To date, there have been only a few studies focusing on the assignment of X-ray diffraction (XRD) patterns in graphitic carbon nitrides (g-C3N4) and contradictory determination for a broad peak around 12°–14° has been perplexing. In this study, assignments are carried out both theoretically and experimentally. The cell parameters for g-C3N4 are determined as a = b = 8.1 Å, c = 6.5 Å, α = β = 90°, and γ = 120°. Qualitative and semi-quantitative methods such as fast Fourier transform and residual after 1st and 2nd derivatives are used to confirm and search the hidden peaks. Discrete Fourier transform is applied for the extraction of peak profiles and separation of overlapping peaks. In the broad peak around 12°–14° (with Cu Kα as referring source), two peaks are selected and determined as (100) and (001), which is fairly consistent with the (200) diffraction peak and (002) diffraction peak obtained by 2nd derivative method, respectively. In addition, g-C3N4 nanorods, MOF-doped g-C3N4 nanorods, and oxidized bulk g-C3N4 are successively investigated to present the 7.0 Å d-spacing of (100), hexagonal system of bulk g-C3N4, defect (1/2 0 0) structure with 14.0 Å d-spacing, and ABA stacking sequence. The structural transition in the oxidation of bulk g-C3N4 is presented by XRD to show accordance with the interpretation. Specific phenomena reported in other studies are also reinterpreted successfully, such as the appearance of peak at ∼12.4°.

The bottom-up fabrication of carbon nitride nanorods is realized through the direct infrared heating of dicyandiamide. The approach requires no templates or extra organics. The controlled infrared heating has a major influence on the morphology of the obtained carbon nitrides. The precursors assemble into carbon nitride nanorods at low power levels, and they grow into nanoplates at high power levels. The formation mechanism of the carbon nitride nanorods is proposed to be a kinetically driven process, and the photocatalytic activity of the carbon nitride nanorods prepared at 50% power for hydrogen evolution is about 2.9 times that of carbon nitride nanoplates at 100% power. Structural, optical, and electronic analysis demonstrates that the enhancement is primarily attributed to the elimination of structural defects and the improved charge-carrier separation in highly condensed and oriented carbon nitride nanorods.Keywords: carbon nitrides; hydrogen evolution; infrared heating; nanorods; photocatalytic

Hydrophilic treatment of bulk graphene-like carbon nitride (g-C3N4) for future applications has aroused extensive interest, due to its enhanced specific surface area and unusual electronic properties. Herein, water-dispersible g-C3N4 with a porous structure can be obtained by chemical oxidation of bulk g-C3N4 with K2Cr2O7–H2SO4. Acid oxidation results in the production of hydroxyl and carboxyl groups on its basal plane and the formation of a porous structure of g-C3N4 at the same time. The porous g-C3N4 appears as networks with tens of micrometers in width and possesses a high specific surface area of 235.2 m2 g−1. The final concentration of porous g-C3N4 can be up to 3 mg mL−1. Compared with bulk g-C3N4, the as-obtained porous g-C3N4 exhibits excellent water dispersion stability and shows great superiority in photoinduced charge carrier separation and transfer. The photocatalytic activities of porous g-C3N4 towards degradation of organic pollutants are much higher than those of the bulk due to the larger band gap (by 0.2 eV) and specific surface areas.

In this study, a one-pot route was illustrated to synthesize stable water-soluble CdS nanoparticles stabilized by poly-(4-styrenesulfonic acid-co-maleic acid) (PSSMA). The CdS nanoparticles synthesized in alkaline solutions (pH 10.0) were irregular and small in size (~1.1 nm), while those generated in acid solutions (pH 4.5) tended to aggregate to form larger particles (~74.5 nm). Some bridge-like CdS wires linking several CdS particles were observed by tuning the molar ratio of elemental Cd to S. The ligand-detachment mechanism has been proposed to be the main reason for the formation of CdS assemblies synthesized in acid solutions. Further, photoluminescence (PL) studies confirmed that the use of the PSSMA stabilizer induces incomplete quenching of PL emissions in an acid solution, but complete quenching in an alkaline solution.

A strategy of co-reaction of Fe and TiO2 with concentrated NaOH was designed to prepare Na2Ti3O7 nanosheets grown epitaxially by Fe3O4 crystallites, for the purpose of modifying interlayer structures and ion exchange properties of the layered compound Na2Ti3O7. TiO2 could react with NaOH to form lamellar intermediates while Fe could be converted into Fe3O4 to deposit on the surface of the intermediates. Eventually, free-standing Fe3O4@Na2Ti3O7 nanosheets were successfully synthesized in an extremely high yield (∼95% efficiency). Fluorescein and its derivatives utilized as probes to study the ion exchange property of Fe3O4@Na2Ti3O7 nanosheets, which could provide visual observations of the degree of ion exchange. The results indicate that the as-prepared Fe3O4@Na2Ti3O7 nanosheets possess much more sensitive Na+ exchange performance than isolated Na2Ti3O7 nanostructures, and hence they should have potential application in the extraction of trace active components, such as cationic amino acid and peptides in biology. Furthermore, the present strategy is also helpful in the design synthesis of other layered compounds grown epitaxially by magnetic clusters to achieve enhanced physicochemical properties.

