Strategies for Improving the Photocatalytic Hydrogen Evolution Reaction of Carbon Nitride-Based Catalysts.

Due to the depletion of fossil fuels and their-related environmental issues, sustainable, clean, and renewable energy is urgently needed to replace fossil fuel as the primary energy resource. Hydrogen is considered as one of the cleanest energies. Among the approaches to hydrogen production, photocatalysis is the most sustainable and renewable solar energy technique. Considering the low cost of fabrication, earth abundance, appropriate bandgap, and high performance, carbon nitride has attracted extensive attention as the catalyst for photocatalytic hydrogen production in the last two decades. In this review, the carbon nitride-based photocatalytic hydrogen production system, including the catalytic mechanism and the strategies for improving the photocatalytic performance is discussed. According to the photocatalytic processes, the strengthened mechanism of carbon nitride-based catalysts is particularly described in terms of boosting the excitation of electrons and holes, suppressing carriers recombination, and enhancing the utilization efficiency of photon-excited electron-hole. Finally, the current trends related to the screening design of superior photocatalytic hydrogen production systems are outlined, and the development direction of carbon nitride for hydrogen production is clarified.

Thermally Managed, Injectable Optoelectronic Probe with Heat Dissipation Guide for Photodynamic Therapy.

The development of fabrication technologies and appearance of new materials has resulted in dramatic increase in the performance of electronic devices, while the overall size has decreased. Recent electronic devices made of micro/nano-size components show high efficiency and outstanding performance with compact size, but these devices have revealed several fatal problems. In particular, the isolated heat that is generated by numerous components concentrated in a limited small area at high density, such as bio-integrated devices, is an issue that needs to be urgently addressed, because it is closely related to the performance and lifetime of electronic devices. To solve these problems, the microscale light emitting diode (µLED)-based neural probe is introduced on an injectable heat dissipation guide. The heat dissipation guide is made of boron nitride (BN) nanomaterials with high thermal conductivity. The heat management noticeably improves the optical output performance of the µLEDs, in which BN effectively dissipates heat, and allows enhanced lighting from the LEDs to be transmitted through brain tissue without thermal damage. Moreover, it shows remarkable improvement in the therapeutic effect of photodynamic therapy of mouse cancer cells.

Silica-Based Nanoparticles as Drug Delivery Vehicles for Prostate Cancer Treatment.

Prostate cancer (PCa) is one of the most commonly diagnosed cancers and is the fifth common cause of cancer-related mortality in men. Current methods for PCa treatment are insufficient owing to the challenges related to the non-specificity, instability and side effects caused by the drugs and therapy agents. These drawbacks can be mitigated by the design of a suitable drug delivery system that can ensure targeted delivery and minimise side effects. Silica based nanoparticles (SBNPs) have emerged as one of the most versatile materials for drug delivery due to their tunable porosities, high surface area and tremendous capacity to load various sizes and chemistry of drugs. This review gives a brief overview of the diagnosis and current treatment strategies for PCa outlining their existing challenges. It critically analyzes the design, development and application of pure, modified and hybrid SBNPs based drug delivery systems in the treatment of PCa, their advantages and limitations.

Thermodynamically Stable Mesoporous C3 N7 and C3 N6 with Ordered Structure and Their Excellent Performance for Oxygen Reduction Reaction.

