Solid-state Nanoparticles Research Articles

Correlative Fluorescence and Transmission Electron Microscopy Assisted by 3D Machine Learning Reveals Thin Nanodiamonds Fluoresce Brighter.

Nitrogen vacancy (NV) centers in fluorescent nanodiamonds (FNDs) draw widespread attention as quantum sensors due to their room-temperature luminescence, exceptional photo- and chemical stability, and biocompatibility. For bioscience applications, NV centers in FNDs offer high-spatial-resolution capabilities that are unparalleled by other solid-state nanoparticle emitters. On the other hand, pursuits to further improve the optical properties of FNDs have reached a bottleneck, with intense debate in the literature over which of the many factors are most pertinent. Here, we describe how substantial progress can be achieved using a correlative transmission electron microscopy and photoluminescence (TEMPL) method that we have developed. TEMPL enables a precise correlative analysis of the fluorescence brightness, size, and shape of individual FND particles. Augmented with machine learning, TEMPL can be used to analyze a large, statistically meaningful number of particles. Our results reveal that FND fluorescence is strongly dependent on particle shape, specifically, that thin, flake-shaped particles are up to several times brighter and that fluorescence increases with decreasing particle sphericity. Our theoretical analysis shows that these observations are attributable to the constructive interference of light waves within the FNDs. Our findings have significant implications for state-of-the-art sensing applications, and they offer potential avenues for improving the sensitivity and resolution of quantum sensing devices.

Lipidic Formulations Inspired by COVID Vaccines as Smart Coatings to Enhance Nanoparticle-Based Cancer Therapy.

Recent advances in nanomedicine have led to the introduction and subsequent establishment of nanoparticles in cancer treatment and diagnosis. Nonetheless, their application is still hindered by a series of challenges related to their biocompatibility and biodistribution. In this paper, we take inspiration from the recently produced and widely spread COVID vaccines, based on the combinational use of ionizable solid lipid nanoparticles, cholesterol, PEGylated lipids, and neutral lipids able to incorporate mRNA fragments. Here, we focus on the implementation of a lipidic formulation meant to be used as a smart coating of solid-state nanoparticles. The composition of this formulation is finely tuned to ensure efficient and stable shielding of the cargo. The resulting shell is a highly customized tool that enables the possibility of further functionalizations with targeting agents, peptides, antibodies, and fluorescent moieties for future in vitro and in vivo tests and validations. Finally, as a proof of concept, zinc oxide nanoparticles doped with iron and successively coated with this lipidic formulation are tested in a pancreatic cancer cell line, BxPC-3. The results show an astonishing increase in cell viability with respect to the same uncoated nanoparticles. The preliminary results presented here pave the way towards many different therapeutic approaches based on the massive presence of highly biostable and well-tolerated nanoparticles in tumor tissues, such as sonodynamic therapy, photodynamic therapy, hyperthermia, and diagnosis by means of magnetic resonance imaging.

Composite Hydrogels with Included Solid-State Nanoparticles Bearing Anticancer Chemotherapeutics.

Hydrogels have many useful physicochemical properties which, in combination with their biocompatibility, suggest their application as a drug delivery system for the local and prorogated release of drugs. However, their drug-absorption capacity is limited because of the gel net's poor adsorption of hydrophilic molecules and in particular, hydrophobic molecules. The absorption capacity of hydrogels can be increased with the incorporation of nanoparticles due to their huge surface area. In this review, composite hydrogels (physical, covalent and injectable) with included hydrophobic and hydrophilic nanoparticles are considered as suitable for use as carriers of anticancer chemotherapeutics. The main focus is given to the surface properties of the nanoparticles (hydrophilicity/hydrophobicity and surface electric charge) formed from metal and dielectric substances: metals (gold, silver), metal-oxides (iron, aluminum, titanium, zirconium), silicates (quartz) and carbon (graphene). The physicochemical properties of the nanoparticles are emphasized in order to assist researchers in choosing appropriate nanoparticles for the adsorption of drugs with hydrophilic and hydrophobic organic molecules.

In situ study of Au nanoparticle formation in a mechanochemical-aging-based method.

