The influence of combination mode on the structure and properties of porphyrin–graphene oxide composites

Efficient photohydrogen production by edge-modified carbon nitride with nonmetallic group

As an efficient photocatalyst, graphitic carbon nitride (g-C3N4) has been widely used in the field of photocatalytic hydrogen production. However, how to prepare hydrogen efficiently and stably has become a challenge. Herein, we successfully realize metal-free edge modification with phenyl groups by one-step thermal polymerization of urea with 4-phenyl-3-thiosemicarbazide. Consequently, the optimal photocatalytic hydrogen production rate for the modified graphitic carbon nitride is increased by three times to a value of 2390.6 μmol h-1 g-1, while the apparent quantum efficiency (AQE) reaches 8.3 % at a wavelength of 420 nm. We also provide a theoretical explanation for the experiments using density functional theory (DFT) calculations, which suggest that energy level changes and electron redistribution for the modified carbon nitride materials contribute to the observed changes in catalytic performance. This work provides an effective solution for improving the photocatalytic activity of carbon nitride materials and provides theoretical support for the edge modification of carbon nitride materials to promote their photocatalytic hydrogen production efficiency.

Control of the Biodegradability of Piezoelectric Peptide Nanotubes Integrated with Hydrophobic Porphyrin

Diphenylalanine (FF) is a piezoelectric material that is widely known for its high piezoelectric constant, self-assembly characteristics, and ease of manufacture. Because of its biocompatible nature, it is useful for implantable applications. However, its use in real applications is challenging because it degrades too easily in the body due to its solubility in water (0.76 g/mL). Upon incorporation of hydrophobic and biocompatible porphyrins into the FF, the degradability of the piezoelectric FF and their piezoelectric nanogenerators (PENGs) is controlled. Porphyrin-incorporated FFs are also formed as piezoelectric nanostructures well aligned on the substrate through self-assembly, and their piezoelectric properties are comparable to those of FF. The FF-based PENG degrades in only 5 min, whereas the FF-porphyrin-based PENG produces a stable output for >15 min in phosphate-buffered saline. This strategy for realizing biodegradable functional materials and devices with tunable degradation rates in the body can be applied to many implantable electronics.

Surface modification of graphene oxide via noncovalent functionalization with porphyrins for selective photocatalytic oxidation of alcohols

GO–porphyrin composites were simply prepared by a self-assembly process. The noncovalent interactions between the porphyrins and oxygen-containing functional groups on GO play a crucial role in controlling their photocatalytic activities.

Mitochondria-targeted tri-triphenylphosphonium substituted meso-tetra(4-carboxyphenyl)porphyrin(TCPP) by conjugation with folic acid and graphene oxide for improved photodynamic therapy

Mitochondria are extensively researched as target sites to maximize photodynamic therapy (PDT) effects because they play crucial roles in metabolism. Here, a mitochondria targeting PDT agent, tri-triphenylphosphonium substituted meso-tetra(4-carboxyphenyl)porphyrin (TCPP-TPP) is prepared for the first time. Considering that many porphyrin derivatives are quick to aggregate, thereby reducing the PDT effect, our photosensitizer (PS) was loaded on a folic acid (FA) decorated graphene oxide (GO) nanosystem, called GF@TCPP-TPP, by electrostatic and [Formula: see text]–[Formula: see text] stacking or hydrophobic cooperative interactions, to improve the transportation of photosensitizers and enhance the therapeutic effect. Herein, we have performed a detailed study of photodynamic activity of GF@TCPP-TPP nanocomposites and evaluated their potential as a photosensitizer in PDT. An MTT assay showed that GF@TCPP-TPP inhibited HeLa cells in a concentration-dependent manner under light (650 ± 10 nm, 5 mW [Formula: see text] and 10 min), and presented remarkably improved PDT efficiency (IC[Formula: see text] g [Formula: see text] mL[Formula: see text] of equivalent TCPP-TPP) over free TCPP (IC[Formula: see text] after irradiation. Furthermore, our research indicated that Type I mechanisms (the generation of hydroxyl radicals) play a predominant role in the GF@TCPP-TPP induced PDT process. This coincides with the low singlet oxygen (1O[Formula: see text] quantum yield ([Formula: see text] [Formula: see text] 33.6%) in a DMF solution. Moreover, cell morphological changes after GF@TCPP-TPP PDT further demonstrated that GF@TCPP-TPP could induce damage and apoptotic cell death efficiently. In particular, precise delivery of photosensitizers to mitochondria was proven by organelle localization.

