Large-sized Nanoparticles Research Articles

Separation of 100 nm-sized nanoparticles using a poly-Lys-modified monolith column.

Nanoparticles (approximately 100 nm in diameter) composed of lipid layers containing drugs or biologically active substances are attracting increasing attention in various fields, including medicine, as well as for signal transduction between cells. However, the separation of such nanoparticles via conventional HPLC is challenging, often resulting in the clogging and collapse of nanoparticles, as well as a low separation efficiency. Thus far, no HPLC column capable of efficiently separating two types of 100 nm-sized nanoparticles in a short time has been reported. In this study, a poly-Lys-modified monolithic column was prepared for nanoparticle analysis via HPLC using anticancer drug-encapsulated nanoparticles (Doxil®) and small extracellular vesicles (sEVs) to examine their elution behaviors. The zeta potentials of Doxil® and the sEVs were -24.4 and -45.5 V, respectively. A column with a low surface coverage (0.96 mg mL-1) of poly-Lys adsorbed the nanoparticles but did not elute them, whereas a column with a high surface coverage (2.06 mg mL-1) of poly-Lys retained these nanoparticles owing to the ion-exchange effect; sEVs with highly negative charges were strongly retained in the column. Using gradient elution with different 2-amino-2-hydroxymethyl-1,3-propanediol concentrations in the mobile phase, the two types of nanoparticles (Doxil® and sEVs) were eluted and successfully separated within 10 min. Thus, the developed column is a valuable tool for evaluating the safety and performance of larger-sized nanoparticles.

Comparative analysis: particle size and bactericidal efficacy of zinc oxide nanoparticles with aloe vera gel versus aloe vera gel-honey

In the realm of nanoscience, the inherent antibacterial potential of nanoparticles (NPs) stands as an alluring prospect for the development of pharmaceutical interventions. Yet, conventional chemical and physical NPs fabrication methods pose environmental and safety concerns. The aim of this study is to greenly-synthesize zinc oxide nanoparticles (ZnO NPs) using aloe vera gel (AVG) and aloe vera gel-honey (AVG-honey) under different reactant-to-chemical reductant (or precursor-to-reducing agent) ratio conditions, facilitated by sonication. Structural and optical characteristics of synthesized ZnO NPs were explicated through Fourier Transformation Infrared Spectroscopy (FTIR) and Ultraviolet-visible Spectroscopy (UV–vis). Concurrently, x-ray diffraction (XRD) and Field Emission Scanning Electron Microscope (FESEM) delineated the crystalline disposition and morphological behaviors. The antibacterial susceptibility of ZnO NPs against Methicillin-resistant Staphylococcus aureus (MRSA) and Klebsiella Pneumoniae (K. pneumoniae) was investigated using the disc diffusion method. The structures of biosynthesized ZnO NPs were confirmed through distinctive peaks in FTIR and UV–vis spectra. XRD unveils hexagonal wurtzite crystallinity, while FESEM captured distinct morphologies, which are spherical and rice-shaped, in ZnO NPs/AVG, while ZnO NPs/AVG-honey revealed micro-size spherical structures surrounded by numerous tiny lumps. Notably, ZnO NPs/AVG at a 1:6 ratio exhibits a 26.5 nm size, showcasing superior antibacterial efficacy against MRSA (ZOI = 12 mm) and K. pneumoniae (ZOI = 13 mm) compared to other reactant-to-chemical reductant ratios and ZnO NPs/AVG-honey. In conclusion, the study revealed that ZnO NPs synthesized solely using AVG exhibited finer particle sizes and slightly enhanced antibacterial efficacy compared to ZnO NPs formulated with a combination of AVG and honey. This outcome shows that utilization of two reducing agents will contribute to large size of nanoparticles, thus reduce the efficiency of the antibacterial susceptibility. Moreover, the concentration ratios of reactants-to-chemical reductants emerged as crucial determinants in the nanoparticle synthesis process.

Confined Synthesis of Noble Metal Clusters Assisted by Liquid Film for Photocatalytic CO2 Reduction.

