Surface Plasmon Absorption Peak Research Articles

Utilization of herbivore defensive latex from the weed Calotropis procera L in the green synthesis of silver nanoparticles and its potential application in the control of dengue vector Aedes aegypti

Milky latex produced by few and not all the plants are the treasure chest of various bioactive compounds with defensive potential against herbivores, insects and pathogens. Mankind have utilized latices in the preparation of novel plant-based therapies for centuries. Therefore, an attempt has been made to synthesis silver nanoparticles (AgNPs) using AgNO3 as a precursor and latex from C. procera as a reducing agent. The surface plasmon absorption peak at 430 nm confirmed AgNPs formation. The sharp peak with narrow width illustrated the homogenous nature. The face centre cubic structure of AgNPs was confirmed by the XRD pattern. FT-IR analysis deduced that the bio-molecules in the latex of C. procera are responsible for the reduction of AgNO3 to AgNPs. Biosynthesised L-AgNPs possessed well pronounced antibacterial activity against P. aeruginosa and K. pneumoniae. Anti-inflammatory activity of the nanoparticle determined by membrane stabilization and proteinase inhibitory assay was found to be in dose-dependent. LC50 value of L-AgNPs was found to be 63.09 µg/mL against IV instar larvae of A. aegypti. Distinct morphological changes were observed in the mosquito larva on exposure to various concentrations of L-AgNPs.

Green Synthesis Of Zno Nanoparticles Using Pomegranate Fruit Extract

Today, environmentally friendly solvent systems and eco-friendly reducing and capping agents have been used to create "Green" nanoparticles. The goal of the current work was to examine the manufacture of zinc oxid nanoparticles using pomegranate fruit extract as a reducing agent. In UV-vis spectra, the distinctive surface plasmon absorption peak of zinc at 370 nm served as proof that nanoscale zinc had formed. Scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDAX), X-ray diffraction (XRD), and Fourier transform infrared (FTIR) spectroscopy were used to analyze the morphology and crystalline nature of the produced zinc molecule. Study the chemical composition of the peel extract by GC-MS chromatogram (Phytochemical analysis). Twenty-one significant peaks and the components matching to the peaks were found in the Punica granatum peel ethanolic extract used in the current study's chemical composition GC-MS chromatogram (Phytochemical) analysis. The current findings suggest that Punica granatum includes a number of bioactive ingredients.

Characterization and Biological Activities of Silver Nanoparticles Synthesized using Grewia tiliifolia Vahl Leaf Extract

Background: An eco-friendly approach for the synthesis of noble metal nanoparticles employing various plant extracts has become of great interest in the field of nanotechnology. In the present study, the efficacy of Grewia tiliifolia leaf extract in reducing 1mM silver nitrate to silver nanoparticles(AgNPs) has been reported for the first time and also we investigated the anticancer, antituberculosis and antioxidant activity. Methods: Characterization of biosynthesized AgNPs using G. tiliifolia leaf extract was evaluated by Uv-Vis, FTIR, XRD, DLS and TEM with SAED. Efficacy of biosynthesized AgNPs using G. tiliifolia leaf extract was tested for cytotoxicity against A549 Lung cancer cell lines by MTT Assay and also against the infectious agent Mycobacterium tuberculosis using MABA Assay. Further antioxidant activity was evaluated by DPPH radical scavaging assay. Results: The biosynthesis of AgNPs was evident by color change of reaction mixture from dark yellow to reddish-brown. Biofabricated AgNPs was further confirmed by characteristic surface plasmon absorption peak at 409nm by UV-vis analysis. FTIR data reveals the presence of phytochemicals involved in bioreduction and biocapping of AgNPs, XRD analysis depicted crystallographic nature of AgNPs. Further, size, charge, and polydispersity nature were studied using DLS (40.2nm with polydispersity index 0.361) and Zeta potential (-35.8mV). The morphology of AgNPs was determined by TEM analysis with size ranging from 11-34nm. The plant derived AgNPs exhibited a cytotoxic effect on the Lung cancer cell line with IC50 value of 23.45µg/ml and also found to be effective against M. tuberculosis with a MIC of 6.25µg/ml in comparison to the leaf extract (MIC 50µg/ml). Antioxidant activity observed by AgNPs was moderate with IC50 value 49.60 µg/ml. Conclusion: The findings indicate that the AgNPs synthesized from leaf extract of G. tiliifolia are eco-friendly, cost-effective, non-toxic and can be the effective natural anticancer, antituberculosis agents and antioxidant agent.

