Laser-Driven Rapid Synthesis of Metal-Organic Frameworks and Investigation of UV-NIR Optical Absorption, Luminescence, Photocatalytic Degradation, and Gas and Ion Adsorption Properties.

In this study, we designed a platform based on a laser-driven approach for fast, efficient, and controllable MOF synthesis. The laser irradiation method was performed for the first time to synthesize Zn-based MOFs in record production time (approximately one hour) compared to all known MOF production methods with comparable morphology. In addition to well-known structural properties, we revealed that the obtained ZnMOFs have a novel optical response, including photoluminescence behavior in the visible range with nanosecond relaxation time, which is also supported by first-principles calculations. Additionally, photocatalytic degradation of methylene blue with ZnMOF was achieved, degrading the 10 ppm methylene blue (MB) solution 83% during 1 min of irradiation time. The application of laser technology can inspire the development of a novel and competent platform for a fast MOF fabrication process and extend the possible applications of MOFs to miniaturized optoelectronic and photonic devices.

Encapsulation of antioxidant beta-carotene by cyclodextrin complex electrospun nanofibers: Solubilization and stabilization of beta-carotene by cyclodextrins.

Carotenoids act as effective antioxidant defense systems in humans as they scavenge molecular oxygen and peroxyl radicals. However, their poor water solubility and being susceptible to degradation driven by light and oxygen hinder their bioactivity, therefore, they should be stabilized by host matrices against oxidation. Here, ß-carotene was encapsulated in electrospun cyclodextrin (CD) nanofibers to increase its water-solubility and photostability to enhance its antioxidant bioactivity. ß-carotene/CD complex aqueous solutions were electrospun into nanofibers. The bead-free morphology of the ß-carotene/CD nanofibers was confirmed by SEM. The formation of ß-carotene/CD complexes was explored through computational modeling and experimentally by FTIR, XRD and solubility tests. The antioxidant activity of the fibers exposed to UV irradiation was demonstrated via a free radical scavenger assay, where ß-carotene/CD nanofibers revealed protection against UV radiation. Overall, this work reports the water-borne electrospinning of antioxidant ß-carotene/CD inclusion complex nanofibers, which stabilize the encapsulated ß-carotene against UV-mediated oxidation.

Building an Iron Chromophore Incorporating Prussian Blue Analogue for Photoelectrochemical Water Oxidation.

Invited for the cover of this issue is the Ferdi Karadas and Ekmel Ozbay groups at Bilkent University and co-workers. The image presents an utopic city in Iron Age, which is powered by an iron photosensitizer that bridges semiconductor buildings (TiO2 nanowires) and the catalyst (cobalt site). Read the full text of the article at 10.1002/chem.202100654.

Building an Iron Chromophore Incorporating Prussian Blue Analogue for Photoelectrochemical Water Oxidation.

The replacement of traditional ruthenium-based photosensitizers with low-cost and abundant iron analogs is a key step for the advancement of scalable and sustainable dye-sensitized water splitting cells. In this proof-of-concept study, a pyridinium ligand coordinated pentacyanoferrate(II) chromophore is used to construct a cyanide-based CoFe extended bulk framework, in which the iron photosensitizer units are connected to cobalt water oxidation catalytic sites through cyanide linkers. The iron-sensitized photoanode exhibits exceptional stability for at least 5 h at pH 7 and features its photosensitizing ability with an incident photon-to-current conversion capacity up to 500 nm with nanosecond scale excited state lifetime. Ultrafast transient absorption and computational studies reveal that iron and cobalt sites mutually support each other for charge separation via short bridging cyanide groups and for injection to the semiconductor in our proof-of-concept photoelectrochemical device. The reorganization of the excited states due to the mixing of electronic states of metal-based orbitals subsequently tailor the electron transfer cascade during the photoelectrochemical process. This breakthrough in chromophore-catalyst assemblies will spark interest in dye-sensitization with robust bulk systems for photoconversion applications.