The important concept of confined synthesis is considered a promising strategy for the design and synthesis of definable nanostructured materials with controllable compositions and specific morphology, such as highly loaded single-atom catalysts capable of providing abundant active sites for photocatalytic reactions. In recent years, researchers have been working on developing new confined reaction systems and searching for new confined spaces. Here, we present for the first time the concept of a bubble liquid film as a novel confined space. The liquid film has a typical sandwich structure consisting of a water layer, sandwiched between the upper and lower surfactant layers, with the thickness of the intermediate water layer at the micro- and nanometer scales, which can serve as a good confinement. Based on the above understanding and combined with the photodeposition method, we successfully confined synthesized Ag/TiO2, Au/TiO2, and Pd/TiO2 photocatalysts in liquid film. By HAADF-STEM, it can be seen that the noble metal morphologies are all nanoclusters of about 1 nm and are highly uniformly dispersed on the TiO2 surface. Compared with photodeposition in solution, we believe that the surfactant molecular layer restricts a limited amount of precursor to the liquid film, avoiding the accumulation of noble metals and the formation of large particle size nanoparticles. The liquid film, meanwhile, restricts the migration path of noble metal precursors, allowing for thorough in situ photodeposition and enables the complete and uniform dispersion of noble metal precursors, greatly reducing the photodeposition time. The uniform loading of the three noble metals proved the universality of the method, and the catalysts showed high activity for photocatalytic CO2 reduction. The rates of reduction of CO2 to CO over the Ag/TiO2 photocatalytic reached 230 μmol g-1 h-1.This study provides a new idea for the expansion of the confined reaction system and a reference for the study of liquid film as the confined space.

Nanoparticle Delivery in Microvascular after Cerebral Ischemia: A Simulation Study

Nanodrug delivery systems have been used in the diagnosis and treatment of ischemic stroke. However, the delivery mechanisms of nanoparticles within microvascular after cerebral ischemia have not been systematically revealed. This study aims to investigate the binding of different nanoparticles to the walls of ischemic brain microvascular through numerical simulations. In this study, 3D models of cerebral microvascular based on ischemic pathological changes are constructed. After building the mesh of microvascular, computational fluid dynamics is used to simulate blood flow and nanoparticle delivery. The simulation results show that the total amount of binding nanoparticles with small size is higher than that with large size. The large-sized nanoparticles are more easily delivered to the stenosis. The density of the nanoparticles has no significant effect on delivery. Furthermore, the study finds that the presence of red blood cells can significantly enhance the delivery efficiency of nanoparticles. In addition to evaluating the forces exerted on the nanoparticles, the impact of the binding affinity of the modified ligand on nanoparticles to the target receptor on delivery is investigated. In summary, selecting suitable nanoparticles according to different targets will improve the delivery efficiency of nanodrugs. The microvascular delivery model of nanoparticles proposed in this study may be helpful in the design of nanoparticles for diagnosis and treatment of cerebral ischemia.

Unprecedented selectivity behavior in the direct dehydrogenation of n-butane to n-butenes with similar active Pt nanoparticle size: unveiling structural and electronic characteristics of supported monometallic catalysts.

In this work, supported Pt monometallic catalysts were prepared using oxide and carbon supports by conventional impregnation methods. Similar Pt metallic nanoparticle sizes (mean sizes about 1.8-2 nm) have been obtained using different Pt precursor loadings (0.3 to 5 wt%). For comparison, catalysts with larger nanoparticle sizes were prepared using the liquid phase reduction method. Characterization results indicate different electronic and structural characteristics for the Pt nanoparticles, comparing nanoparticles with similar and different sizes, implying that both the Pt loading and the preparation method affect the formation of different metallic phases. We used the direct dehydrogenation of n-butane to n-butenes reaction as a test reaction to study the catalytic behavior of the Pt nanoparticles obtained at different Pt atomic concentrations. Surprisingly, Pt catalysts with the lowest metallic loading show the highest selectivities to olefins. Besides, Pt catalysts supported on carbon materials showed higher selectivity to butenes than those supported on oxide materials, this was attributed to a higher electron density in the Pt active sites. Likewise, at low Pt loadings, the CNP-supported Pt nanoparticles could be confined at the defect in the nanotube structure as crystalline agglomerates of atoms with few layers or monolayers with very few surface adatom or stepped adatom nanostructures or simply as a group of atoms, thus creating active Pt sites that favor the dehydrogenation reaction over secondary reactions.

