Skip to main content

Graphitic Carbon Nitride as a Platform for the Synthesis of Silver Nanoclusters

Abstract

Graphitic carbon nitride (CN) synthetized by the thermal polycondensation of melamine at 550 °C for 4 h was further exfoliated by heating at 500 °C for 3 h. Silver cations were adsorbed on the exfoliated graphitic carbon nitride (CNE) and then reduced by sodium borohydride forming silver nanoclusters (NCs) with a size of less than 1 nm. The NCs were located on the CNE surface and did not change the CNE properties except for its pore size distribution and thereby specific surface area (SSA). The Ag NCs were able to collect the photoinduced electrons of CNE and thus reduce their recombination with the holes. It was also documented by the increase in the CNE photocatalytic activity in terms of the degradation of antibiotic Ofloxacin. This study demonstrates the ability of CNE to serve as a platform for a simple and fast synthesis of Ag NCs without any stabilizing compounds.

Graphic Abstract

Introduction

Graphitic carbon nitride is a two-dimensional (2D) metal-free polymeric material of the theoretical composition CN with remarkable chemical and electronic properties. This metal-free semiconductor allows the absorption of visible light due to its band gap energy of 2.7 eV. Important properties, such as high thermal, physical, chemical and photochemical stability, allow for the application of CN for solar cell production, imaging and sensing of some compounds [11, 20, 44], 66, 81.

One drawback of CN photocatalysts is connected with the rapid recombination of photoinduced electrons and holes and low quantum efficiency (about 0.1% under irradiation with 420–460 nm light wavelength) [33]. Another drawback is its low SSA, which can, however, be increased by the thermal exfoliation of bulk CN [60] leading to the formation of nanosheets and their clusters. For example, the CN mesoporous material with an SSA of about 281 m2 g−1 can be obtained by the direct application of various platforms [61]. Additionally, a nitrogen-rich intervening space between tri-s-triazine units allows CN to have unique properties for the stabilization of metal single atoms, clusters or nanoparticles [25].

CN has been applied as a catalyst for a variety of reactions, such as the Biginelli [8] and Friedel–Crafts reactions of benzene [19], the Knoevenagel condensation [73] and the CO2 capture and conversion [62]. Over the last years, it has become an increasingly engrossing topic in the field of photocatalysis [21, 32, 69]. As an n-type semiconductor, CN demonstrates a serious possibility for realizing processes, such as hydrogen evolution [42, 53, 80, 82], CO2 reduction [23, 41] and organic pollutants degradation [34, 67].

Noble metal nanoparticles (NPs) demonstrate great potential for numerous applications in chemical, biological, electronic, medical and catalytic areas due to their exclusive properties [3, 4, 26], compared to their bulk analogues. For example, gold NPs are widely used for drug delivery, various biological applications and catalysis. The antimicrobial properties of silver NPs and their usage in photodynamic antimicrobial chemotherapy, promising capabilities in biosensors and in fuel cells [7, 31] are well-known as well.

The preparation of Ag NPs by the reduction of silver salts is a widely applicable procedure. The reducing agents very often include borohydride, sodium citrate, ascorbic acid, alcohols, hydrazine compounds and plant extracts. Many papers have been published on the synthesis and properties of Ag NPs so far, for example, [1, 28, 40, 43, 45, 54, 57, 65, 71, 77]. The NPs tend to agglomerate and have to be stabilized using various capping agents, such as various polymers and surfactants [30, 56]. Another approach is in using inert supports which promote the high dispersion of Ag NPs, preventing their agglomeration and stabilizing them. Some supports have been used for this purpose, such as SiO2, TiO2, ZrO2 [29], ZnO [13], montmorillonite [52], sepiolite [37], zeolite [22], metal–organic frameworks [9], nitrogen-doped carbon [46], macro-/mesoporous carbon [12] and graphitic carbon nitride [14] as well.

A special new nanoscience issue is the synthesis and stabilization of ultra-small metal nanoparticles, as well as metal nanoclusters. The synthesis of single atoms and atom clusters is of great importance for biosensing and detection, cancer and antibacterial therapy, catalysis, etc. [15, 35, 36, 58, 75].

The attempts to improve the photocatalytic activity of CN by Ag-doping and coupling with Ag compounds have been highly increased in recent years. The photoassisted reduction method was applied by Bu et al. [5] to prepare Ag-modified CN. The Ag NPs were synthesized by thermal treatment of Ag+ ions in a mixture with melamine and NH4OH [68] or by the deposition of Ag+ ions on CN followed by their reduction [18, 70], 72, 74.

Even if the idea of using CN as a platform for the deposition of nanoparticles is not quite new, because, for example, we also synthetized SnO2 nanoparticles in the presence of CN [49], the synthesis of Ag nanoparticles or Ag nanoclusters using CNE with high SSA and micro- and mesoporous structure has not yet been published. In this work, we applied CNE as a platform for the synthesis of Ag NCs without any stabilizing agent. The simple procedure was based on the adsorption of Ag+ ions on exfoliated CN followed by their reduction with NaBH4. The prepared nanomaterials were characterized by various methods including testing their photocatalytic activity by means of the degradation of Ofloxacin.

Experimental

Synthesis of Bulk and Exfoliated CN

Bulk CN was synthesized by the thermal polycondensation of melamine according to a previously reported method [48]. Typically, 10 g of analytical grade melamine powder was placed into a covered ceramic crucible at room temperature and heated in a muffle furnace in air. The temperature was gradually elevated with a heating rate of 3 °C min−1 and kept at 550 °C for 4 h. The crucible was removed from the furnace, cooled down to an ambient temperature and then ground in an agate mortar.

For the CN exfoliation, bulk CN placed on a ceramic plate was heated in a muffle furnace with a heating rate of 10 °C min−1 to 500 °C and kept at this temperature for 3 h. The exfoliated CN (labelled as CNE) was cooled down to an ambient temperature out of the oven.

Adsorption of Ag+ on CNE

CNE was dispersed into an aqueous AgNO3 solution (100 mL) with a concentration of 0.5, 1.0, 2.5 and 5.0 mmol L−1, respectively, to obtain Ag+ deposited CNE materials with the various Ag loadings (0.1, 0.5, 1.0, 2.0 and 5.0 wt%). These suspensions were stirred over 2 h, after that the solids were separated by centrifugation. The concentration of Ag+ ions in filtrates was determined by a silver electrode (Theta 90, Czech Republic). The sample used for further analyses was labelled as Ag+CNE2.

Reduction of Ag+ on CNE

The reduction of Ag+ ions adsorbed on CNE was performed with NaBH4 (molar ratio Ag/NaBH4 = 1:2). 15 mL of the NaBH4 solution was added to 35 mL of the aqueous Ag+ and CNE suspension under stirring. After 10 min of stirring, the solid part was centrifuged, thoroughly washed with distilled water and dried at 105 °C for 2 h. The samples were labelled as AgCNE1, AgCNE2, AgCNE3, AgCNE4.

Determination of Ag

The silver content in the AgCNE nanomaterials was determined by an X-ray fluorescence spectrometer (XRF) SPECTRO Xepos (SPECTRO Analytical Instruments GmbH, Kleve, Germany).