Carbon nitrides with a high N/C atomic ratio (>2) are expected to offer superior basicity and unique electronic properties. However, the synthesis of these nanostructures is highly challenging since many parts of the CN frameworks in the carbon nitride should be replaced with thermodynamically less stable NN frameworks as the nitrogen content increases. Thermodynamically stable C3 N7 and C3 N6 with an ordered mesoporous structure are synthesized at 250 and 300 °C respectively via a pyrolysis process of 5-amino-1H-tetrazole (5-ATTZ). Polymerization of the precursor to the ordered mesoporous C3 N7 and C3 N6 is clearly proved by X-ray and electron diffraction analyses. A combined analysis including diverse spectroscopy and FDMNES and density functional theory (DFT) calculations demonstrates that the NN bonds are stabilized in the form of tetrazine and/or triazole moieties in the C3 N7 and C3 N6 . The ordered mesoporous C3 N7 represents the better oxygen reduction reaction (ORR) performances (onset potential: 0.81 V vs reversible hydrogen electrode (RHE), electron transfer number: 3.9 at 0.5 V vs RHE) than graphitic carbon nitride (g-C3 N4 ) and the ordered mesoporous C3 N6 . The study on the mechanism of ORR suggests that nitrogen atoms in the tetrazine moiety of the ordered mesoporous C3 N7 act as active sites for its improved ORR activity.

Bio-Inspired Supramolecular Self-Assembled Carbon Nitride Nanostructures for Photocatalytic Water Splitting.

Fast production of hydrogen and oxygen in large amounts at an economic rate is the need of the hour to cater to the needs of the most awaited hydrogen energy, a futuristic renewable energy solution. Production of hydrogen through simple water splitting via visible light photocatalytic approach using sunlight is considered as one of the most promising and sustainable approaches for generating clean fuels. For this purpose, a variety of catalytic techniques and novel catalysts have been investigated. Among these catalysts, carbon nitride is presently deemed as one of the best candidates for the visible light photocatalysis due to its unique molecular structure and adequate visible-range bandgap. Its bandgap can be further engineered by structural and morphological manipulation or by doping/hybridization. Among numerous synthetic approaches for carbon nitrides, supramolecular self-assembly is one of the recently developed elegant bottom-up strategies as it is bio-inspired and provides a facile and eco-friendly route to synthesize high surface area carbon nitride with superior morphological features and other semiconducting and catalytic properties. The current review article broadly covers supramolecular self-assembly synthesis of carbon nitride nanostructures and their photocatalytic water-splitting applications and provides a comprehensive outlook on future directions.

Tailoring the mesoporous texture of graphitic carbon nitride.

Recently, graphitic carbon nitride (g-C3N4) materials have received a great attention from many researchers due to their various roles as a visible light harvesting photocatalyst, metal-free catalyst, reactive template, nitrogen source of nitridation reaction, etc. g-C3N4 could be prepared by temperature-induced polymerization of cyanamide or melamine. In this study, we report a preparation of mesoporous graphitic carbon nitrides with tailored porous texture including pore size, and specific surface area from cyanamide and colloidal silica nanoparticles (Ludox). At first, cyanamide-silica nanocomposites were prepared by mixing colloidal silica with different size in the range of 7-22 nm and cyanamide, followed by evaporating the solvent in the resulting mixture. Mesoporous g-C3N4 samples were prepared by calcining cyanamide-silica nanocomposite at 550 degrees C for 4 hrs and removing the silica nanoparticles by using ammonium hydrogen fluoride. The formation of g-C3N4 was confirmed by the sharp (002) peak (d = 3.25 A) of graphitic interlayer stacking, and the broad (100) peak (d = 6.86 A) of in-plane repeating unit in the X-ray diffraction patterns. According to N2 adsorption-desorption analysis, the pore size of mesoporous carbon nitrides was similar to the size of colloidal silica used as hard template (7-22 nm). The specific surface area of mesoporous g-C3N4 could be tailored in the range of 189 m2/g-288 m2/g.

Heterostructured layered aluminosilicate-itraconazole nanohybrid for drug delivery system.

