We explore the intramolecular spin interactions of the core-modified porphyrin diradicals with a C═C unit (R-(C═C) and R-(C═C)2+) featuring (C═C)porphyrin and (C═C)porphyrin2+ as the couplers and verdazyl, nitronyl nitroxide, and imino nitroxide as spin sources (R) at the B3LYP/6-31G(d) level and the C═C effect through comparison with the porphine-coupled diradicals (R-(Null)). Structurally, modifications of porphine through introducing radical groups to the edge sites and a C═C unit to its core lead to a nonplanar diradical structure featuring a curved (C═C)porphyrin coupler and twist linkages of radical groups. Although such nonplanar structures seem unfavorable to the spin coupling between spin sources, our results suggest that the core modification with a C═C unit noticeably enhances the spin couplings in R-(C═C) and R-(C═C)2+ compared with R-(Null) with a planar porphine coupler, and R-(C═C) possess mild ferromagnetic couplings but R-(C═C)2+ present strong antiferromagnetic ones, indicating that two-electron redox can switch the magnetisms. The differences in the magnetic properties and coupling magnitudes should be attributed to distinctly different spin-interacting pathways among R-(Null), R-(C═C), and R-(C═C)2+. Besides, the energies of the lowest unoccupied molecular orbitals of the couplers regulate the magnetic couplings, and the linking modes of the radical groups to the couplers also affect the magnetic coupling strengths especially for R-(C═C)2+. The observed magnetic coupling regularities are reasonably analyzed by the modified spin alternation rule. This work provides a promising strategy for rational designs of the porphyrin-based diradicaloids and new insights into the spin interaction mechanisms in such diradicaloids which are useful bases for further applications in the future.

Multi-beryllium-expanded small graphene-like molecules including oligoacenes (mBe-nA) and graphene patches (mBe-GP) are computationally designed through introducing two or three Be atoms into the specific benzenoid rings of the graphene-like molecules, leading to replacement of some C–C bonds by the C–Be–C linkages with elongated C···C distances of about 3.3 Å in them. As a result, the elongation of the C···C bonds and insertion of more Be atoms make the two radical moieties in each molecule relatively separated and their interaction relatively weak. Both density functional theory and CASSCF calculations indicate that all these multi-Be-expanded graphene-like molecules exhibit well-defined polyradical characters: an open-shell singlet diradical for all mBe-nA and an open-shell singlet diradical or quintet tetraradical for mBe-GP depending on the Be-insertion patterns of the patches. The main findings in this work are that (i) a switching from the parent graphene-like closed-shell molecules (e.g., linear oligoacenes and graphene patches) to the open-shell singlet (diradical) or quintet (tetraradical) ground states can be realized by introducing Be as linkers into the graphene-like molecules; (ii) more importantly, the spin-coupling interactions of such mBe-nA and mBe-GP are remarkably large; and (iii) in these Be-modified molecules the Be–C bonds exhibit considerable covalent character and the Be···Be distances are 2.67–2.84 Å, implying weak Be(s2)···Be(s2) metallophilic interaction. This work would open a new perspective for the rational design of perfect and stable singlet diradicals or polyradicals with large spin-coupling constants on the basis of small closed-shell graphene-like molecules by multimetal incorporation and also encourage experimentalists to pursue and realize these interesting structures with enhanced magnetic properties in the future.

Developing a green and economical synthetic strategy for ZnS nanotubes is of great interest. In this work, ZnS nanotubes are successfully fabricated using only three raw materials (Zn(CH3COO)2, NaHCO3 and Na2S) through a simple two step synthetic route at ambient temperature. It is worth noting that the process is economical and environmentally friendly, without the need for high pressure or elevated temperature conditions. Interestingly, a very obvious feature is the existence of abundant sulfur surface defects on the as-prepared ZnS nanotubes, which not only produces strong defect-related fluorescence properties, but also leads to abundant water adsorbed on the surface of zinc sulfide. Furthermore, the as-prepared ZnS nanotubes as an adsorbent are exploited in the adsorption of organic dyes. Notably, the resultant products display superior selective adsorption ability for anionic dyes with amine (–NH2/NH) functional groups over a wide pH range through the synergistic effect of hydrogen bonding and electrostatic attraction between the dye molecules and the adsorbent. Taking CR dye as an example, the maximum adsorption capacity for the removal of Congo red reaches 724.6 mg g−1 in water, much higher than many composite adsorbents reported in the literature. Thus, the present study not only presents a promising strategy for fabrication of ZnS nanotubes but also indicates their great potential application as environmentally friendly adsorbents in organic dye separation technologies or dye removal.

