Multi-walled carbon nanotubes wrapped with polyvinylpyrrolidone can control the leaf yellowing of Alstroemeria cut flowers.

The rapid yellowing of the leaves on cut flowers with leafy stems severely limits their vase life and commercial value. In this study, the effect of a composite of multi-walled carbon nanotubes (MWCNTs) and polyvinyl pyrrolidone (PVP) on the longevity of cut Alstroemeria flowers (Alstroemeria hybrida) was investigated to obtain a solution to this problem. A range of MWCNTs/PVP composite concentrations (0, 3, 6, and 9 mg L-1) was applied in a vase solution (for 24 h) as pulse treatments. Our findings indicate that the composite of MWCNTs and PVP exhibits excellent dispersibility in a vase solution. The results demonstrate that a 3 mg L-1 MWCNTs/PVP concentration was the most effective, extending the vase life of cut Alstroemeria flowers by up to 27 days. Pulsing with MWCNTs/PVP delayed the onset of floret abscission and leaf yellowing by 5 and 18 days, respectively. Additionally, when MWCNTs/PVP solution was applied to cut stems, water uptake remained consistently greater than that of the control. Additionally, MWCNTs/PVP increased the total chlorophyll content, soluble protein content, and POX enzyme activity of leaves while decreasing the malondialdehyde (MDA) content. The results indicate that this composite exhibited antimicrobial activity against gram-positive and -negative bacteria, particularly at a concentration of 3 mg L-1. This study demonstrated that adding MWCNTs/PVP to a vase solution of Alstroemeria cut flowers increased their longevity with minimal leaf yellowing symptoms compared to untreated cut stems. As a result, this nanocomposite can be used safely and effectively in vase solutions and in combination with other preservatives.

Tuned MWCNT/CuO/Fe3O4/Polyaniline nanocomposites with exceptional microwave attenuation and a broad frequency band.

In this study, novel quaternary MWCNT/CuO/Fe3O4/PANI nanocomposites were synthesized with three different weight ratios of CuO/Fe3O4/PANI to MWCNT (1:3), (1:4), and (1:5), where all of its components were synthesized separately and then combined in specific weight ratios. CuO/Fe3O4/PANI transmission electron microscopy (TEM) images revealed that most nanoparticles were in a CuO/Fe3O4 hybrid form, with a narrow size distribution uniformly dispersed in a polymer background. The TEM and scanning electron microscopy (SEM) images of the MWCNT/CuO/Fe3O4/PANI nanocomposite revealed that the MWCNT was uniformly coated with CuO/Fe3O4/PANI. All three nanocomposites samples demonstrated superior microwave attenuation performance in terms of reflection loss and absorption bandwidth. The minimum reflection losses for MWCNT/CuO/Fe3O4/PANI nanocomposites (1:3), (1:4), and (1:5) were 45.7, 58.7, and 85.4, 87.4 dB, respectively. The absorption bandwidths (RL ≤ -10 dB) of MWCNT/CuO/Fe3O4/PANI nanocomposites (1:3), (1:4), and (1:5) were 6, 7.6, and 6 GHz, respectively.

Preparation and optimization photocatalytic activity of polymer-grafted Ag@AgO core-shell quantum dots.

A linear-dendric copolymer containing polyethylene glycol-polycitric acid used as a capping agent to the green inter-matrix synthesis of silver/silver oxide core-shell quantum dots (Ag@AgO QDs). Water-soluble Ag@AgO QDs were synthesized with high yield and narrow size distribution. Here, Ag ions were trapped in the polymer branches and covalently bonded to it. Another sample of Ag@AgO QDs was synthesized through the same method and conditions without any capping agent (raw nanoparticles). Structure, size distribution, and morphology of raw and copolymer-grafted nanoparticles were identified using X-Ray diffraction, field emission scanning electron microscopy (FESEM), and high-resolution transmission electron microscopy (HRTEM). The results from XRD pattern and UV spectra confirmed the Ag@AgO structure of both nanoparticles. From the FESEM image, the size of Ag nanoparticles obtained at the range of 1-20 nm. HRTEM image of grafted nanoparticles directly showed that these nanoparticles have very tiny size in the range of 1-2 nm and presented in the form of core-shell Ag@AgO. Thus, both raw and polymer-grafted samples are in the range of quantum dots (QDs). Raw and polymer-grafted Ag@AgO QDs which take the advantage of water solubility and biosafety, were used as photocatalyst for degradation of cationic methylene blue (MB) and anionic methyl orange (MO) dyes at low and high concentrations of each dye. Results shows using polymer-grafted QDs leads to a significant enhancement both in the efficiency and rate of dye degradation, compared to the case of using raw nanoparticles.