A nanohybrid, consisting of layered aluminosilicate as a host material and itraconazole as a guest molecule, was successfully synthesized through the interfacial intercalation reaction across the boundary between water and water-immiscible liquid at the various pH. According to the powder X-ray diffraction pattern, the basal spacing of the intraconazole-layered aluminosilicate nanohybrid increased from 14.7 to 22.7 A depending on the pH of the aqueous suspension. The total amounts of itraconazole in the hybrids were determined to be 2.3-25.4 wt% by HPLC analysis. The in vivo pharmacokinetics study was performed in rats in order to compare the absorptions of itraconazole for the itraconazole-layered aluminosilicate nanohybrid and a commercial product, Sporanox. The pharmacokinetic data for the nanohybrid and Sporanox showed that the mean area under the plasma concentration-time curve (AUC, 2477 +/- 898 ng x hr/mL and 2630 +/- 953 ng x hr/mL, respectively) and maximum concentration (Cmax, 225.4 +/- 77.4 ng x hr/mL and 223.6 +/- 51.9 ng x hr/mL, respectively), were within the bioequivalence (BE) range. Therefore, we concluded that this drug-layered aluminosilicate nanohybrid system has a great potential for its application in formulation of poorly soluble drugs.

Egg-yolk core-shell mesoporous silica nanoparticles for high doxorubicin loading and delivery to prostate cancer cells.

Mesoporous silica-based nanoparticles (MSNs) have gained rapid interest as a drug delivery system (DDS) and demonstrated their versatility in delivering drugs for the treatment of various cancers. However, the drug loading efficiency of MSNs is low and is usually improved by improving textural properties through complicated synthesis methods or by post synthesis modification of the surface that can result in the loss of surface area and modify its drug release properties. In this study, we report a direct single-step synthesis of MSNs with a unique egg-yolk core-shell morphology, large pore volume and a hydrophilic surface, decorated with nitrogen rich surface functionalities for increasing its drug loading capacity. This combination of excellent textural properties and surface functionalisation was achieved by a simple soft templating method using dual surfactants and the silica sources assisted by employing either triethylamine (TEA) or triethanolamine (TEO) as the hydrolysis agent. The morphology and well-ordered mesoporous structure can simply be tuned by changing the pH of the synthesis medium that affects the self-assembly mechanism of the micelles. HRTEM image of samples clearly revealed an egg-yolk core-shell morphology with a thin mesoporous silica shell. The optimised MSN samples synthesized at a pH of 11 using either TEA or TEO depicted a higher doxorubicin (Dox) loading capacity of 425 µg mg-1 and 481 µg mg-1 respectively, as compared to only 347 µg mg-1 for MSN samples due to the uniform distribution of nitrogen functionalities. The anticancer activity of Dox loaded MSNs evaluated in two different prostate cancer cell lines (PC-3 and LNCaP) showed a higher cytotoxicity of the drug loaded on optimised MSN samples as compared to pristine MSNs without affecting the cellular uptake of the particles. These results suggest that the unique single-step synthesis and functionalisation method resulted in successfully achieving higher drug loading in egg-yolk core-shell nitrogen functionalised MSNs and could be implemented as an effective carrier of chemotherapeutic drugs.

Influence of Partial Gelatinization Treatment on the Quality Changes of Puffed Rice.

The objective of this study was to examine the quality enhancement of puffed products made with partial gelatinized waxy and non-waxy type rice. The partial gelatinization process increased water holding capacity of samples, regardless of the gelatinization time, with the puffed waxy rice exhibiting higher water holding capacities than the puffed non-waxy rice. The hardness of puffed rice using partial gelatinized waxy or non-waxy type rice was lower compared with non-partial gelatinized samples. Partial gelatinization also increased the final viscosity of the samples, which was decreased by the puffing treatment. The setback viscosity was higher in the partially gelatinized rice than in the non-gelatinized rice and was lower for the puffing treatment. The in vitro starch digestibility of waxy and non-waxy type rice was improved by a puffing treatment. These results suggest that puffed rice using partial gelatinization treatment enhances the quality and digestibility of soft-textured foods.

A geopolymer route to micro- and meso-porous carbon.