X-Ray Diffraction

X-ray diffraction (XRD) technique was used to study the phase composition and microstructural properties of the AgCNE nanomaterials. XRD patterns were obtained using a Rigaku SmartLab diffractometer Rigaku (Tokyo, Japan) with a detector D/teX Ultra 250. The source of X-ray irradiation was a Co tube (CoKα, λα1 = 0.178892 nm, λα2 = 0.179278 nm) operated at 40 kV and 40 mA. The XRD patterns were collected in the 2θ range of 5°–90° with the step size of 0.01° and the speed of 0.5° min−1. The calculation of crystallite size L was performed by the Debye–Scherrer formula:

$$B\left(2\theta \right)=\frac{K\lambda }{L{\mathrm{cos}}\theta }$$
(1)

where θ is Bragg’s angle, λ is the wavelength of X-rays, and K is the constant equal to 0.94 for cubic and 0.89 for spherical crystallites. In this work, K = 0.90.

Fourier-Transform Infrared Spectrometry

Fourier-transform infrared spectrometry (FTIR) was performed using a Nicolet iS50 device (Thermo Scientific, Waltham, MA, USA). The FTIR spectra were collected in an attenuated total reflection (ATR) mode using a diamond ATR crystal. The spectra were collected in the wavenumber range of 400–4000 cm−1. The ATR correction followed by baseline subtracting was applied on each spectrum using the OMNIC software (Waltham, MA USA).

Specific Surface Area Measurements

Specific surface area measurements were performed with a SORPTOMATIC 1990 device (Thermo Scientific, Waltham, MA, USA). SSA was determined by the analysis of N2 adsorption isotherms recorded at − 196 °C by means of the Brunauer–Emmett–Teller (BET) method. The Barrett–Joyner–Halenda (BJH) model was used for the calculation of pore size distributions.

UV–Vis Diffuse Reflectance Spectrometry

UV–Vis diffuse reflectance spectra (DRS) were obtained with a spectrophotometer Shimadzu UV-2600 (IRS-2600Plus) in the range of 220–1000 nm. DRS was transformed to the Kubelka–Munk function F(R) as follows:

$$F{(R}_{\infty })=\frac{{\left(1-{R}_{\infty }\right)}^{2}}{{2R}_{\infty }}$$
(2)

where R is the diffuse reflectance from a semi-infinite layer. The values of band gap energies (Eg) were determined according to the well-known Tauc’s procedure [63].

Transmission and Scanning Electron Microscopy

Transmission electron microscopy (TEM) was carried out using a JEOL 2100 microscope with a LaB6 electron gun. An accelerating voltage of 160 kV was applied. TEM micrographs were taken by a camera Tengra (EMSIS). The samples were prepared by their suspension in ethanol and sonication for 5 min. One drop of this suspension was placed on a copper grid with a holey carbon film and dried at room temperature.

High-resolution transmission electron microscopy (HRTEM) was carried out using a Titan G2 microscope (FEI) with an image corrector on the accelerating voltage of 80 kV. HRTEM micrographs were recorded with a BM UltraScan CCD camera (Gatan). Energy-dispersive spectrometry (EDS) was performed in a Scanning TEM (STEM) mode by a Super-X system with four silicon drift detectors (Bruker). STEM micrographs were taken with a high-angle annular dark-field (HAADF) detector 3000 (Fishione). The CNE materials were dispersed in methanol and sonicated for 5 min, and one drop was put on a copper grid with a holey carbon film. After drying in air at room temperature, the HRTEM analysis was performed.

Scanning electron microscopy (SEM) was performed using a microscope Hitachi SU6600 with the accelerating voltage of 5 kV, and the acquisition time was 300 s. Before the analysis, the samples were placed on a conductive carbon tape.

X-Ray Photoelectron Spectroscopy

The superficial elemental analysis was performed by means of an X-ray photoelectron spectrometer (XPS) ESCA 3400 (Kratos Analytical Ltd., UK) with a base pressure in the analysis chamber of 5.0 × 107 Pa. Electrons were excited with an Mg Kα radiation ( = 1253.6 eV) generated at 12 kV and 10 mA. For all spectra, the Shirley background was subtracted. Peaks ascribed to the sp2 hybridized nitrogen (C=N–C) were set to 398.8 eV as a charge correction.

Photoluminescence Spectrometry

Photoluminescence (PL) spectra were obtained with a spectrometer FLS920 (Edinburgh Instrument Ltd., UK). The spectrometer was equipped with a 450 W Xenon lamp (Xe900). The excitation wavelength was 325 nm.

Photocatalytic Experiments

The photocatalytic activity of the AgCNE nanomaterials was investigated by means of the degradation of Ofloxacin in a concentration of 20 mg L−1. In the dark, 10 mg of each AgCNE material was added into 150 mL of the tested solution and stirred for 60 min to reach adsorption–desorption equilibrium. Then, the stirred suspension in a glass vessel of 250 mL with 52 mm in height and diameter of 90 mm was irradiated from the top with a LED source (420 nm, 7.1 mW cm−2); the temperature was kept at 20 °C.

The photocatalytic degradation of Ofloxacin was monitored by high-performance liquid chromatography (HPLC). For the HPLC separation, a Waters 2996 chromatograph with a photodiode array (PDA) detector (Waters Corporation Milford, MA, USA) and a Synergi 4 µm Polar-RP 80 Å (100 × 3 mm) column were used. The mobile phase consisted of acetonitrile and 0.04 mol L−1 chloroacetic acid (25:75, v/v), and pH = 3 was adjusted with NH4OH.

Results and Discussion

The AgCNE materials were prepared by the adsorption of Ag+ ions on exfoliated graphitic carbon nitride and the reduction with NaBH4. As demonstrated in Table 1, the content of silver after the reduction was lower than the theoretical content of Ag+ likely due to the loss of metallic Ag which was not captured in CNE pores. Some physico-chemical properties of the prepared materials were characterized by the following methods.

Table 1 The content of Ag in AgCNE nanomaterials

Structure and Texture Properties of AgCNE Nanomaterials

The structure of prepared AgCNE nanomaterials was studied by TEM, HRTEM, SEM, XRD, FTIR, XPS, UV–Vis DRS and PL spectrometry. Specific surface area and pore size distribution were analysed based on the physisorption of nitrogen. The photocatalytic activity was tested in terms of the degradation of Ofloxacin.

Analysis by Electron Transmission Microscopy

The morphology and microstructure of the prepared AgCNE nanomaterials were studied by electron microscopy. All these nanomaterials exhibited similar flake-like structures consisting of single flakes as well as their agglomerates. Figure 1 demonstrates the typical TEM micrograph of graphitic carbon nitride; no Ag nanosize objects are visible. In order to confirm their presence, an HRTEM analysis was performed as well.