As we strive to perform chemical transformations in a more sustainable fashion, enabling solid-state reactions through mechanochemistry has emerged as a highly successful approach. Due to the wide-ranging applications of gold nanoparticles (AuNPs), mechanochemical strategies have already been employed for their synthesis. However, the underlying processes surrounding gold salt reduction, nucleation and growth of AuNPs in the solid state are yet to be understood. Here, we present a mechanically activated aging synthesis of AuNPs, through a solid-state Turkevich reaction. Solid reactants are only briefly exposed to input of mechanical energy before being aged statically over a period of six weeks at different temperatures. This system offers an excellent opportunity for an in situ analysis of both reduction and nanoparticle formation processes. During the aging period, the reaction was monitored using a combination of X-ray photoelectron spectroscopy, diffuse reflectance spectroscopy, powder X-ray diffraction and transmission electron microscopy, to gain meaningful insights into the mechanisms of solid-state formation of gold nanoparticles. The acquired data allowed for the establishment of the first kinetic model for solid-state nanoparticle formation.

Artificial and Naturally Derived Phospholipidic Bilayers as Smart Coatings of Solid-State Nanoparticles: Current Works and Perspectives in Cancer Therapy

Recent advances in nanomedicine toward cancer treatment have considered exploiting liposomes and extracellular vesicles as effective cargos to deliver therapeutic agents to tumor cells. Meanwhile, solid-state nanoparticles are continuing to attract interest for their great medical potential thanks to their countless properties and possible applications. However, possible drawbacks arising from the use of nanoparticles in nanomedicine, such as the nonspecific uptake of these materials in healthy organs, their aggregation in biological environments and their possible immunogenicity, must be taken into account. Considering these limitations and the intrinsic capability of phospholipidic bilayers to act as a biocompatible shield, their exploitation for effectively encasing solid-state nanoparticles seems a promising strategy to broaden the frontiers of cancer nanomedicine, also providing the possibility to engineer the lipid bilayers to further enhance the therapeutic potential of such nanotools. This work aims to give a comprehensive overview of the latest developments in the use of artificial liposomes and naturally derived extracellular vesicles for the coating of solid-state nanoparticles for cancer treatment, starting from in vitro works until the up-to-date advances and current limitations of these nanopharmaceutics in clinical applications, passing through in vivo and 3D cultures studies.

A comparative analysis of low intensity ultrasound effects on living cells: from simulation to experiments

Ultrasounds are already broadly exploited in clinical diagnostics and are now becoming a powerful and not harmful tool in antitumoral therapies, as they are able to produce damages towards cancer cells, thank to inertial cavitation and temperature increase. The use of US alone or combined to molecular compounds, microbubbles or solid-state nanoparticles is the focus of current research and clinical trials, like thermoablation, drug sonoporation or sonodynamic therapies. In the present work, we discuss on the non-thermal effects of ultrasound and the conditions which enable oxygen radical production and which role they can have in provoking the death of different cancer cell lines. In this perspective, we set a mathematical model to predict the pressure spatial distribution in a defined water sample volume and thus obtain a map of acoustic pressures and acoustic intensities of the applied ultrasound at different input powers. We then validate and verify these numerical results with direct acoustic measurements and by detecting the production of reactive oxygen species (ROS) by means of sonochemiluminescence (SCL) and electron paramagnetic resonance (EPR) spectroscopy, applied to the same water sample volume and using the same US input parameters adopted in the simulation. Finally, the various US conditions are applied to two different set of cancer cell lines, a cervical adenocarcinoma and a hematological cancer, Burkitt’s lymphoma. We hypothesize how the ROS generation can influence the recorded cell death. In a second set of experiments, the role of semiconductor metal oxide nanocrystals, i.e. zinc oxide, is also evaluated by adding them to the water and biological systems. In particular, the role of ZnO in enhancing the ROS production is verified. Furthermore, the interplay among US and ZnO nanocrystals is evaluated in provoking cancer cell death at specific conditions. This study demonstrates a useful correlation between numerical simulation and experimental acoustic validation as well as with ROS measurement at both qualitative and quantitative levels during US irradiation of simple water solution. It further tries to translate the obtained results to justify one of the possible mechanisms responsible of cancer cell death. It thus aims to pave the way for the use of US in cancer therapy and a better understanding on the non-thermal effect that a specific set of US parameters can have on cancer cells cultured in vitro.Graphical abstract

