Absorption Of Nanoparticles Research Articles

Nano-molar to milli-molar level Ag (I) determination using absorption of light by ZnS QDs without organic ligand

Despite of useful applications of Ag, it is hazardous to health and environment and hence early detection is required. Crystal defects influencing optical property is less likely utilized for Ag detection using prevalent UV–vis technique. Quantum dots (QDs) ZnS prepared by soft chemical route are exploited for the detection of Ag+ in aqueous solution for nM to mM concentrations. UV–vis and photoluminescence (PL) measurements reveal quantum confinement effect and presence of defects in ZnS nanoparticles (NPs). Controlled synthesis of ZnS NPs allows appearance of defects related peak at 400–550 nm in UV–vis spectra. A plausible mechanism is presented and elucidated by XRD and PL studies for chemical interaction between ZnS with Ag+. The interaction affects prominently the defects related absorption of ZnS NPs and allows single step Ag+ detection in aqueous medium. This absorption method is extended to other ions (Na+, K+, Mg+, Ca+, Ba+) including ‘S’ prone heavy and toxic ions like Pb, Hg, and Cd. Among them, Ag+ shows the best response with ZnS NPs. This demonstration using a portable and cost effective technique with no organic component opens up possibility for other inorganic materials.

Effects of Interactions between ZnO Nanoparticles and Saccharides on Biological Responses.

Zinc oxide (ZnO) nanoparticles (NPs) are widely used as a Zn supplement, because Zn plays a role in many cellular and immune functions but public concern about their potentially undesirable effects on the human body is growing. When NPs are added in food matrices, interactions between NPs and food components occur, which can affect biological systems. In this study, interactions between ZnO NPs and saccharides were investigated by measuring changes in hydrodynamic radius, zeta potential and solubility and by quantifying amounts of adsorbed saccharides on NPs; acacia honey, sugar mixtures (containing equivalent amounts of fructose, glucose, sucrose and maltose) and monosaccharide solutions were used as model compounds. Biological responses of NPs dispersed in different saccharides were also evaluated in human intestinal cells and rats in terms of cytotoxicity, cellular uptake, intestinal transport and oral absorption. The results demonstrate that the hydrodynamic radii and zeta potentials of NPs were highly affected by saccharides. In addition, trace nutrients influenced NP/saccharide interactions and interactive effects between saccharides on the interactions were found. NPs in all saccharides increased inhibition of cell proliferation and enhanced cellular uptake. Oral absorption of NPs was highly enhanced by 5% glucose, which is in-line with intestinal transport result. These findings show that ZnO NPs interact with saccharides and these interactions affects biological responses.

Light-enabled reversible self-assembly and tunable optical properties of stable hairy nanoparticles

The ability to dynamically organize functional nanoparticles (NPs) via the use of environmental triggers (temperature, pH, light, or solvent polarity) opens up important perspectives for rapid and convenient construction of a rich variety of complex assemblies and materials with new structures and functionalities. Here, we report an unconventional strategy for crafting stable hairy NPs with light-enabled reversible and reliable self-assembly and tunable optical properties. Central to our strategy is to judiciously design amphiphilic star-like diblock copolymers comprising inner hydrophilic blocks and outer hydrophobic photoresponsive blocks as nanoreactors to direct the synthesis of monodisperse plasmonic NPs intimately and permanently capped with photoresponsive polymers. The size and shape of hairy NPs can be precisely tailored by modulating the length of inner hydrophilic block of star-like diblock copolymers. The perpetual anchoring of photoresponsive polymers on the NP surface renders the attractive feature of self-assembly and disassembly of NPs on demand using light of different wavelengths, as revealed by tunable surface plasmon resonance absorption of NPs and the reversible transformation of NPs between their dispersed and aggregated states. The dye encapsulation/release studies manifested that such photoresponsive NPs may be exploited as smart guest molecule nanocarriers. By extension, the star-like block copolymer strategy enables the crafting of a family of stable stimuli-responsive NPs (e.g., temperature- or pH-sensitive polymer-capped magnetic, ferroelectric, upconversion, or semiconducting NPs) and their assemblies for fundamental research in self-assembly and crystallization kinetics of NPs as well as potential applications in optics, optoelectronics, magnetic technologies, sensory materials and devices, catalysis, nanotechnology, and biotechnology.

