Effect Of Nanoparticles Research Articles

Uptake and Effects of Nanoplastics on the Dinoflagellate Gymnodinium corollarium.

Plastic nanoparticles (NPs) are the final state of plastic degradation in the environment before they disintegrate into low-molecular-weight organic compounds. Unicellular organisms are highly sensitive to the toxic effects of nanoplastics, because they are often capable of phagotrophy but are unable to consume a foreign material such as synthetic plastic. We studied the effect of polystyrene, poly(vinyl chloride), poly(methyl acrylate), and poly(methyl methacrylate) NPs on the photosynthetic dinoflagellate Gymnodinium corollarium Sundström, Kremp et Daugbjerg. Fluorescent tagged particles were used to visualize plastic capture by dinoflagellate cells. We found that these dinoflagellates are capable of phagotrophic nutrition and thus should be regarded as mixotrophic species. This causes their susceptibility to the toxic effects of plastic NPs. Living cells ingest plastic NPs and accumulate in the cytoplasm as micrometer-level aggregates, probably in food vacuoles. The action of nanoplastics leads to a dose-dependent increase in the level of reactive oxygen species in dinoflagellate cells, indicating plastic degradation in the cells. The introduction of a methyl group into the main chain in the α-position in the case of poly(methyl methacrylate) causes a drastic reduction in toxicity. We expect that such NPs can be a tool for testing unicellular organisms in terms of heterotrophic feeding ability. We suggest a dual role of dinoflagellates in the ecological fate of plastic waste: the involvement of nanoplastics in the food chain and its biochemical destruction. Environ Toxicol Chem 2023;42:1124-1133. © 2023 SETAC.

Au/ZnO Nanocomposites Prepared by Laser Ablation for Enhancement of Antibacterial Activity and Cytotoxic Properties against Cancer Cells

This study presents a comprehensive look into the potential therapeutic, antibacterial, and anticancer properties of a nanocomposite (NC) of gold (Au) and zinc oxide (ZnO). In this study, we analyzed the adherence between Au nanoparticles (NPs) and ZnO NPs. X-ray diffraction analysis showed high crystallinity and small crystallite sizes of Au NPs and ZnO NPs, while transmission electron microscopy showed spherical NPs. Furthermore, histogram analysis showed that the average particle size of Au NPs is 27 nm, while that of ZnO NPs is 35 nm. The adherence of ZnO NPs on the surface of Au NPs increased their combined particle size to 51 nm and revealed a high-population core-shell structure. The activity of Au/ZnO NCs against Escherichia coli was more potent when compared to that of elemental Au and ZnO NPs alone. The cytotoxic effects of Au NPs, ZnO NPs, and Au/ZnO NCs against human breast cancer cells (AMG13) and human esophageal adenocarcinoma cancer cells (SK-GT4) were investigated in this study. We found that AMG13 is more sensitive than SK-GT4 to the activity of Au/ZnO NCs. The cytotoxicity of Au/ZnO NCs against AMG13 was 89%, while that against SK-GT4 was 85%. Less cytotoxic effects were recorded against normal cells (MCF7) when compared with those of cancer cells. Based on these findings, the synthesized Au/ZnO NCs could be used as a promising strategy for biomedical applications.

Noble metal nanoparticles functionalized conductive Co3(hexaiminotriphenylene)2 chemiresistor for hydrogen sulfide detection at Room-Temperature

Metal-organic frameworks (MOFs) applied in chemiresistors is principally limited by their poor conductivity and low catalytic activity. Herein, we report an intrinsically conductive two-dimensional (2D) MOF Co3(hexaiminotriphenylene)2 [Co3(HITP)2], for hydrogen sulfide (H2S) sensing at room temperature (RT). The proposed conductive Co3(HITP)2 sensor exhibits high sensitivity and good selectivity toward H2S under various relative humidity (RH) at RT. Meanwhile, different amounts of catalytic Pd nanoparticles (NPs) are embedded in conductive Co3(HITP)2 for further improving the gas sensing performances. The sensing results confirm that the 2 mol% Pd functionalized Co3(HITP)2 gas sensor presents the best sensing properties to H2S under different humidity at RT. We extended the catalytic metal NPs to Au and Pt, and Au or Pt loading conductive Co3(HITP)2 sensors also show remarkably enhanced H2S sensing performance including high response and low limit of detection (LOD). While, the pristine and noble metal NPs functionalized Co3(HITP)2 gas sensors are affected by humid atmosphere due to water vapor adsorption on Co3(HITP)2. Finally, the catalytic effect of noble metal NPs on conductive Co3(HITP)2 for H2S sensing is also discussed. The obtained results provide a key insight into the high-performance conductive Co3(HITP)2 based gas sensors work at RT for H2S detection.