Chirality-influenced antibacterial behavior of gold nanoclusters

Chirality exists widely in living systems and plays a crucial role in pharmaceutical production and theranostics. Gold nanoclusters (AuNCs) have recently been developed as potential antibacterial therapeutics, but the influence of chirality on their antibacterial behavior is unexplored. Here we prepare ultrasmall L-, D-, and DL-histidine templated AuNCs (denoted as L-AuHis, D-AuHis, and DL-AuHis, respectively) using a simple method. The three AuNCs possess the same physicochemical properties and maintain the chirality consistent with histidine. Antibacterial assay results using Staphylococcus aureus as a representative demonstrate the chirality-influenced antibacterial behavior of these AuNCs. An in-depth investigation revealed that the antibacterial activity of these chiral AuNCs was mainly attributed to cell structure damage and thiol-redox homeostasis imbalance. D-AuHis exhibit more potent antibacterial activity compared to their enantiomers. This difference in antibacterial behavior is mainly since the L-AuHis and DL-AuHis can react with bacterial cell wall components, such as lipoteichoic acid, to form large-sized nanoparticles, thereby weakening the antibacterial activity compared with the D-AuHis. The antibacterial effect of AuHis was further validated in a bacterial-infected wound model. Our findings provide a deeper insight into the establishment of unique chiral inorganic antibacterial constructions and hint at the potentiality of dextrorotatory AuNCs having strengthened antibiotic activity.

Characterizing bubble interaction effects in synchronous-double-pulse laser ablation for enhanced nanoparticle synthesis

To further advance nanomaterial applications and reduce waste production during synthesis, greener and sustainable production methods are necessary. Pulsed laser ablation in liquid (PLAL) is a green technique that enables the synthesis of nanoparticles. This study uses synchronous-double-pulse PLAL to understand bubble interaction effects on the nanoparticle size. By adjusting the lateral separation of the pulses relative to the maximum bubble size, an inter-pulse separation is identified where the nanoparticle size is fourfold. The cavitation bubble pair interaction is recorded using a unique coaxial diffuse shadowgraphy system. This system allows us to record the bubble pair interaction from the top and side, enabling the identification of the bubble’s morphology, lifetime, volumetric, and displacement velocity. It is found that the collision and collapse of the bubbles generated at a certain inter-pulse separation results in a larger nanoparticle size. These results mark a significant advancement by controlling the abundance of larger nanoparticles in PLAL, where previous efforts were primarily focused on reducing the average nanoparticle size. The experimentally observed trends are confirmed by numerical simulations with high spatial and temporal resolution. This study serves as a starting point to bridge the gap between upscaled multi-bubble practices and fundamental knowledge concerning the determinants that define the final nanoparticle size.

Coalescence behavior of Cu nanoparticles during sintering: Based on atomic scale to macro scale

Due to the excellent electrothermal properties, outstanding resistance to electromigration and cost-effectiveness, Cu nanoparticles are considered as a promising bonding material for high-power device. However, few studies have analyzed the coalescence behavior mechanism of Cu nanoparticles during sintering under temperature dependent conditions. In this paper, a novel method combining atomic and macroscopic scales was adopted to investigate the coalescence behavior of Cu nanoparticles. The sintering microstructure and bonding quality of Cu nanoparticles at different temperatures were evaluated via in-situ Transmission electron microscopy (TEM) heating, and the evolution of dislocations and phase transitions was analyzed. Molecular dynamics (MD) simulation was employed to characterize the atomic scale evolution of solid-state liquid sintering process of Cu nanoparticles. The role of temperature and nanoparticle size in the sintering mechanism were investigated. The results indicate that high temperature during constant temperature sintering is beneficial for the formation of stable crystal structures in the sintering neck and reduces the generation of dislocations. Shockley dislocations can contribute to the constitution of HCP stacking fault within Cu nanoparticles, which deteriorates the sintering performance. The increase in sintering temperature prompts Cu atoms at the sintering neck to migrate horizontally rather than vertically. Compared to small-sized nanoparticles, significant driving energy was required in the sintering of large-sized nanoparticles during the continuous heating process. Shockley dislocations play a dominant role in phase transition stacking fault at high temperature. Additionally, the mechanical failure forms of Cu/Nano-Cu/Cu joints at different sintering temperatures were studied and verified through MD simulation.