Green Synthesis, Characterization and Biological Activity of Silver Nanoparticles Using Ruta Leaf Extract

In this paper, green synthesis of AgNPs is carried out by means of an environmentally friendly, cost-effective and safe technology using Ruta leaf extract as a reducing agent for silver. Furthermore, biological activity of produced AgNPs was examined against different microorganism with multiple resistances to antibiotics, which isolated from different disease states. The produced AgNPs were characterized by UV-Vis spectroscopy, Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and Field Emission Scanning electron microscopy (FESEM) and Dynamic light scattering (DLS). The biosynthesized silver nanoparticles by Ruta leaf extract were confirmed by their change of color from colorless to yellow and lastly to reddish brown. UV-visible spectrophotometric analysis of the AgNPs synthesized showed characteristic surface plasmon absorption peak at 415 nm. Where the X-ray diffraction showed that, the nanoparticles were crystalline in nature with a face-centered cubic structure (FCC). Field Emission scanning electron microscopy (FESEM) micrograph showed the creation of spherical nanoparticles with size from 30 to 50 nm in diameter. The element silver of the sample was obtained from the Energy Dispersive Analysis of X-ray (EDX). The stability and distribution size were detected using zeta potential and DLS analysis.

Tunable plasmon-assisted electrochemiluminescence strategy for determination of the rapidly accelerated fibrosarcoma B-type (BRAF) gene using concave gold nanocubes.

Atunable plasmon-assisted electrochemiluminescence (ECL) strategy is reportedusing concave Au nanocubes (Au CBs) for rapidly accelerated fibrosarcoma B-type (BRAF) detection. Concave Au CBs exhibit a strong surface plasmon coupling (SPC) effect between its sharp apexes and edges. The high spectral overlap with graphite phase carbon nitride quantum dots (g-C3N4 QDs) is achieved by tuning surface plasmon absorption peak of the concave Au CBs. It maximizes the SPC effect and enhances the ECL signal of g-C3N4 QDs 3-fold. The SPC effect of Au CBs is twice as high as with Au NPs. We also employed a toehold-mediated strand displacement (TMSD) strategy for sensitive target recycling amplification. Under optimal conditions, this sensor can determine BRAF gene from 1pM to 1nM with a detection limit of 3.06 × 10-5nM (S/N = 3) and RSD 3.67%. With the aid of the TMSD strategy and tunable plasmon-assisted ECL sensing mode, this sensor also exhibits goodanalytical performance in human serum with satisfactory recovery of 90.2~109%. The proposed strategyprovides a promising method to effectively enhance spectral overlap and detect BRAF gene.

Synthesis and characterization of silver nanoparticles as a potential sensor for volatile organosulfides for visual detection of postharvest storage in garlic

Garlic, one of the most popular spices used in manufacturing many food products, is subjected to fungal and bacterial diseases resulting to substantial losses in quantity and quality. Specific detection tools for garlic spoilage will be an asset in relieving these losses during postharvest storage. In this study, stable yellow-colored silver nanoparticle colloidal solution was studied as a potential sensor for volatile organosulfides in garlic. The silver nanoparticles (AgNPs) were synthesized by chemical reduction method where silver nitrate was taken as metal precursor, sodium borohydride as reducing agent, and polyethylene glycol as stabilizing agent. The silver nanoparticles were characterized by UV-Vis Spectroscopy and Dynamic Light Scattering (DLS). The spectral analysis revealed the formation of silver nanoparticles by exhibiting the typical surface plasmon absorption peak at around 395 nm. The DLS results show two populations of AgNPs with particle sizes of 3 nm and 50 nm. The volume ratio of sodium sulfite to be added in the silver nanoparticle and the reaction time was also determined. Synthesized AgNPs could detect sodium sulfite at 0.52 to 50 µM concentration range. This simple method indicated the potential of silver nanoparticles as a powerful detection tool for volatile organosulfides in garlic.