Well-defined Cu/reduced graphene oxide (rGO) hybrid materials are successfully synthesized by controlling the amount of ascorbic acid and maintaining an appropriate pH value. We found that graphene oxide (GO) served not only as the precursor for graphene, but also as an effective surfactant to hamper the aggregation of copper nanoparticles, resulting in a small size of the copper nanoparticles. Furthermore, the as-prepared copper composites can serve as an effective catalyst for 4-nitrophenol in aqueous conditions and exhibit surface enhanced Raman scattering in the detection of crystal violet (CV). Notably, the obtained copper nanoparticle hybrids with rGO have extremely high air stability after exposure to air. Density functional theory calculations firstly reveal that rGO can effectively prevent Cu nanoparticles from spontaneous oxidation due to its slightly lower ionization potential than that of Cu nanoparticles. We expect the as-prepared rGO-stabilized copper nanocrystals with small size to meet the increasing demands of industrial applications at reduced costs.

Ternary spherical Ag–Cu2O/reduced graphene oxide (rGO) nanohybrids with excellent hierarchical structures are developed through a simple one-pot, two-stage reduction synthetic route at room temperature without any surfactant. In the resultant complex heterostructures, both Ag and rGO are in direct contact with Cu2O, and Ag nanocrystals are mainly deposited on the surface of Cu2O spheres. The resultant ternary spherical Ag–Cu2O/rGO composite exhibits excellent photocatalytic activity in photocatalytic degradation of methyl orange (MO) under visible light irradiation, which is much higher than that of either the single component (Cu2O) or two component systems (spherical Cu2O/rGO and Ag–Cu2O). In particular, the resultant ternary composites possess excellent stability and extend the light absorption range. The PL spectrum results have demonstrated that not only Ag but also rGO could capture the photogenerated electrons from Cu2O, thus leading to effective separation of electrons and holes. In particular, it is found that the direct junction and interaction between Ag and Cu2O in the ternary composites are more beneficial for charge transportation than the direct contact between Ag and rGO (labeled as sample Ag-rGO-Cu2O), and thereby the resultant Ag–Cu2O/rGO composites with such complex heterostructures exhibit a better photoactivity than the sample Ag-rGO-Cu2O. This work provides an insight into designing and synthesizing new Cu2O-based hybrid materials for effectively improving the photocatalytic performance.

We unravel intriguing dynamical diradical behavior governed by structural fluctuation in pentacene using ab initio molecular dynamics simulation. In contrast to static equilibrium configuration of pentacene with a closed-shell ground state without diradical character, due to structural fluctuation, some of its dynamical snapshot configurations exhibit an open-shell broken-symmetry singlet ground state with diradical character, and such diradical character presents irregular pulsing behavior in time evolution. Not all structural changes can lead to diradical character, only those involving the shortening of cross-linking C–C bonds and variations of the C–C bonds in polyacetylene chains are the main contributors. This scenario about diradicalization is distinctly different from that in long acenes. The essence is that structural distortion cooperatively raises the HOMO and lowers the LUMO, efficiently reducing the HOMO–LUMO and singlet–triplet energy gaps, which facilitate the formation of a broken-symmetry open-shell singlet state. The irregular pulsing behavior originates from the mixing of normal vibrations in pentacene. This fascinating behavior suggests the potential application of pentacene as a suitable building block in the design of new electronic devices due to its magnetism-controllability through energy induction. This work provides new insight into inherent electronic property fluctuation in acenes.