Controlling the Self‐Assembly of Hierarchical PS‐b‐P4VP Structures Prepared by Dip‐Coating and Emulsion Breath Figure Techniques

AbstractThe breath figure (BF) method is a common laboratory‐scale pathway for fabricating porous structures. The emulsion BF approach, one of the BF variations, has attracted increasing attention since it bypasses the high humidity requirement, which is characteristic for the conventional BF method. In this paper, we used the emulsion BF technique with PS‐b‐P4VP block copolymer (BCP) and SiO2 nanoparticles (NPs) as the stabilizers for water droplets. We combined this with the dip‐coating technique to obtain a hierarchical structure consisting of BF pores and BCP nanodomains. By altering the dip‐coating speeds and the NPs’ surface wetting properties and size, the average diameters of BF pores could be controlled. Notably, we were able to achieve both nano and microscale BF pores in the network. The effect of NPs for stabilization and dip‐coating parameters on BF pores and BCP nanodomains formation was established, extending the comprehension of this underdeveloped subject.

Evaluation of the Effect of the Size of Ramalina fraxinea Based Ag NPs on the Antimicrobial Activity

For the first time in this study, the effect of nanoparticles (NP) sizes on the antimicrobial activity of Ag NPs of different sizes obtained by the reaction of Ramalina fraxinea(R. fraxinea) extract and silver nitrate (AgNO3) at different concentrations was evaluated. For this purpose, characteristic light absorption points, and charge of the surface were determined by ultraviolet-visible spectroscopy (UV-Vis), and zeta potential, hydrodynamic diameters by dynamic light scattering (DLS) analysis, morphology, and diameters of NPs were determined by scanning electron microscope (SEM) analysis. The crystal structures of Ag NPs were confirmed by the X-ray diffraction (XRD) analysis map. The functional groups of the R. fraxinea extract, which plays an active role in the synthesis of Ag NP, were revealed by the peaks obtained by Fourier transform infrared spectroscopy (FT-IR) analysis. As a result of the characterization tests, the average diameter of Ag NPs increased from 14 nm to 48 nm with the increase in Ag NO3 concentration used in the synthesis of Ag NP (from 10-3 M to 5*10-2 M). The antimicrobial activity of Ag NPs against Staphylococcus aureus, Escherichia coli, and Candida albicans strains was evaluated depending on the size of the NPs. The antimicrobial effect of small-sized Ag NPs against the studied strains was quite effective compared to large-sized Ag NPs. As a result, it is seen that Ag NPs synthesized by using R. fraxinea extract in different sizes with a biologically inexpensive and eco friendly method exhibit antimicrobial activity depending on the size. It is thought that the study data will be a guide for nanotechnology and biomedical field studies.

Ocean acidification enhances the embryotoxicity of CuO nanoparticles to Oryzias melastigma

Concerns are raised towards individual effects of ocean acidification (OA) and engineered nanoparticles (NPs) on marine organisms. However, there are scarce studies regarding nanotoxicity under OA conditions. We investigated the combined effects of OA (pHs, 7.70 and 7.40) and CuO NPs on the embryotoxicity of marine medaka Oryzias melastigma and the bioavailability of CuO NPs in embryos. The results showed that OA alleviated the aggregation of CuO NPs and promoted the dissolution of CuO NPs in seawater (increased by 0.010 and 0.029 mg/L under pHs 7.70 and 7.40, respectively). Synergistic effects of OA with CuO NPs on medaka embryos were observed as indicated by much higher mortality and oxidative damage. Importantly, the enhanced toxicity of CuO NPs to medaka embryos under OA conditions mainly originated from the higher bioavailability of particulate CuO (e.g., 30.28 mg/kg at pH 7.40) rather than their released Cu2+ ions (e.g. 3.04 mg/kg at pH 7.40). The weaker aggregation of NPs under OA conditions resulted in higher penetration of individual particles (or small aggregates) into embryos through the micropyle and chorionic pores, causing enhanced bioavailability of NPs. The obtained results provided underlying insights into understanding the risk of NPs to marine ecosystem under OA conditions.

