanoparticles (NPs) size can alter their optical and electronic properties, which is an important feature for many optoelectronic device applications. In this study, we ...demonstrated a simple and economical approach to synthesize size-controlled Cu2ZnSnS4 (CZTS) NPs and their application as an absorber layer in solar cells. The size of the CZTS NPs has been controlled from 2.5 to 8 ( ± 0.5) nm by variation of the amine to the precursor mole ratio. The impact of the particle size on the structural, optical, and electrical performance of the devices are studied systematically. XRD and Raman spectroscopy measurements reveal the formation of pure kesterite phase of the CZTS. Moreover, the UV–vis spectroscopy data show that the CZTS NP films have a high optical absorption coefficient (104 cm−1) in the visible region, and its optical band gap is in the range of 1.50–1.62 eV. The power conversion efficiency of a solar cell fabricated using CZTS NPs is enhanced considerably from 3.6% to 4.8% with an increase of nanoparticles size, within an active area of 1.0 ± 0.1 cm2. The maximum external quantum efficiency of 59% is obtained for the solar cell with CZTS thin film comprising 8 nm particles. The observed changes in the device performance parameters might be due to the variation of the thin film microstructure.
A simple cation exchange reaction has been adapted to produce the Co
x
Fe
3−x
O
4
nanorods with different concentration of Co. The substitution of Fe
2+
with Co
2+
ions increase the ...magnetocrystalline anisotropy and coercivity of pristine superparamagnetic Fe
3
O
4
nanorods. Atomic concentration of 5–11% of Co
2+
in Fe
3
O
4
nanorods renders coercivity of 300–460 Oe at room temperature and 2200–4050 Oe at 10 K. Hydrocarbon long‐chain amine (oleylamine) functionalized nanorod assemblies form a multiple tunnel junction, where organic amine monolayers act as insulating tunnel barriers. Co
x
Fe
3−x
O
4
nanorods show a magnetoresistance switching behavior at room temperature and the switching field is consistent with the magnetic coercivity. A 14–15% TMR is recorded at room temperature in Co
x
Fe
3−x
O
4
nanorod assemblies, which increases to 23–26% at 150 K at a magnetic field of ±2 T. The calculated spin polarization for Co
0.33
Fe
2.67
O
4
nanorods at room temperature is 52%. A similar spin polarization and TMR as Fe
3
O
4
in Co‐doped Fe
3
O
4
nanorod assemblies is obtained. Thus, controlled doping of Co ions engineers the coercivity and remanence of the “super‐paramagnetic” Fe
3
O
4
without hindering their TMR performances, which could be very useful for memory devices.
For the first time, X-ray excited luminescence of Sr2MgSi2O7:Eu2+, Dy3+, an efficient persistent phosphor with good potential for lighting, biological imaging and photodynamic activation, is reported ...in this paper. A modified Sol-Gel method is used to synthesize Sr2MgSi2O7:Eu2+, Dy3+ phosphors and their luminescence properties are highly associated with the synthesis conditions. The dependences of the X-ray excited optical luminescence and persistent luminescence of Sr2MgSi2O7:Eu2+, Dy3+ on the reaction pH, temperature, ratio of Eu/Dy, and the calcination duration time are investigated and the association of the luminescence behaviors with the synthesis conditions is explored as a good strategy to optimize the phosphors for practical applications.
Caused by severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2), coronavirus disease 2019 (COVID‐19) has shown extensive lung manifestations in vulnerable individuals, putting lung imaging and ...monitoring at the forefront of early detection and treatment. Magnetic particle imaging (MPI) is an imaging modality, which can bring excellent contrast, sensitivity, and signal‐to‐noise ratios to lung imaging for the development of new theranostic approaches for respiratory diseases. Advances in MPI tracers would offer additional improvements and increase the potential for clinical translation of MPI. Here, a high‐performance nanotracer based on shape anisotropy of magnetic nanoparticles is developed and its use in MPI imaging of the lung is demonstrated. Shape anisotropy proves to be a critical parameter for increasing signal intensity and resolution and exceeding those properties of conventional spherical nanoparticles. The 0D nanoparticles exhibit a 2‐fold increase, while the 1D nanorods have a > 5‐fold increase in signal intensity when compared to VivoTrax. Newly designed 1D nanorods displayed high signal intensities and excellent resolution in lung images. A spatiotemporal lung imaging study in mice revealed that this tracer offers new opportunities for monitoring disease and guiding intervention.
Magnetic particle imaging (MPI) offers high contrast, sensitivity, and signal‐to‐noise ratios for lung imaging, enhancing theranostic strategies in respiratory disease. Innovations in MPI tracers promise further gains, bolstering clinical applicability. This work introduces a superior nanotracer, leveraging magnetic nanoparticle shape anisotropy, elevating sensitivity and resolution beyond conventional spherical counterparts for lung MPI.