Fig. 1
figure1

TEM micrographs of AgCNE4 with different resolutions

The STEM micrographs of AgCNE4 in Fig. 2 show small Ag objects with a size equal to or less than 1 nm spread on the CNE surface. Such objects can be composed of several Ag atoms which are not arranged in a regular crystalline structure. That is the reason why no Ag diffractions were observed in the XRD patterns, see below (Fig. 4). These small objects can be considered as Ag nanoclusters, and therefore, the term “nanoclusters” was further used instead of “nanoparticles”.

Fig. 2
figure2

STEM micrographs of AgCNE4 (left) and its detail view (right)

The STEM analysis with the HAADF imaging (HAADF-STEM) is shown in Fig. 3. The Ag nanoclusters marked by red spots are well dispersed on the CNE surface. The EDS spectrum in Fig. 3 demonstrates the Kα lines of present elements. Some minor elements, such as Na and Si, were impurities coming from glassware. Cu was present due to using the copper grid, and the presence of O was due to the synthesis in air and the presence of adsorbed water. The EDS spectrum with the log scale of intensities (Additional file 1: Fig. S1), as well as the element compositions (Additional file 1: Table S1), is given in Supplementary materials. The content of Ag was estimated from the area marked by a green rectangle at 1.8 wt%, which is close to the value of 2.4 wt% found by XRF (Table 1). Moreover, the porous structure of AgCNE4 is visible as well.

Fig. 3
figure3

HAADF-STEM micrographs and EDS spectrum (down) of AgCNE4

XRD Analysis

The structure of synthesized AgCNE nanomaterials was studied by XRD analysis. The hexagonal phase of graphitic carbon nitride (JCPDS 87-1526) was confirmed for CNE by the presence of two diffraction peaks in the XRD patterns, see Fig. 4. The low intensive peak (100) at around 2Θ = 15° is ascribed to the in-plane ordering of nitrogen-linked heptazine units [64]. The more intensive peak (002) at 2Θ = 32.2° corresponds to the interlayer diffraction of the conjugated aromatic system of CNE. Due to the low intensive (100) peaks, the XRD patterns with log intensity coordinates were used for the detail peak description, see Additional file 1: Fig. S2 and Table 2.

Fig. 4
figure4

XRD patterns of AgCNE nanomaterials

Table 2 Two main diffraction peaks, crystallite sizes and interlayer distances of AgCNE nanomaterials

These XRD patterns demonstrated the typical CN peaks (Fig. 4 and Additional file 1: Fig. S2), but no diffraction peaks of metallic silver were observed due to the low content of Ag and the small size of Ag NCs in contrast to our previous work concerning the bigger Ag NPs with the average size of 7 nm deposited on montmorillonite [52]. No influence of deposited Ag (Ag+) on the interlayer AgCNE distances was observed because the calculated crystallite sizes L(002) were very similar, 6.9–7.4 nm (Table 2). These findings indicate that no Ag NCs were intercalated between the CNE layers.

FTIR Analysis

The surface chemical state of the AgCNE nanomaterials was studied with FTIR spectrometry, see Fig. 5. The spectral bands at 3100–3400 cm−1 correspond to the stretching vibration modes of N–H and O–H bonds which can be related to uncondensed amino groups and absorbed H2O molecules, respectively. The spectral bands at 1100–1680 cm−1 can be ascribed to the stretching vibrations of C=N and C–N bonds of heterocyclic rings. The medium band at 804 cm−1 corresponds to the breathing mode of tri-s-triazine ring moieties [10]. All these spectra are typical for graphitic carbon nitride, and their explanation is in good agreement with other reports on CN layered structures [47, 51].

Fig. 5
figure5

FTIR spectra of AgCNE nanomaterials

All the FTIR spectra are very similar, which is well visible in their overly spectrum shown in Figure S3. No effects of deposited Ag NCs on the stretching and deformation vibrations mentioned above indicate that (1) the CNE structure was not influenced by Ag NCs and (2) the amount of deposited silver was small. Similar findings were observed by other authors [14, 39, 55, 59, 78]. Unlike [76], the interaction of Ag+ ions with CNE amino groups decreasing their N–H vibrational bands was not observed. The likely reason is the small amount of Ag+ as well.

XPS Analysis

The XPS analysis was conducted in order to study the valence states of Ag NCs. In addition, the XPS spectra of C, N and O, as well as their survey spectrum, were also recorded, but they showed common information of graphitic carbon nitride which can be found elsewhere [48]. These spectra are given in Supplementary materials, see Additional file 1: Figs. S4 to S7.

Figure 6 shows the XPS spectrum of AgCNE4 with the highest content of silver. The peaks at 368.5 eV and 374.5 eV are typical for Ag 3d5/2 and Ag 3d3/2 [2, 27]. However, the same XPS spectrum was obtained for the CNE with adsorbed Ag+ ions without reduction, see Fig. 6.

Fig. 6
figure6

XPS spectra of Ag 3d of Ag+ adsorbed on CNE (left) and AgCNE4 (right)

In order to identify the valence states of Ag in the metallic silver NCs, the Auger spectra of Ag MNN (transitions between the electron shells of atom) of AgCNE4 and Ag+ adsorbed on CNE were recorded, see Fig. 7. In all the spectra, the peak at 891.7 eV corresponding to N KLL was present. In these spectra, three peaks corresponding to Ag MNN were observed at 910.4 eV, 905.6 eV (905.3 eV) and 899.0 eV. The Ag MNN spectra are formed of double peaks which originate from M4N45N45 and M5N45N45 lines (Ferraria et al. [16]) exhibiting a specific peak to peak splitting and intensity ratio. In the case of Ag+CNE2, two peaks centred at 905.3 eV and 910.4 eV were ascribed to double peaks from oxidized Ag. It is not possible to differentiate between Ag+ and Ag2+ in oxides at these low concentrations.

Fig. 7
figure7

XPS spectra of Auger line Ag MNN of Ag+CNE2 (left) and AgCNE4 (right)

For AgCNE4, the peak at 899.0 eV was ascribed to metallic Ag0 M4N45N45 line. The line M5N45N45 corresponding to Ag0 overlapped with the silver oxide line at 905.6 eV resulting in the higher intensity and shift of this peak in comparison with the spectra of Ag+CNE2. In the sample AgCNE4, it is visible that it contains metallic Ag; however, it also contains a portion of Ag+ representing likely oxidized Ag. As NaBH4 is a relatively strong reduction agent with a good solubility, it can be expected that all Ag+ ions were reduced. On the other hand, Ag is easy to oxidize, so it can be expected that the Ag NCs would be oxidized on their surface after the exposure to air; however, the cores of the nanoclusters remained metallic.

Texture Analysis

Nitrogen physisorption experiments were performed to study the texture properties of the AgCNE nanomaterials. The adsorption–desorption isotherms and pore size distribution curves are presented in Figs. 8 and 9, respectively. All the nanomaterials exhibited isotherms with hysteresis loops indicating the existence of slit-like mesopores formed likely under the overlapping and stacking of carbon nitride nanosheets.

Fig. 8
figure8

Nitrogen adsorption–desorption isotherms of AgCNE nanomaterials

Fig. 9
figure9

BJH pore size distribution curves of AgCNE nanomaterials

The pore size distributions calculated from the nitrogen desorption isotherms by the BJH method show the broad range of pores due to the presence of mesopores and macropores (Fig. 9). It is remarkable that the presence of Ag nanoclusters, as well as that of Ag+, significantly changed the CNE pore size distribution by filling CNE pores, which resulted in the decrease in the specific surface area of CNE.