Optical characterization of surface plasmon resonance of Pt nanoparticles in TiO2-SiO2 nanocomposite films

The surface plasmon resonance (SPR) of Pt nanoparticles (NPs) in TiO2-SiO2 nanocomposite films, in which Pt NPs of about 5 nm are incorporated, is investigated by using spectroscopic ellipsometry. After obtaining the dielectric functions of Pt NPs from the Pt-SiO2 nanocomposite film, Pt-TiO2-SiO2 nanocomposite films are analyzed by applying a homogenous single layer model with an effective medium approximation. The effects of Pt NPs on the optical properties of the nanocomposite films are clearly revealed in the imaginary part of the dielectric functions, showing an increase in broadband absorption near the band gap of the films with the increasing volume fraction of Pt NPs in the films. Particularly, the maximum of extinction cross-section of Pt NPs in the films coincides with the broadband absorption, indicating that the localized SPR of Pt NPs is responsible for the enhanced light absorption at the visible-light wavelengths. This work emphasizes that, although SPR absorption of Pt NPs is not so distinctive in the visible-light wavelengths, proper tuning of the dielectric environment as well as the volume fraction of Pt NPs can enhance the photoactivity of the nanocomposite films.

Nano and bulk ZnO trigger diverse Zn-transport-related gene transcription in distinct regions of the small intestine in mice after oral exposure

The oral ingestion of ZnO nanoparticles (NPs) has attracted considerable attention because of the wide usage in food packaging and additives. The small intestine is the major absorption site for ZnO NPs. Unfortunately, studies on the absorption of ZnO NPs in the GIT were still scarce. This study evaluated the absorption characteristics of ZnO NPs (30 nm) and bulk ZnO (rod morphology with a mean size of 139–846 nm). Results showed that ZnO NPs and bulk ZnO were absorbed and redistributed in various organs of mice at 4 h after exposure. Significantly higher levels of MT1 were observed in the duodenums of bulk ZnO and ZnO NPs groups than those of the control (9.8 and 5660.11 fold increases, respectively). The MT4 levels in the bulk ZnO and ZnO NPs groups also showed 4.07 and 43.21fold increases, respectively. In addition, the transcript levels of ZIPs, ZnTs, and MTs in the jejunum of bulk ZnO group were higher than those of ZnO NPs group. And the transcript levels of ZIPs, ZnTs, and MTs were all lower in the ileum than in the jejunum. The results suggested that ZnO NPs were mainly absorbed in the duodenum in the form of particles and can be absorbed as Zn2+ in the jejunum and secondly in the ileum. By contrast, bulk ZnO was more easily absorbed as Zn2+ in the jejunum and secondly in the ileum.

Amplified singlet oxygen generation in metallated-porphyrin doped conjugated polymer nanoparticles