Eco-friendly walnut shell powder based facile fabrication of biogenic Ag-nanodisks, and their interaction with bovine serum albumin

Walnut shell biomass was used for the extraction of juglone by water as a solvent at room temperature. Upon addition of AgNO3 to a dye solution, prefect transparent pale brown color develops within the reaction time. UV–visible spectroscopy revealed the appearance of surface plasmon absorption (SRP) peak at 410 nm for spherical silver nanoparticles (AgNPs). Transmission electron microscopy suggested the formation of spherical and truncated triangular nano-plate geometry of AgNPs with average diameter 25 nm. Juglone-surfactant interactions (micellization and incorporation) have been studied spectrophotometrically by using cationic cetyltrimethylammonium bromide (CTAB). The presence of CTAB has significant impacts on size, shape and the size distribution of AgNPs. The nucleation, growth, and adsorption processes depend on the [CTAB]. It also catalyzes the Ag+ ions reduction by juglone with a rate enhancement of ca. 100-fold. Activation parameters (activation energy, enthalpy of activation and entropy of activation) were evaluated to the synthesis of silver nano-disks. Antioxidant activity of juglone was accessed by the scavenging effect on DPPH radical. Silver nanoparticles was also used as quencher to determine their interaction with bovine serum albumin (BSA). The quenching constant were found to be 1.4 × 103 M−1 L s−1 and 4.8 × 103 M−1 L s−1 for two BSA concentrations.

Optimization of silver nanoparticle biosynthesis process using cell-free filtrate of Aspergillus niger

Nanotechnology and nanoparticle (NPs) research has attracted a lot of interest in recent decades, and there is growing attention to find more effective ways for their synthesis. The use of biological organism as bionanofactories provides a clean and promising alternative process for the fabrication of silver nanoparticles. This study confirmed the production of silver nanoparticles (SNPs) by a cost effective, safe and environment-friendly technique using silver nitrate and cell free filtrate of the fungus Aspergillus niger as the reducing agent. The optimization of different parameters, including the culture media, pH, reaction temperature, concentration of silver nitrate solution and reduction time, were carried out to achieve better control of size, shape, stability, and to increase the yield of SNPs production. The UV-visible spectrophotometric analysis of the biosynthesized silver nanoparticles by Aspergillus niger cell-free filtrate showed characteristic surface plasmon absorption peak at 420 nm. The presence of proteins as viable reducing agents for the formation and stability of SNPs was recorded using Fourier transform infrared spectroscopic analysis (FTIR) .Further scanning electron microscopy (SEM) micrograph showed the formation of spherical, well-dispersed nanoparticles with size ranging between 15 and 50 nm in diameter. The element composition of the mixture sample was obtained from the Energy Dispersive Analysis of X-ray (EDX). It concluded that the optimum condition for biosynthesis of SNPs were the use of Potato dextrose broth medium at pH 9, 30°C for 120 h with 1mM silver nitrate.

Controlling the Surface Plasmon Absorption of Silver Nanoparticles via Green Synthesis Using <i>Pennisetum purpureum</i> Leaf Extract

We report on the green synthesis of silver nanoparticles utilizing theP.purpureumleaf extract. Controlling the surface plasmon absorption of silver nanoparticles was achieved by regulating the amount of extract concentration and the molarity of silver nitrate solution. The surface plasmon absorption peak is found at around 430nm. The surface plasmon absorption peak have shifted to lower wavelength as the amount of extract is increased, while plasmon absorption peak shifts on a higher wavelength as the concentration of silver nitrate is increased before it stabilized at 430nm. This can be explained in terms of the available nucleation sites promoted by the plant extract as well as the available silver ions present in silver nitrate solution.

Green synthesis of silver nanoparticles from aqueous leaf extract of Pomegranate (Punica granatum) and their anticancer activity on human cervical cancer cells

