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Herein, we demonstrate a hydrothermal route to the one-pot synthesis of polymeric mesoporous silica microcubes (P@MSMCs) for the adsorption of heavy metal ions. During the synthesis of P@MSMCs from column silica gel, the roles and combination of the polymer and an etchant were characterized. Moreover, the porosity of P@MSMCs was tailored by adjusting the reaction temperature between 75 °C and 200 °C. The characterization through UV, FTIR, FESEM, XRD, BET, and EDX techniques exhibited that P@MSMCs have a well-ordered mesoporous structure with cubic morphology. The P@MSMCs had a diameter of 2 μm, with an average pore volume and pore size of 0.69 cm3 g−1 and 10.08 nm, respectively. The results indicated that the P@MSMCs have excellent adsorption capacity for Ag(I), Ti(IV), and Zn(II) due to the formation of an aggregated complex. These aggregations led to affordable density difference-based separation of these metal ions through centrifugation, filtration or simple decantation. The removal efficiencies for Ag(I), Ti(IV), and Zn(II) were observed to be 520, 720, and 850 mg g−1, respectively. The kinetic studies demonstrated that the adsorption performance fitted well to the pseudo-second-order kinetic model. The as-synthesized P@MSMCs were stable in the wide pH range of 4–8. Significantly, the recycling or reuse results displayed effective adsorption performance of these P@MSMCs for up to 5 cycles. The adsorption results obtained herein will promote the development of similar strategies for the removal of heavy metal ions from natural water. [ABSTRACT FROM AUTHOR]

Abstract Carbon based materials are emerging as a sustainable alternative to their metal-oxide counterparts. However, their transport behavior under natural aqueous environment is poorly understood. This study investigated the transport and retention profiles of carbon nanoparticles (CNPs) and graphene oxide quantum dots (GOQDs) through column experiments in saturated porous media. CNPs and GOQDs (30 mg/L) were dispersed in natural river water (RW) and passed through the column at a flow rate of 1 mL/min, which mimicking the natural water flow rate. After every 10 min, the column effluents were collected and the mass recovery and retention profiles were monitored. Results indicated that the transport of both carbonaceous colloids was predominantly controlled by surface potential and ionic composition of natural water. The CNPs with its high surface potential (−40 mV) exhibited more column transport and was less susceptible to solution pH (5.6–6.8) variation as compared to GOQDs (−24 mV). The results showed that, monovalent salt (NaCl) was one of the dominating factors for the retention and transport of carbonaceous colloids compared to divalent salt (CaCl 2). Furthermore, the presence of natural organic matter (NOM) increased the transport of both carbonaceous colloids and thereby decreases the tendency for column retention. Graphical abstract Image 1 Highlights • Transport of CNPs and GOQDs under natural water was explored. • Transport capacity was decreased with increasing ionic strength of solution. • GOQDs showed less transport compared to CNPs due to less surface potential. • Presence of NOM enhanced the transport of CNPs and GOQDs. • One-site kinetic deposition model described well the experimental BTCs. [ABSTRACT FROM AUTHOR]

Abstract The toxicity and kinetic uptake potential of zinc oxide (ZnO) and titanium dioxide (TiO 2) nanomaterials into the red bean (Vigna angularis) plant were investigated. The results obtained revealed that ZnO, due to its high dissolution and strong binding capacity, readily accumulated in the root tissues and significantly inhibited the physiological activity of the plant. However, TiO 2 had a positive effect on plant physiology, resulting in promoted growth. The results of biochemical experiments implied that ZnO, through the generation of oxidative stress, significantly reduced the chlorophyll content, carotenoids and activity of stress-controlling enzymes. On the contrary, no negative biochemical impact was observed in plants treated with TiO 2. For the kinetic uptake and transport study, we designed two exposure systems in which ZnO and TiO 2 were exposed to red bean seedlings individually or in a mixture approach. The results showed that in single metal oxide treatments, the uptake and transport increased with increasing exposure period from one week to three weeks. However, in the metal oxide co-exposure treatment, due to complexation and competition among the particles, the uptake and transport were remarkably decreased. This suggested that the kinetic transport pattern of the metal oxide mixtures varied compared to those of its individual constituents. Graphical abstract Image 1 [ABSTRACT FROM AUTHOR]