Organic molecules with switchable magnetic properties have extensively technological applications due to the fact that magnetic conversion can be realized through diverse methods. In particular, the redox-induced magnetic reversal is easy to accomplish and exhibits promising application in the field of magnetic materials, and thus it is an imperative task to find magnetism-switchable systems. Herein, we computationally design two couples of nitroxy–pyrazinyl–nitroxy diradicals in which two nitroxy radical groups are connected to a redox-active pyrazinyl coupler in the para or meta modes. We find that the magnetic conversion can occur from ferromagnetic to antiferromagnetic exchange coupling or vice versa by means of the redox method in these designed magnetic organic molecules, and their magnetic exchange coupling constants are considerably large no matter for ferromagnetic or antiferromagnetic couplings, as evidenced at both the B3LYP and M06-2X levels of theory. Analyses indicate that redox-induced structural change of the coupler leads to conversion of its aromaticity and considerable spin delocalization from the π-conjugated structure and spin polarization from non-Kekule structure, which thus determine the spin coupling between two spin centers in the magnetic molecules. In addition, the spin alternation rule, singly occupied molecular orbital (SOMO) effect, and SOMO–SOMO energy splitting of triplet state are utilized to analyze the diradical characters of the molecules, suggesting effective tools for predicting molecular ground states (ferromagnetic, antiferromagnetic, or nonmagnetic). This work provides helpful information for the rational design of promising organic magnetic switches.

Effective surface and interface control of metal nanomaterials provides a powerful tool for achieving their enhanced catalytic properties. This article reports a remarkably simple approach for the preparation of copper nanowires with a rough surface. Surface roughness of Cu nanowires can be successfully controlled by adjusting the reactant ratio of the same type of element ions with different valence state (Cu+ and Cu2+). Furthermore, it is noted that the as-prepared rough Cu nanowires have higher BET surface areas and a porous structure with a total pore volume of 4.212 nm. Cu nanowires–Ag heterostructures are further prepared using the as-prepared rough Cu wires as the “substrate”. Our experimental results reveal that Ag nanocrystals preferentially grow on nanowires with a rough surface morphology compared to smooth nanowires. Due to the surface effects and synergistic effect of their constituents, the as-prepared rough copper nanowires and Cu nanowires–Ag heterostructures demonstrated highly enhanced catalytic performance for the reduction of 4-nitrophenol. In particular, the Cu nanowires–Ag heterostructures show superior catalytic activity than the as-obtained Cu nanowires with smooth surface, and some recently reported noble metal catalysts, such as pure Ag nanowires, magnetic Au nanocrystals, and Au/graphene hydrogel. This study offers a simple strategy that could be applied for the fabrication of other promising one dimensional Cu-based bimetallic nanomaterials.

Due to the difficulty in morphology control of planar copper structures, far fewer studies have explored the shape effect on catalytic activity of copper materials. Here, PVP-stabilized copper plates are prepared via the reduction of the Cu(II)–tartrate complex by NaH2PO2 in the presence of PVP under an ambient atmosphere. Based on the systematic studies of varying growth parameters and theoretical simulations, we have discovered the critical factors for synthesizing planar copper crystals. The size of the copper plates can be tuned by adjusting the relative amounts of tartrate, or by changing the types of complex regents with different complexing abilities. The oxidative stability of the resultant copper plates is examined, and their catalytic properties are evaluated. In all cases, the as-prepared submicro/nanoplates show excellent catalytic activity compared with other copper catalysts. Notably, the resultant PVP-stabilized Cu catalyst with submicron size exhibits high stability not only in ambient air, but also toward reduction of p-nitrophenol. It is found that Cu plates are stable and do not lose their structural integrity during reduction catalysis. High stability under the reaction conditions enables the recyclability of the as-fabricated copper plates. We expect catalysts based on copper with plate shapes to meet the increasing demands of industrial applications at reduced costs.

A simple and efficient approach of preparing copper oxide/reduced graphene oxide (CuO/rGO) nanocomposite has been demonstrated. CuO/rGO nanocomposites were successfully synthesized through a one-step redox reaction between graphene oxide (GO) sheets and cuprous ions in CuCl without extra reducing agent. Notably, the reduction of GO and the deposition of CuO on the rGO sheets occurred simultaneously during the reaction process, resulting in a uniform and tight distribution of CuO nanoparticles on the reduced GO sheets. Furthermore, the as-prepared CuO/rGO composite (CuCl = 0.02 g) had a large BET surface area (235 m2 g−1) and a porous structure with macropores and mesopores. The as-prepared nanocomposite was exploited in the catalytic oxidation of catechol in aqueous media. The results indicated that the as-prepared copper oxide/rGO nanocomposite exhibited a higher electrocatalytic activity towards catechol oxidation than original CuO nanoparticles or reduced graphene oxide samples. This strategy opens a new facile and simple chemical route to synthesize copper oxide/rGO nanocomposites with excellent properties.