Pd nanoparticles capped by thiol derivatives were prepared in AOT reverse micelles. Studies of UV–vis spectra have indicated that nitrogen purging plays an important role in the formation of Pd nanoparticles while without nitrogen purging results in the formation of Pd(II)–S complexes. Experimental results have also shown that thiolated poly(ethylene glycol) and tiopronin, which could be used to form water-soluble gold nanoparticles, did not favor the formation of isolated water-soluble Pd nanoparticles. However, tiopronin-capped Pd nanoparticles are found to be able to self-organize into nearly spherical aggregates.

Control over size and size distribution of nanoparticles has been the subject of much interest during the past decade. In the present study, a simple strategy is described for obtaining monodisperse Pd nanoparticles with size less than 5 nm and size distribution around 10%. Without size-selective precipitation but with a simple reducing agent, hypophosphite, the synthesized Pd nanoparticles can form 2D well-ordered arrays on the TEM grids. When reducing agents were changed, no obvious size change of Pd nanoparticles was observed within experimental errors but the size distribution varied dramatically. In addition, stability, self-organized pattern, and solubility can be controlled by changing the capping agent. The present route is very simple and reproducible, and further study on the properties of the Pd nanoparticles is underway.

Preparation of Fe and Pd co-doped g-C3N4 was described, using dicyandiamide monomer, and [1, 1′-Bis (diphenylphosphino) ferrocene] dichloropalladium (II) as precursor. X-ray powder diffraction, Fourier transform infrared spectra, Raman spectra and transmission electron microscopy were used to confirm the formation of bulk Fe-Pd/C3N4, X-ray photoelectron spectroscopy and energy dispersive X-ray spectroscopy were used to analysis the chemical states and element content of Fe-Pd/C3N4. N2 adsorption and desorption isotherms, UV–vis diffuse reflectance spectroscopy, electrochemical impedance spectroscopy, photoluminescence and Mott-Schottky capacitance measurement were used to further investigate the semiconducting properties of Fe-Pd/C3N4. The results indicated that the addition of dopants enriched the nitrogen content of graphitic carbon nitride, induced more structural defects, expanded the surface area, decreased the band gap energy, reduced the charge-transfer resistance, raised the flat band potential and restrained the recombination of photogenerated electrons and holes. Consequently, Fe and Pd co-doped g-C3N4 exhibited higher Rhodamine B photodegradation rate than raw g-C3N4. The most possible coordination sites of Fe and Pd were inferred as the CNHC defect sites.

Hydrophilic treatment of bulk graphene-like carbon nitride (g-C3N4) for future applications has aroused extensive interest, due to its enhanced specific surface area and unusual electronic properties. Herein, water-dispersible g-C3N4 with a porous structure can be obtained by chemical oxidation of bulk g-C3N4 with K2Cr2O7–H2SO4. Acid oxidation results in the production of hydroxyl and carboxyl groups on its basal plane and the formation of a porous structure of g-C3N4 at the same time. The porous g-C3N4 appears as networks with tens of micrometers in width and possesses a high specific surface area of 235.2 m2 g−1. The final concentration of porous g-C3N4 can be up to 3 mg mL−1. Compared with bulk g-C3N4, the as-obtained porous g-C3N4 exhibits excellent water dispersion stability and shows great superiority in photoinduced charge carrier separation and transfer. The photocatalytic activities of porous g-C3N4 towards degradation of organic pollutants are much higher than those of the bulk due to the larger band gap (by 0.2 eV) and specific surface areas.

A strategy of co-reaction of Fe and TiO2 with concentrated NaOH was designed to prepare Na2Ti3O7 nanosheets grown epitaxially by Fe3O4 crystallites, for the purpose of modifying interlayer structures and ion exchange properties of the layered compound Na2Ti3O7. TiO2 could react with NaOH to form lamellar intermediates while Fe could be converted into Fe3O4 to deposit on the surface of the intermediates. Eventually, free-standing Fe3O4@Na2Ti3O7 nanosheets were successfully synthesized in an extremely high yield (∼95% efficiency). Fluorescein and its derivatives utilized as probes to study the ion exchange property of Fe3O4@Na2Ti3O7 nanosheets, which could provide visual observations of the degree of ion exchange. The results indicate that the as-prepared Fe3O4@Na2Ti3O7 nanosheets possess much more sensitive Na+ exchange performance than isolated Na2Ti3O7 nanostructures, and hence they should have potential application in the extraction of trace active components, such as cationic amino acid and peptides in biology. Furthermore, the present strategy is also helpful in the design synthesis of other layered compounds grown epitaxially by magnetic clusters to achieve enhanced physicochemical properties.