Cellulose nanocrystals polyelectrolyte complexes as flame retardant treatment for cotton fabrics

In this work, polyelectrolyte complexes (PECs) are employed as an efficient way for the deposition of functional flame retardant coatings based on cellulose nanocrystals (CNCs). To this aim, CNCs have been combined with branched polyethyleneimine (BPEI) obtaining gel-like PECs to be deposited on cotton by an easy doctor-blading approach. The morphology of the coated fabrics was investigated by scanning electron microscopy. The thermal stability was evaluated by thermogravimetric analyses while the achieved flame retardant properties were assessed by horizontal flammability tests. The deposition of the CNCs/BPEI PECs produces a homogeneous coating capable of self-extinguishing the flame with only 8 % of weight added to the fabric. Post combustion residue investigations highlighted how these CNCs/BPEI PECs can produce a swelled charred barrier consisting of polyaromatic structures embedded within an amorphous carbon. The results reported in this paper open up to a practical and industrially viable strategy for the exploitation of CNCs in the field of flame retardant coatings

Fluidic actuation of an elastomeric grating

A fluidic chamber with an elastomeric grating membrane is fabricated. Grating groove spacing is modified through membrane deformation via fluid injection. Tunable diffraction output is demonstrated. At normal incidence, the diffraction angle changes by 14.2° and 9.8° for incident wavelengths 632.8 and 488 nm, respectively, with an injected fluid volume of 1 ml

Functional nanocellulose films as fluorescent media

Fluorescent nanocellulose films fabricated via 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)-mediated oxidation of cellulose nanofibers were prepared using two methods. In the first process, fluorescent particles were added halfway through the last vacuum filtration step of film fabrication. Three different particles were used: micro-pSi, micro-pSi with COOH, and Si-COOH nanocrystals. Several optical techniques were employed to characterize resulting films: UV-Vis spectrophotometry, fluorescence spectrophotometry, scanning electron microscopy (SEM), and Fourier transform infrared (FTIR) microscopy. All techniques revealed that particles retained their intrinsic properties after deposition on the film. Photoluminescence spectra of resulting films at λexcitation = 350 nm exhibited the following fluorescence peaks: λmicro-pSi = 600 nm, λmicro-pSi with COOH = 596 nm, λSi-COOH nanocrystals = 618 nm. A blue shift of at most 20 nm was observed when comparing particle fluorescence peak emission before and after deposition on the film. The peak shift was attributed to oxidation, as the particles remained in an aqueous solution during film fabrication. Continued observation of film fluorescence spectra showed that peak emission values are maintained for a month. A second method of fluorescent film fabrication involved the immersion of a dry, transparent nanocellulose film in a chlorophyll in acetone solution. Fluorescence spectra of the resulting hybrid film were taken using a UV laser as the excitation source (λexcitation = 355 nm). The fluorescence peak was found to be λchlorophyll = 683.21 nm. Both methods of film hybridization were effective in preparing nanocellulose films that show promise as stable fluorescent media