Photocatalytic applications with CdS•block copolymer/exfoliated graphene nanoensembles: Hydrogen generation and degradation of Rhodamine B

Amphiphilic block copolymer poly (isoprene-b-acrylic acid) (PI-b-PAA) stabilized exfoliated graphene in water and allowed the immobilization of semiconductor CdS nanoparticles forming CdS•PI-b-PAA/graphene. Characterization with HR-TEM and EDX justified the success of preparation and revealed the presence of spherical CdS. Moreover, UV-Vis and photoluminescence assays suggested that electronic interactions within CdS•PI-b-PAA/graphene exist as evidenced by the significant quenching of the characteristic emission of CdS by exfoliated graphene. Photoillumination of CdS•PI-b-PAA/graphene, in the presence of ammonium formate as quencher for the photogenerated holes, resulted on the generation of hydrogen by water splitting, monitored by the reduction of 4-nitroaniline to benzene-1,4-diamine (> 80±4% at 20 min; 100% at 24 min), much faster and efficient as compared when reference CdS•PI-b-PAA was used as photocatalyst (< 30±3% at 20 min; 100% at 240 min). Moreover, Rhodamine B was photocatalytically degraded by CdS•PI-b-PAA/graphene, with fast kinetics under visible light illumination in the presence of air. The enhancement of both photocatalytic processes by CdS•PI-b-PAA/graphene was rationalized in terms of effective separation of holes–electrons, contrary to reference CdS•PI-b-PAA, in which rapid recombination of the hole–electron pair is inevitable due to the absence of exfoliated graphene as suitable electron acceptor

Sulfur-doped carbon nanohorn bifunctional electrocatalyst for water splitting

Sulfur-doped carbon nanohorns (S-CNHs) were prepared by an easy one-pot solvothermal process and were employed as efficient electrocatalysts towards water splitting. Initially, oxidation of CNHs followed by thermal treatment with the Lawesson’s reagent resulted in the formation of S-CNHs with the sulfur content determined as high as 3%. The S-CNHs were thoroughly characterized by spectroscopic, thermal and electron microscopy imaging means and then electrocatalytically screened. Specifically, S-CNHs showed excellent activity and durability for both O2 and H2 evolution reactions, by showing low overpotential at 1.63 and -0.2 V vs. RHE for oxygen and hydrogen evolution reaction, respectively. Additionally, S-CNHs showed significantly lower Tafel slope value and lower current resistance compared to oxidized and pristine CNHs for both electrocatalytic reactions. The outstanding electrocatalytic properties and high conductivity, along with the high S-doping level, render S-CNHs a promising bifunctional electrocatalyst for water splitting

Chemical Functionalization of 2D Materials

This Special Issue of Chemistry-A European Journal is dedicated to the Chemical Functionalization of 2D Materials, and features some great contributions from experts in the field of 2D materials. This issue was originally assembled to support the Symposium G "Chemical Functionalization of 2D Materials" at the European Materials Research Society (E-MRS) 2020 Spring Meeting, which was originally scheduled to be held in Strasbourg, France, from May 25th to 29th, 2020. Although the E-MRS 2020 Spring Meeting has been cancelled due to the COVID-19 outbreak, the publication of this Special Issue has proceeded and has become even more important as the contributors discuss diverse and timely research themes related to 2D materials. In this Editorial, a brief overview of the different types of 2D materials is given, together with the chemical functionalization schemes that can be applied to them to achieve new properties as well as enable improved performance in applications. Some of the articles featured in this Special Issue are also highlighted, with the hope that they will inspire readers and further advance the field

Oligothiophene/graphene supramolecular ensembles managing light induced processes: Preparation, characterization, and femtosecond transient absorption studies leading to charge‐separation

Advances  in  organic  synthetic  chemistry  combined  with  the  exceptional  electronic  properties  of  carbon  allotropes,  particularly graphene, is the basis to design and fabricate novel electron donor-­‐acceptor ensembles with desired properties for technological applications. Thiophene-­‐based materials, mainly thiophene-­‐containing polymers, are known for  their  notable  electronic  properties.  In  this  frame  moving  from  polymer  to  oligomer  forms,  new  fundamental  information would help to the better understanding of their electrochemical and photophysical properties. Furthermore, a successful  combination  of  their  electronic  properties  with  those  of  graphene  is  a  challenging  goal.  In  this  work  two  oligothiophene compounds consists of three and nine thiophene-­‐rings, abbreviated as 3T and 9T, respectively, were synthesized and noncovalently associated with liquid phase exfoliated few-­‐layered graphene sheets (abbreviated as eG), forming donor-­‐acceptor 3T/eG and 9T/eG nanoensembes. Markedly, intra-­‐ensemble electronic interactions between the two  components  in  the  ground  and  excited  states  were  evaluated  with  the  aid  of  UV-­‐Vis  and  photoluminescence  spectroscopy. Furthermore, redox assays revealed an one-­‐electron oxidation of 3T accompanied by one-­‐electron reduction due  to  eG  in  3T/eG,  while  two  reversible  one-­‐electron  oxidations  of  9T  accompanied  by  one-­‐electron  reduction  of  eG  9T/eG. The electrochemical band gap for 3T/eG and 9T/eG ensembles were calculated and verified that the negative free-­‐energy change for the charge-­‐separated state of 3T/eG and 9T/eG via the singlet excited state of 3T and 9T respectively, were  thermodynamically  favorable.  Finally,  results  of  transient  pump-­‐probe  spectroscopic  studies  at  the  femtosecond  time scale were supportive of charge transfer type interactions in the 3T/eG and 9T/eG ensembles. The estimated rates for intra-­‐ensemble charge separation were found to be 9.52 x 109 s-­‐1 and 2.2 x 1011 s-­‐1, respectively, for 3T/eG and 9T/eG in THF, revealing moderate to ultrafast photoinduced events in the oligothiophene/graphene supramolecular ensemble