Rapid ground-state cooling of a solid-state nanoparticle assisted by a magnetic-field gradient

Cooling a solid-state nanoparticle, as a significant prerequisite of the mesoscale quantum sensing, is experimentally challenging. Here we propose an efficient cooling scheme assisted by a strong magnetic-field gradient to cool a nanoparticle down to the ground state of the vibrational degrees of freedom. By combining the Zeeman effect with quantum interference effect, the scheme can accomplish the precooling of the nanoparticle from room temperature to the Doppler cooling limit in several seconds, and can then further cool the precooled nanoparticle to the vibrational ground state within milliseconds. We specify the scheme by exemplifying the nanocrystal of diamond nitrogen-vacancy center suspended in an electromagnetic potential, indicating that this cooling scheme can accomplish the ground-state cooling from room temperature within a few seconds under the condition of currently available techniques. Our work lays a foundation for further three-dimensional cooling of suspended nanoparticles and also for realizing quantum sensing using mesoscopic particles in the future.

Effect of electrolyte conductivity and local electric field inhomogeneity on heating of an aqueous suspension of solid-state nanoparticles

This work theoretically investigates the process of heat release in an electrolyte near a solid-state nanoparticle when exposed to an external radio-frequency electromagnetic field. The effect on the heat release of the effect of a change in the electrical conductivity of the electrolyte near the nanoparticle due to the redistribution of the ion concentration and the inhomogeneity of the electric field caused by the difference in the dielectric constants of the electrolyte and the nanoparticle is taken into account. The proposed model can be useful for choosing the optimal parameters of nanoparticles and radio frequency radiation when used in biomedicine for tumor hyperthermia.

Temperature monitoring through nanoparticle-activated proton relaxation for magnetic resonance imaging application

An effect of temperature on the proton relaxation times in aqueous suspensions of solid-state nanoparticles (NPs) is comparatively investigated for the NPs’ composition varied from pure silicon (Si) with natural isotope content to Si with iron impurities as well as for Si NPs enriched with Si-29 isotope. For all types of the investigated NPs both the longitudinal and transverse relaxation times become shorter compared with that for pure water because of the interaction of electron spin centers in those NPs with nuclear spins of the protons in water molecules. The obtained results allow us to evaluate the temperature sensitivity of NP-based systems for their biomedical applications in magnetic resonance imaging (MRI).

Environmentally Friendly Energy Harvesting Using Magnetocaloric Solid-State Nanoparticles as Magnetic Refrigerator

A phenomenological model (PM) is applied to simulate the magnetocaloric (MC) effect of iron oxide nanoparticles (IONs). Based on modeling results, MC parameters of IONs are deduced as the consequences of simulation for magnetization vs. temperature under 1 T magnetic field. There is a remarkable value of full-width at half-maximum of 213 K, giving an important practice for functioning IONs in the magnetic refrigerator (MR). Since IONs can be functioned over a large temperature range as an effective material for MR, covering a substantial and important range of temperatures, including room temperature and cryogenic temperatures. It is concluded that IONs can function as an auspicious MC magnet for the MR; especially IONs have tiny eddy current and hysteresis loss.

Ultrasensitive Monitoring of Museum Airborne Pollutants Using a Silver Nanoparticle Sensor Array.

The preservation of cultural heritage materials requires extremely low concentration limits for indoor pollutants. This poses an unmet challenge for monitoring the artwork in museums and on exhibit, especially to do so in a cost-effective manner for a large number of locations. A novel type of colorimetric sensor array based on printed inks of 10 nm silver nanoparticles (AgNPs) with several different capping agents has been developed as an alternative to metal coupons or other passive sampling indicators traditionally used by conservators. The AgNP colorimetric sensor array, combined with digital imaging, offers ultrasensitive dosimetric identification of acidic and oxidizing gases and other air pollutants commonly found in a museum; the limits of detection are sub-ppb for 1 h exposures. For an array of AgNP inks with various capping agents, a unique and distinguishable color response pattern is observed for each specific analyte. Excellent discrimination among 11 gas pollutants over a wide range of concentrations was demonstrated using standard chemometric methods. The observed changes in color during pollutant exposure originate from the sintering of solid-state nanoparticles that leads to changes in the localized surface plasmon resonance. Such chemically induced sintering mechanism of nanoparticles paves the way for a new class of field-deployable solid-state optical sensor arrays. As an example, we have demonstrated the use of AgNP sensor arrays for the nondestructive analysis of acidic volatile emission from five types of printing paper, relevant for the conservation of cultural heritage objects, including ancient manuscripts and books.