Plants contain different important phytochemicals that can be used as a potential treatment for various ailments including cancer. The green synthesis of silver nanoparticles from the extract of different plant parts has gained a wide range of engrossment among the researchers due to its unique optical and structural property. The aim of this study is green synthesis of silver nanoparticles from the aqueous leaf extract of pomegranate (Punica granatum) and to investigate its anticancer activity on human cervical cancer cells (HeLa). The synthesis of silver nanoparticle was depicted by the colour change from golden yellowish to dark brownish, UV-visible spectral analysis gave a characteristic surface plasmon absorption peak at . Further morphological characterization was done by Zeta potential where the size analysis was depicted to be 46.1 nm and zeta potential as . Fourier transform infrared spectroscopy (FTIR) inferred 3 intense sharp peaks at , , , confirmed the presence of flavonoids and polyphenols. The scanning electron microscopy (SEM) analysis with energy diffraction spectroscopy (EDS) confirmed the presence of silver nanoparticles with size ranged from to . X-ray diffraction (XRD) confirmed the crystallographic nature of silver. The cell proliferation activity of nanoparticles was tested by 3, −4, 5 dimethylthiazol-2,5 diphenyl tetrazolium bromide (MTT) assay where the inhibitory concentration () was found at inhibiting of HeLa cell line. The anticancer activity of nanoparticles was determined by lactate dehydrogenase (LDH) assay where showed of cytotoxicity. Furthermore, the anticancer property of nanoparticles was confirmed by the DNA fragmentation assay.

Green synthesis of biocompatible silver nanoparticles mediated by Osmanthus fragrans extract in aqueous solution

A practical, convenient and green method for the synthesis of highly stable and small sized silver nanoparticles with narrow distribution from 2nm to 30nm is reported. Silver nitrate was used as silver precursor, and Osmanthus fragrans extract was acted as capping agent as well as reducing agent. The formation of silver nanoparticles was observed by the change of color from colorless to yellow. The as-prepared silver nanoparticles were characterized by scanning electron microscope (SEM), transmission electron microscopy (TEM), high resolution transmission electron microscopic (HRTEM), UV–vis spectroscopy (UV-vis), X-ray diffraction (XRD) and Fourier transform infra-red spectroscopic (FT-IR). The formation of silver nanoparticles was confirmed by its characteristic surface plasmon absorption peak at 400–450nm in UV–vis spectra. The TEM and SEM images showed that the as-synthesized silver fine spherical particles are distributed uniformly with a narrow distribution from 2nm to 30nm. The HRTEM and XRD results demonstrated that the obtained metallic nanoparticles were single crystalline silver nanoparticles. FT-IR data revealed that the silver nanoparticles are coated with Osmanthus fragrans extract. The effects of the silver nitrate and Osmanthus fragrans extract concentrations on the particle size were investigated. The green synthesis method is simple and may be extended to preparation of other noble metal nanoparticles.

Electroluminescence Enhancement of Polymer Light Emitting Diodes Through Surface Plasmons by Ag Nanoplates

This paper reports a study on the surface plasmon effect of Ag nanoplates on electroluminescent property of polymer light emitting diodes. The diode is a single layer light emitting device made of poly [9,9-di-(2-ethylhexyl)fluorenyl-2,7-diyl] (PEHF). 5 wt.% of Ag nanoplates were incorporated into the PEHF layer. The results showed that the electroluminescence intensity of the diodes is increased by 51.85%, compared with the device without the Ag nanoplates. The enhancement is due to the coupling process between the Ag surface plasmon with the emission light from the PEHF. The occurrence of the coupling process was proved firstly based on the fact that the exciton lifetime of the PEHF:Ag layer is shorter than that without Ag, as measured by time-resolved photoluminescence spectroscopy. Secondly, the PEHF photoluminescence peak at 425 nm is overlaping with the surface plasmon absorption peak of Ag nanoplates.

Physiological Responses of Two Varieties of Common Bean (Phaseolus VulgarisL.) to Foliar Application of Silver Nanoparticles

This study reported the synthesis of aqueous dispersions of highly stable silver nanoparticles (AgNPs) using gamma radiation with gum acacia (GA) as the stabilizing and protecting agent. The formation of nanosized silver GA-AgNPs at a gamma irradiation dose of 15 kGy was confirmed by the appearance of the characteristic surface plasmon absorption peak at 456 nm and in UV–vis spectra. The particle size distribution of silver nanoparticles that was determined by Dynamic Light Scattering (DLS) was approximately 22 nm. By using Transmission Electron Microscopy (TEM), mostly spherical GA-AgNPs particles with a mean diameter of 16.7 nm and crystalline in shape were confirmed by an X-ray diffraction (XRD) pattern. Fourier Transform Infrared (FTIR) spectroscopic analysis indicates the bonding of AgNPs with the COO- group of gum acacia. To increase our understanding of the mechanisms involved in plant responses to GA-AgNPs and AgNO3, in order to differentiate between particle-specific and ionic-silver effects, we ...