Impact of polymeric precursor and auto-combustion on the structural, microstructural, magnetic, and magnetocaloric properties of La0.8Sr0.2MnO3

In this work, La0.8Sr0.2MnO3 (LSMO) nanopowders are synthesized using two different methods: Pechini (LSMO-PC) and auto-combustion (LSMO-AC). Nanoparticle sizes, structural, magnetic, and magnetocaloric properties were determined and compared. The X-ray diffraction confirms the coexistence of two phases; rhombohedral symmetry with space group R-3c and orthorhombic symmetry with space group Pbnm. The rhombohedral phase is dominant. The scanning electron microscope images show that LSMO-PC has larger nanoparticle sizes (∼495 nm) than LSMO-AC (∼195 nm). The samples exhibit ferromagnetic properties with distinct hysteresis loops and Curie temperatures of 340 K and 290 K for LSMO-PC and LSMO-AC, respectively. The variation of the magnetic entropy was measured indirectly using the Maxwell approach with increasing magnetic field. For LSMO-PC it reaches a maximum -ΔSM = 1.69 J/kg.K at 340 K and ΔH = 5 T. The associated adiabatic temperature change ΔTM is 1.04 K. While LSMO-PC demonstrates superior magnetic and magnetocaloric properties, LSMO-AC displays significant magnetocaloric thermal stability. The obtained values make LSMO-PC and LSMO-AC promising candidates for eco-friendly room-temperature magnetocaloric applications.

Intelligent Responsive Nanoparticles with Multilevel Triggered Drug Penetration for Tumor Photochemotherapy.

Nanomedicines have contradictory size requirements to overcome systemic barriers and penetrate the tumor extracellular matrix (ECM). Larger-sized nanoparticles (50-200 nm) exhibit prolonged blood circulation half-life and improved tumor enrichment, while small-sized nanoparticles (4-20 nm) easily penetrate deep tumor tissues. Therefore, the development of intelligent responsive nanomedicine systems can not only increase nanodrug tumor accumulation but also improve their penetration into the ECM. Herein, we propose an intelligent responsive nanoparticle triggered by near-infrared light (NIR). The nanoparticle was constructed by a temperature-sensitive liposome (TSL) encapsulating ultrasmall melanin nanoparticles (MNPs) loaded with doxorubicin (MNP/doxorubicin (DOX)@TSL). When exposed to NIR irradiation, the tailor-made nanoparticles not only effectively ablated the tumor cells around blood vessels but also destroyed the structural integrity and released loaded ultrasmall MNP/DOX (<10 nm) to promote deep tumor penetration and enhance interior tumor cell killing. This NIR-triggered intelligent nanoparticle successfully integrated photothermal therapy (PTT) for perivascular tumor cells and chemotherapy for deep tumor cell inhibition. The in vivo results showed remarkable tumor regression in 4T1 breast tumor-bearing mice by 74.2%. This controllable size switchable nanosystem with efficient tumor accumulation and penetration has shown great potential in improving synergistic antitumor effects of photochemotherapy.

Morphology effect of Pd/In2O3/CeO2 catalysts on methanol steam reforming for hydrogen production

Catalyst support morphology strongly influences its surface and structural properties, therefore, may have a significant impact on their reactivity in heterogeneous catalysis. Herein, the Pd/In2O3/CeO2-x (loaded with 1 wt% Pd and In2O3) catalysts with different morphologies of rods(r), cubes(c) and irregularity(w) shapes were prepared by hydrothermal method and impregnation method. At temperature of 275–425 °C, as-prepared catalysts were evaluated for hydrogen production from methanol steam reforming (MSR). The activity data showed the outstanding performance of the rod-shaped Pd/In2O3/CeO2 catalysts, exhibiting the complete conversion of methanol and particularly low CO (1.3%) at 375 °C. The structural properties and physicochemical of Pd/In2O3/CeO2-x with different morphologies were characterized by means of X-ray diffraction (XRD), high resolution transmission microscopy (HR-TEM), CO pulse chemisorption, X-ray photoelectron spectroscopy (XPS) and temperature programmed desorption of methanol (CH3OH-TPD). Activity data and catalyst characterization results correlated, and indicated that the excellent reactivity for the rod-shaped Pd/In2O3/CeO2 catalysts in MSR is ascribed to the large particle size of palladium nanoparticles and the abundant oxygen vacancies induced by the strong interaction between Pd, In and Ce. HR-TEM results revealed that rod-like CeO2 mainly expose (110) crystalline surface with high mobility of surface oxygen and possess the most abundant surface oxygen vacancies with the low formation energy, facilitating the formation of active species of Pd0 on catalyst surface, and promoting the activation and adsorption of methanol and water molecules. Furthermore, the rod-shaped Pd/In2O3/CeO2 catalysts showed excellent reactivity and stability in MSR for 30 h, demonstrating its potential of being used as catalysts in methanol steam reforming in PEMFC systems.