This effect is easily visible in the case of the CNE pores with radii up to 10 nm. It indicates that the CNE porous structure served as a platform for the synthesis of the Ag NCs. The pore size distributions of Ag+CNE2 and AgCNE2-AgCNE4 were similar. The specific surface areas are summarized in Table 3.

Table 3 The specific surface areas, pore sizes and band gap energies of AgCNE nanomaterials

In order to demonstrate the pore distribution changes, the SEM micrographs of CNE and AgCNE were taken as shown in Fig. 10. The left micrograph displays the porous structure of CNE which was changed after the deposition of Ag NCs as shown in the right one.

Fig. 10
figure10

SEM micrographs of CNE (left) and AgCNE4 (right)

Optical Properties of AgCNE Nanomaterials

UV–Vis Absorption Study

The optical properties of the AgCNE nanomaterials were examined by UV–Vis DRS. The presence of Ag NCs did not cause a significant change in the CNE optical absorption (Fig. 11) likely due to the low content of Ag. The band gap energies were determined according to common Tauc’s plots which were constructed from the UV–Vis DRS spectra. They are summarized in Table 3 and show no significant influence of the Ag NCs on the CNE band gap energy as well.

Fig. 11
figure11

UV–Vis spectra of AgCNE nanomaterials

Photoluminescence Study

The photoluminescence spectra were recorded to study the optical properties of the AgCNE nanomaterials as well, see Fig. 12. A strong and broad emission band from 400 to 600 nm with a maximum around 450 nm (2.76 eV) is related to multiple processes consisting of the band-to-band transition of photoinduced electrons and holes in CN [24], as well as the transition between lone pair and π* conduction band [79].

Fig. 12
figure12

Photoluminescence spectra of AgCNE nanomaterials. Left—(1) CNE, (2) AgCNE1, (3) AgCNE2, (4) AgCNE3, (5) AgCNE4. Right—CNE, Ag+CNE2 and AgCNE2

The emission peak intensity decreased with the increasing content of silver which can be explained by the transfer of electrons from CNE to the Ag NCs and, thus, the reduction of electrons–holes recombination [17, 38]. The PL spectra of AgCNE3 and AgCNE4 demonstrated a similar intensity which implies the silver loading probably did not play a role at these content levels. It should be mentioned that adsorbed Ag+ ions also caused the decrease in the PL intensity, likely due to the Ag+ ions reduction to metallic silver (Fig. 12).

Photocatalytic Activity

The photocatalytic activity of the AgCNE nanomaterials was tested using the antibiotic Ofloxacin as shown in Fig. 13. No photolysis of Ofloxacin was observed. The reaction rate constants (k) were calculated according to the first-order reaction model as

Fig. 13
figure13

Photocatalytic degradation of Ofloxacin. LED source of 420 nm and 7.1 mW cm−2; the temperature was kept at 20 °C

$${\mathrm{ln}}\frac{c}{{c}_{0}}=-k\tau$$
(3)

where τ is the time, and c0 and c are the concentrations of Ofloxacin at τ = 0 and τ = τ, respectively. The rate constants are summarized in Table 3. They decrease in the order AgCNE2 > AgCNE3 ≥ CNE > AgCNE4 ≥ AgCNE1. It is obvious that in the cases of AgCNE2 and AgCNE3, the ability of CNE for the photocatalytic degradation of Ofloxacin can be further enhanced by the loading of silver nanoclusters. On the other hand, in the cases AgCN1 and AgCN4, the added silver NCs decreased the CNE activity.

As mentioned above, the Ag nanoclusters worked as collectors of photoinduced electrons and allowed them to be separated from holes, which led to the decrease in PL intensity [6]. The decreasing PL should be associated with an increasing photocatalytic activity, but it does not explain the above-mentioned order of the decreasing rate constants from AgCNE2 to AgCNE1. Comparing the photocatalytic activities with CNE, the smallest and the highest content of Ag reduced the photoactivity likely due to the shielding of the CNE surface covered with Ag NCs [50]. In the case of AgCNE2 and AgCNE3, the Ag NCs enhanced the photocatalytic activity of CNE due to the reduced recombination of photoinduced electrons and holes.

Conclusion

Bulk graphitic carbon nitride was synthetized by the thermal polycondensation of melamine at 550 °C for 4 h and then was exfoliated by its heating at 500 °C for 3 h. Silver cations were adsorbed on the exfoliated graphitic carbon nitride (SSA of 180 mg−1) and then reduced by sodium borohydride. In this way, the silver nanoclusters with a size of less than 1 nm were formed as observed by HRTEM. They were located on the CNE surface and substantially changed the pore size distribution of CNE. However, the Ag NCs were not intercalated between the CNE layers. The Ag NCs were likely partially oxidized due to their small size and reactive surface as indicated by XPS.

The formation of bonds between the Ag NCs and CNE was not observed in the FTIR and XPS spectra as well. The band gap energy of CNE (2.75–2.78 eV) was not changed by the silver presence as observed by UV–Vis DRS. The photoluminescence spectra indicated that the silver nanoclusters were able to collect photoinduced electrons of CNE and thus to reduce their recombination with holes. This effect was confirmed by testing the photocatalytic activity of the AgCNE nanomaterials. The Ag NCs enhanced the photocatalytic degradation of Ofloxacin in comparison with bare CNE.

The exfoliated graphitic carbon nitride was found to be the suitable platform for the synthesis of Ag nanoclusters with no need of further stabilization by means of chemical compounds. The synthesis of other metal nanoclusters in the presence of CNE for various applications of the resulting composite nanomaterials will be investigated in future research.

Availability of data and materials

Not applicable.

Abbreviations

CN:

Graphitic carbon nitride

CNE:

Exfoliated graphitic carbon nitride

NCs:

Nanoclusters

SSA:

Specific surface area

2D:

Two-dimensional

NPs:

Nanoparticles

XRF:

X-ray fluorescence spectrometry

XRD:

X-ray diffraction

FTIR:

Fourier-transform infrared spectrometry

ATR:

Attenuated total reflection

BET:

Brunauer–Emmett–Teller

BJH:

Barrett–Joyner–Halenda

DRS:

Diffuse reflectance spectrometry

TEM:

Transmission electron microscopy

HRTEM:

High-resolution transmission electron microscopy

EDS:

Energy-dispersive spectrometry

STEM:

Scanning transmission electron microscopy

HAADF:

High-angle annular dark-field

XPS:

X-ray photoelectron spectrometry

JPSD:

Joint committee on powder diffraction standards

PL:

Photoluminescence

LED:

Light-emitting diode

HPLC:

High-performance liquid chromatography

PDA:

Photodiode array

AgCNE:

Ag deposited on CNE

Ag+CNE:

Ag+ deposited on CNE

References

  1. 1.