Hexagonal and wormhole-type mesoporous geopolymers were developed by controlling the concentration of a structure directing agent (cetrimonium bromide, CTAB) with fixed ratios of Si/Al, KOH/(Si + Al), and H2O/(Si + Al), and their detailed porous structures were confirmed by TEM, N2 adsorption-desorption and X-ray diffraction measurements. The as-prepared geopolymers were then used as templates to replicate porous carbons with various structures and porosities for CO2 adsorption. To understand the correlation between the CO2 adsorptivity and porous structures, we tuned the porosity of the geopolymer-templated carbons by modifying the structures of the geopolymers. The porous carbons obtained from the hexagonal-type porous geopolymers were found to be composed of the aggregates of carbon nanowires exhibiting large particles, while those obtained from the wormhole-like porous geopolymers were determined to be wormhole type as well, as evidenced by TEM and X-ray diffraction studies. According to the CO2 adsorption isotherms of the porous carbons, the aggregates of carbon nanowires exhibited the highest CO2 adsorptivity due to their highest microporosity and largest specific surface area.

A novel geopolymer route to porous carbon: high CO2 adsorption capacity.

The nanostructure and morphology of mesoporous carbon obtained from a newly designed porous geopolymer template were characterized by low-voltage high-resolution scanning electron microscopy. The present porous carbon exhibited a large specific surface area and pore volume, resulting in a high CO2 uptake capacity.

Intercalative hybridization of layered double hydroxide nanocrystals with mesoporous g-C3N4 for enhancing visible light-induced H2 production efficiency.

Efficient visible light active hybrid photocatalysts for H2 production can be synthesized by the intercalative hybridization of Zn-Cr-layered double hydroxide (Zn-Cr-LDH) with a mesoporous g-C3N4 lattice. Small Zn-Cr-LDH nanocrystals with a size of ∼6 nm are immobilized in the mesopores of g-C3N4. Beyond an optimal LDH/g-C3N4 molar ratio of 0.3, a further increase in the LDH content leads to the surface deposition of LDH crystals on the g-C3N4 material as well as the intercalative immobilization of LDH into its mesopores, indicating the controllability of the LDH deposition site. The Zn-Cr-LDH-g-C3N4 nanohybrids exhibit smaller surface areas than the pristine g-C3N4, confirming the intercalative stabilization of Zn-Cr-LDH nanocrystals in the mesopore of g-C3N4. The hybridization between Zn-Cr-LDH and g-C3N4 is effective in enhancing visible light absorptivity and also in depressing electron-hole recombination, which is attributable to an efficient electronic coupling between both the hybridized components. The present Zn-Cr-LDH-g-C3N4 nanohybrid exhibits promising photocatalytic activities for visible light-induced H2 production at a rate of 155.7 µmol g-1 h-1, which is much superior to that of the pristine g-C3N4 (21.7 µmol g-1 h-1). The present study underscores that the intercalative immobilization of Zn-Cr-LDH crystals in the limited space of a mesopore is quite useful in improving the visible light active photocatalyst functionality of mesoporous carbon nitride.

Intracrystalline structure and physicochemical properties of mixed SiO2-TiO2 sol-pillared aluminosilicate.

Highly porous layered inorganic-inorganic nanohybrids were prepared by pillaring SiO2-TiO2 nanosol particles with aluminosilicate layers. According to powder X-ray diffraction analysis, the basal spacing of SiO2-TiO2 pillared aluminosilicate (STPC) calcined at 400 degrees C was determined to be larger than 40 A. N2 adsorption-desorption isotherm measurements showed the STPC to have a large Brunauer-Emmett-Teller surface area of approximately 590 m2/g, of which approximately 70% originates from micropores with a size range of 8-16 A. The sorption behavior of various solvent vapors such as hexane, methanol, and water reveals internal pore surfaces of the STPC to be hydrophobic. A distinct blue shift of absorption edge in UV-vis spectra clearly demonstrates that the nanosized TiO2 particles are formed between silicate layers as a pillar. Fourier transform infrared and extended X-ray absorption fine structure analysis at the Ti K edge reveals that the pillared titania exists in the form of anatase-structured TiO2 nanocrystals, not in the form of covalently bonded mixed particles of TiO2-SiO2. On the basis of the present findings, we are able to conclude that the quantum-sized TiO2 and SiO2 particles are independently intercalated to form a multilayer stacking intracrystalline structure in the gallery space of aluminosilicate clay.