Porphyrin-functionalized graphene oxide sheets: An efficient nanomaterial for micro solid phase extraction of non-steroidal anti-inflammatory drugs from urine samples

In this work, porphyrin-functionalized graphene oxide nanosheets (GO@meso-tetrakis(4-hydroxyphenyl)porphyrin) were synthesized and employed as the sorbent. Porphyrins owing to their unique structures and tunable terminal functional groups are expected to be promising media for extraction of the desired analytes. Also, GO with a high specific surface area has exhibited good potential for the extraction purposes. Inspired by these intriguing properties, the combination of GO and porphyrin can benefit both of these amazing features. The synthesized sorbent was utilized for micro solid phase extraction of non-steroidal anti-inflammatory drugs followed by HPLC-UV. Optimization of the experimental factors including sorbent amount, sample pH, sample and eluent flowrates, eluent volume, and the number of desorption cycles were performed with the aid of central composite design. Under the optimal conditions, the calibration curves were linear within the range of 2.0-600 ng mL^-1 and limits of detection were found between 0.5-2.0 ng mL^-1. The preconcentration factors and absolute recoveries were obtained in the range of 4.80-9.79 and 29%-59%, respectively. The matrix effect for the urine samples varied between 81.9%-91.6% at two concentrations of 50 and 300 ng mL^-1, respectively. Intra- and inter-day RSD% (n = 3) of the spiked urine samples at three level concentrations of 25, 100, and 300 ng mL^-1 were less than 10%. The relative recoveries of the urine samples were calculated in the range of 85.2-98.6%. Eventually, the method exhibits proper sensitivity, excellent repeatability, high reusability, and acceptable precision and accuracy.

Cationic Porphyrin-Graphene Oxide Hybrid: Donor-Acceptor Composite for Efficient Photoinduced Electron Transfer

Non-covalent nanohybrids composed of cationic 5,10,15,20-tetra(4-trimethylammoniophenyl)porphyrin tetra(p-toluenesulfonate) (TMAP) and the graphene oxide sheets were prepared under two pH values (6.2 vs. 1.8). The TMAP molecule was positively charged, regardless of the pH value during preparation. However, protonation of the imino nitrogens increased the overall charge of the porphyrin molecule from +4 to +6 (TMAP⁴⁺ and TMAP⁶⁺ ). It was found that at acidic pH, interaction of TMAP⁶⁺ with GO was largely suppressed. On the other hand, results of FTIR, Raman spectroscopy, thermogravimetric analysis, atomic force microscopy (AFM) and elemental analysis confirmed effective non-covalent functionalization of graphene oxide with cationic porphyrin at pH 6.2. The TMAP⁴⁺ -GO hybrids exhibited well defined structure with a monolayer of TMAP⁴⁺ on the GO sheets as confirmed by AFM. Formation of the ground-state TMAP⁴⁺ -GO complex in solution was monitored by the red-shift of the porphyrin Soret absorption band. This ground-state interaction between TMAP⁴⁺ and GO is responsible for the static quenching of the porphyrin emission. Fluorescence was not detected for the nanohybrid which indicated that a very fast deactivation process had to take place. Ultrafast time-resolved transient absorption spectroscopy clearly demonstrated the occurrence of electron transfer from the photoexcited TMAP⁴⁺ singlet state to GO sheets, as proven by the formation of a porphyrin radical cation.

Supramolecular Complexes of Graphene Oxide with Porphyrins: An Interplay between Electronic and Magnetic Properties

Graphene oxide (GO) was modified by two modified porphyrins (THPP and TCPP) to form GO–porphyrin hybrids. Spectroscopic measurements demonstrated the formation of stable supramolecular aggregates when mixing two components in solution. The Fourier transform infrared (FTIR) and Raman scattering measurements confirm π-stacking between hydrophobic regions of GO nanoflakes and porphyrin molecules. On the number and the kind of paramagnetic centers generated in pristine GO samples, which originate from spin anomalies at the edges of aromatic domains within GO nanoflakes. More significant changes in electronic properties have been observed in hybrid materials. This is particularly evident in the drastic increase in the number of unpaired electrons for the THPP-GO sample and the decrease in the number of unpaired electrons for the TCPP-GO. The difference of paramagnetic properties of hybrid materials is a consequence of π-stacking between GO and porphyrin rings. An interesting interplay between modifiers and the surface of GO leads to a significant change in electronic structure and magnetic properties of the designed hybrid materials. Based on the selection of molecular counterpart we can affect the behavior of hybrids upon light irradiation in a different manner, which may be useful for the applications in photovoltaics, optoelectronics, and spintronics.

Graphene quantum dots supported by graphene oxide as a sensitive fluorescence nanosensor for cytochrome c detection and intracellular imaging

A new class of Cyt c detection fluorescence sensor based on graphene quantum dots supported by graphene oxide has been facilely developed. The sensor shows a high sensitivity and selectivity for Cyt c detection, and further exhibits favorable intracellular imaging in A549 cells.

Molecular engineering of Ni-/Co-porphyrin multilayers on reduced graphene oxide sheets as bifunctional catalysts for oxygen evolution and oxygen reduction reactions

Ni- and Co-porphyrin multilayers on reduced graphene oxide (rGO) sheets are reported as novel bifunctional catalysts for the oxygen evolution reaction (OER) and the oxygen reduction reaction (ORR). After binding with organic porphyrin molecules, the catalytically-active Ni2+ and Co2+ ions are periodically constructed onto the rGO surfaces via the layer-by-layer (LBL) assembly technique. The resulting catalysts exhibit good performance towards both OER and ORR, which is achieved with accurate control of the composition and thickness of the multilayer structures. This work highlights the potential for the fabrication of efficient electrocatalysts via molecular design.