Abstract
Superparamagnetic iron oxide nanoparticles (SPIONs) are widely investigated and utilized as magnetic resonance imaging (MRI) contrast and therapy agents due to their large magnetic moments. ...Local field inhomogeneities caused by these high magnetic moments are used to generate T
2
contrast in clinical high-field MRI, resulting in signal loss (darker contrast). Here we present strong T
1
contrast enhancement (brighter contrast) from SPIONs (diameters from 11 nm to 22 nm) as observed in the ultra-low field (ULF) MRI at 0.13 mT. We have achieved a high longitudinal relaxivity for 18 nm SPION solutions, r
1
= 615 s
−1
mM
−1
, which is two orders of magnitude larger than typical commercial Gd-based T
1
contrast agents operating at high fields (1.5 T and 3 T). The significantly enhanced r
1
value at ultra-low fields is attributed to the coupling of proton spins with SPION magnetic fluctuations (Brownian and Néel) associated with a low frequency peak in the imaginary part of AC susceptibility (
χ
”). SPION-based T
1
-weighted ULF MRI has the advantages of enhanced signal, shorter imaging times, and iron-oxide-based nontoxic biocompatible agents. This approach shows promise to become a functional imaging technique, similar to PET, where low spatial resolution is compensated for by important functional information.
Exchange coupling between hard and soft magnetic materials at the nanoscale exhibits novel or improved physical properties for energy and data storage applications. Recently, exchange coupling has ...also been explored in core/shell magnetic nanostructures (MNS) composed of hard and soft magnetic spinel ferrites, but applications have been limited in biomedicine due to the presence of “toxic” cobalt based ferrites as hard magnetic component. We report core/shell MNS where both core and shell components are soft magnetic ferrites (Fe3O4, MnFe2O4, and Zn0.2Mn0.8Fe2O4) and show that exchange coupling still exists due to the difference in their anisotropy. The physical properties (saturation magnetization, susceptibility, anisotropy, r 2 relaxivity, and specific absorption rate) of core/shell MNS are compared with the same size single phase counterparts which excludes any size dependent effect and gives the direct effect of exchange coupling. After optimization of core and shell components and their proportions, we have shown that a core/shell MNS shows significantly higher contrast enhancement and thermal activation properties than their single phase counterparts due to exchange coupling between core and shell ferrites. Our finding provides a novel way to improve theranostic properties of spinel ferrite based MNS while maintaining their biocompatibility.
The development of external stimuli‐controlled payload systems has been sought after with increasing interest toward magnetothermally‐triggered drug release (MTDR) carriers due to their non‐invasive ...features. However, current MTDR carriers present several limitations, such as poor heating efficiency caused by the aggregation of iron oxide nanoparticles (IONPs) or the presence of antiferromagnetic phases which affect their efficiency. Herein, a novel MTDR carrier is developed using a controlled encapsulation method that fully fixes and confines IONPs of various sizes within the metal–organic frameworks (MOFs). This novel carrier preserves the MOF's morphology, porosity, and IONP segregation, while enhances heating efficiency through the oxidation of antiferromagnetic phases in IONPs during encapsulation. It also features a magnetothermally‐responsive nanobrush that is stimulated by an alternating magnetic field to enable on‐demand drug release. The novel carrier shows improved heating, which has potential applications as contrast agents and for combined chemo and magnetic hyperthermia therapy. It holds a great promise for magneto‐thermally modulated drug dosing at tumor sites, making it an exciting avenue for cancer treatment.
A novel magnetothermally‐triggered drug release carrier is developed by fixing iron oxide nanoparticles within a metal–organic framework, enhancing heating efficiency and overcoming limitations, such as poor efficiency due to nanoparticle aggregation or antiferromagnetic phases. It features a magnetothermally‐responsive nanobrush for on‐demand drug release, showing promise for combined chemotherapy and magnetic hyperthermia therapy in cancer treatment, and potentially as a contrast agent.
The MFe2O4 magnetic nanoparticle nanoassemblies (MNNAs) have been synthesized via thermal decomposition of metal chloride in ethylene glycol (EG) in the presence of ethylenediamine (EDA). The size of ...the nanoassemblies is controlled in the range of 25-60 nm by manipulation of Fe-precursor mole content to ethylene glycol (EG) content and from 60 to 135 nm by using a bi-solvent mixture of ethylene glycol and polyethylene glycol (PEG-400). In this study, we demonstrate optimization of magnetic fluid heat activation by tailoring the size of MFe2O4 (M = Mn, Fe, Co and Ni) MNNAs. The densely packed nanocrystals within the MNNAs induce strong exchange as well as dipolar interactions between the nanocrystals, which increases the total magnetic moment for MNNAs. Additionally the magnetization (MS, magnetization in a field of 20 kOe) of MNNAs decreases in the order Mn > Fe > Co > Ni due to the cationic distribution of ions with varying magnetic moments in these spinel oxides. A sharp increase of heating efficiency for 25-60 nm assembled particles could be attributed to the collective Neel relaxation of nanocrystals within the assemblies and also due to high particle magnetic moment, which increases with the MNNAs size. Furthermore, among all the MFe2O4 nanoassemblies of various sizes, Fe3O4 MNNAs with an average diameter of 80 nm show an excellent SAR value of 646 W g-1 of Fe3O4 at 247 kHz with an applied AC magnetic field of 310 Oe, which is 4 times higher than that of the single domain assembled nanoparticles. The moderate anisotropy constant and high MS values of Fe3O4 MNNAs make it a most suitable candidate to produce the highest heating power. These magnetic MNNAs are efficient in killing the cancer cells by the application of an AC magnetic field even for a short treatment time of 30 min.
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