Optimizing energy generation in power-law nanofluid flow through curved arteries with gold nanoparticles

The investigation of blood flow into curved arteries is fascinating and essential to prevent the advancement of vascular disease. Motivated by electro-kinetic manipulation, gold nanoparticles, and their size applications, a mathematical model is developed to explain blood flow, entropy generation, and electro-kinetic energy conversion (EKEC) efficiency in curved arterial flow. To make this study more realistic, a patient-specific overlapped stenosis condition and non-Newtonian (power-law fluid) blood flow model have been considered. The effects of a magnetic field, external heating, and chemical reactions are also included. The Stone’s strongly implicit scheme has been considered to solve the system of non-linear partial differential equations (PDE’s) in the” MATLAB” software. In this numerical investigation, an error tolerance of 10 − 6 has been considered for every iteration step under Stone’s scheme. The significance of various physical parameters, such as nanoparticle volume fraction (m), their size (dp), magnetic field intensity (M), inverse Debye length ( κ ¯ ), flow behavior index (Sc), heat source (H), and chemical reaction parameter (ξ) on the blood flow velocity, temperature, concentration, EKEC efficiency, and entropy generation have been explained graphically. This study also developed stream function contours to describe flow trapping patterns. The findings of this study conclude that the blood flow EKEC efficiency reduces with the presence of nanoparticles and stenosis in the artery. In addition, both flow velocity and entropy enhance by adopting large-size nanoparticles instead of small diametric nanoparticles. Clinical researchers and biologists may use the results of this computational study to forecast endothelial cell damage and plaque deposition in curved arteries with WSS profiles, by which the severity of these conditions can be reduced.

Shape-controlled preparation of nano gold (Au), Au clusters, and Au single atoms based on layered double hydroxide with closo-dodecaborate and their utilization for selective nitrobenzene reduction

Single-atom (SA) catalysts are superior in terms of catalytic activity, selectivity, and metal utilization. However, the complex preparation methods of SAs hinder their widespread application. Herein, layered double hydroxides (LDHs) with unique charge distributions were ingeniously combined with the dodecahydro-closo-dodecaborate anion [closo-B12H12]2−. We designed two different gold(Au) catalysts based on LDHs with closo-dodecaborate for the selective reduction of nitrobenzenes: composite dual-site Au SA/Au cluster catalysts (B12H12-MgAl-LDH-Au) were prepared using the anion exchangeability and spatial domain–limiting properties of LDH and the reducibility of [closo-B12H12]2−, and other Au nanoparticle catalysts (MgAl-LDH@B12H12@Au) were obtained using the reducibility of [closo-B12H12]2− immobilized on the LDH laminate. Up to 27 different nitrobenzene substrates can be selectively reduced to the corresponding azoxybenzenes (AOBs) with high efficiency at a wavelength of 450-nm radiation catalyzed by B12H12-MgAl-LDH-Au. However, large-size nanoparticles were more efficient in absorbing visible light energy. Therefore, 10 different AOB compounds were prepared using the MgAl-LDH@B12H12@Au system.

Enhanced room temperature gas sensing performance of ZnO with atomic-level Pt catalysts facilitated by the polydopamine mediator

The poor sensitivity of metal-oxide (MO) sensing material at room temperature can be enhanced by the modification of noble metal catalysts. However, the large size and uncontrollable morphology of metal nanoparticles (NPs) compromise the catalytic activity and selectivity. Downsizing metal NPs to the atomic level is a promising solution because it offers high activity and selectivity. Nevertheless, a facile and universal approach for stable loading atomic-level metal on MO-based sensing materials is still challenging. Herein, we present a strategy to construct synergetic coordination interface for uniform loading of atomic-level metal catalysts on MO-based gas-sensing materials using a difunctional mediator layer. In this work, atomically dispersed Pt catalysts are coordinately anchored on ZnO nanorods (NRs) using polydopamine (PDA) as a mediator. As a result, compared with pristine ZnO NRs, a six-fold enhanced response of 18,489% is achieved toward 100 ppm NO2 on 0.20 wt%Pt–ZnO@PDA-1.5 nm, and the selectivity is also promoted. Such sensitivity is higher than that of most reported noble metal-modified MO NO2-sensing materials. This work provides a simple and general strategy for building highly sensitive and selective gas-sensing materials using atomic-level noble metal catalyst.

