Effects of Glycine‐Based Ionic Liquid on Spherulite Morphology of Poly(l‐Lactide)

Crystalline morphology, lamellar assembly, spherulitic growth rate, and physical properties of poly(l ‐lactide acid) (PLLA) modified by a room‐temperature ionic liquid (IL), N‐alkyl‐substituted‐glycine ester [N,N‐dimethyl‐N‐propyl glycine ethyl ester (DMPGlyET)⁺] bis(fluoromethanesufonyl)imide [TFSI^?], are investigated by using polarized optical microscopy, optical microscopy, differential scanning calorimetric, and atomic‐force microscopy. Thermal analyses and in situ microscopy characterization reveal the PLLA/IL mixture with upper‐critical‐solution‐temperature behavior. Crystalline morphology of PLLA is significantly changed by the addition of IL to display massive diversification of spherulites morphology which has never been reported before in neat PLLA or PLLA blends with polymers. The morphological change and diversifications in PLLA/IL mixture are associated with strong interactions between PLLA and IL, which impede the melt crystallization of PLLA and tend to form PLLA nuclei of various geometry shapes. In addition, neat PLLA is generally brittle with extensive crack formation during postcrystallization cooling process; however, with the addition of IL, cracks are reduced or diminished entirely, potentially to enhance the performance and properties of PLLA.

     

Coexisting Straight,Radial, and Banded Lamellae on the Six Corners of Hexagon‐Shaped Spherulites in Poly(l‐Lactide)

A novel six‐petal spherulite morphology composed of a combination of a central hexagonal core, hexagon‐shaped ring bands, and six fibrous stalks is discovered in a low‐molecular‐weight poly(l ‐lactide acid) (LM_w‐PLLA) that is melt crystallized at a specific T_c = 110 °C and confined in thin films. The structures are analyzed by using polarized optical microscopy (POM) and atomic force microscopy (AFM). Discrete lamellae, consisting of sequenced wide and small lamellae, all in flat‐on orientation with periodically up‐and‐down topology, are packed in a ring‐banded alignment, while continuous lamellae in flat‐on, tilted, or edge‐on orientations are arranged in the fibrous region. On the six corners of a symmetric hexagon‐banded spherulite, the radial fibrous lamellae overlap with ring‐band lamellae to show a mixed combination of ring‐banded and fibrous patterns. The formation of coexisting ring‐banded and fibrous patterns in a mixed morphology is associated with the lamellar packing and orientation. The radial fibrous lamellae at the six corners favorably occur in the growth fronts, which are closer to the reservoir of materials of diffusing species. Superimposed on the radial lamellae, hexagon‐shaped ring bands repeat themselves on the outskirts of the central hexagon nuclei. The geometry of the initial crystal is believed to be the influencing factors in final spherulite patterns.

     

Comparison of the effects of synthesis methods of B,N, S,and P-doped carbon dots with high photoluminescence properties on HeLa tumor cells

Although heteroatom doping is widely used to promote the optical properties of carbon dots for biological applications, the synthesis process still has problems such as multi-step process, complicating the setting of instrument along with uncontrolled products. In the present study, some elements such as boron, nitrogen, sulfur, and phosphor were intentionally doped into citric acid-based carbon dots by furnace- and microwave-assisted direct and simple carbonization processes. The process produced nanoparticles with an average diameter of 5–9 nm with heteroatoms (B, N, S, and P) placed on the core and surface of carbon dots. Among the doped carbon dots prepared, boron-doped carbon dots obtained by the microwave-assisted (B-CDs2) process showed the highest photoluminescence intensity with a quantum yield (QY) of about 32.96%. All obtained carbon dots exhibit good stability (at pH 6–12 and high ionic strength concentrations up to 0.5 M), whereas cytotoxicity analysis showed that all doped carbon dots are low-toxic with an average cell viability percentage above 80% up to 500 μg mL⁻¹. It can be observed from the CLSM image of all doped carbon dots that the doping process not only increases the QY percentage, but also might accelerate the HeLa uptake on it and produce strong carbon dot emission at the cytoplasm of the cell. Thus, the proposed synthesis process is promising for high-potency bioimaging of HeLa cancer cells.

Investigation of the effect of nitrogen, boron, sulphur, and phosphor as doping elements on carbon dots, where boron-carbon dots performed good potential for bioimaging application with best optical properties and specific targeting features.