Heterostructured nanohybrid of zinc oxide-montmorillonite clay.

We have synthesized heterostructured zinc oxide-aluminosilicate nanohybrids through a hydrothermal reaction between the colloidal suspension of exfoliated montmorillonite nanosheets and the sol solution of zinc acetate. According to X-ray diffraction, N2 adsorption-desorption isotherm, and field emission-scanning electron microscopic analyses, it was found that the intercalation of zinc oxide nanoparticles expands the basal spacing of the host montmorillonite clay, and the crystallites of the nanohybrids are assembled to form a house-of-cards structure. From UV-vis spectroscopic investigation, it becomes certain that calcined nanohybrid contains two kinds of the zinc oxide species in the interlayer space of host lattice and in mesopores formed by the house-of-cards type stacking of the crystallites. Zn K-edge X-ray absorption near-edge structure/extended X-ray absorption fine structure analyses clearly demonstrate that guest species in the nanohybrids exist as nanocrystalline zinc oxides with wurzite-type structure.

2D Inorganic-Antimalarial Drug-Polymer Hybrid with pH-Responsive Solubility.

Artesunic acid (ASH), an antimalarial drug, has low oral bioavailability due to its low aqueous solubility. To overcome this problem, artesunate (AS) was intercalated into zinc basic salt (ZBS) via co-precipitation. AS was immobilized with a tilted double layer arrangement, which was also confirmed by XRD and 1-D electron density mapping. In order to decrease the release rate of AS under gastrointestinal conditions and to simultaneously increase the release rate of AS under intestinal conditions, ZBS-AS was coated with EUDRAGIT L100 (ZBS-AS-L100). Finally, we performed an in-vivo pharmacokinetic study to compare the oral bioavailability of AS of ZBS-AS-L100 with that of ASH. Surprisingly, it was found that the former is 5.5 times greater than the latter due to an enhanced solubility of AS thanks to the ternary hybridization with ZBS and EUDRAGIT L100. Therefore, the present ZBS-AS-L100 system has a great potential as a novel antimalarial drug formulation with pH selectivity and enhanced bioavailability.

Drug-inorganic-polymer nanohybrid for transdermal delivery.

For transdermal drug delivery, we prepared a drug-inorganic nanohybrid (FB-LDH) by intercalating a transdermal model drug, flurbiprofen (FB), into the layered double hydroxides (LDHs) via coprecipitation reaction. The X-ray diffraction patterns and FT-IR spectra of the FB-LDH indicated that the FB molecules were successfully intercalated via electrostatic interaction within the LDH lattices. The in vitro drug release revealed that the Eudragit(®) S-100 in release media could facilitate the drug out-diffusion by effectively replacing the intercalated drug and also enlarging the lattice spacing of the FB-LDH. In this work, a hydrophobic gel suspension of the FB-LDH was suggested as a transdermal controlled delivery formulation, where the suspensions were mixed with varying amounts of Eudragit(®) S-100 aqueous solution. The Frantz diffusion cell experiments using mouse full-skins showed that a lag time and steady-state flux of the drug could be controlled from 12.8h and 3.28µgcm(-2)h(-1) to less than 1h and 14.57µgcm(-2)h(-1), respectively, by increasing the mass fraction of Eudragit(®) S-100 solution in gel suspensions from 0% to 20% (w/w), respectively. Therefore, we conclude gel formulation of the FB-LDH have a potential for transdermal controlled drug delivery.