Two classes of multi-Zn-expanded oligoacenes from benzene to pentacene are computationally designed through introducing a Zn array into acene rings in two ways: acene-chain axial versus single-ring quasi-transversal direction. Combined density functional theory, CASSCF, and CCSD calculations predict that all these multi-Zn-expanded oligoacenes have the open-shell singlet diradical ground states, in contrast with the common fact that their parent oligoacenes are closed-shell systems or may have a triplet ground state and only acenes larger than octacene have open-shell singlet diradical ground states. These results offer the first theoretical prediction that the multi-Zn introduction into the acene ring(s), forming the Zn-expanded oligoacenes, can lead them to diradical structures. The diradical character of the ground states of these molecules arises from the Zn-participation-induced disjoint nature of the nonbonding molecular orbitals that are singly occupied in the diradicals. This work provides a strategy to design perfect and stable singlet diradicals from oligoacenes or their derivatives.

A facile solution-phase process has been demonstrated for the selective preparation of single-crystalline Cu nanoplates and nanowires by reducing Cu+ with ascorbic acid (VC) in the presence of cetyltrimethylammonium bromide (CTAB) or cetyltrimethylammonium chloride (CTAC). To study the formation process of nanoplates and nanowires, samples obtained at various stages of the growth process were studied by TEM and XRD. The possible mechanism was discussed to elucidate the formation of different morphologies of Cu nanostructures. UV–vis spectra of the Cu nanoplates and nanowires were recorded to investigate their optical properties, which indicated that the as-prepared Cu nanostructures exhibited morphology-dependent optical property.

Pentagonal silver nanowires with diameters in range of 20–40 nm, and lengths up to ~ 10 µm were successfully synthesized via a simple and effective alcohol-thermal route. These nanowires were prepared by reducing silver nitrate in ethanol solution with dodecylamine which acted as complexing, reducing and capping agent. The molar ratio of dodecylamine to AgNO3 played an important role in controlling aspect ratio of the products. Samples were characterized in detail by X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM) technologies. UV–vis absorption spectrum of the nanowires in solution has been taken to study their optical properties. Based on the analysis of the experimental results, the possible formation mechanism of nanowires was proposed as well.

In this paper, we reported an effective method for controlling CaSO4 crystal growth in organic media. Ca2+ and SO42− ions were extracted into the organic phase using different extractants. Different morphologies and sizes of CaSO4 nanocrystals including nanoparticles and nanosheets and long fibers were prepared by changing the molar ratio of [SO42−]∶[Ca2+] in the organic solvent at room temperature. The effect of the molar ratio of [SO42−]∶[Ca2+] on the CaSO4 growth process was studied principally by TEM. In addition, it was found that the diluent polarity could also affect the growth process of CaSO4 crystals.

A facile, template-free method is reported to prepare Cu2O/Au core–shell nanospheres in aqueous medium at room temperature. In this synthesis, Cu2O nanospheres with definite diameter were first synthesized via the reduction reaction between Cu(NO3)2 and hydrazine (N2H4). Then, the as-prepared Cu2O nanospheres were employed as nucleation centers for deposition of Au shell, resulting in the formation of core–shell nanospheres. The samples obtained at various stages after the addition of the HAuCl4 were studied by TEM observation. These TEM images revealed that the formation hollow interior space between the core and the shell. In addition, UV–vis spectra results indicated that the optical property of the Cu2O/Au core–shell nanospheres was influenced by the size of the hollow interior spaces between the cores and the shells.