Polymer-free nanofibers from vanillin/cyclodextrin inclusion complexes: high thermal stability, enhanced solubility and antioxidant property.

Vanillin/cyclodextrin inclusion complex nanofibers (vanillin/CD-IC NFs) were successfully obtained from three modified CD types (HPßCD, HPγCD and MßCD) in three different solvent systems (water, DMF and DMAc) via an electrospinning technique without using a carrier polymeric matrix. Vanillin/CD-IC NFs with uniform and bead-free fiber morphology were successfully produced and their free-standing nanofibrous webs were obtained. The polymer-free CD/vanillin-IC-NFs allow us to accomplish a much higher vanillin loading (∼12%, w/w) when compared to electrospun polymeric nanofibers containing CD/vanillin-IC (∼5%, w/w). Vanillin has a volatile nature yet, after electrospinning, a significant amount of vanillin was preserved due to complex formation depending on the CD types. Maximum preservation of vanillin was observed for vanillin/MßCD-IC NFs which is up to ∼85% w/w, besides, a considerable amount of vanillin (∼75% w/w) was also preserved for vanillin/HPßCD-IC NFs and vanillin/HPγCD-IC NFs. Phase solubility studies suggested a 1 : 1 molar complexation tendency between guest vanillin and host CD molecules. Molecular modelling studies and experimental findings revealed that vanillin : CD complexation was strongest for MßCD when compared to HPßCD and HPγCD in vanillin/CD-IC NFs. For vanillin/CD-IC NFs, water solubility and the antioxidant property of vanillin was improved significantly owing to inclusion complexation. In brief, polymer-free vanillin/CD-IC NFs are capable of incorporating a much higher loading of vanillin and effectively preserve volatile vanillin. Hence, encapsulation of volatile active agents such as flavor, fragrance and essential oils in electrospun polymer-free CD-IC NFs may have potential for food related applications by integrating the particularly large surface area of NFs with the non-toxic nature of CD and inclusion complexation benefits, such as high temperature stability, improved water solubility and an enhanced antioxidant property, etc.

Encapsulation of gallic acid/cyclodextrin inclusion complex in electrospun polylactic acid nanofibers: Release behavior and antioxidant activity of gallic acid.

Cyclodextrin-inclusion complexes (CD-ICs) possess great prominence in food and pharmaceutical industries due to their enhanced ability for stabilization of active compounds during processing, storage and usage. Here, CD-IC of gallic acid (GA) with hydroxypropyl-beta-cyclodextrin (GA/HPßCD-IC) was prepared and then incorporated into polylactic acid (PLA) nanofibers (PLA/GA/HPßCD-IC-NF) using electrospinning technique to observe the effect of CD-ICs in the release behavior of GA into three different mediums (water, 10% ethanol and 95% ethanol). The GA incorporated PLA nanofibers (PLA/GA-NFs) were served as control. Phase solubility studies showed an enhanced solubility of GA with increasing amount of HPßCD. The detailed characterization techniques (XRD, TGA and (1)H-NMR) confirmed the formation of inclusion complex between GA and HPßCD. Computational modeling studies indicated that the GA made an efficient complex with HPßCD at 1:1 either in vacuum or aqueous system. SEM images revealed the bead-free and uniform morphology of PLA/GA/HPßCD-IC-NF. The release studies of GA from PLA/GA/HPßCD-IC-NF and PLA/GA-NF were carried out in water, 10% ethanol and 95% ethanol, and the findings revealed that PLA/GA/HPßCD-IC-NF has released much more amount of GA in water and 10% ethanol system when compared to PLA/GA-NF. In addition, GA was released slowly from PLA/GA/HPßCD-IC-NF into 95% ethanol when compared to PLA/GA-NF. It was also observed that electrospinning process had no negative effect on the antioxidant activity of GA when GA was incorporated in PLA nanofibers.