    Ahmed S, Ahmad M, Swami BL, Ikram S (2016) A review on plants extract mediated synthesis of silver nanoparticles for antimicrobial applications: a green expertise. J Adv Res 7:17–28. https://doi.org/10.1016/j.jare.2015.02.007

    CAS  Article  Google Scholar 

  2. 2.

    Alex AV, Deosarkar TNC, Mukherjee A (2021) An ultra-sensitive and selective AChE based colorimetric detection of malathion using silver nanoparticle-graphene oxide (Ag-GO) nanocomposite. Anal Chim Acta 1142:73–83. https://doi.org/10.1016/j.aca.2020.10.057

    CAS  Article  Google Scholar 

  3. 3.

    Amirjani A, Rahbarimehr E (2021) Recent advances in functionalization of plasmonic nanostructures for optical sensing. Microchim Acta 188:17. https://doi.org/10.1007/s00604-021-04714-3

    CAS  Article  Google Scholar 

  4. 4.

    Behzad F, Naghib SM, Kouhbanani MAJ, Tabatabaei SN, Zare Y, Rhee KY (2021) An overview of the plant-mediated green synthesis of noble metal nanoparticles for antibacterial applications. J Ind Eng Chem 94:92–104. https://doi.org/10.1016/j.jiec.2020.12.005

    CAS  Article  Google Scholar 

  5. 5.

    Bu YY, Chen ZY, Li WB (2014) Using electrochemical methods to study the promotion mechanism of the photoelectric conversion performance of Ag-modified mesoporous g-C3N4 heterojunction material. Appl Catal B Environ 144:622–630. https://doi.org/10.1016/j.apcatb.2013.07.066

    CAS  Article  Google Scholar 

  6. 6.

    Cai J et al (2019) Crafting mussel-inspired metal nanoparticle-decorated ultrathin graphitic carbon nitride for the degradation of chemical pollutants and production of chemical resources. Adv Mater 31:1806314. https://doi.org/10.1002/adma.201806314

    CAS  Article  Google Scholar 

  7. 7.

    Crisan CM, Mocan T, Manolea M, Lasca LI, Tabaran FA, Mocan L (2021) Review on silver nanoparticles as a novel class of antibacterial solutions. Appl Sci Basel. https://doi.org/10.3390/app11031120

    Article  Google Scholar 

  8. 8.

    Devthade V, Kamble G, Ghugal SG, Chikhalia KH, Umare SS (2018) Visible light-driven biginelli reaction over mesoporous g-C3N4 Lewis-base. Catal ChemistrySelect 3:4009–4014. https://doi.org/10.1002/slct.201800591

    CAS  Article  Google Scholar 

  9. 9.

    Dhakshinamoorthy A, Garcia H (2012) Catalysis by metal nanoparticles embedded on metal–organic frameworks. Chem Soc Rev 41:5262–5284. https://doi.org/10.1039/C2CS35047E

    CAS  Article  Google Scholar 

  10. 10.

    Dong F, Wu LW, Sun YJ, Fu M, Wu ZB, Lee SC (2011) Efficient synthesis of polymeric g-C3N4 layered materials as novel efficient visible light driven photocatalysts. J Mater Chem 21:15171–15174. https://doi.org/10.1039/c1jm12844b

    CAS  Article  Google Scholar 

  11. 11.

    Dong G, Zhang Y, Pan Q, Qiu J (2014) A fantastic graphitic carbon nitride (g-C3N4) material: electronic structure, photocatalytic and photoelectronic properties. J Photochem Photobiol C Photochem Rev 20:33–50. https://doi.org/10.1016/j.jphotochemrev.2014.04.002

    CAS  Article  Google Scholar 

  12. 12.

    Dong J, Sun T, Li S, Shan N, Chen J, Yan Y, Xu L (2019) 3D ordered macro-/mesoporous carbon supported Ag nanoparticles for efficient electrocatalytic oxygen reduction reaction. J Colloid Interface Sci 554:177–182. https://doi.org/10.1016/j.jcis.2019.06.087

    CAS  Article  Google Scholar 

  13. 13.

    Faisal M, Bouzid H, Harraz FA, Ismail AA, Al-Sayari SA, Al-Assiri MS (2015) Mesoporous Ag/ZnO multilayer films prepared by repeated spin-coating for enhancing its photonic efficiencies. Surf Coat Technol 263:44–53. https://doi.org/10.1016/j.surfcoat.2014.12.063

    CAS  Article  Google Scholar 

  14. 14.

    Faisal M, Ismail AA, Harraz FA, Al-Sayari SA, El-Toni AM, Al-Assiri MS (2016) Synthesis of highly dispersed silver doped g-C3N4 nanocomposites with enhanced visible-light photocatalytic activity. Mater Des 98:223–230. https://doi.org/10.1016/j.matdes.2016.03.019

    CAS  Article  Google Scholar 

  15. 15.

    Fan Y, Liu S, Yi Y, Rong H, Zhang J (2021) Catalytic nanomaterials toward atomic levels for biomedical applications: from metal clusters to single-atom catalysts. ACS Nano 15:2005–2037. https://doi.org/10.1021/acsnano.0c06962

    CAS  Article  Google Scholar 

  16. 16.

    Ferraria AM, Carapeto AP, Botelho do Rego AM. X-ray photoelectron spectroscopy: Silver salts revisited. Vacuum 2012;86:1988–91. https://doi.org/10.1016/j.vacuum.2012.05.031.

    CAS  Article  Google Scholar 

  17. 17.

    Fu Y, Huang T, Zhang L, Zhu J, Wang X (2015) Ag/g-C3N4 catalyst with superior catalytic performance for the degradation of dyes: a borohydride-generated superoxide radical approach. Nanoscale 7:13723–13733. https://doi.org/10.1039/C5NR03260A

    CAS  Article  Google Scholar 

  18. 18.

    Ge L, Han C, Liu J, Li Y (2011) Enhanced visible light photocatalytic activity of novel polymeric g-C3N4loaded with Ag nanoparticles. Appl Catal A General 409–410:215–222. https://doi.org/10.1016/j.apcata.2011.10.006

    CAS  Article  Google Scholar 

  19. 19.

    Goettmann F, Fischer A, Antonietti M, Thomas A (2006) Chemical synthesis of mesoporous carbon nitrides using hard templates and their use as a metal-free catalyst for friedel-crafts reaction of benzene. Angew Chem Int Edit 45:4467–4471. https://doi.org/10.1002/anie.200600412

    CAS  Article  Google Scholar 

  20. 20.

    Hasija V et al (2019) Recent advances in noble metal free doped graphitic carbon nitride based nanohybrids for photocatalysis of organic contaminants in water: a review Applied. Mater Today 15:494–524. https://doi.org/10.1016/j.apmt.2019.04.003

    Article  Google Scholar 

  21. 21.

    He F, Wang ZX, Li YX, Peng SQ, Liu B (2020) The nonmetal modulation of composition and morphology of g-C3N4-based photocatalysts. Appl Catal B Environ 269:21. https://doi.org/10.1016/j.apcatb.2020.118828

    CAS  Article  Google Scholar 

  22. 22.

