Size Dependent Dual Functionality of CeO2 Quantum Dots: A Correlation among Parameters for Hydrogen Gas Sensor and Pollutant Remediation.

The metal oxide-based nanostructures of variable size and shape are found effective in optimizing the gas sensing ability and pollutant degradation. The size induced lattice strain and large band gap in 3 nm CeO2 quantum dots evolved the ability towards hydrogen gas sensing and dye degradation compared to nanopebbles and nanoparticles of sizes 15 ± 3, and 30 ± 12 nm. The smaller CeO2 quantum dots than Debye length was found underlying reason for nearly four times sensor response and selectivity towards reducing hydrogen gases than the oxidizing gases at 1 to 10 ppm level. The lattice strain calculated by Rietveld refinement and W-H analysis was found in-line with the size of CeO2 nanostructures. The enhancement in lattice strain and optical band gap (2.66, 2.78, and 2.89 eV) with decrease in size are found critical for determining the overall efficiency of CeO2 nanostructures for photocatalytic activity, attributed to the strong quantum confinement effect. The higher catalytic activity of 98 % was achieved CeO2 quantum dots in comparison to the 95 % and 94 % obtained for CeO2 nanopebbles and nanoparticles. The impact of change in degradation efficacy and gas sensing ability of different CeO2 nanomaterials is discussed in detail. This work offers a novel and simplistic method to produce CeO2 quantum dots as an efficient sensor for selective detection of H2 gas and photocatalyst. The correlation between size, Debye length, band gap, and lattice strain gives an insight for understanding the underlying detection mechanism for selective detection of reducing gas molecules and efficient pollutant remediation.

Miniatured Fluidics-Mediated Modular Self-Assembly of Anticancer Drug-Amino Acid Composite Microbowls for Combined Chemo-Photodynamic Therapy in Glioma.

A particulate carrier with the ability to load a combination of therapeutic molecules acting via diverse modes to initiate cancer cell ablation would help heighten anticancer therapeutic outcomes and mitigate harmful side effects due to high doses of mono drug therapy. Moving a step closer, herein, we have developed doxorubicin-curcumin-amino acid-based composite microbowls (CMBs) following miniaturized fluid flow-based self-assembly. The CMBs were further exploited as dual chemo-photodynamic therapeutic agents in C6 glioma cells cultured in both two-dimensional (2D) monolayer and as three-dimensional (3D) spheroids. These CMBs showed synergistic and visible (blue)-light-sensitive cell-killing effects in both C6 cells and 3D spheroids. Furthermore, these bowl-shaped structures also demonstrated good stability and excellent in vitro cytocompatibility in C6 glioma cells. Our results indicated that CMBs with asymmetric cavities could potentially be used as a combinatorial drug carrier enabling simultaneous chemo- and phototherapy for effective cancer treatment. The use of blue light, from the visible part of the electromagnetic system, to generate the phototherapeutic effect further advocates for the ease and widespread applicability of the systems.

Continuous flow fabrication of Fmoc-cysteine based nanobowl infused core-shell like microstructures for pH switchable on-demand anti-cancer drug delivery.

Asymmetric nanostructures such as nanobowls (NBs) can exhibit superior drug delivery performances owing to their concave structure and interior asymmetric cavities. Here, we present a facile one-step method for the fabrication of NB like structures from a mere single amino acid mimetic, N-(9-fluorenylmethoxycarbonyl)-S-triphenylmethyl-l-cysteine following continuous-flow microfluidics enabled supramolecular self-assembly. Following fabrication, NBs were further infused into a vesicular shell consisting of the amino acid N-(tert-butoxycarbonyl)-S-triphenylmethyl-l-cysteine, carrying dual acid labile groups, the triphenylmethyl and the tert-butyloxycarbonyl groups. The NB infused core-shell like microstructures formed after the shell coating will now be addressed as NB-shells. Presence of pH-responsive shells bestowed the core-shell NB like structures with the ability to actively tune their surface pore opening and closing in response to environmental pH switch. To illustrate the potential use of the NB-shells in the field of anticancer drug delivery, the particles were loaded with doxorubicin (Dox) with an encapsulation efficiency of 42% and Dox loaded NB-shells exhibited enhanced efficacy in C6 glioma cells. Additionally, when tested in an animal model of glioblastoma, the nanoformulations demonstrated significantly higher retardation of tumour growth as compared to free Dox. Thus, this work strives to provide a new research area in the development of well turned-out and neatly fabricated pH switchable on/off anti-cancer drug delivery systems with significant translational potential.

Microflow synthesis and enhanced photocatalytic dye degradation performance of antibacterial Bi2O3 nanoparticles.

Microreactors can play a crucial role in synthesis and rapid testing of various nanocatalyst to be used in addressing the issue of environmental contamination. We have reported the rapid fabrication of polydimethylsiloxane (PDMS) and poly(methyl methacrylate) (PMMA)-based microreactor for the flow synthesis and enhanced inline photocatalysis of bismuth oxide (Bi2O3) nanoparticles. A T-shaped microreactor with uniform circular cross-sectional channel having inner diameter of 450 µm was utilized for synthesizing Bi2O3 nanoparticles with narrow size distribution. Further, photocatalytic dye degradation efficiency for methyl orange (MO) was recorded by coating these Bi2O3 nanoparticles within the inner walls of PMMA-based serpentine microreactors under visible light. The enhanced dye degradation efficiency of as high as 96% within just 15 min of irradiation is reported. A comparative analysis has also been done for both conventional as well as the in-channel photocatalysis highlighting the advantages of microreactor based photocatalysis over the conventional method. Bi2O3 nanoparticles also showed excellent stability even after three cycles indicating reusability of coated microreactors in photocatalysis. The small concentration of as synthesized Bi2O3 nanoparticles also demonstrated high efficacy for the inhibition of Escherichia coli bacterial pathogens.

Continuous Flow Reactor for the Controlled Synthesis and Inline Photocatalysis of Antibacterial Ag2 S Nanoparticles.

The present study is focused on the integration of microreactors to synthesize visible light active nanophotocatalysts for inline photocatalytic degradation of organic dye and antibacterial activity. A wire-assisted and a rapid laser micromachining technique has been employed for the fabrication of polydimethylsiloxane (PDMS) and poly(methyl methacrylate) (PMMA)-based microreactors, respectively. By varying the design and chemical reagents involved, different sizes of visible light active Ag2 S nanoparticles were prepared via a continuous microfluidics approach using fabricated microreactors. When polyvinylpyrrolidone (PVP) was utilized as the capping agent during the reaction, smaller particles of the size of ~ 15 nm were observed. The photocatalytic performance of these nanoparticles has been evaluated inline by employing the single-inlet planar microreactor as a function of flow rate and channel length. The photocatalyst durability test and a comparative photocatalytic efficiency study between the microreactor and the conventional beaker reactor have also been carried out. Under visible light, these nanoparticles exhibit a remarkable enhancement of ~ 94.5% in the inline microreactor-based photocatalytic degradation of methylene blue dye. The slower the flow rate and longer the channel length, gradual enhancement in the performance has been observed. Also, these nanoparticles express an antibacterial effect with very high efficacy even at very low (2 mg mL-1 ) concentration toward the inhibition of Escherichia Coli.