Fabrication and optimization of paper chips from calcinated Fe-MOFs for rapid and in situ visual detection of tetracyclines in water environments.

Antibiotics such as tetracyclines (TCs) have become a major threat to ecosystem safety and human health, as their abuse has caused the occurrence and proliferation of antibiotic-resistant bacteria and genes. Currently, there is still a lack of convenient in situ methods for the detection and monitoring of TC pollution in actual water systems. This research reports a paper chip based on the complexation of iron-based metal organic frameworks (Fe-MOFs) and TCs for rapid and in situ visual detection of representative oxytetracycline (OTC) pollution in water environments. The optimized complexation sample NH2-MIL-101(Fe)- 350 obtained by calcination at 350 °C exhibited the highest catalytic activity and was then used for paper chip fabrication by printing and surface modification. Notably, the paper chip demonstrated a detection limit as low as 17.11 nmol L-1 and good practicability in reclaimed water, aquaculture wastewater, and surface water systems, with OTC recovery rates of 90.6-111.4%. More importantly, the presence of dissolved oxygen (9.13-12.7 mg L-1), chemical oxygen demand (0.52-12.1 mg L-1), humic acid (< 10 mg L-1), Ca2+, Cl-, and HPO42- (< 0.5 mol L-1) had negligible interference on the detection of TCs by the paper chip. Therefore, this work has developed a promising method for rapid and in situ visual monitoring of TC pollution in actual water environments.

Preparation of thermally stable and surface-functionalized cellulose nanocrystals via mixed H2SO4/Oxalic acid hydrolysis.

A mild and efficient approach for the preparation of cellulose nanocrystals (CNCs) was developed by using mixed H2SO4/Oxalic acid hydrolysis. In this process, the mixed acid of sulfuric acid, oxalic acid and H2O in an optimal mass ratio of 1:5:4 was used to produce CNCs from bleached eucalyptus kraft pulp (BEKP) at 80 °C for 2-5 h. The CNCs with a diameter range of 5-20 nm and a length range of 150-400 nm were obtained at a high yield (>70%) and showed excellent dispersion stability in water and good thermal stability. Moreover, the dosage of sulfuric acid can reduce to 2.4 g/g CNCs in this mixed acid hydrolysis, which is far lower than that of the typical 64% sulfuric acid hydrolysis (55 g/g CNCs, tested in this work). In addition, 91±2% of oxalic acid could be recovered by a simple recrystallization operation.