Gold Nanoparticles Of Different Sizes Research Articles

Wet Chemical Engineering of Nanostructured GRIN Lenses

AbstractGradient‐index (GRIN) lenses have long been recognized for their importance in optics as a result of their ability to manipulate light. However, traditional GRIN lenses are limited on a scale of tens of microns, impeding their integration into nanoscale optical devices. This study presents a groundbreaking self‐assembled method that overcomes this limitation, allowing for constructing GRIN lenses at an extremely small dimension. The self‐assembly process offers several advantages, including creating highly precise, scalable, cost‐effective, and complex structures that eliminate the need for intricate and time‐consuming manual assembly. By engineering densely packed arrays of metallic nanoparticles, exceptional control over the local refractive index has been achieved. This is accomplished by layer‐by‐layer assembly of gold nanoparticles of different sizes over silica beads. A GRIN lens light‐sink is built where light is preferentially directed toward the center, which is corroborated by measuring the fluorescence of Rhodamine B (RhB) in the inside. Unlike traditional bulky macroscopic GRIN lenses, light‐sinks boast a size under 2.5 µm. Notably, the self‐focusing effects of this design allowed us to track the growth of single‐nanoparticle layers using SERS (Surface‐Enhanced Raman Spectroscopy). These results pave the way for designing and developing lens‐like devices at the nanoscale, allowing unprecedented light manipulation.

Role of SiO2 in tailoring stability and nonlinear optical behaviour of gold nanoparticles in glass

In the present work, a new approach is introduced to mitigate the loss of gold nanoparticles while preparing the glass through the traditional melt-quench technique. The role of refractory material i.e. SiO2 in loss reduction is studied by comparing the results obtained for bismuth borate (40Bi2O3:60B2O3) and borosilicate (40Bi2O3:40B2O3:20SiO2) glasses containing gold nanoparticles of different sizes (10 nm, 40 nm and 100 nm). The particle density and thermal stability obtained from FESEM and DTA, respectively, increase considerably with the presence of SiO2 as one of the components of glass composition. The nonlinear optical behaviour of both systems in non-resonant regions has been obtained using the Z-scan technique. In addition, the suitability of the prepared glasses for optical limiting and switching applications has been analysed.

Investigating and Optimizing Insulin Partitioning with Conjugated Au Nanoparticles in Aqueous Two-Phase Systems Using Response Surface Methodology.

This study investigated the impact of bioconjugation on the partitioning of insulin, a clinically valuable protein, in an aqueous two-phase system. Gold nanoparticles of different sizes were synthesized and conjugated with insulin. Analysis of the conjugated insulin showed that the insulin remains fully active. Conjugated gold nanoparticles (AuNPs/insulin) were used in polyethylene glycol (PEG)-dextran aqueous two-phase systems to investigate the effect of pH, PEG and dextran molecular weights, PEG and dextran concentrations, AuNPs/insulin dosage, and nanoparticle size on the partition coefficient. These systems were chosen for their biocompatibility and low toxicity. Response surface methodology with D-optimal design was used to model and optimize these systems and their affected parameters. At the optimum condition of a pH = 8 system containing 21% PEG 4000, 5% dextran 100,000, and 100 IU AuNPs/insulin, the partition coefficient of AuNPs/insulin was found to be 192.96, which is in agreement with the empirical partition coefficient of 189.2. This is significantly higher than the partition coefficient of free insulin in a similar system. This approach could be used to overcome limitations in the feasibility of aqueous two-phase systems for industrial-scale purification of biomolecules and biopharmaceuticals.