Assessment the Ag and ZnO Biosynthesized Nanoparticles effects on Giardia lamblia trophozoites which grown in HSP-1 culture media

Chemotherapy with drugs such as Metronidazole (MTZ) derivative products is currently the preferred treatment for giardiasis. However, these agents have been linked to a variety of negative side effects, varying from nausea to probable geno toxicity. Aim of this study to conduct an in vitro study on the efficiency of silver (Ag) and zinc oxide (ZnO) nanoparticles (NPs) biosynthesized by green ecofriendly method using Pseudomonas aeruginosa and Escherichia coli against Giardia trophozoites. Methods Silver and Zinc oxide NPs formation was confirmed based on ability of selected bacteria to biosynthesized these NPs. The particle size arranges of (29.5 nm) for Ag P. aeruginosa and (32 nm) for Ag E. coli. Particle size of ZnO for P. aeruginosa was (25 nm) and (29.7nm) for E. coli. Giardia trophozoites cultivated on HSP-1 media were subjected to different concentration of biosynthesized NPs at (0.025, 0.050, 0.075 mg/ml) for (24, 48, 72 hrs.). Significant reduction (P<0.05) in trophozoite number was recorded by the two groups of Ag and ZnO nanoparticles for both bacteria and was 91% for Ag NPs for both E. coli and P. aeruginosa and 73% for ZnO for both bacteria at concentration of 0.075mg/ml after 72 hrs. Morphological difference appeared as destructive with the release of the cytoplasm outside. The cytotoxic effects of Ag and ZnO NPs on Giardia lamblia trophozoite exceeded that of metronidazole, these particles can be recommended for use, especially at higher concentrations that lead to total death rates.

The synergy of Pd nanoparticles and oxygen vacancy to modulate SnO2 modified reduced graphene oxide hybrids for room-temperature ppb-level NO2 detection

Reduced graphene oxides (RGO)-based materials exhibit high carrier mobility and selective recognition ability to NO2, making them constitute promising platform for room-temperature NO2 detection. However, the low sensitivity becomes the main bottleneck for their further development. Here, we demonstrate that synergy of Pd nanoparticles (NPs) and oxygen vacancies can modulate the surface active sites over SnO2 NPs modified RGO hybrids (labeled as SR), leading to improving the sensitivity of room-temperature NO2 sensors. Experimentally, a wet-chemical method was used to introduce oxygen vacancies onto SR, leading to forming SR with rich oxygen vacancies (labeled as SR-Vo), which were subsequently deposited with Pd NPs, resulting in preparing Pd NPs loaded SR-Vo hybrids (labeled as Pd-SR-Vo). Impressively, the response value to 1 ppm NO2 of Pd-SR-Vo hybrids reaches to 9.8, which is much higher than that of R-Vo hybrids (5.6) and SR hybrids (3.3). The improvement of sensitivity toward NO2 for Pd-SR-Vo hybrids is attributed to the synergy effect of Pd NPs and oxygen vacancies, including shortening the band gap of Pd-SR-Vo hybrids with raising conduction band level, widening the width of electron depletion layer between SnO2-Vo and RGO, introducing Schottky contact between Pd and SnO2-Vo, improving efficiency for gas sensing reaction. This work not only provides an efficient approach to fabricate high-performance NO2 sensors, but also opens a new avenue for sensing materials design and modification.