We report on the mechanism and efficiencies of singlet oxygen O2(1Δg) generation of nanoparticles (NP) of the conjugated polymer (CP) poly(9,9-dioctylfluorene-alt-benzothiadiazole) (F8BT) doped with platinum octaethylporphyrin (PtOEP) suspended in water. A detailed study of the photophysics of these NP, using stationary and time-resolved absorption and emission techniques, indicates that O2(1Δg) is generated by the triplet excited state of F8BT and not by that of PtOEP, as previously observed for other porphyrin doped CP NP. O2(1Δg) quantum yields (ΦΔ) were measured by quantifying the characteristic phosphorescence of O2(1Δg) in the NIR region (∼1268 nm). It was found that incorporation of relatively small amounts of PtOEP to F8BT NP results in a significant increase of ΦΔ. NP containing 10% PtOEP (w/w) show a ΦΔ ∼ 0.24, which is 3 times larger than that observed for undoped F8BT NP, and larger than the reported for most water-soluble porphyrins. ΦΔ were also calculated from the oxidation rates (v0) of 3-[10-(2-carboxyethyl)anthracen-9-yl]propanoic acid (ADPA), a well-known chemical O2(1Δg) trap. Unexpectedly, this method was found to significantly overestimate the ΦΔ values due to the adsorption of ADPA on the surface of NP. The ADPA/NP adsorption process was characterized using a simple adsorption model yielding an (average) equilibrium constant of ∼8 × 103 M−1 and an (average) number of NP-binding sites of ∼14000. These results necessarily caution about the use of ADPA as a probe to evaluate ΦΔ in these NP systems. In addition, the interaction of F8BT NP with other anionic, cationic and zwitterionic dyes (dissolved in water) was studied. It was found that even at nano-molar concentrations all the dyes efficiently adsorb on the NP surface. This general and simple self-assembly strategy can be used to prepare superficially-dye-doped CP NP with potentially interesting technological applications.

Tunable Black Gold: Controlling the Near‐Field Coupling of Immobilized Au Nanoparticles Embedded in Mesoporous Silica Capsules

AbstractEfficient light‐to‐heat conversion is central for various applications such as thermo‐photovoltaics and solar steam generation. Although metals can strongly absorb light and generate heat, their free electrons shield the electric field before any substantial penetration in the metal. Excitation of surface plasmons can suppress metal reflection and convert it into a black metal, for example, black gold. In this work, mesoporous silica capsules grafted with immobilized Au nanoparticles (NPs) with different sizes via controlled chemical synthesis are synthesized. It is shown that changing the size of immobilized NPs modifies the interparticle coupling strength, thus, modifying the NPs absorption. The broadness of the plasmon resonance is tuned across the visible, near‐infrared, and short wavelength infrared regions. The ability to control the broadness of black gold absorption is not possible in other systems based on bottom‐up synthesis. The proposed approach broadens the possibilities of utilizing black gold in many applications such as thermo‐photovoltaics, and solar energy harvesting especially in hybrid solar converters.

Dependence of Nonlinear Optical Response of Anatase TiO2 on Shape and Excitation Intensity**Supported by the National Natural Science Foundation of China under Grant Nos 11404410 and 11504105.

Nonlinear optical (NLO) properties of anatase TiO2 with nanostructures of nanoparticle (NP), nanowire (NW) and annealed nanowire (NWA) are studied by open-aperture and closed-aperture Z-scan techniques with a femtosecond pulsed laser at wavelengths of 532 nm and 780 nm simultaneously. At 532 nm, when increasing excitation intensity, NLO absorption of TiO2 NPs transforms from saturable absorption to reverse-saturable absorption. However, NWs and NWAs exhibit the opposite change. At 780 nm, all samples show reverse-saturable absorption, but have different sensitivities to excitation intensity. Due to the larger surface-to-volume ratio of NPs and less defects of NWAs by annealing, nonlinear optical absorption coefficients follow the order NPs NWs NWAs. The results also show that these shape and annealing effects are dominant at low excitation intensity, but do not exhibit at the high excitation intensity. The NLO refractive index of NPs shows a positive linear relationship with the excitation intensity, whereas NW and NWAs exhibit a negative linear relationship. The results could provide some foundational guidance to applications of anatase TiO2 in optoelectronic devices or other aspects.