Effect of UV and Gamma Irradiation Sterilization Processes in the Properties of Different Polymeric Nanoparticles for Biomedical Applications.

The sterilization processes of nanoparticles (NP) by autoclaving and filtration are two of the most utilized methods in the pharmaceutical industry but are not always a viable option. For this reason, the search for alternative options such as UV and gamma radiation is of interest. In this work, we evaluated both types of sterilization on two types of NP in solid state widely employed in the literature for biomedical applications, poly-(ε-caprolactone) and poly(d,l-lactide-co-glycolide) acid NP stabilized with polyvinyl alcohol. Physicochemical properties and cell viability were studied pre- and post-sterilization. The efficiency of irradiation sterilization was performed by a test of sterility using 1 × 108 CFU/mL of Escherichia coli, Staphylococcus aureus, and Candida albicans. Microbiological monitoring revealed that both methods were sufficient for sterilization. After the UV irradiation sterilization (100 µJ/cm2), no substantial changes were observed in the physicochemical properties of the NP or in the interaction or morphology of human glial cells, though 5 and 10 kGy of gamma irradiation showed slight changes of NP size as well as a decrease in cell viability (from 100 µg/mL of NP). At 5 kGy of radiation doses, the presence of trehalose as cryoprotectant reduces the cell damage with high concentrations of NP, but this did not occur at 10 kGy. Therefore, these methods could be highly effective and low-processing-time options for sterilizing NP for medical purposes. However, we suggest validating each NP system because these generally are of different polymer-composition systems.

Highly Efficient Aggregation-Induced Electrochemiluminescence of Polyfluorene Derivative Nanoparticles Containing Tetraphenylethylene.

SummaryThe aggregation-induced electrochemiluminescence (AIECL) of polyfluorene derivative nanoparticles containing tetraphenylethylene (TPE) in aqueous media is reported in this work. The TPE unit limits the intramolecular free rotation of phenyl rings, as well as the π-π stacking interactions of molecules, which significantly enhances ECL signal of the polyfluorene nanoparticles. With co-reactants of tri-n-propylamine (TPrA) and S2O82−, the copolymer nanoparticles show visualized ECL emissions at both positive and negative potentials. The ECL efficiency of copolymer nanoparticles in solid state is 163% compared with that of standard ECL species, Ru(bpy)32+. And at negative potential, the ECL intensity of copolymer nanoparticles is even stronger with 6.5 times compared with that at positive potential. The ECL generation mechanisms are analyzed detailed by annihilation and co-reactant route transient ECL test (millisecond scale). This work provides a reference for the organic structure design for AIECL and shows promising potential in luminescent device and biological applications.

Self-Assembly of Hybrid Oxidant POM@Cu-BTC for Enhanced Efficiency and Long-Term Stability of Perovskite Solar Cells.

The controllable oxidation of spiro-OMeTAD and improving the stability of hole-transport materials (HTMs) layer are crucial for good performance and stability of perovskite solar cells (PSCs). Herein, we report an efficient hybrid polyoxometalate@metal-organic framework (POM@MOF) material, [Cu2 (BTC)4/3 (H2 O)2 ]6 [H3 PMo12 O40 ]2 or POM@Cu-BTC, for the oxidation of spiro-OMeTAD with Li-TFSI and TBP. When POM@Cu-BTC is introduced to the HTM layer as a dopant, the PSCs achieve a superior fill factor of 0.80 and enhanced power conversion efficiency 21.44 %, as well as improved long-term stability in an ambient atmosphere without encapsulation. The enhanced performance is attributed to the oxidation activity of POM anions and solid-state nanoparticles. Therefore, this research presents a facile way by using hybrid porous materials to accelerate oxidation of spiro-OMeTAD, further improving the efficiency and stability of PSCs.