Materno-Fetal and Teratogenic Effects of Different Size Gold Nanoparticles (AuNPs) in Pregnant Rats

The widespread use of gold nanoparticles (AuNPs) in many fields has increased; however, their potential effects on embryofetal development have not been explored. This study was designed to investigate the potential effects of different sizes of gold nanoparticles

Revealing the Impact of Polystyrene Functionalization of Au Octahedral Nanocrystals of Different Sizes on the Formation and Structure of Mesocrystals

AbstractThe self‐assembly of anisotropic nanocrystals (stabilized by organic capping molecules) with pre‐selected composition, size, and shape allows for the creation of nanostructured materials with unique structures and features. For such a material, the shape and packing of the individual nanoparticles play an important role. This work presents a synthesis procedure for ω‐thiol‐terminated polystyrene (PS‐SH) functionalized gold nanooctahedra of variable size (edge length 37, 46, 58, and 72 nm). The impact of polymer chain length (Mw: 11k, 22k, 43k, and 66k g⋅mol−1) on the growth of colloidal crystals (e. g. mesocrystals) and their resulting crystal structure is investigated. Small‐angle X‐ray scattering (SAXS) and scanning transmission electron microscopy (STEM) methods provide a detailed structural examination of the self‐assembled faceted mesocrystals based on octahedral gold nanoparticles of different size and surface functionalization. Three‐dimensional angular X‐ray cross‐correlation analysis (AXCCA) enables high‐precision determination of the superlattice structure and relative orientation of nanoparticles in mesocrystals. This approach allows us to perform non‐destructive characterization of mesocrystalline materials and reveals their structure with resolution down to the nanometer scale.

Size-Dependent Penetration of Nanoparticles in Tumor Spheroids: A Multidimensional and Quantitative Study of Transcellular and Paracellular Pathways.

Tumor penetration of nanoparticles is crucial in nanomedicine, but the mechanisms of tumor penetration are poorly understood. This work presents a multidimensional, quantitative approach to investigate the tissue penetration behavior of nanoparticles, with focuses on the particle size effect on penetration pathways, in an MDA-MB-231 tumor spheroid model using a combination of spectrometry, microscopy, and synchrotron beamline techniques. Quasi-spherical gold nanoparticles of different sizes are synthesized and incubated with 2D and 3D MDA-MB-231 cells and spheroids with or without an energy-dependent cell uptake inhibitor. The distribution and penetration pathways of nanoparticles in spheroids are visualized and quantified by inductively coupled plasma mass spectrometry, two-photon microscopy, and synchrotron X-ray fluorescence microscopy. The results reveal that 15nm nanoparticles penetrate spheroids mainly through an energy-independent transcellular pathway, while 60nm nanoparticles penetrate primarily through an energy-dependent transcellular pathway. Meanwhile, 22nm nanoparticles penetrate through both transcellular and paracellular pathways and they demonstrate the greatest penetration ability in comparison to other two sizes. The multidimensional analytical methodology developed through this work offers a generalizable approach to quantitatively study the tissue penetration of nanoparticles, and the results provide important insights into the designs of nanoparticles with high accumulation at a target site.

Investigation of Coulomb blockade diamonds of 7-helicenes interacting with gold nanoparticles

Helicene molecules show promising properties for future applications in optoelectronics due to their impressive optical properties and long effective conjugation. In this work, we thus study the properties of [7]-Helicenes in junctions with gold nanoparticles with emphasis on charge transport. The two helicenes are positioned between gold nanoparticles of different sizes creating to emulate molecular junctions and we utilize a combined quantum mechanical/molecular mechanical methodology using the polarizable embedding scheme to compute Coulomb blockade diamonds for the helicenes. Both molecules create Coulomb blockade diamonds following the 1-3-2 pattern.

Enhancing fibre optic sensor signals via gold nanoparticle-decorated agarose hydrogels

The main objective of this work was to create a novel sensing material using different sizes of gold nanoparticles (AuNPs) embedded in agarose hydrogel (AG) encapsulated fibre optic sensors. AuNPs (4 nm–40 nm) were synthesized using the chemical reduction method with a reducing agent of sodium borohydride (1% w/v) and trisodium citrate (40 mM). The core of the fibre optic was coated either using a single-layer (4 nm AuNPs, 15 nm AuNPs and AG) or two-layer coating (Au-AG) with the first layer being AG then followed by AuNPs (4 nm or 15 nm). The signal resulting from the AuNPs-AG coated fibre optic probe was tested using spectroscopy with a scanning range from 200 to 1000 nm to establish which sample generated the highest sensing signal. The result demonstrated that the smaller size of AuNPs provides a higher signal compared to a larger size, while the two-layered coating of 4 nm Au-AG significantly boosts the signal of the fibre optic sensor up to 47%. The overall performance of the 4 nm Au-AG coated fibre optic probe was highly promising, demonstrating a refractive index (RI) sensitivity of 3669.8 ± 5.232 RIU−1, with an R2 value of 0.9802. This optimized configuration of coating materials presents the sensor platform as an excellent candidate for further exploration in designing specific sensing applications, such as gas sensors or biosensors. Its remarkable ability to enhance sensor sensitivity holds great promise for advancing sensing technologies.