Biokinetic study of selenium nanoparticles and salt forms in living organisms

An experimental study of absorption, distribution, metabolism, and excretion from the body of radioisotope-labeled nanoparticles (NPs) of elemental Se in comparison with the traditional form of this trace element (sodium selenite) has been performed, being administered in the gastrointestinal tract of rats that were normally supplied with Se or experiencing its nutritional deficiency. Nuclear activation analysis is used for the detection of Se in the biological tissue, which is based on the measurement of a gamma-emitting label [75Se34] that is introduced in the Se NPs or its salt by thermal neutron irradiation in a nuclear reactor. It is shown that Se NPs administered into the gastrointestinal tract have bioavailability comparable to the salt form of this element. According to some experimental data, the metabolic assimilation of both forms of Se is greater in animals that suffer from a deficiency in this element when compared to those that are normally supplied with it. There are some differences in the kinetics of accumulation of Se NPs and its salts in the blood and liver, which can be explained by the presence of limiting steps in the absorption and biotransformation of Se-containing NPs. The retention of Se that is administered in the form of NPs or salts to Se-deficient animals differs significantly. These results demonstrate the capacity of the Se NPs to be a source of Se in a new generation of biologically active food supplements.

Preparation and characterization of CdS coated multiwalled carbon nanotubes

In this work, we described a simple method to prepare cadmium sulfide (CdS) nanoparticles (NPs) coated multi-walled carbon nanotubes (MWCNTs). The hexagonal phase of CdS NPs coated on MWCNTs has been detected form the X-ray diffraction (XRD) analysis. The results of transmission electron microscopy (TEM) portray a dense coating of spherical CdS NPs on the MWCNT surface with the diameter in the range of 4–8nm. Fourier transform infrared (FTIR) study indicates that the functionalized MWCNT surface is bounded chemically to the CdS NPs via carboxylate. The optical absorption of CdS NPs coated MWCNTs displays a significant improvement compared with the functionalized MWCNTs.

Plasmon resonance induced photoconductivity of ZrO2(Y) films with embedded Au nanoparticles

We report on the experimental observation of photoconductivity (PC) in ultrathin (≈ 40 nm thick) ZrO2(Y) films with single layered arrays of Au nanoparticles (NPs) of 1 to 3 nm in diameter. The samples were prepared by the deposition of islanded Au films of ∼1 nm in thickness sandwiched between two ZrO2(Y) layers by Magnetron Sputtering followed by annealing. The effect of PC was attributed to the photoexcitation of the collective plasmon oscillations in dense Au NP arrays. The temperature dependencies and kinetics of PC have been studied. At 300 K, the PC has been found to originate mainly from heating of ZrO2(Y) due to plasmon optical absorption in Au NPs (the bolometric effect). At 77 K, the photoresponse has been attributed to plasmon-assisted electron transport between NPs via the vacancy α-band in ZrO2(Y) barriers.

Metal nanoparticles induced photocatalysis

Abstract Photocatalysis induced by light absorption of metal nanoparticles (NPs) has emerged as a promising strategy for exploiting efficient visible-light-responsive composites for solar-energy conversion. In this review, we first introduce the light absorption of metal NPs and the mechanisms proposed in metal-induced photocatalysis (MIP). Then, its applications in water splitting, artificial photosynthesis and inert molecular activation are summarized. To address the challenge of low efficiency in this field, strategies in promoting catalytic activity are reviewed, and particular attention is paid to the particle-size effect of metal. Finally, the challenges and possible development directions of MIP are briefly discussed.

Enhanced optical absorption in semiconductor nanoparticles enabled by nearfield dielectric scattering

The optical absorption of semiconducting AgBr nanocubes is significantly increased by up to 5 times in the measured spectral range when they are bonded to the surface of dielectric SiO2 nanospheres through electrostatic interaction. The absorption enhancement factor depends on the wavelength and the size of the SiO2 nanoparticles (NPs). Finite-difference time-domain calculations provide the nearfield intensity mapping of a heterostructure that is composed of a AgBr nanocube in close contact with a SiO2 nanosphere. The electric-field distributions indicate the field enhancement near the SiO2/AgBr interface due to light scattering and absorption enhancement in the AgBr nanocube, implying that the enhanced scattering nearfield increases the absorption cross section of the AgBr nanocube. The absorption cross-section spectra calculated using Mie theory agree with the experimental observations. This discovery sheds light on the utilization of dielectric spherical particles to increase the absorption in semiconductor NPs, thus improving the light-harvesting efficiency for solar-energy conversion.