A molecular simulation study on the sintering mechanism of TiO2

AbstractThe sintering process of TiO2 nanoparticles with different particle sizes and temperatures was studied thoroughly using equilibrium molecular dynamics simulations. The results show that when two nanoparticles contact, the sintering process was initiated by the merge of surface atoms of nanoparticles, and the process subsequently drives the internal atom to merge until two particles being merged homogeneously. There is mutual attraction between atoms and the particles gain kinetic energy to migrate due to the heating at high temperatures, leading to a faster sintering reaction. Moreover, there is a large difference in the sintering speed between 1600 and 1800 K. In the vicinity of the melting point, a small change in temperature makes a great impact on the sintering rate of TiO2 nanoparticles. Furthermore, by using the Lindemann index, it can be found that the larger particles have higher lattice structure stability compared to the smaller ones. The larger particle has a greater effect on the sintering behaviors when particles with different sizes’ contact. As a consequence, the sintering of two particles with different sizes is mainly initiated by the smaller particles moving toward the larger particle and is ended up with the atoms of smaller particle spreading around the larger particle. Therefore, the large nanoparticle size reduces the overall sintering rate.

Bactericidal potential of different size sericin-capped silver nanoparticles synthesized by heat, light, and sonication.

Present study was aimed to assess the bactericidal potential of sericin-capped silver nanoparticles (Se-AgNPs) synthesized by heat, light, and sonication. Se-AgNPs were characterized by size analyzer, UV spectrophotometry, energy-dispersive X-ray spectroscopy, and Fourier transform infrared spectroscopy. Average size of Se-AgNPs synthesized by heat, light and sonication was 53.60, 78.12, and 7.49 nm, respectively. All (10) bacterial strains were exposed to Se-AgNPs prepared from different methods to compare their antibacterial potentials. Largest zone of inhibition (13 ± 1.15 mm) was observed for sonication-based nanoparticles (NPs) against Klebseilla pneumoniae while the smallest zone of light assisted NPs against Serratia rubidaea (5 ± 1 mm). Bacterial strains were also exposed to different concentrations (0.2%, 0.3%, and 0.6%) of Se-AgNPs which showed largest zone (12 ± 1 mm) of inhibition for 0.4% of Se-AgNPs against Protius mirabilis and smallest zone (5 ± 1.154 mm) for 0.3% of Se-AgNPs against Escherichia coli. Furthermore, effect of different temperatures (5°C, 37°C, and 60°C) and pH (3, 7, and 12) on the efficacy and stability of Se-AgNPs was also evaluated against different bacterial strains. Sonication mediated NPs showed highest bactericidal results against K. pneumoniae (F3,8 = 6.154; p = 0.018) with smallest size NPs (7.49 nm) while lowest bactericidal results against S. rubidaea (5 ± 1 mm) were shown with largest size (78.12 nm) NPs prepared by natural light. These variations of bactericidal activities of NPs with difference size endorse that the Se-AgNPs with smallest size have highest antibacterial activity than larger size NPs. Moreover, Se-AgNPs maintain their bactericidal potency at wide range of temperature and pH, hence seemed stable.

Optimization of Coherent Dynamics of Localized Surface Plasmons in Gold and Silver Nanospheres; Large Size Effects

Noble metal nanoparticles have attracted attention in recent years due to a number of their exciting applications in plasmonic applications, e.g., in sensing, high-gain antennas, structural colour printing, solar energy management, nanoscale lasing, and biomedicines. The report embraces the electromagnetic description of inherent properties of spherical nanoparticles, which enable resonant excitation of Localized Surface Plasmons (defined as collective excitations of free electrons), and the complementary model in which plasmonic nanoparticles are treated as quantum quasi-particles with discrete electronic energy levels. A quantum picture including plasmon damping processes due to the irreversible coupling to the environment enables us to distinguish between the dephasing of coherent electron motion and the decay of populations of electronic states. Using the link between classical EM and the quantum picture, the explicit dependence of the population and coherence damping rates as a function of NP size is given. Contrary to the usual expectations, such dependence for Au and Ag NPs is not a monotonically growing function, which provides a new perspective for tailoring plasmonic properties in larger-sized nanoparticles, which are still hardly available experimentally. The practical tools for comparing the plasmonic performance of gold and silver nanoparticles of the same radii in an extensive range of sizes are also given.

