Novel,
high-efficiency, and halogen-free flame retardants with
reactive groups, casein-based FRs, were synthesized based on a casein
hydrolysis solution for cotton fabrics. After treated by the casein-based
FRs, cotton fabrics exhibited high-efficiency flame retardancy; the
limiting oxygen index (LOI) of treated cotton fabric increased to
39.5%. Compared with other nature flame retardants, the novel flame
retardants could impart durable flame retardancy to cotton fabrics.
The LOI value could sustain at 26.7% after 40 laundering cycles (LCs).
Cone calorimetry and vertical burning test confirmed that the cotton
fabrics treated by the casein-based FRs achieved markedly enhanced
flame retardancy. X-ray photoelectron spectroscopy (XPS) and Fourier-transform
infrared (FTIR) indicated that the casein-based FRs were grafted on
cellulose by P(O)–O–C and C(O)–O–C
bonds. Scanning electron microscopy (SEM) revealed that the modification
was facile. Thermogravimetry (TG), energy-dispersive X-ray (EDX),
TG-FTIR and SEM revealed that the casein-based FRs played an important
role in condensed phase, together with the flame retardant behavior
in gaseous phase. The casein-based FRs mainly prevented the formation
of levoglucosan by phosphorylation of cellulose and catalyzed the
dehydration of cellulose. The tensile strength and whiteness of cotton
fabrics treated by the casein-based FRs were substantially retained.
Although a notable feature of Noyori's Ru-TsDPEN complex is that the transfer hydrogenation reaction is highly chemoselective for the C=O functional group and tolerant of alkenes, our early report indicated that the chemoselectivity could be switched from C=O to C=C bonds in the transfer hydrogenation of activated alpha,beta-unsaturated ketones. Now we have found that a variety of alpha,beta-unsaturated ketones, even without other electron-withdrawing functional groups, could be reduced on the alkenic double bonds with high selectivities employing amido-rhodium hydride complex in aqueous media, and up to 100% chemoselectivity has been achieved. It is notable that the chemoselectivity was improved significantly on going from organic solvent to water. Moreover, a 1,4-addition mechanism has been proposed on the basis of the corresponding experimental details and computational analysis.
In this article, we developed an effective approach to generate gold nanoflowers (AuNFs) by vesicles made from a series of gemini amphiphiles (G2-G10) with different spacer lengths. The gemini amphiphiles were found to form vesicles in aqueous solution. Upon mixing with vesicles in the presence of AgNO(3), HAuCl(4) could be reduced into gold nanoflowers by ascorbic acid. The vesicles directed the growth of the AuNFs, and the spacer length of the gemini amphiphiles showed obvious control of the morphology and optical properties of the formed AuNFs. At a lower HAuCl(4) concentration, the minimum-sized AuNFs were formed when vesicles from the amphiphile with a spacer length of 4 were applied. Upon increasing the spacer length, branched nanoflowers are predominantly produced. A seed-growth mechanism together with the conformational change of the spacer of the gemini amphiphiles was proposed according to the studies on reaction processes. In addition, the formed gold nanoflowers showed obvious surface-enhanced Raman scattering activity for R6G. The present method provided an efficient, controllable way to synthesize branched gold nanostructures.
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