Titanium Dioxide Nanoparticle-Biomolecule Interactions Influence Oral Absorption.

Titanium dioxide (TiO2) nanoparticles (NPs) have been widely applied in various industrial fields, such as electronics, packaging, food, and cosmetics. Accordingly, concerns about the potential toxicity of TiO2 NPs have increased. In order to comprehend their in vivo behavior and potential toxicity, we must evaluate the interactions between TiO2 NPs and biomolecules, which can alter the physicochemical properties and the fate of NPs under physiological conditions. In the present study, in vivo solubility, oral absorption, tissue distribution, and excretion kinetics of food grade TiO2 (f-TiO2) NPs were evaluated following a single-dose oral administration to rats and were compared to those of general grade TiO2 (g-TiO2) NPs. The effect of the interactions between the TiO2 NPs and biomolecules, such as glucose and albumin, on oral absorption was also investigated, with the aim of determining the surface interactions between them. The intestinal transport pathway was also assessed using 3-dimensional culture systems. The results demonstrate that slightly higher oral absorption of f-TiO2 NPs compared to g-TiO2 NPs could be related to their intestinal transport mechanism by microfold (M) cells, however, most of the NPs were eliminated through the feces. Moreover, the biokinetics of f-TiO2 NPs was highly dependent on their interaction with biomolecules, and the dispersibility was affected by modified surface chemistry.

Consideration of interaction between nanoparticles and food components for the safety assessment of nanoparticles following oral exposure: A review.

Nanoparticles (NPs) are increasingly used in food, and the toxicity of NPs following oral exposure should be carefully assessed to ensure the safety. Indeed, a number of studies have shown that oral exposure to NPs, especially solid NPs, may induce toxicological responses both in vivo and in vitro. However, most of the toxicological studies only used NPs for oral exposure, and the potential interaction between NPs and food components in real life was ignored. In this review, we summarized the relevant studies and suggested that the interaction between NPs and food components may exist by that 1) NPs directly affect nutrients absorption through disruption of microvilli or alteration in expression of nutrient transporter genes; 2) food components directly affect NP absorption through physico-chemical modification; 3) the presence of food components affect oxidative stress induced by NPs. All of these interactions may eventually enhance or reduce the toxicological responses induced by NPs following oral exposure. Studies only using NPs for oral exposure may therefore lead to misinterpretation and underestimation/overestimation of toxicity of NPs, and it is necessary to assess the synergistic effects of NPs in a complex system when considering the safety of NPs used in food.

Bioavailability enhancement, Caco-2 cells uptake and intestinal transport of orally administered lopinavir-loaded PLGA nanoparticles

Nanoparticles (NPs) can be absorbed via M cells of Peyer’s patches after oral delivery leading to passive lymphatic targeting followed by systemic drug delivery. Hence, the study was aimed to formulate PLGA NPs of lopinavir. The NPs were prepared by nanoprecipitation, optimized by 33 factorial design and characterized by TEM, DSC, FTIR studies and safety was assessed by MTT assay. In vivo pharmacokinetic studies were performed in rats. The NPs were discrete spherical structures having particle size of 142.1 ± 2.13 nm and entrapment of 93.03 ± 1.27%. There was absence of drug-polymer interaction. Confocal images revealed the penetration and absorption of coumarin-loaded NPs in Caco-2 cells and intestine after oral delivery. There was 3.04 folds permeability and 13.9 folds bioavailability enhancement from NPs. The NPs can be promising delivery system for antiretroviral drug by delivering the drug to lymph (major HIV reservoir site) via direct absorption through intestine before reaching systemic circulation.

