The influence of amine structures on the stability and catalytic activity of gold nanoparticles stabilized by amine-modified hyperbranched polymers

Temperature modulating the peroxidase-mimic activity of poly(N-isopropyl acrylamide) protected gold nanoparticles for colorimetric detection of glutathione

More recently, loading polymer-ligand onto the surface of gold nanoparticles (AuNPs) as nanozymes has gained considerable attention. However, the efficient modulation of the nanozymes catalytic capability depending on external stimuli remains challenging. Herein, utilizing the thermo-responsive poly(N-isopropyl acrylamide) (PNIPAM) as a stabilizer and a reducing agent to make PNIPAM@AuNPs, we reported a straightforward and efficient protocol for modulating the peroxidase-mimic catalytic capability of PNIPAM@AuNPs in oxidation of 3,3',5,5'-tetramethyl benzidine (TMB)-H₂O₂ system by change of environmental temperature. More hydroxylradicals yielded and surface confinement effect induced by the coiled PNIPAM chains at high temperature could further significantly boost the nanozymes catalytic capability. In the presence of glutathione, the generation of oxidized TMB was inhibited and the absorption intensity of the reaction system decreased at 650 nm. The color-fadingproperty provided a highly selective assay for visualized and quantitative test of glutathione ranging 1.0 ～ 17.0 μM (R² = 0.993), the limit of detection was 0.8 μM. Moreover, the proposed method exhibited a promising application in analysis of rat serum glutathione following an intravenous injection. The strategy supplies a facile guideline for preparation of stimuli-responsive polymer@AuNPs with improved peroxidase-mimic catalytic activity toward application in real living bio-systems.

Controlled Synthesis of Platinum and Silver Nanoparticles Using Multivalent Ligands

Here, the controlled formation of platinum nanoparticles (PtNPs) and silver nanoparticles (AgNPs) using amine-functionalized multivalent ligands are reported. The effects of reaction temperature and ligand multivalency on the growth kinetics, size, and shape of PtNPs and AgNPs were systematically studied by performing a stepwise and a one-step process. PtNPs and AgNPs were prepared in the presence of amine ligands using platinum (II) acetylacetonate and silver (I) acetylacetonate, respectively. The effects of ligands and temperature on the formation of PtNPs were studied using a transmission electron microscope (TEM). For the characterization of AgNPs, additionally, ultraviolet-visible (UV-Vis) absorption was employed. The TEM measurements revealed that PtNPs prepared at different temperatures (160–200 °C, in a stepwise process) are monodispersed and of spherical shape regardless of the ligand multivalency or reaction temperature. In the preparation of PtNPs by the one-step process, ligands affect the shape of the PtNPs, which can be explained by the affinity of the ligands. The TEM and UV-Vis absorption studies on the formation of AgNPs with mono-, di-, and trivalent ligands showed narrower size distributions, while increasing the temperature from 80 °C to 120 °C and with a trivalent ligand in a one-step process.

Poly(N,N-dimethylacrylamide)-stabilized gold nanoparticles as nanozymes with enhancement of catalytic activity for detection of lomefloxacin

Recently, polymer-protected gold nanoparticles (AuNPs) have attracted extensive attention due to their good catalytic activities. However, how to regulate their catalytic activities by changing the polymer chain morphologies or the interactions between the ligands and the analytes through external stimuli is still a great challenge. This study describes a simple synthesis of AuNPs capped by thermo-responsive poly(N,N-dimethylacrylamide) (PDMAM). In comparison with three kinds of PDMAMs@AuNPs, PDMAM-2@AuNPs exhibited better peroxidase-mimic ability via the catalytic oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) with hydrogen peroxide (H₂O₂) to generate oxidized TMB (oxTMB). Interestingly, its catalytic activity could be regulated by changing environmental temperature. Importantly, the addition of the antibiotic lomefloxacin endowed the PDMAM-2@AuNPs with enhancement in catalytic efficiency due to electrostatic interactions and the increased levels of reactive oxygen species. Based on this principle, a protocol for highly selective and sensitive monitoring of lomefloxacin has been constructed with the color change from pale blue to deep blue. The ultraviolet-visible absorbance of oxTMB at the wavelength of 650 nm showed a good linear relationship with antibiotic concentration in the range of 0.25-10.0 µM (R² = 0.990). The limit of detection was 0.1 µM. The practical application of the proposed protocol with the promoted peroxidase-mimic activity for the measurement of lomefloxacin in capsules was realized.