Evaluation and prediction of rise velocity and drag coefficient of an ascending bubble affected by the impurity in continuous and discrete phases, distinctly and concurrently

Obtaining a deep knowledge about the bubbly flow systems, which are widely applied in various chemical and industrial processes, is crucial for scholars and engineers to achieve more accurate equipment design and processes control. This paper is dedicated to experimentally investigate the distinctly and concurrently effects of fumed silica nanoparticles (NPs) and hexane vapor molecules as impurities in continuous and discrete phases, respectively, on the terminal velocity and drag coefficient of a single rising bubble in aqueous solutions. The obtained experimental data were compared to the calculated data by derived correlations in literatures. As a result, none of those can predict the experimental data and a new correlation for considering the SiO2 NPs as an impurity in liquid is required. As a novelty, this work proposed two new correlations for prediction of terminal velocity and drag coefficient of a rising bubble in NPs solutions as a function of NPs concentration in aqueous solutions. The proposed correlations of terminal velocity and drag coefficient are in excellent agreements with the experimental data over the range of Re <310 and We <1.8, and with the maximum average relative errors of about 0.5% and 1.3%, respectively. Moreover, an interesting synergistic effect at the bubble interface was shown, due to creation of hexane oily layer at the interface and its interaction with rotational and vibrational effects of NPs in 200 ppm solution, where the exerted drag force on the rising bubble was reduced by 12.5% in comparison to the pure water (Air) case.

Influence of Fe2O3 Nanoparticles on the Anaerobic Digestion of Macroalgae Sargassum spp.

The anaerobic digestion (AD) of biomass is a green technology with known environmental benefits for biogas generation. The biogas yield from existing substrates and the biodegradability of biomasses can be improved by conventional or novel enhancement techniques, such as the addition of iron-based nanoparticles (NPs). In this study, the effect of different concentrations of Fe2O3-based NPs on the AD of brown macroalga Sargassum spp. has been investigated by 30 days trials. The effect of NPs was evaluated at different concentrations. The control sample yielded a value of 80.25 ± 3.21 NmLCH4/gVS. When 5 mg/g substrate and 10 mg/g substrate of Fe2O3 NPs were added to the control sample, the yield increased by 24.07% and 26.97%, respectively. Instead, when 50 mg/g substrate of Fe2O3 NPs was added to the control sample, a negative effect was observed, and the biomethane yield decreased by 38.97%. Therefore, low concentrations of Fe2O3 NPs favor the AD process, whereas high concentrations have an inhibitory effect. Direct interspecies electron transfer (DIET) via Fe2O3 NPs and their insolubility play an important role in facilitating the methanogenesis process during AD.

Ag NPs and MoS2 QDs double modified graphene/GaAs near-infrared photodetector

The light absorption enhancement ability of quantum dots (QDs) and the localized surface plasmon resonance (LSPR) effect of metal nanoparticles (NPs) can effectively improve the performance of photodetectors. In this paper, an Ag NPs and MoS2 QDs double modified graphene/GaAs near-infrared photodetector is investigated. The performance of the detector is improved by adopting the LSPR effect of Ag NPs and the dielectric confinement effect of MoS2 QDs. After subsequent testing and analysis, the photodetector responsivity is 21.1 mA W−1 and the detectivity is 8.4 × 1012 cm Hz1/2 W−1 at 808 nm wavelength; the responsivity and detectivity at 1064 nm wavelength can be up to 18.4 mA W−1 and 3.39 × 1012 cm Hz1/2 W−1, respectively. At the same time, under a 4 kHz pulsed illumination, the rise time and fall time are 15.87 μs and 89.95 μs respectively. Compared with previous devices, the new device has lower dark current and higher detectivity while having good responsivity and response time.

A mechanistic study of low salinity water-based nanoparticle-polymer complex fluid for improved oil recovery in sandstone reservoirs