Ternary spherical Ag–Cu2O/reduced graphene oxide (rGO) nanohybrids with excellent hierarchical structures are developed through a simple one-pot, two-stage reduction synthetic route at room temperature without any surfactant. In the resultant complex heterostructures, both Ag and rGO are in direct contact with Cu2O, and Ag nanocrystals are mainly deposited on the surface of Cu2O spheres. The resultant ternary spherical Ag–Cu2O/rGO composite exhibits excellent photocatalytic activity in photocatalytic degradation of methyl orange (MO) under visible light irradiation, which is much higher than that of either the single component (Cu2O) or two component systems (spherical Cu2O/rGO and Ag–Cu2O). In particular, the resultant ternary composites possess excellent stability and extend the light absorption range. The PL spectrum results have demonstrated that not only Ag but also rGO could capture the photogenerated electrons from Cu2O, thus leading to effective separation of electrons and holes. In particular, it is found that the direct junction and interaction between Ag and Cu2O in the ternary composites are more beneficial for charge transportation than the direct contact between Ag and rGO (labeled as sample Ag-rGO-Cu2O), and thereby the resultant Ag–Cu2O/rGO composites with such complex heterostructures exhibit a better photoactivity than the sample Ag-rGO-Cu2O. This work provides an insight into designing and synthesizing new Cu2O-based hybrid materials for effectively improving the photocatalytic performance.

Effective surface and interface control of metal nanomaterials provides a powerful tool for achieving their enhanced catalytic properties. This article reports a remarkably simple approach for the preparation of copper nanowires with a rough surface. Surface roughness of Cu nanowires can be successfully controlled by adjusting the reactant ratio of the same type of element ions with different valence state (Cu+ and Cu2+). Furthermore, it is noted that the as-prepared rough Cu nanowires have higher BET surface areas and a porous structure with a total pore volume of 4.212 nm. Cu nanowires–Ag heterostructures are further prepared using the as-prepared rough Cu wires as the “substrate”. Our experimental results reveal that Ag nanocrystals preferentially grow on nanowires with a rough surface morphology compared to smooth nanowires. Due to the surface effects and synergistic effect of their constituents, the as-prepared rough copper nanowires and Cu nanowires–Ag heterostructures demonstrated highly enhanced catalytic performance for the reduction of 4-nitrophenol. In particular, the Cu nanowires–Ag heterostructures show superior catalytic activity than the as-obtained Cu nanowires with smooth surface, and some recently reported noble metal catalysts, such as pure Ag nanowires, magnetic Au nanocrystals, and Au/graphene hydrogel. This study offers a simple strategy that could be applied for the fabrication of other promising one dimensional Cu-based bimetallic nanomaterials.

Due to the difficulty in morphology control of planar copper structures, far fewer studies have explored the shape effect on catalytic activity of copper materials. Here, PVP-stabilized copper plates are prepared via the reduction of the Cu(II)–tartrate complex by NaH2PO2 in the presence of PVP under an ambient atmosphere. Based on the systematic studies of varying growth parameters and theoretical simulations, we have discovered the critical factors for synthesizing planar copper crystals. The size of the copper plates can be tuned by adjusting the relative amounts of tartrate, or by changing the types of complex regents with different complexing abilities. The oxidative stability of the resultant copper plates is examined, and their catalytic properties are evaluated. In all cases, the as-prepared submicro/nanoplates show excellent catalytic activity compared with other copper catalysts. Notably, the resultant PVP-stabilized Cu catalyst with submicron size exhibits high stability not only in ambient air, but also toward reduction of p-nitrophenol. It is found that Cu plates are stable and do not lose their structural integrity during reduction catalysis. High stability under the reaction conditions enables the recyclability of the as-fabricated copper plates. We expect catalysts based on copper with plate shapes to meet the increasing demands of industrial applications at reduced costs.

We unravel intriguing dynamical diradical behavior governed by structural fluctuation in pentacene using ab initio molecular dynamics simulation. In contrast to static equilibrium configuration of pentacene with a closed-shell ground state without diradical character, due to structural fluctuation, some of its dynamical snapshot configurations exhibit an open-shell broken-symmetry singlet ground state with diradical character, and such diradical character presents irregular pulsing behavior in time evolution. Not all structural changes can lead to diradical character, only those involving the shortening of cross-linking C–C bonds and variations of the C–C bonds in polyacetylene chains are the main contributors. This scenario about diradicalization is distinctly different from that in long acenes. The essence is that structural distortion cooperatively raises the HOMO and lowers the LUMO, efficiently reducing the HOMO–LUMO and singlet–triplet energy gaps, which facilitate the formation of a broken-symmetry open-shell singlet state. The irregular pulsing behavior originates from the mixing of normal vibrations in pentacene. This fascinating behavior suggests the potential application of pentacene as a suitable building block in the design of new electronic devices due to its magnetism-controllability through energy induction. This work provides new insight into inherent electronic property fluctuation in acenes.