    Hu X, Bai J, Li C, Wu Y (2017) Ag-doped 4A-zeolite as an efficient catalyst in the epoxidation of styrene reaction Kinetics. Mech Catal 120:359–370. https://doi.org/10.1007/s11144-016-1081-y

    CAS  Article  Google Scholar 

  23. 23.

    Huang Q, Yu JG, Cao SW, Cui C, Cheng B (2015) Efficient photocatalytic reduction of CO2 by amine-functionalized g-C3N4. Appl Surf Sci 358:350–355. https://doi.org/10.1016/j.apsusc.2015.07.082

    CAS  Article  Google Scholar 

  24. 24.

    Chen J, Dong CL, Du YC, Zhao DM, Shen SH (2015) Nanogap engineered plasmon-enhancement in photocatalytic solar hydrogen conversion. Adv Mate Interfaces. https://doi.org/10.1002/admi.201500280

    Article  Google Scholar 

  25. 25.

    Chen ZP et al (2017) Stabilization of single metal atoms on graphitic carbon nitride. Adv Funct Mater 27:12. https://doi.org/10.1002/adfm.201605785

    CAS  Article  Google Scholar 

  26. 26.

    Iqbal M et al (2021) Search of excellence: convex versus concave noble metal nanostructures for electrocatalytic applications. Adv Mater. https://doi.org/10.1002/adma.202004554

    Article  Google Scholar 

  27. 27.

    Kang SY, Kim K (1998) Comparative study of dodecanethiol-derivatized silver nanoparticles prepared in one-phase and two-phase systems. Langmuir 14:226–230. https://doi.org/10.1021/la970696i

    CAS  Article  Google Scholar 

  28. 28.

    Khodashenas B, Ghorbani HR (2019) Synthesis of silver nanoparticles with different shapes. Arab J Chem 12:1823–1838. https://doi.org/10.1016/j.arabjc.2014.12.014

    CAS  Article  Google Scholar 

  29. 29.

    Krylova GV, Gnatyuk YI, Smirnova NP, Eremenko AM, Gun’ko VM (2009) Ag nanoparticles deposited onto silica, titania, and zirconia mesoporous films synthesized by sol–gel template method. J Sol Gel Sci Technol 50:216–228. https://doi.org/10.1007/s10971-009-1954-x

    CAS  Article  Google Scholar 

  30. 30.

    Kvítek L et al (2008) Effect of surfactants and polymers on stability and antibacterial activity of silver nanoparticles (NPs). J Phys Chem C 112:5825–5834. https://doi.org/10.1021/jp711616v

    CAS  Article  Google Scholar 

  31. 31.

    Le Ouay B, Stellacci F (2015) Antibacterial activity of silver nanoparticles: a surface science insight. Nano Today 10:339–354. https://doi.org/10.1016/j.nantod.2015.04.002

    CAS  Article  Google Scholar 

  32. 32.

    Liu GQ, Xue MW, Liu QP, Yang H, Zhou YM (2019) Carbon doped honeycomb-like graphitic carbon nitride for photocatalytic hydrogen production. J Colloid Interface Sci 552:728–734. https://doi.org/10.1016/j.jcis.2019.05.106

    CAS  Article  Google Scholar 

  33. 33.

    Liu J (2016) Effect of phosphorus doping on electronic structure and photocatalytic performance of g-C3N4: insights from hybrid density functional calculation. J Alloys Compd 672:271–276. https://doi.org/10.1016/j.jallcom.2016.02.094

    CAS  Article  Google Scholar 

  34. 34.

    Liu XL, Ma R, Zhuang L, Hu BW, Chen JR, Liu XY, Wang XK. Recent developments of doped g-C3N4 photocatalysts for the degradation of organic pollutants. Crit Rev Environ Sci Technol. https://doi.org/10.1080/10643389.2020.1734433

  35. 35.

    Ma H, Wang J, Zhang X-D (2021) Near-infrared II emissive metal clusters: from atom physics to biomedicine. Coord Chem Rev 448:214184. https://doi.org/10.1016/j.ccr.2021.214184

    CAS  Article  Google Scholar 

  36. 36.

    Ma J, Niu H, Gu S (2021) The spatial organization of trace silver atoms on a DNA template. RSC Adv 11:1153–1163. https://doi.org/10.1039/D0RA08066G

    CAS  Article  Google Scholar 

  37. 37.

    Ma Y, Wu X, Zhang G (2017) Core-shell Ag@Pt nanoparticles supported on sepiolite nanofibers for the catalytic reduction of nitrophenols in water: enhanced catalytic performance and DFT study. Appl Catal B Environ 205:262–270. https://doi.org/10.1016/j.apcatb.2016.12.025

    CAS  Article  Google Scholar 

  38. 38.

    Meng F, Sun Z (2009) Enhanced photocatalytic activity of silver nanoparticles modified TiO2 thin films prepared by RF magnetron sputtering. Mater Chem Phys 118:349–353. https://doi.org/10.1016/j.matchemphys.2009.07.068

    CAS  Article  Google Scholar 

  39. 39.

    Meng Y, Shen J, Chen D, Xin G (2011) Photodegradation performance of methylene blue aqueous solution on Ag/g-C3N4 catalyst. Rare Met 30:276–279. https://doi.org/10.1007/s12598-011-0284-7

    CAS  Article  Google Scholar 

  40. 40.

    Mittal AK, Chisti Y, Banerjee UC (2013) Synthesis of metallic nanoparticles using plant extracts. Biotechnol Adv 31:346–356. https://doi.org/10.1016/j.biotechadv.2013.01.003

    CAS  Article  Google Scholar 

  41. 41.

    Mo Z et al (2019) Porous nitrogen-rich g-C3N4 nanotubes for efficient photocatalytic CO2 reduction. Appl Catal B Environ 256:7. https://doi.org/10.1016/j.apcatb.2019.117854

    CAS  Article  Google Scholar 

  42. 42.

    Mun SJ, Park SJ (2019) Graphitic carbon nitride materials for photocatalytic hydrogen production via water splitting: a short review. Catalysts 9:17. https://doi.org/10.3390/catal9100805

    CAS  Article  Google Scholar 

  43. 43.

    Nadagouda MN, Speth TF, Varma RS (2011) Microwave-assisted green synthesis of silver nanostructures. Acc Chem Res 44:469–478. https://doi.org/10.1021/ar1001457

    CAS  Article  Google Scholar 

  44. 44.

    Ong W-J, Tan L-L, Ng YH, Yong S-T, Chai S-P (2016) Graphitic carbon nitride (g-C3N4)-based photocatalysts for artificial photosynthesis and environmental remediation: are we a step closer to achieving sustainability? Chem Rev 116:7159–7329. https://doi.org/10.1021/acs.chemrev.6b00075

    CAS  Article  Google Scholar 

  45. 45.

    Panáček A et al (2006) Silver colloid nanoparticles: synthesis, characterization, and their antibacterial activity. J Phys Chem B 110:16248–16253. https://doi.org/10.1021/jp063826h

    CAS  Article  Google Scholar 

  46. 46.