Low salinity water flooding has gained tremendous attention in these days due to its cost-effectiveness and environment-friendly nature. Fine tuning of physico-chemical properties of low saline water by addition of suitable chemicals and nanoparticle (NP) can increase the oil recovery significantly because of synergistic effects. In this study, an attempt has been made to explore the benefit of adding nanoparticle and polymer into low salinity water (LSW) for increased oil recovery. Two complex chemical slugs were prepared with formation water (FW) and LSW as base fluids consisting of different concentrations of polymer and NP. The target viscosity for maximum sweep efficiency was estimated through the total minimum relative mobility concept. The rheological studies of the complex chemical slugs revealed that the addition of NP into polymer solution increased the viscosity significantly because of formation of macromolecular structure. It has been observed that a lower concentration of polymer is required to reach the target viscosity in LSW than FW. The benefits of low salinity effects over high saline formation water are evidenced by the reduction of interfacial tension (IFT), which is further reduced by addition of NP. A low IFT is always desirable for enhanced oil recovery. Contact angle showed a decreasing trend with FW, LSW and Nano fluid solutions respectively but presence of polymer in the slugs shows reverse effect on contact angle. LSW showed higher recovery as compared to FW in secondary recovery stage due to different reported mechanisms. Injection of LSW based complex fluid showed incremental recovery of 13.3 % of OOIP as compared to LSW and 22.0 % of OOIP as compared to conventional FW flooding in secondary stage. Synergistic effect of NP and polymer to form a complex macromolecular structure through hydrogen bonding and low salinity effect led to the improved oil recovery.”

The effect of the TiC-TiB2 nanoparticles on the microstructure and mechanical properties of Al-Mn-Si strips fabricated by twin-roll casting

In this work, Al-Mn-Si and TiC-TiB2/Al-Mn-Si strips were prepared by vertical-type twin-roll casting (TRC), and the effect of TiC-TiB2 nanoparticles (NPs) on the microstructure and mechanical properties of TRC Al-Mn-Si strips were studied. The TRC strips had the characteristics of coarse grains near the surface and fine grains in the center. The introduction of NPs resulted in the formation of uniform and fine grain structures due to the grain refinement effect of NPs. The refining effect on the surface grains was much greater than that on the central grains because the larger thermal undercooling of the melt at the surface led to the improvement of the nucleation efficiency of NPs. TiC-TiB2 particles could eliminate the central segregation of TRC Al-Mn-Si strips due to the control of solute diffusion by the uniform and fine grain structures, thereby reducing α-Al(Mn, Fe)Si formation in the central region. The mechanical properties of the TRC Al-Mn-Si strips were improved with the introduction of NPs. The yield strength at room temperature was increased from 79.0 MPa to 92.9 MPa, and the uniform elongation was increased from 7.2% to 10.1%, due to the fewer eutectic α-Al(Mn, Fe)Si, refined precipitates and grain structures caused by the addition of the TiC-TiB2 particles.

Probing the interaction between niobium pentoxide nanoparticles and serum albumin proteins by Spectroscopic approaches

Nanoparticles (NPs) can directly or indirectly enter into the body because of their small size; then they tend to alter the conformation and function of proteins upon interaction with them. Thus, it is crucial to understand the impact of NPs in a biological medium. Recently, niobium pentoxide nanoparticles (Nb2O5 NPs) are finding increasing applications in the biological system, for example, bone tissue and dental material, matrix for biosensing of proteins, etc. In all such applications, the Nb2O5 NP interacts with proteins and other biomolecules. Hence, the study of such interactions is of considerable importance. Here in this work, we present the impact of Nb2O5 NP on the structure, stability and activity of blood proteins, bovine serum albumin (BSA) and human serum albumin (HSA) by means of various spectroscopic approaches. Steady-state fluorescence studies indicated that intrinsic fluorescence intensities of both serum albumin proteins got quenched upon their interaction with NP. The nature of the quenching was elucidated by time-resolved fluorescence and absorption measurements. Using circular dichroism (CD) and synchronous fluorescence spectroscopy (SFS), the structural perturbations of the protein molecules after interaction with NP were investigated. Moreover, the role of temperature on protein stability upon complexation with NP was also explored. In addition, the effect of NP on protein functionality was probed by esterase-like activity assays. Communicated by Ramaswamy H. Sarma

Overview of mechanism and consequences of endothelial leakiness caused by metal and polymeric nanoparticles.