Developments in Methods for Measuring the Intestinal Absorption of Nanoparticle-Bound Drugs

With the rapid development of nanotechnology, novel drug delivery systems comprising orally administered nanoparticles (NPs) have been paid increasing attention in recent years. The bioavailability of orally administered drugs has significant influence on drug efficacy and therapeutic dosage, and it is therefore imperative that the intestinal absorption of oral NPs be investigated. This review examines the various literature on the oral absorption of polymeric NPs, and provides an overview of the intestinal absorption models that have been developed for the study of oral nanoparticles. Three major categories of models including a total of eight measurement methods are described in detail (in vitro: dialysis bag, rat gut sac, Ussing chamber, cell culture model; in situ: intestinal perfusion, intestinal loops, intestinal vascular cannulation; in vivo: the blood/urine drug concentration method), and the advantages and disadvantages of each method are contrasted and elucidated. In general, in vitro and in situ methods are relatively convenient but lack accuracy, while the in vivo method is troublesome but can provide a true reflection of drug absorption in vivo. This review summarizes the development of intestinal absorption experiments in recent years and provides a reference for the systematic study of the intestinal absorption of nanoparticle-bound drugs.

Ag Nanoparticle-Sensitized WO3 Hollow Nanosphere for Localized Surface Plasmon Enhanced Gas Sensors.

Ag nanoparticle (NP)-sensitized WO3 hollow nanospheres (Ag-WO3-HNSs) are fabricated via a simple sonochemical synthesis route. It is found that the Ag-WO3-HNS shows remarkable performance in gas sensors. Field-emission scanning electron microscope (FE-SEM) and transmission electron microscope (TEM) images reveal that the Agx-WO3 adopts the HNS structure in which WO3 forms the outer shell framework and the Ag NPs are grown on the inner wall of the WO3 hollow sphere. The size of the Ag NPs can be controlled by adjusting the addition amount of WCl6 during the reaction. The sensor Agx-WO3 exhibits extremely high sensitivity and selectivity toward alcohol vapor. In particular, the Ag(15nm)-WO3 sensor shows significantly lower operating temperature (230 °C), superior detection limits as low as 0.09 ppb, and faster response (7 s). Light illumination was found to boost the sensor performance effectively, especially at 405 and 900 nm, where the light wavelength resonates with the absorption of Ag NPs and the surface oxygen vacancies of WO3, respectively. The improved sensor performance is attributed to the localized surface plasmon resonance (LSPR) effect.

Aggravated hepatotoxicity occurs in aged mice but not in young mice after oral exposure to zinc oxide nanoparticles

The potential toxic effects of nanoparticles (NPs) might be more severe in susceptible populations such as the elderly. To confirm such effects, we built an aged mouse model and evaluated the effects after giving model mice oral doses of zinc oxide (ZnO) NPs. We observed enhanced ZnO NP absorption in aged mice compared with young mice most likely because of an age-related increase in intestinal permeability. The liver deposition of ZnO NPs was higher in aged mice compared with young mice. As a result, liver injuries were observed in aged mice, whereas young mice were not affected. ZnO NPs induced increases in oxidative stress and inflammation levels in both aged and young mice. Because aged mice have already endured age-related increases in oxidative stress and inflammation, ZnO NPs caused additional damage and resulted in acute liver injury. The above evidence suggests that the elderly are more vulnerable to NP exposure, and more caution should be taken with regard to the application of or accidental exposure to ZnO NPs among the elderly.

The MTT and Crystal Violet Assays: Potential Confounders in Nanoparticle Toxicity Testing.

The toxicological effects of nanoparticles (NPs) on humans, animals, and environment are largely unknown. Assessment of NPs cytotoxicity depends on the choice of the test system. Due to NPs optical activity and absorption values, they can influence the classical cytotoxicity assay. Eight NPs were spiked in the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and crystal violet assays and tested with HaCaT human skin cells. The MTT assay standard curve optical density (OD) measurements were altered by the presence of trisilanol phenyl and trisilanol isooctyl polyhedral oligomeric silsesquioxane particles. The crystal violet standard curve OD measurements were significantly shifted by gold NPs, but they did not affect the MTT assay. Carbon black decreased ODs in the MTT and crystal violet assays and was localized in the cell cytoplasm. These findings strongly indicate that a careful choice of in vitro viability systems is required to avoid flawed measurement of NPs toxicity.