Roles of titania and plasmonic gold nanoparticles of different sizes in photocatalytic methane coupling at room temperature

Methane, one of the most abundant molecules on Earth and a major greenhouse gas, comes from renewable and fossil resources. The utilization of methane as a starting material for synthesis of chemicals is attractive but encounters numerous challenges due to high thermodynamic stability and extreme inertness of methane. Most of methane reactions occur at high temperatures and coincide with major emissions of CO2. Semiconductor photocatalysis offers an efficient alternative for methane conversion at room temperature.In this paper, we studied the plasmonic gold nanoparticles (NPs) with size from 6 nm to 60 nm supported on titania semiconductor in methane nonoxidative and oxidative couplings and elucidated their roles in the reactions. Strikingly, an efficient oxidative coupling with ethane production of 819 μmol/g/h and a coupling selectivity up to 86% was achieved in a flow reactor under optimized conditions. The reaction proceeded through methane activation over oxygen vacancies on Ultraviolet-excited titania. Gold NPs played important roles in charge separation and provided sites for soft oxygen activation. The size of gold NPs was found to be not noticeably affecting methane coupling.

Physical Characteristics, Blue-Green Band Emission and Photocatalytic Activity of Au-Decorated ZnO Quantum Dots-Based Thick Films Prepared Using the Doctor Blade Technique.

Nanoscale ZnO is a vital semiconductor material whose versatility can be enhanced by sensitizing it with metals, especially noble metals, such as gold (Au). ZnO quantum dots were prepared via a simple co-precipitation technique using 2-methoxy ethanol as the solvent and KOH as the pH regulator for hydrolysis. The synthesized ZnO quantum dots were deposited onto glass slides using a simple doctor blade technique. Subsequently, the films were decorated with gold nanoparticles of different sizes using a drop-casting method. The resultant films were characterized via various strategies to obtain structural, optical, morphological, and particle size information. The X-ray diffraction (XRD) reveals the formation of the hexagonal crystal structure of ZnO. Upon Au nanoparticles loading, peaks due to gold are also observed. The optical properties study shows a slight change in the band gap due to Au loading. Nanoscale sizes of particles have been confirmed through electron microscope studies. P.L. studies display blue and blue-green band emissions. The significant degradation efficiency of 90.2% methylene blue (M.B.) was attained in natural pH in 120 min using pure ZnO catalyst while one drop gold-loaded catalysts, ZnO: Au 5 nm, ZnO: Au 7 nm, ZnO: Au 10 nm and ZnO: Au 15 nm, delivered M.B. degradation efficiency of 74.5% (in 245 min), 63.8% (240 min), 49.6% (240 min) and 34.0% (170 min) in natural pH, respectively. Such films can be helpful in conventional catalysis, photocatalysis, gas sensing, biosensing, and photoactive applications.

Nanoparticles separation by different conditions at asymmetric flow field-flow fractionation

Abstract As semiconductor manufacturing enters the era of sub-10 nm and 3D stacking, “cleanliness” in the process becomes a crucial factor for process yield. The measurement of nanoparticle concentration, size, and shape in various solutions that may cause contamination during the manufacturing process is currently an important research topic. Although there are various nanoparticle measurement techniques available, further technological development and breakthroughs are still needed for measuring low concentrations and complex mixtures of nanoparticles. Therefore, in this study, we attempted to address the measurement challenges posed by mixed particles by applying asymmetric flow field-flow fractionation in combination with dynamic light scattering and ultraviolet. The strategy involved separating the samples before measurement. For a nanomixture containing five different sizes of gold nanoparticles with diameters of 20, 40, 60, 80, and 100 nm, three different methods were employed to control the driving force for particle separation during the elution stage: constant cross flow rate, linearly decreasing cross flow rate, and exponentially decreasing cross flow rate. The results demonstrated that different flow rate control methods indeed yielded variations in nanoparticle separation, with the constant flow rate method showing the best separation efficiency. Additionally, it was observed that the thickness of the experimental chamber played a significant role in affecting the retention time of the nanoparticles during separation.