Nanoparticles (NPs) exhibit unique physicochemical properties that enable them to overcome biological barriers and to be considered one of the best materials with anticancer properties. Most of the administered NPs that end up in the bloodstream interact with the endothelial layer. The interaction of the NPs with the endothelium widens the existing gaps or induces new ones in the monolayer of vascular endothelial cells, thus increasing the access to the target sites in the organism. This type of interaction can lead to NP-modulated endothelial leakiness (NanoEL). The most important factors determining NanoEL are the physicochemical properties of the NPs. NP-modulated endothelial leakiness can lead to the discovery of new therapeutic targets and strategies to improve drug delivery through controlling and regulating NanoEL. Nevertheless, the NanoEL mechanism also carries some limitations that result from an incomplete understanding of NP metabolism and toxicity, and the possibility of their participation in the unintended bidirectional vascular permeability, which may contribute to the formation of cancer metastases. In this review we are focusing on the effect of metal and polymeric NPs on mechanism and degree of induction of NanoEL, as well as on the benefits and risks of using NPs that induce endothelial leakiness.

Methacrylate Cationic Nanoparticles Activity against Different Gram-Positive Bacteria.

Nanotechnology is a developing field that has boomed in recent years due to the multiple qualities of nanoparticles (NPs), one of which is their antimicrobial capacity. We propose that NPs anchored with 2-(dimethylamino)ethyl methacrylate (DMAEMA) have antibacterial properties and could constitute an alternative tool in this field. To this end, the antimicrobial effects of three quaternised NPs anchored with DMAEMA were studied. These NPs were later copolymerized using different methylmethacrylate (MMA) concentrations to evaluate their role in the antibacterial activity shown by NPs. Clinical strains of Staphylococcus aureus, S. epidermidis, S. lugdunensis and Enterococcus faecalis were used to assess antibacterial activity. The minimal inhibitory concentration (MIC) was determined at the different concentrations of NPs to appraise antibacterial activity. The cytotoxic effects of the NPs anchored with DMAEMA were determined in NIH3T3 mouse fibroblast cultures by MTT assays. All the employed NPs were effective against the studied bacterial strains, although increasing concentrations of the MMA added during the synthesis process diminished these effects without altering toxicity in cell cultures. To conclude, more studies with other copolymers are necessary to improve the antibacterial effects of NPs anchored with DMAEMA.

Nanotechnology in combating biofilm: A smart and promising therapeutic strategy.

Since the birth of civilization, people have recognized that infectious microbes cause serious and often fatal diseases in humans. One of the most dangerous characteristics of microorganisms is their propensity to form biofilms. It is linked to the development of long-lasting infections and more severe illness. An obstacle to eliminating such intricate structures is their resistance to the drugs now utilized in clinical practice (biofilms). Finding new compounds with anti-biofilm effect is, thus, essential. Infections caused by bacterial biofilms are something that nanotechnology has lately shown promise in treating. More and more studies are being conducted to determine whether nanoparticles (NPs) are useful in the fight against bacterial infections. While there have been a small number of clinical trials, there have been several in vitro outcomes examining the effects of antimicrobial NPs. Nanotechnology provides secure delivery platforms for targeted treatments to combat the wide range of microbial infections caused by biofilms. The increase in pharmaceuticals' bioactive potential is one of the many ways in which nanotechnology has been applied to drug delivery. The current research details the utilization of several nanoparticles in the targeted medication delivery strategy for managing microbial biofilms, including metal and metal oxide nanoparticles, liposomes, micro-, and nanoemulsions, solid lipid nanoparticles, and polymeric nanoparticles. Our understanding of how these nanosystems aid in the fight against biofilms has been expanded through their use.

Effects of ROS-Sensitive Nanoparticles Loaded with Interstitial Cell Derived Factors on Vascular Smooth Cell Adhesion, Proliferation, and Endothelialization