Manipulating the degradation rate of PVA nanoparticles by a novel chemical‐free method

The high water solubility of poly (vinyl alcohol) (PVA) is one of the challenging problems in its application. In order to rectify this problem, PVA needs to be crosslinked. Freeze‐thawing in solid state as a novel physical crosslinking method was employed for enhancement the stability of PVA nanoparticles in aqueous solutions during this study. PVA nanoparticles were successfully prepared by electrospraying and electrospray conditions were optimized in the view points of polymer concentration and solvent system. The morphology of nanoparticles was tailored from collapsed particles and mixture of particles/fibers to spherical particle by manipulating of polymer solution concentration and solvent system. After preparation of PVA nanoparticles in optimum condition, they were frozen at −20°C and subsequently thawed at 25°C for different cycles of 1, 2, and 3. Field‐emission scanning electron microscope (FE‐SEM), Fourier‐transform infrared (FTIR), X‐ray diffraction (XRD), differential scanning calorimeter (DSC), and biodegradation were used to evaluate the effect of freeze‐thawing on properties of PVA nanoparticles. FE‐SEM showed the spherical morphology of the PVA nanoparticles with sizes ranging from 200 to 300 nm. The FTIR spectroscopy indicated that the crystallinity of PVA nanoparticles increases after freeze‐thawing process. Moreover, by increasing the number of cycles, degree of crystallinity of nanoparticles increases. The XRD and DSC analysis of PVA nanoparticles again demonstrated the increasing of crystallinity of nanoparticles after freeze‐thawing process. The biodegradation behavior of PVA nanoparticles after freeze‐thawing exhibited the decreasing of degradation rate by increasing the number of cycles. Our overall results present a solvent‐less and safe method for crosslinking of PVA nanoparticles in solid state, which make it suitable for biomedical applications.

Effect of Nano-SiC on Microstructure and Mechanical Properties of AZ91 Magnesium Alloy Processed by Thixomolding

Magnesium injection molding technology was used to produce Mg based nanocomposites. AZ91 chips were mixed with 5 wt.% of β-SiC nanoparticles in solid state and fed to pre-heated cylinder of prototype injection molding machine. Using screw rotation, granules were transferred to nozzle area at simultaneous intensive shearing and mixing of slurry containing reinforcement phases. Injection process was conducted at 595 °C, which corresponded to about 90% liquid phase and cast to steel die preheated to 150 °C. Detailed characterization of microstructure was performed using SEM and TEM microscopes. Composite microstructure consisted of α(Mg) globular grains with size of about 60 μm and volume of 7-10% surrounded by mixture of proeutectic magnesium solid solution with irregular shape and average size of 12 μm as well as fine eutectic mixture (α(Mg) + β-Mg17Al12). Additionally, TEM-BF image showed β-SiC nanoparticles with size of 20-50 nm in the area of eutectic. Hardness and compression strength of AZ91 nanocomposites increased from 58 to 75 HV and from 200 to 235 MPa, respectively.

Design of ion-conductive core-shell nanoparticles via site-selective quaternization of triazole–triazolium salt block copolymers

Triazolium-based ion-conductive nanoparticles (NPs) with cross-linked cores were synthesized using a self-assembled block copolymer comprising N-vinyl-4-ethyl-1,2,4-triazolium bis(trifluoromethanesulfonyl)imide (NVETri-NTf2) and N-vinyl-1,2,4-triazole (NVTri) and site-selective cross-linking quaternization in a selective solvent. Four different dihalide compounds, namely diiodoethane, diiodooctane, dibromoethane, and dibromooctane, afforded four core-shell NPs NP(C2-I), NP(C8-I), NP(C2-Br), and NP(C8-Br), respectively. DLS analyses demonstrated the formation of stable NPs with uniform sizes (mean diameter = 192 nm for NP(C2-I), 196 nm for NP(C8-I), and 195 nm for NP(C2-Br)). Among these, NP(C2-Br) exhibited the highest ionic conductivities. In the presence of 30 wt% ionic liquid, high ionic conductivities of 1.26 × 10−3, 3.31 × 10−4, and 1.36 × 10−4 S/cm were achieved with solid-state NP(C2-Br) at 90, 55, and 25 °C, respectively, which are due to the enhanced segmental molecular motion and the formation of a preferable ionic-conductive path composed of the hydrophobic ionic-liquid based shell with the added ionic liquid.