Size- and Ligand-Dependent Transport of Nanoparticles in Matricaria chamomilla as Demonstrated by Mass Spectroscopy and X-ray Fluorescence Imaging.

Matricaria chamomilla flowers were incubated with gold nanoparticles of different sizes ranging from 1.4 to 94 nm. After different incubation times of 6, 12, 24, and 48 h, the gold distribution in the flowers was destructively measured by inductively coupled plasma mass spectrometry (ICP-MS) and non-destructively measured by X-ray fluorescence imaging (XFI) with high lateral resolution. As a control, the biodistribution of iodine ions or iodine-containing organic molecules (iohexol) was determined, in order to demonstrate the feasibility of mapping the distribution of several elements in parallel. The results show a clear size-dependent transport of the nanoparticles. In addition, the surface chemistry also plays a decisive role in disposition. Only the 1.6 nm nanoparticles coated with acetylcysteine could be efficiently transported through the stem of the flowers into the petals. In this case, almost 80% of the nanoparticles which were found within each flower were located in the petals. The study also highlights the potential of XFI for in situ recording of in vivo analyte biodistribution.

Nanoparticle-Driven Controllable Mitochondrial Regulation through Lysosome-Mitochondria Interactome.

Precise subcellular manipulation remains challenging in quantitative biological studies. After target modification and hierarchical assembly, nanoparticles can be functionalized for intracellular investigation. However, it remains unclear whether nanoparticles themselves can progressively manipulate subcellular processes, especially organellar networks. Mitochondria act as the energetic supply, whose fission dynamics are often modulated by molecular reagents. Here, using different-sized gold nanoparticles (AuNPs) as a model, we demonstrated the nanoparticle-driven controllable regulation on mitochondria. Compared with molecular reagents, AuNPs could induce size-dependent mitochondrial fission without detectable cell injury, and this process was reversible along with intracellular AuNPs' clearance. Mechanistically, it was attributed to the AuNPs-induced enhanced organelle interactome between lysosomes and mitochondria. Lysosomal accumulation of AuNPs induced lysosomal swelling and lysosomal motility alterations, promoting mitochondrial fission through the increased "kiss" events during the "kiss-and-run" moving of the lysosome-mitochondria interactome. This study highlights the fundamental understanding to fully explore the intrinsic capability of nanoparticles by engineering their basic properties. Also, it provides practical guidance to investigate the delicate nanolevel regulation on biological processes.

Physical stability of stealth nanobeacon using surface-enhanced Raman scattering for anti-counterfeiting and monitoring medication adherence: Deposition on various coating tablets

Microtaggant technologies can encode individual numbers on coating tablet to authenticate pharmaceutical products and, therefore, combat the global spread of falsified medicine. In this study, a novel microtaggant, stealth nanobeacon (NB), with surface-enhanced Raman scattering (SERS) activity was applied to various coating tablets and its physical stability was evaluated. The NBs were composed of a reporter molecule (AH, adenine hydrochloride) and prepared with different sizes of gold nanoparticles (AuNPs). The NBs were directly deposited on the surface of various model coatings (e.g., hydroxypropyl cellulose, hydroxypropyl methyl cellulose, Eudragit® RS30D, ethyl cellulose). To investigate physical stability of the NB on the coating tablets, SERS spectra of the NB after friability test and acceleration test (store at 75% RH, 40 °C) were evaluated using a portable Raman spectrometer. After the friability test, there was no significant decrease in the peak intensity of the SERS signal (PH) for authentication in all samples. In the acceleration test, the SERS signals of the samples were attenuated, but sufficient SERS signal intensity (PH > 70) was maintained in the seven types of coating for authentication. These results demonstrate that the microtaggant NB has the potential to be used for a wide range of coating tablets.