Local high concentrations of stromal cell-derived factor 1 (SDF-1) attract and trap stem cells to involve in the vascular repair when the skin is damaged. In this research, mercaptan ketone polymer (PRGY) was selected as a nano-carrier to prepare ROS-sensitive nanoparticles (NPs) loaded with SDF-1 by means of volatilization of a complex emulsion solvent. The NPs were characterized by a transmission electron microscope (TEM) and a particle size (PS) analyzer, the protein content of the NPs was evaluated by a BCA method, the cytotoxicity was evaluated by CCK8, and the NPs were subjected to the in vitro release (IVR) test. An acute mouse wound model was established, the pathological effect of NP solution on major organs of mice was observed by HE staining after intravenous injection, and the effect of targeted release of NP on animal model was evaluated. To analyze the effect of NPs on wound healing, the mouse models were rolled into different groups. They were sacrificed two weeks after the wound healing was completed, the blood vessels were fixed with perfusion solution, and the common artery where the wound was located was taken for follow-up study. The results suggested that the NPs exhibited a PS of 122.57±18.33 nm, a loading rate of 1.7%, and spherical and uniform surfaces. The IVR tests showed that the NPs could release rapidly under high ROS conditions. The wound model of mice was established, and the injection of NP solution revealed that it could target the wound area. The healing speed in the NP group was the fastest (P &lt;0.05). Smooth muscle cells (SMCs) and endothelial cells (ECs) were isolated from common artery, and proliferation of them in the NP group was found to be obvious (P &lt;0.05), and the adhesion of vascular SMCs could be accelerated at the same time.

Enhanced ammonia sensing response based on Pt-decorated Ti3C2T x /TiO2 composite at room temperature

Herein, we report a Pt-decorated Ti3C2T x /TiO2 gas sensor for the enhanced NH3 sensing response at room temperature. Firstly, the TiO2 nanosheets (NSs) are in situ grown onto the two-dimensional (2D) Ti3C2T x by hydrothermal treatment. Similar to Ti3C2T x sensor, the Ti3C2T x /TiO2 sensor has a positive resistance variation upon exposure to NH3, but with slight enhancement in response. However, after the loading of Pt nanoparticles (NPs), the Pt-Ti3C2T x /TiO2 sensor shows a negative response with significantly improved NH3 sensing performance. The shift in response direction indicates that the dominant sensing mechanism has changed under the sensitization effect of Pt NPs. At room temperature, the response of Pt-Ti3C2T x /TiO2 gas sensor to 100 ppm NH3 is about 45.5%, which is 13.8- and 10.8- times higher than those of Ti3C2T x and Ti3C2T x /TiO2 gas sensors, respectively. The experimental detection limit of the Pt-Ti3C2T x /TiO2 gas sensor to detect NH3 is 10 ppm, and the corresponding response is 10.0%. In addition, the Pt-Ti3C2T x /TiO2 gas sensor shows the fast response/recovery speed (23/34 s to 100 ppm NH3), high selectivity and good stability. Considering both the response value and the response direction, the corresponding gas-sensing mechanism is also deeply discussed. This work is expected to shed a new light on the development of noble metals decorated MXene-metal oxide gas sensors.

Combined toxic effects of TiO2 nanoparticles and organochlorines on Chlorella pyrenoidosa in karst area natural waters

With the discharge of nanoparticles (NPs) into the environment, NPs can interact with coexisting organic pollutants, resulting in combined toxic effects. In order to more realistically evaluate the potential toxic effects of NPs and coexisting pollutants on aquatic organisms. We evaluated the combined toxicities of TiO2 nanoparticles (TiO2 NPs) and three different organochlorines(OCs)-pentachlorobenzene (PeCB), 3,3′,4,4′-tetrachlorobiphenyl (PCB-77) and atrazine to algae (Chlorella pyrenoidosa) in three karst natural waters. The results indicate that the individual toxicities of TiO2 NPs and OCs in natural waters were less than those of OECD medium, and the combined toxicities were different from but generally similar to those of OECD medium. The individual and combined toxicities were the largest in UW. The correlation analysis showed that the toxicities of TiO2 NPs and OCs were mainly related to TOC, ionic strength, Ca2+ and Mg2+ in natural water. The binary combined toxicities of PeCB and atrazine with TiO2 NPs to algae were synergistic. The binary combined toxicity of TiO2 NPs and PCB-77 to algae was antagonistic. The presence of TiO2 NPs increased the algae-accumulations of OCs. PeCB and atrazine all increased the algae-accumulations of TiO2 NPs, while PCB-77 showed the opposite result. The above results indicated that due to the influence of different hydrochemical properties in karst natural waters, there were differences between TiO2 NPs and OCs in their toxic effects, structural and functional damage, and bioaccumulation.