Electrolytic conductivity-related radiofrequency heating of aqueous suspensions of nanoparticles for biomedicine.

The development of suitable contrast agents can significantly enhance the efficiency of modern imaging and treatment techniques, such as thermoacoustic (TA) tomography and radio-frequency (RF) hyperthermia of cancer. Here, we examine the heating of aqueous suspensions of silicon (Si) and gold (Au) nanoparticles (NPs) under RF irradiation in the MHz frequency range. The heating rate of aqueous suspensions of Si NPs exhibited non-monotonic dependency on the electrical conductivity of the suspension. The experimental results were explained by the mathematical model considering oscillating solvated ions as the main source of Joule heating. These ions could be the product of the dissolution of Si NPs or organic coating of Au NPs. Thus, the ions governed the conductivity of the suspensions, which in turn governs both the heating rate and the near-field RF TA response. The model predicted the contrast in different tissues taking into account both Joule heating and dielectric losses.

Synthesis and characterization of yttrium iron garnet (YIG) nanoparticles - Microwave material

Magnetic Yttrium Iron Garnet (YIG) nanoparticles (NPs) were prepared by sol–gel (SG) and solid-state (SS) reaction methods to elucidate the nanoscale size on the magnetic behavior of NPs. It is found that YIG prepared by these two methods are different in many ways. The average NP sizes prepared by SG and SS methods were calculated by Scherrer formula from XRD data. SEM images show the change in grain size for both types of NPs. The sintering temperature required to form pure garnet phase is 750°C for SG and 1000°C for SS NPs. The saturation magnetizations (Ms) were 1070 Oe for SG and 1125 Oe for SS NPs, respectively. The coercivity (Hc) of SS NPs are twice larger than SG NPs. This is due to the larger crystal sizes of the SS NPs, hence more crystal boundaries. Dynamic properties were studied by ferromagnetic resonance (FMR) technique in field-sweep and frequency-sweep mode at different fixed frequencies and at different fixed magnetic fields, respectively. Resonance field (Hr) observed to increase linearly with frequency both for SS and SG NPs. The stop-band bandwidth (frequency linewidth) is narrower for SG NPs in comparison to SS NPs. Microwave absorption property make this material as a strong candidate for microwave device applications.

Ligand-Sensitized Lanthanide Nanocrystals: Merging Solid-State Photophysics and Molecular Solution Chemistry.

To date, the breadth of scientific research that has been devoted to investigating the photochemical and photophysical behavior of the lanthanide elements has generally fallen into one of two camps: solution studies of luminescent lanthanide metal-ligand complexes or investigations of solid-state nanoparticles, composed primarily of, or doped with, lanthanide lumiphores. In the latter case, most research of lanthanide nanocolloids has precluded any investigations regarding the use of organic ligands to overcome the difficulties associated with f-f excitation of lanthanides. Instead, most work on condensed-phase lanthanide luminescence has centered on strategies such as d-f charge separation in divalent lanthanides and the sensitization of lanthanide excited states using quantum dots. Current work now aims at bridging the camps of condensed-phase lanthanide photophysics and the solution chemistry of ligand-lanthanide molecular complexes. Recent efforts have partly focused on the fundamental characterization of NaGd1-xLnxF4 nanoparticles featuring surface display of the sensitizer ligand 3,4,3-LI(1,2-HOPO), showing these structures to be capable of converting absorbed UV light into luminescence from Eu3+ and Tb3+ ions. These results suggest such a use of the ligand sensitization as a tool of choice to overcome the constraints of UV solar spectrum/semiconductor band-gap mismatch and low absorption cross sections in solid-state lanthanide systems.