Role of pretreatment and evidence for the enhanced biodegradation and mineralization of low-density polyethylene films by greater waxworm

The present study reports the role of pretreatment for the enhanced biodegradation of low-density polyethylene (LDPE) with Galleria mellonella (Greater waxworm). The pretreatment of the LDPE film was carried out under solar radiation. The pretreated LDPE (PTLDPE) and untreated LDPE (UTLDPE) were characterized with AFM, FTIR and ¹H NMR techniques. The qualitative analysis for the biodegradation of pretreated and untreated LDPE was examined by analysing the Excreta residue (ER) of Galleria mellonella fed with LDPE. The mineralization of the ER of waxworm fed on Waxcomb (WC), UTLDPE and PTLDPE were studied by analysing the changes in physiochemical properties through FTIR, ¹H NMR and GC-MS techniques in addition to weight loss percentage of PTLDPE and survival rates of the tested greater waxworms. Solar pretreatment of LDPE led to increased surface roughness which favoured the waxworms to feed voraciously on PTLDPE. The post degradation studies of Waxcomb (WC), PTLDPE and UTLDPE showed 92.03 ± 2.1%, 18.57 ± 1.8% and 55.8 ± 1.2% weight loss, respectively. The FTIR, ¹H NMR and GC-MS results confirm that the ER of waxworm fed on WC, UTLDPE and PTLDPE showed the presence of new carbonyl and alcoholic groups with increase in unsaturated hydrocarbon indicating enhanced mineralization of LDPE. The efficient mineralization of PTLDPE by waxworm was observed without affecting its survivability. A plausible mechanism of LDPE degradation has also been proposed. The rapid and cost effective biodegradation of PTLDPE through waxworm paves a new and facile route for hazardous plastic waste treatment.

Thermal Conductivity and Stability of Hydrocarbon-Based Nanofluids with Palladium Nanoparticles Dispersed by Modified Hyperbranched Polyglycerol

Palladium nanoparticles, which were prepared by modified hyperbranched polyglycerol (mHPG) as stabilizers, can be dispersed well in nonpolar organic solvents and form highly stable nanofluids. The influences of three mHPG products modified with cyclohexanethiol (CSHPG), dodecanethiol (DSHPG), and octadecanethiol (OSHPG) on the preparation and stability of the palladium nanoparticles were investigated. The stability and thermal conductivity enhancement of the hydrocarbon-based nanofluids with Pd@mHPG (Pd@CSHPG, Pd@DSHPG, and Pd@OSHPG) compared to the corresponding base fluid were investigated at different temperatures. The average diameters of nanoparticles stabilized by CSHPG, DSHPG, and OSHPG are within 2.7-3.6 nm. The palladium nanoparticles could be dispersed well in the nonpolar base fluid such as decalin. The nanofluids with Pd@DSHPG and Pd@OSHPG could remain stable for up to 330 days at room temperature. The nanofluid with Pd@DSHPG or Pd@OSHPG could be stable for more than 24 h at 110 °C. The thermal conductivity of the nanofluids improved with increasing temperature and the mass fraction of nanoparticles compared to the corresponding base fluid. The long alkyl chain-modified HPG can give better protection for nanoparticles from agglomeration and assist metal nanoparticles in enhancing the thermal conductivity of nanofluids.

Advances in amphiphilic hyperbranched copolymers with an aliphatic hyperbranched 2,2-bis(methylol)propionic acid-based polyester core

Amphiphilic hyperbranched copolymers with an aliphatic hyperbranched 2,2-bis(methylol)propionic acid-based polyester core were highlighted.