Formation of nano and micro scale hierarchical structures in MgO and ZnO quantum dots doped LC media: the role of competitive forces

In this paper, we have studied the effect of doping of ZnO and MgO nanoparticles (NPs) in 4-(trans-4-n-hexylcyclo-hexyl) isothiocyanatobenzoate. A thorough comparison of dielectric properties, optoelectronic properties, and calorimetric phase transition properties has been done for MgO and ZnO NP doped LC. We prepare their homogenous mixture of MgO and ZnO NPs in toluene and transfer into cells made of glass and Indium Tin-Oxide (ITO) coated glass. The observed microstructures in the hybrid system can be classified into three main categories: grain like structures formed by aggregation of smaller size MgO nanoparticles while liquid crystal molecules anchor over the surfaces of nanoparticles, the grtu grain-like structures further integrate to form inorganic polymeric type of honeycomb-like mesostructures in presence of glass surface, and flower-like clusters of MgO nanoparticles on ITO surface. The smaller size nanoparticles can maintain the energy balance by allowing the anchoring of liquid crystal molecules over their surfaces whereas the larger size nanoparticles cannot compromise or maintain the energy balance with the liquid crystal molecules and are separated out to nucleate and form bigger size nanoaggregate or clusters. The energy preference of the substrate and nanoparticle’s surface to liquid crystal molecules plays an important role in the formation of different types of hierarchical nano- and microstructures. We account the reasons for the formation of nano and micro scale hierarchical structures on the basis of the competition between the forces: NP-NP, LC-LC, NP-LC, Glass/ITO-NP, and Glass/ITO-LC interactions. We observed a considerable change in the dielectric properties, transition temperature, bandgap, and other parameters of LC molecules when MgO NPs are doped, but a minor change occurs when ZnO NPs are doped in LC. Optical microscopy, FTIR, Raman, IR, HR-XRD and FESEM-EDX characterization data confirm and validate our guiding conceptions.

Applications and challenges of ultra-small particle size nanoparticles in tumor therapy.

With the development of nanotechnology, nanomedicines are widely used in tumor therapy. However, biological barriers in the delivery of nanoparticles still limit their application in tumor therapy. As one of the most fundamental properties of nanoparticles, particle size plays a crucial role in the process of the nanoparticles delivery process. It is difficult for large size nanoparticles with fixed size to achieve satisfactory outcomes in every process. In order to overcome the poor penetration of larger size, nanoparticles with ultra-small particle size are proposed, which are more conducive to deep tumor penetration and uniform drug distribution. In this review, the latest progresses and advantages of ultra-small nanoparticles are systematically summarized, the perspectives and challenges of ultra-small nanoparticles strategy for cancer treatment are also discussed.

Synthesis of nanoparticles of Poly (ethyleneimine) and their characterization by transmission electron microscopy, thin layer chromatography, and infrared spectroscopy

Intracellular gene delivery alters the expression of a gene and corrects a defective gene that may be the cause of a disease or a disorder. Nonviral gene delivery is more appropriate than viral-mediated due to their low cytotoxicity and immunogenicity. Amongst these, polycationic nanoparticles i.e. Polyethyleneimine (PEI) were used most successfully. The PEGylation of such cationic polymer reduces its cytotoxicity. Different molecular weight poly (ethylene glycol) was used for the PEGylation of such cationic nanoparticles which have an individual effect. For this purpose, the PEG is esterified, which was then reacted with a cationic polymer. Four different molecular weights of PEG were used. The size of nanoparticles so formed depends upon the molecular weight of PEG. So formed nanoparticles were dialyzed, lyophilized, and then characterized by IR and TEM. The nanoparticles so formed are directly affected by the different molecular weights of PEG. Higher the molecular weights of PEG smaller size of nanoparticles so formed but only up to a limited extent. The decreasing order of nanoparticles as an increment of molecular weight of PEG was found as a -0.85 coefficient of correlation. The smaller-sized nanoparticles have higher transfection efficiency than larger-sized nanoparticles. So, the higher the molecular weight of PEG higher will be the transfection efficiency.