    Panomsuwan G, Chantaramethakul J, Chokradjaroen C, Ishizaki T (2019) In situ solution plasma synthesis of silver nanoparticles supported on nitrogen-doped carbons with enhanced oxygen reduction activity. Mater Lett 251:135–139. https://doi.org/10.1016/j.matlet.2019.05.052

    CAS  Article  Google Scholar 

  47. 47.

    Papailias I, Giannakopoulou T, Todorova N, Demotikali D, Vaimakis T, Trapalis C (2015) Effect of processing temperature on structure and photocatalytic properties of g-C3N4. Appl Surf Sci 358:278–286. https://doi.org/10.1016/j.apsusc.2015.08.097

    CAS  Article  Google Scholar 

  48. 48.

    Praus P, Smýkalová A, Foniok K, Matějka V, Kormunda M, Smetana B, Cvejn D (2020) The presence and effect of oxygen in graphitic carbon nitride synthetized in air and nitrogen atmosphere. Appl Surf Sci 529:147086. https://doi.org/10.1016/j.apsusc.2020.147086

    CAS  Article  Google Scholar 

  49. 49.

    Praus P, Svoboda L, Dvorský R, Reli M (2018) Nanocomposites of SnO2 and g-C3N4: preparation, characterization and photocatalysis under visible LED irradiation. Ceram Int 44:3837–3846. https://doi.org/10.1016/j.ceramint.2017.11.170

    CAS  Article  Google Scholar 

  50. 50.

    Praus P, Svoboda L, Dvorský R, Reli M, Kormunda M, Mančík P (2017) Synthesis and properties of nanocomposites of WO3 and exfoliated g-C3N4. Ceram Int 43:13581–13591. https://doi.org/10.1016/j.ceramint.2017.07.067

    CAS  Article  Google Scholar 

  51. 51.

    Praus P, Svoboda L, Ritz M, Troppova I, Sihor M, Koci K (2017) Graphitic carbon nitride: synthesis, characterization and photocatalytic decomposition of nitrous oxide. Mater Chem Phys 193:438–446. https://doi.org/10.1016/j.matchemphys.2017.03.008

    CAS  Article  Google Scholar 

  52. 52.

    Praus P, Turicová M, Karlíková M, Kvítek L, Dvorský R (2013) Nanocomposite of montmorillonite and silver nanoparticles: characterization and application in catalytic reduction of 4-nitrophenol. Mater Chem Phys 140:493–498. https://doi.org/10.1016/j.matchemphys.2013.03.059

    CAS  Article  Google Scholar 

  53. 53.

    Putri LK, Ng BJ, Er CC, Ong WJ, Chang WS, Mohamed AR, Chai SP (2020) Insights on the impact of doping levels in oxygen-doped gC3N4 and its effects on photocatalytic activity. Appl Surf Sci. https://doi.org/10.1016/j.apsusc.2019.144427

    Article  Google Scholar 

  54. 54.

    Rafique M, Sadaf I, Rafique MS, Tahir MB (2017) A review on green synthesis of silver nanoparticles and their applications. Artif Cells Nanomed Biotechnol 45:1272–1291. https://doi.org/10.1080/21691401.2016.1241792

    CAS  Article  Google Scholar 

  55. 55.

    Ren T, Dang Y, Xiao Y, Hu Q, Deng D, Chen J, He P (2021) Depositing Ag nanoparticles on g-C3N4 by facile silver mirror reaction for enhanced photocatalytic hydrogen production. Inorgan Chem Commun. 123:108367. https://doi.org/10.1016/j.inoche.2020.108367

    CAS  Article  Google Scholar 

  56. 56.

    Restrepo CV, Villa CC (2021) Synthesis of silver nanoparticles, influence of capping agents, and dependence on size and shape: a review. Environ Nanotechnol Monit Manag 15:100428. https://doi.org/10.1016/j.enmm.2021.100428

    Article  Google Scholar 

  57. 57.

    Rycenga M et al (2011) Controlling the synthesis and assembly of silver nanostructures for plasmonic applications. Chem Rev 111:3669–3712. https://doi.org/10.1021/cr100275d

    CAS  Article  Google Scholar 

  58. 58.

    Santillán JMJ, Muñetón Arboleda D, Muraca D, Schinca DC, Scaffardi LB (2020) Highly fluorescent few atoms silver nanoclusters with strong photocatalytic activity synthesized by ultrashort light pulses. Sci Rep 10:8217. https://doi.org/10.1038/s41598-020-64773-z

    CAS  Article  Google Scholar 

  59. 59.

    Shu T, Yang W, Li K, Yan L, Dai Y, Guo H (2015) Design of silver-deposited carbon nitride nanotubes by a one-step solvothermal treatment strategy and their efficient visible-light photocatalytic activity toward methyl orange degradation energy and environment. Focus 4:107–115. https://doi.org/10.1166/eef.2015.1143

    Article  Google Scholar 

  60. 60.

    Svoboda L et al (2018) Graphitic carbon nitride nanosheets as highly efficient photocatalysts for phenol degradation under high-power visible LED irradiation. Mater Res Bull 100:322–332. https://doi.org/10.1016/j.materresbull.2017.12.049

    CAS  Article  Google Scholar 

  61. 61.

    Talapaneni SN et al (2019) 3D cubic mesoporous C3N4 with tunable pore diameters derived from KIT-6 and their application in base catalyzed Knoevenagel reaction. Catal Today 324:33–38. https://doi.org/10.1016/j.cattod.2018.08.003

    CAS  Article  Google Scholar 

  62. 62.

    Talapaneni SN et al (2020) Nanostructured carbon nitrides for CO2 capture and conversion. Adv Mater 32:21. https://doi.org/10.1002/adma.201904635

    CAS  Article  Google Scholar 

  63. 63.

    Tauc J, Grigorovici R, Vancu A (1966) Optical properties and electronic structure of amorphous germanium. Phys Status Solidi (b) 15:627–637. https://doi.org/10.1002/pssb.19660150224

    CAS  Article  Google Scholar 

  64. 64.

    Thomas A, Fischer A, Goettmann F, Antonietti M, Muller JO, Schlogl R, Carlsson JM (2008) Graphitic carbon nitride materials: variation of structure and morphology and their use as metal-free catalysts. J Mater Chem 18:4893–4908. https://doi.org/10.1039/b800274f

    CAS  Article  Google Scholar 

  65. 65.

    Tran QH, Nguyen VQ, Le A-T (2013) Silver nanoparticles: synthesis, properties, toxicology, applications and perspectives. Adv Nat Sci Nanosci Nanotechnol. 4:033001. https://doi.org/10.1088/2043-6262/4/3/033001

    CAS  Article  Google Scholar 

  66. 66.

    Wang A, Wang C, Fu L, Wong-Ng W, Lan Y (2017) Recent advances of graphitic carbon nitride-based structures and applications in catalyst sensing, imaging, and LEDs. Nano-Micro Lett 9:47. https://doi.org/10.1007/s40820-017-0148-2

    CAS  Article  Google Scholar 

  67. 67.