Biological Impact of the Interaction of Functionalized and Bioconjugated Gold Nanoparticles of Different Sizes on HeLa and SH-SY5Y Human Cell Lines

Nanotechnology opens new perspectives in many science and technology fields through new materials, such as metal nanoparticles. The biomedical field is one of these areas where nanoparticles offer promising application in the diagnosis and therapy of disease, generating biosensors for disease detection, bioimaging, and drug delivery. However, the controversy about whether nanoparticles are inert or exhibit different degrees of toxicity related to their physicochemical properties remains a subject of study and debate. This work shows how gold nanoparticles and nanorods were simultaneously functionalized with 4-aminothiophenol (4-ATP) and methoxypolyethylene glycol thiol (mPEG-SH). Then, folic acid (FA) gold nanoparticle bioconjugates caused diverse biological effects on HeLa and SH-SY5Y cell cultures after 24 h of incubation, when they were evaluated in the range of gold concentrations from 0.17 to 350 μM. We found notable changes in cell metabolic activity, viability, and biomass. 16 nm nanoparticles produced the most enhanced damage for functionalized (AuNPs) and bioconjugated (AuNPs-FA) nanoparticles, which we expected to be more biocompatible when coated with FA. Besides, epifluorescence images showed damage to F-actin microfilaments, adhesion and cell attachment loss, morphology changes (cells became round and detached), presence of blebs, and rupture of cell membrane. These results suggested that both AuNPs and AuNPs-FA have significant biological impact on HeLa and SH-SY5Y cell cultures, whereas gold nanorods showed significant changes only in the metabolic activity of SH-SY5Y cells when they were exposed to gold nanorods of 23 and 27 nm in length with a diameter of 5 nm, and crystal violet did not show evidence of toxicity.

Self-assembling plasmonic film of different-sized gold nanoparticles as a SERS substrate: the optimization study

The features of improving self-assembled films based on different-sized gold particles were investigated in this work. A study of the SERS signal was carried out to compare SPF samples consisting of gold nanoparticles of different sizes. For this purpose, colloids with different particle sizes were synthesized. These are spherical particles 20 nm and 40 nm in diameter and lamellar particles with an approximate size of 60x40x15 nm. Optimization of the concentration of the self-assembly agent of the reaction mixture in the preparation of the self-assembled plasmon film (SPF) has been carried out. The concentration of the self-collecting agent in the organic phase, at which the maximum values of the SERS enhancement of the signal were observed, is 10−5 M. The showing the reproducibility of the SERS signal for samples with the maximum enhancing of the SERS signal value is close for the all the studied particle sizes consisted SPF.

Size-Dependent Cytotoxic and Molecular Study of the Use of Gold Nanoparticles against Liver Cancer Cells

The size of nanomaterials influences physicochemical parameters, and variations in the size of nanomaterials can have a significant effect on their biological activities in cells. Due to the potential applicability of nanoparticles (NPs), the current work was designed to carry out a size-dependent study of gold nanoparticles (GNPs) in different dimensions, synthesized via a colloidal solution process. Three dissimilar-sized GNPs, GNPs-1 (10–15 nm), GNPs-2 (20–30 nm), and GNPs-3 (45 nm), were prepared and characterized via transmission electron microscopy (TEM), high-resolution TEM (HR-TEM), hydrodynamic size, zeta potential, and UV-visible spectroscopy, and applied against liver cancer (HepG2) cells. Various concentrations of GNPs (1, 2, 5, 10, 50, and 100 µg/mL) were applied against the HepG2 cancer cells to assess the percentage of cell viability via MTT and NRU assays; reactive oxygen species (ROS) generation was also used. ROS generation was increased by 194%, 164%, and 153% for GNPs-1, GNPs-2, and GNPs-3, respectively, in the HepG2 cells. The quantitative polymerase chain reaction (qPCR) data for the HepG2 cells showed up-regulation in gene expression of apoptotic genes (Bax, p53, and caspase-3) when exposed to the different-sized GNPs, and defined their respective roles. Based on the results, it was concluded that GNPs of different sizes have the potential to induce cancer cell death.

The Effect of Gold Nano Particles with Different Sizes on Streptococcus Species.