Structure and properties of the stable two-dimensional conducting polymer Mg5C60

We present a study on the structural, spectroscopic, conducting, and magnetic properties of Mg5C60, which is a two-dimensional (2D) fulleride polymer. The polymer phase is stable up to the exceptionally high temperature of 823 K. The infrared and Raman studies suggest the formation of single bonds between the fulleride ions and possibly Mg-C-60 covalent bonds. Mg5C60 is a metal at ambient temperature, as shown by electron spin resonance and microwave conductivity measurements. The smooth transition from a metallic to a paramagnetic insulator state below 200 K is attributed to Anderson localization driven by structural disorder

Adsorption of fullerene and azafullerene on Cu(111) studied by electron energy loss spectroscopy

Fullerene and azafullerene films were studied by electron energy loss spectroscopy in reflection geometry. Compared to C60, (C59N)2 multilayers show additional vibrational modes that are characteristic of the dimer structure. The (C59N)2 is semiconductor-like and giant optically allowed excitonic transitions are found in the gap in drastic contrast with C60. The azafullerene monolayer on Cu(111) no longer shows the presence of dimers, indicating monomer adsorption. Similarly to C60, azafullerene molecules in contact with the metal substrate receive a transferred charge between two and three electrons. However, the C59N appears more covalently bound to Cu because it decomposes when heated above 660 K while C60 only desorbs.

Donor-acceptor nanoensembles of soluble carbon nanotubes

Donor-acceptor nanoensembles, prepared via electrostatic interactions of single wall carbon nanotubes and porphyrin salts, give rise to photoinduced intra-complex charge separation that lasts tens of microseconds.Peer reviewedChemistr

Synthesis of Novel Porphyrin and its Complexes Covalently Linked to Multi-Walled Carbon Nanotubes and Study of their Spectroscopy

Novel covalent porphyrin and its complexes (Co2+, Zn2+) functionalized multi-walled carbon nanotubes (MWNTs) have been successfully synthesized by the reaction of the carboxyl on the surface of MWNTs which was synthesized to use carbon radicals generated by the thermal decomposition of azodiisobutyronitrile (AIBN) with 5-p-hydroxyphenyl-10,15,20-triphenyl-porphyrin and its complexes (Co2+, Zn2+). Three resulting nanohybrids were characterized by spectroscopy (FT-IR, Raman, and UV-vis), TGA, and TEM. The quality of porphyrin attached to the MWNTs was determined from thermogravimeric analysis (TGA) of the MWNTs, which showed a weight loss of about 60%. The Raman and absorption spectroscopy data showed that the electronic properties of modified MWNTs were mostly retained, without damaging their one-dimensional electronic properties. From fluorescence measurements, it was observed that the porphyrin and its complexes (Co2+, Zn2+) were nearly quenched by MWNTs, indicating that this covalently modified mode facilitated the effective energy or electron transfer between the excited porphyrin moiety and the extended π-system of MWNTs

Zinc Phthalocyanine−Graphene Hybrid Material for Energy Conversion: Synthesis, Characterization, Photophysics and Photoelectrochemical Cell Preparation

Graphene exfoliation upon tip sonication in o-­‐DCB was accomplished. Then, covalent grafting of (2-­‐ aminoethoxy)(tri-­‐tert-­‐butyl) zinc phthalocyanine (ZnPc), to exfoliated graphene sheets was achieved. The newly formed ZnPc-­‐graphene hybrid material was found soluble in common organic solvents without any precipitation for several weeks. Application of diverse spectroscopic techniques verified the successful formation of ZnPc-­‐graphene hybrid materi-­‐ al, while thermogravimetric analysis revealed the amount of ZnPc loading onto graphene. Microscopy analysis based on AFM and TEM was applied to probe the morphological characteristics and to investigate the exfoliation of graphene sheets. Efficient fluorescence quenching of ZnPc in the ZnPc-­‐graphene hybrid material suggested that photoinduced events occur from the photoexcited ZnPc to exfoliated graphene. The dynamics of the photoinduced electron transfer was evaluated by femtosecond transient absorption spectroscopy, thus, revealing the formation of transient species such as ZnPc+ yielding the charge-­‐separated state ZnPc•+–graphene•–. Finally, the ZnPc-­‐graphene hybrid material was integrated into a photoactive electrode of an optical transparent electrode (OTE) cast with nanostructured SnO2 films (OTE/SnO2), which exhibited sta le and reproducible photocurrent responses and the incident photon-­‐to-­‐current conversion efficien-­‐ cy was determine