Many chemical and biomedical systems require delivery and controlled release of small molecules, which cannot be achieved by conventional polyelectrolyte-based layer-by-layer capsules. This work proposes an innovative hybrid microcapsule by incorporating in situ formed silica nanoparticles within or on the shell. The influence of various experimental conditions on the stability, mechanical strength and morphology of capsules w as investigated, and characterised by SEM, TEM, XRD, EDX and FTIR. The multifunctional capabilities of formed capsules were examined by encapsulating a small molecule Rhodamine B (Rh-B), which could be further released by an ultrasonic trigger. The results show that in situ formed SiO2 nanoparticles through hydrolysis greatly reduced the permeability of the shell yet with increased mechanical strength and ultrasound response. SiO 2 nanoparticles were shown to be distributed on the surface or inside polyelectrolyte shell, acting as supports for free -standing capsules in both liquid and dry environment. Rapid Rh-B molecules release and the fragmentation of the capsule shells were observed under 50W ultrasound irradiation for a few seconds. Such innovative capsules with capability of small molecule encapsulation and high ultrasound sensitivity could be promising for many applications where pulse release of small molecules is required.
This work aims to improve the rheological properties of partially hydrolysed polyacrylamide (HPAM) for enhanced oil recovery by using SiO 2 nanoparticles (NPs).Novel aqueous HAPM based SiO 2 nanocomposites were formulated and their rheological properties were investigated under different salinities, temperature and aging time. The results show that the inclusion of silica NPs improved significantly the viscosity and viscoelastic properties of HPAM especially under high temperature and high salinities. The NP/HPAM hybrid showed an impressive thermal stability at T= 80 ºCafter 12 days, and the viscosity reached ~5 times of that HPAM at 0.8w% NP loading. The FT-IR spectra data confirmed that the formation of hydrogen bond between the carbonyl groups in HPAM and the silanol functionalities on the surface of silica NPs, which attributed to the improved performance. The oscillation test indicated that seeding SiO 2 remarkably facilitated the cross links among polymer molecules and made the hybrids more elastically dominant. For a given HPAM concentration, it was observed that there was acritical NP concentration (CNC)which many indicating the absorption status of SiO 2 NPsonto HPAM, and the salinity also affected the viscosity value.
Electrochemically
active covalent organic frameworks (COFs) are
promising electrode materials for Li-ion batteries. However, improving
the specific capacities of COF-based electrodes requires materials
with increased conductivity and a higher concentration of redox-active
groups. Here, we designed a series of pyrene-4,5,9,10-tetraone COF
(PT-COF) and carbon nanotube (CNT) composites (denoted as PT-COFX,
where
X
= 10, 30, and 50 wt % of CNT) to address
these challenges. Among the composites, PT-COF50 achieved a capacity
of up to 280 mAh g
–1
as normalized to the active
COF material at a current density of 200 mA g
–1
,
which is the highest capacity reported for a COF-based composite cathode
electrode to date. Furthermore, PT-COF50 exhibited excellent rate
performance, delivering a capacity of 229 mAh g
–1
at 5000 mA g
–1
(18.5C). Using
operando
Raman microscopy the reversible transformation of the redox-active
carbonyl groups of PT-COF was determined, which rationalizes an overall
4 e
–
/4 Li
+
redox process per pyrene-4,5,9,10-tetraone
unit, accounting for its superior performance as a Li-ion battery
electrode.
low specific capacity of 73 mAh g −1 at 500 mA g −1 in a Li-ion cell. However, the electrochemical performance was greatly enhanced by forming the tube-type core-shell structure of the composites (DAPQ-COFX). Using this approach, we achieved specific capacities of up to 162 mAh g −1 at 500 mA g −1 . By varying the composition of the DAPQ-COFX composite, it was found that DAPQ-COF50, which contained 50 wt% of CNT, exhibited the highest utilization of the redox-active sites (95%). Notably, the DAPQ-COF50 composite presents the best rate performance in COF-based electrode materials reported so far, facilitating ultrafast charge/discharge rates as high as 50 A g −1 -this means that the device can be fully charged in just 11 s.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.