Study of the solution thermal conductivity effect on nonlinear refraction of colloidal gold nanoparticles

In nanoparticle colloidal systems, the thermal nonlinearity is affected by the thermal parameters of the surrounding solution. Having a low temperature gradient rate solution may be a key factor in producing high thermal nonlinear properties in colloids. In this manuscript, the effect of the thermal conductivity of the surrounding liquid environment on the thermal nonlinear refraction of gold nanoparticles (AuNPs) synthesized by laser ablation of a gold target in different solutions is investigated. Gold nanoparticles colloids have been fabricated by the nanosecond pulsed laser ablation of a pure gold plate in different liquid environments with a thermal conductivity range of 0.14–0.60 W mK−1 including cyclohexanone, castor oil, dimethyl sulfoxide, ethylene glycol, glycerin and water. The AuNPs colloids exhibit a UV-Vis absorption spectrum with a surface plasmon absorption peak at about 540 ± 20 nm. The thermal nonlinear optical responses of the gold colloids are measured using the Z-scan technique under low power CW laser irradiation at 532 nm near the surface plasmon peak of the nanoparticles. Our results show that the nonlinear refractive index of the nanoparticle colloids is considerably affected by the thermal conductivity of liquid medium. The largest nonlinear refractive index of −3.1 × 10–7 cm2 W−1 is obtained for AuNP in cyclohexanone with the lowest thermal conductivity of 0.14 W mK−1 whereas the lowest one of −0.1 × 10−7 cm2 W−1 is obtained for AuNP in water with the highest thermal conductivity of 0.60 W mK−1. This study shows that the nonlinear refractive index value of colloids can be controlled by the thermal conductivity of the used liquid’s environment. This allows us to design low threshold optical limiters by choosing a solution with low thermal conductivity for colloidal nanoparticles.

Thermal conductivity measurement of organic solvents incorporated with silver nanoparticle using photothermal techniques

The present paper summarizes our recent work on heat transfer of nanofluid in different organic solvents determined using photothermal techniques. UV- Visible absorption spectrum shows an intense surface plasmon absorption peak at 427 nm. TEM indicates the presence of well dispersed silver nanoparticles having spherical morphology with particle size ranging from 10 to13 nm. The experimental results show that thermal conductivity of organic solvents increases with the incorporation of silver nanoparticles.

Bio-functionalized silver nanoparticles: a novel colorimetric probe for cysteine detection.

Chemical interactions between nanoparticles and biomolecules are vital for applying nanoparticles in medicine and life science. Development of sensitive, rapid, low-cost, and eco-friendly sensors for the detection of molecules acting as disease indicator is need of an hour. In the present investigation, a green trend for silver nanoparticle synthesis was followed using leaf extract of Calotropis procera. Silver nanoparticles exhibited surface plasmon absorption peak at 421 nm, spherical shape with average size of 10 nm, and zeta potential of -22.4 mV. The as-synthesized silver nanoparticles were used for selective and sensitive detection of cysteine. Cysteine induces aggregation in stable silver nanoparticles owing to selective and strong interaction of -SH group of cysteine with silver nanoparticle surface. Cysteine-induced silver nanoparticle aggregation can be observed visually by change in color of silver nanoparticles from yellow to pink. Cysteine concentration was estimated colorimetrically by measuring absorption at surface plasmon wavelength. Limit of detection for cysteine using silver nanoparticles is ultralow, i.e., 100 nM. The mechanistic insight into cysteine detection by silver nanoparticles was investigated using FT-IR, TEM, DLS, and TLC analysis. Proposed method can be applied for the detection of cysteine in blood plasma and may give rise to a new insight into development of eco-friendly fabricated nanodiagnostic device in future.