Metal nanoparticles (MNPs), due to its increasingly wide applications in consumer products, raises its concern towards ecotoxicology. Once released into the environment, the zero-valent metal (M°) readily oxidized to ionic metal (M) which is reported as the main source of toxicity related to MNPs. The current study investigated the oxidative dissolution and M release profiles, from polymer-coated and uncoated MNPs. The polyethylene imine coated silver nanoparticles (PEI@AgNPs), polyethylene glycol coated zinc oxide micro-rods (PEG@ZnOMRs), and uncoated titanium dioxide nanoparticles (TiONPs) were synthesized with different size, shape, and surface functionalities, and M flow behavior was investigated through column transport experiment. The results obtained revealed that the ionic dissolution and M loss was 1.6-3.3% for PEI@AgNPs, 8.3-12.6% for TiONPs, and 13.6-19.0% for PEG@ZnOMRs. These results suggested that PEI surface coating greatly inhibit the M release and maximum column retention occurs in order of PEI@AgNPs ˃ TiONPs ˃ PEG@ZnOMRs. [ABSTRACT FROM AUTHOR]

Abstract: Polymers either serve as shielding or capping agents to restrict the nanoparticle size. This study demonstrates the polymer depositions and their effects in synthesis and sharp stabilization of gold nanoparticles (AuNPs) and to develop gold/silver nanoalloys (Au/Ag nanoalloys). Effects of different polymers are tested to justify their role in synthesis and stability of phloroglucinol (PG) coated AuNPs and Au/Ag nanoalloys. Cationic and anionic i.e. [Polydiallyldimethylammonium]+ (PDDA), [Polyethyleneimine]+ (PEI), [Polystyrene sulfonate]2− (PSS) and neutral polymer Polychlorotriflouroethylene (PCTFE) produce praiseworthy stable AuNPs and Au/Ag nanoalloy. To prove polymer effects characterization protocols including UV–vis, Fluorescence (PL), IR and AFM imaging are performed to fully investigate the mechanism and size characteristics of these nanoparticles/nanoalloys. In this study sharp size controlling/sheilding effects were observed particularly with cationic polymers simply through the favorable electrostatic interactions with the terminal ends of PG Potent/significant detection of doxorubicin (DOX, an antileukemic agent) via fluorescence resonance energy transfer (FRET) between PEI shielded AuNPs (AuNPEI) and DOX was achieved upto 10pM level, while PDDA protected AuNPs facilitated the detection of ascorbic acid based on fluorescence enhancement effects in wide range (10–200nM) and with detection limit of 200pM. Similarly sensing performance of PEI stabilized Au/Ag nanoalloys on addition of halides (Cl−, Br-, I−) is evaluated through red shifted SPR along with continuous increase in absorbance and also through AFM. Moreover the addition of halide ions also helped the regeneration of AuNPs by taking away silver from the Au/Ag nanoalloys enabling their detections upto subnanomolar levels. [Copyright &y& Elsevier]

Current research efforts have demonstrated the facile hydrothermal oxidative synthetic route to develop highly fluorescent boron/nitrogen co-doped carbon nanodots (CNDs). During this process, N-(4-hydroxyphenyl)glycine served as a source of N doping and a carbon precursor as well, while boric acid H3BO3 is used as an oxidizing agent in the N2 environment. Surface passivation through ultrasonic treatment of CNDs was performed to induce modifications by using various surface passivating agents. Polyethyleneimine (PEI) remarkably enhanced the fluorescence performance and monodispersity of polymerized carbon nanodots (P-CNDs) in aqueous phase with an enhanced quantum yield of 23.71%, along with an increase in size from ~3 nm to ~200 nm. For characterization of CNDs and P-CNDs, UV, infrared, photoluminescence, transmission electron microscopy, x-ray photoelectron spectra, and atomic force microscopy techniques were utilized. Application potentials of synthesized P-CNDs were developed via introduction of protoporphyrin (PPD, a photosensitizer) which has great doping affinity with polymer PEI to switch-off the fluorescence of P-CNDs, leading to the production of dye-doped nanoprobes. Fluorescence resonance energy transfer (FRET) was also observed during dye-doping, and PPD was detected with a limit of detection (LOD, 3s) of 15 pM. The fluorescence recovery of this switched-off nanoprobe was made possible by using Sudan red III (carcinogenic dye), which was oxidized by PPD doped in P-CNDs. Sudan red III was detected in the concentration range of 9.9 pM-0.37 nM. Meanwhile, it was also confirmed that the dye-doped nanoprobe is highly selective and exceptionally sensitive to detect this carcinogenic agent in commercial products with a LOD (3σ) of 90 fM. [ABSTRACT FROM AUTHOR]