    Wang FL et al (2017) Facile synthesis of N-doped carbon dots/g-C3N4 photocatalyst with enhanced visible-light photocatalytic activity for the degradation of indomethacin. Appl Catal B Environ 207:103–113. https://doi.org/10.1016/j.apcatb.2017.02.024

    CAS  Article  Google Scholar 

  68. 68.

    Wang K-L, Li Y, Sun T, Mao F, Wu J-K, Xue B (2019) Ultrafine silver nanoparticles deposited on sodium-doped graphitic carbon nitride towards enhanced photocatalytic degradation of dyes and antibiotics under visible light irradiation. Appl Surf Sci 476:741–748. https://doi.org/10.1016/j.apsusc.2019.01.168

    CAS  Article  Google Scholar 

  69. 69.

    Wang YQ, Shen SH (2020) Progress and prospects of non-metal doped graphitic carbon nitride for improved photocatalytic performances. Acta Phys-Chim Sin 36:14. https://doi.org/10.3866/pku.whxb201905080

    Article  Google Scholar 

  70. 70.

    Wei F, Li J, Dong C, Bi Y, Han X (2020) Plasmonic Ag decorated graphitic carbon nitride sheets with enhanced visible-light response for photocatalytic water disinfection and organic pollutant removal. Chemosphere 242:125201. https://doi.org/10.1016/j.chemosphere.2019.125201

    CAS  Article  Google Scholar 

  71. 71.

    Wei L, Lu J, Xu H, Patel A, Chen Z-S, Chen G (2015) Silver nanoparticles: synthesis, properties, and therapeutic applications. Drug Discov Today 20:595–601. https://doi.org/10.1016/j.drudis.2014.11.014

    CAS  Article  Google Scholar 

  72. 72.

    Xu H et al (2020) An electrochemical thrombin aptasensor based on the use of graphite-like C3N4 modified with silver nanoparticles. Microchim Acta 187:163. https://doi.org/10.1007/s00604-020-4111-4

    CAS  Article  Google Scholar 

  73. 73.

    Xu J, Shen K, Xue B, Li YX, Cao Y (2013) Synthesis of three-dimensional mesostructured graphitic carbon nitride materials and their application as heterogeneous catalysts for Knoevenagel condensation reactions. Catal Lett 143:600–609. https://doi.org/10.1007/s10562-013-0994-6

    CAS  Article  Google Scholar 

  74. 74.

    Xu W et al (2020) Visible light photocatalytic degradation of tetracycline with porous Ag/graphite carbon nitride plasmonic composite: degradation pathways and mechanism. J Colloid Interface Sci 574:110–121. https://doi.org/10.1016/j.jcis.2020.04.038

    CAS  Article  Google Scholar 

  75. 75.

    Yang J, Pang R, Song D, Li M-B (2021) Tailoring silver nanoclusters via doping: advances and opportunities. Nanosc Adv 3:2411–2422. https://doi.org/10.1039/D1NA00077B

    CAS  Article  Google Scholar 

  76. 76.

    Yang Y et al (2013) Preparation and enhanced visible-light photocatalytic activity of silver deposited graphitic carbon nitride plasmonic photocatalyst. Appl Catal B 142–143:828–837. https://doi.org/10.1016/j.apcatb.2013.06.026

    CAS  Article  Google Scholar 

  77. 77.

    Yaqoob AA, Umar K, Ibrahim MNM (2020) Silver nanoparticles: various methods of synthesis, size affecting factors and their potential applications—a review. Appl Nanosci 10:1369–1378. https://doi.org/10.1007/s13204-020-01318-w

    CAS  Article  Google Scholar 

  78. 78.

    Ye M et al (2018) Silver nanoparticles/graphitic carbon nitride nanosheets for improved visible-light-driven photocatalytic performance. J Photochem Photobiol A 351:145–153. https://doi.org/10.1016/j.jphotochem.2017.10.016

    CAS  Article  Google Scholar 

  79. 79.

    Zhang Y, Pan Q, Chai G, Liang M, Dong G, Zhang Q, Qiu J (2013) Synthesis and luminescence mechanism of multicolor-emitting g-C3N4 nanopowders by low temperature thermal condensation of melamine. Sci Rep 3:1943. https://doi.org/10.1038/srep01943

    Article  Google Scholar 

  80. 80.

    Zhou YJ, Zhang LX, Huang WM, Kong QL, Fan XQ, Wang M, Shi JL (2016) N-doped graphitic carbon-incorporated g-C3N4 for remarkably enhanced photocatalytic H-2 evolution under visible light. Carbon 99:111–117. https://doi.org/10.1016/j.carbon.2015.12.008

    CAS  Article  Google Scholar 

  81. 81.

    Zhou Z, Zhang Y, Shen Y, Liu S, Zhang Y (2018) Molecular engineering of polymeric carbon nitride: advancing applications from photocatalysis to biosensing and more. Chem Soc Rev 47:2298–2321. https://doi.org/10.1039/C7CS00840F

    CAS  Article  Google Scholar 

  82. 82.

    Zhu AH, Qiu BC, Du MM, Ji JH, Nasir M, Xing MY, Zhang JL (2020) Dopant-induced edge and basal plane catalytic sites on ultrathin C3N4 nanosheets for photocatalytic water reduction. ACS Sustain Chem Eng 8:7497–7502. https://doi.org/10.1021/acssuschemeng.0c02122

    CAS  Article  Google Scholar 

Download references

Acknowledgements

The authors thank Dr. Alexandr Martaus and Dr. Kamil Górecki (both from VŠB-TU Ostrava) for the XRD (A.M.) and FTIR (K.G.) analyses, respectively. The authors thank Aneta Smýkalová for verifying the photocatalytic tests.

Funding

This work was supported by the Czech Science Foundation (Project No. 19-15199S), EU structural funding in Operational Program Research, Development and Education (Project No. CZ.02.1.01/0.0/0.0/16_019/0000853 and CZ.02.1.01/0.0/0.0/17_049/0008419) and by VŠB-TU Ostrava (Project No. SP 2021/46). The authors also thank the Large Research Infrastructure ENREGAT (project No. LM2018098).

Author information

Affiliations

Authors

Contributions

HS prepared the nanomaterials, measured the UV–Vis DRS spectra and wrote the article, MK measured the XPS spectra and edited the article, VM measured the PL spectra and edited the article, and PP supervised the whole work, evaluated the experimental results and wrote the article. All the authors reviewed and approved the final manuscript.

Corresponding author

Correspondence to Petr Praus.

Ethics declarations

Competing interests

The authors declare that they have no competing interests.

Additional information

Publisher's Note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Supplementary Information

Additional file 1

. Graphitic Carbon Nitride as a Platform for the Synthesis of Silver Nanoclusters.

Rights and permissions

Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/.

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark

Cite this article

Starukh, H., Koštejn, M., Matějka, V. et al. Graphitic Carbon Nitride as a Platform for the Synthesis of Silver Nanoclusters. Nanoscale Res Lett 16, 166 (2021). https://doi.org/10.1186/s11671-021-03621-z

Download citation

Keywords

  • Graphitic carbon nitride
  • Silver nanoclusters
  • Synthesis
  • Photocatalysis
  • Ofloxacin