Improvement of Silver Nanoparticles Synthesis by Monascus purpureus using Gamma Irradiation

Aqueous dispersion of highly stable silver nanoparticles were synthesized using gamma irradiation with Monascus purpureus supernatant molecules as reducing and stabilizing agent. The formation of Nano sized silver was confirmed by its characteristic surface Plasmon absorption peak around 420nm in UV-VIS spectra. The size of the silver nanoparticles can be turned by controlling the radiation dose and mixing method of AgNO solution with Monascus purpureus supernatant (irradiation process). Dynamic light scattering (DLS) measurement and Transmission electron microscope (TEM)of the synthesized nanoparticles indicated that the size depend on dose and irradiation process . The irradiation was carried out at doses from 1 to 25kGy . XRD analysis of the silver confirmed the formation of metallic silver. Fourier transform infra-red (FTIR) spectroscopic data indicate abounding of Ag nanoparticles with Monascus purpureus supernatant molecules. The obtained Ag nanoparticle dispersion was stable for over 3 months at room temperature.

Effect of annealing on the surface plasmon resonance of dodecanethiol encapsulated gold nanoparticles Langmuir–Schafer thin films

The effect of annealing time on the optical properties of dodecanethiol encapsulated gold (C12-Au) nanoparticles with 3.04nm in diameter was studied. Monolayer and multilayer films were prepared by the Langmuir–Schafer (LS) deposition method. The films’ morphology and their optical properties were investigated by AFM and absorption spectroscopy respectively. The growth of elongated structures was observed in the as-deposited gold films especially at higher thicknesses with dimensions of about 4nm in thickness and 100 to 400nm in length and increased with the number of layers. The change in the films’ morphology with annealing time was very significant at higher thicknesses. Annealed films showed sharp surface plasmon (SP) absorption peak, which increased with increasing annealing time. Annealing for 30min caused redshift in the SP absorption peak for all thicknesses, however, a blue shift was observed when the films were annealed for 60min. No further significant change in the SP position was observed at higher annealing time.

Synthesis and characterization of monodisperse copper nanoparticles using gum acacia

A simple method was put forward in this paper for preparing colloidal copper nanoparticles in aqueous solutions using copper sulfate, gum acacia and hydrazine hydrate as copper precursor, capping agents and reducing agents, respectively, without any inert gas. The formation of nanosized copper was confirmed by its characteristic surface plasmon absorption peak at 604nm in UV–vis spectra. The transmission electron microscopic (TEM) and scanning electron microscope (SEM) images show that the as-synthesized copper fine spherical particles are distributed uniformly with a narrow distribution from 3nm to 9nm. The X-ray diffraction (XRD) and high resolution transmission electron microscopic (HRTEM) demonstrated that the obtained metallic nanoparticles are single crystalline copper nanoparticles. Fourier transform infra-red (FT-IR) spectroscopic data suggested that the copper nanoparticles are coated with gum acacia. The effects of the quantity of gum acacia on the particle size were investigated by the UV–vis spectra and TEM images. The growth process of the nanoparticles was monitored by the UV–vis spectra. The mechanism of the formation copper nanoparticles was discussed. The process raised in this study can be served as an excellent candidate for the preparation of copper nanoparticles in a large scale production.

Plasmonic excitations in quantum-sized sodium nanoparticles studied by time-dependent density functional calculations

The plasmonic properties of sphere-like bcc Na nanoclusters ranging from Na$_{15}$ to Na$_{331}$ have been studied by real-time time-dependent local density approximation calculations. The optical absorption spectrum, density response function and static polarizability are evaluated. It is shown that the effect of the ionic background (ionic species and lattice) of the clusters accounts for the remaining discrepancy in the principal (surface plasmon) absorption peak energy between the experiments and previous calculations based on a jellium background model. The ionic background effect also pushes the critical cluster size where the maximum width of the principal peak occurs from Na$_{40}$ predicted by the previous jellium model calculations to Na$_{65}$. In the volume mode clusters (Na$_{27}$, Na$_{51}$, Na$_{65}$, Na$_{89}$ and Na$_{113}$) in which the density response function is dominated by an intense volume mode, a multiple absorption peak structure also appears next to the principal peak. In contrast, the surface mode clusters of greater size (Na$_{169}$, Na$_{229}$, Na$_{283}$ and Na$_{331}$) exhibit a smoother and narrower principal absorption peak because their surface plasmon energy is located well within that of the unperturbed electron-hole transitions, and their density responses already bear resemblance to that of classical Mie theory. Moreover, it is found that the volume plasmon that exist only in finite size particles, gives rise to the long absorption tail in the UV region. This volume plasmon manifests itself in the absorption spectrum even for clusters as large as Na$_{331}$ with an effective diameter of $\sim$3.0 nm.