Statement of the Problem: Streptococcus mutans, Streptococcus sanguinis, and Streptococcus salivarius are most common etiologic bacteria for dental caries. Different sizes of gold nanoparticles may have different antibacterial effects on these species.Purpose: This study aimed to compare the antibacterial effect of chlorhexidine and three sizes of gold nano particles (25, 60, 90nm) against clinical and standard strains of Streptococcus mutans, Streptococcus sanguinis, and Streptococcus salivarius.Materials and Method: In this cross-sectional study, the specimens were collected from 75 children aged 3-5 years old. Antibacterial effect of chlorhexidine and three sizes of gold nano particles (25, 60, 90nm) were investigated by evaluating the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) against three bacterial strains.Results: The MIC and MBC of gold nanoparticles with different sizes against Streptococcus mutans, Streptococcus sanguinis, and Streptococcus salivarius were statistically different. The MIC and MBC of smaller gold nano particles (25nm) were significantly lower (p<0.001) than larger ones. Patient-derived bacteria had significantly higher values of MIC and MBC in comparison to standard species (p<0.001).Conclusion:The results of this study confirmed the significant size-dependency of gold nano particles for antibacterial activity. As the size of gold nano particles decrease, the antibacterial properties enhance.

Retention of Activity by Antibodies Immobilized on Gold Nanoparticles of Different Sizes: Fluorometric Method of Determination and Comparative Evaluation.

Antibody–nanoparticle conjugates are widely used analytical reagents. An informative parameter reflecting the conjugates’ properties is the number of antibodies per nanoparticle that retain their antigen-binding ability. Estimation of this parameter is characterized by a lack of simple, reproducible methods. The proposed method is based on the registration of fluorescence of tryptophan residues contained in proteins and combines sequential measurements of first the immobilized antibody number and then the bound protein antigen number. Requirements for the measurement procedure have been determined to ensure reliable and accurate results. Using the developed technique, preparations of spherical gold nanoparticles obtained by the most common method of citrate reduction of gold salts (the Turkevich–Frens method) and varying in average diameter from 15 to 55 nm have been characterized. It was shown that the number of antibodies (immunoglobulins G) bound by one nanoparticle ranged from 30 to 194 during adsorptive unoriented monolayer immobilization. C-reactive protein was considered as the model antigen. The percentage of antibody valences that retained their antigen-binding properties in the conjugate increased from 17 to 34% with an increase in the diameter of gold nanoparticles. The proposed method and the results of the study provide tools to assess the capabilities of the preparations of gold nanoparticles and their conjugates as well as the expediency of seeking the best techniques for various practical purposes.

Gold Nanocatalysts Towards Digital Sensing Probes with Electrochemiluminescence Based Micro Electrodes Array

AbstractThe authors have found that gold nanoparticles (AuNP) function as nanocatalysts for the generation of reactive oxygen species such as hydrogen peroxide from dissolved oxygen in coexistence with tris(hydroxymethyl)aminomethane (Tris) or N‐[tris(hydroxymethyl) methyl]glycine (Tricine) chemicals, and that these can be evaluated by luminol electrochemi‐luminescence (ECL). In the present study, we investigated the effects of reaction time, particle concentration, and temperature on the catalytic properties of gold nanoparticles. Unlike biocatalysts such as enzymes, the gold nanoparticles showed an Arrhenius plot‐like increase in activity with temperature without inactivation. In addition, the catalytic activity of the gold nanoparticles varied with the size and shape of the nanoparticles for spherical gold nanoparticles of different sizes (5, 15, 30, 50 and 400 nm) and the activity per nanoparticle increased with the size and surface area. When compared activity per surface area, 15 nm nanoparticles showed higher activity. We prepared gold nanoparticles with nanoflower (AuNF) structure of approx.200 nm in size which showed higher activity per particle than 400 nm spherical particles. The increase in surface area and the difference in surface condition may have influenced these results. We also prepared microelectrode arrays capable of holding small amounts of nl‐pL test reagents. They showed the possibility of imaging ECL of the activity of gold nanoparticles at the level of tens of nanoparticles which could lead to nanocatalysts as probes for digital analysis.