1 Introduction

Pollution of the environment is an acute problem today. At the same time, important factors are not only emissions from transport and energetics, but also waste pollution from various industries, including pharmaceuticals [1,2,3,4,5,6].

Photocatalysis is one of the effective solutions to this problem. In particular, photocatalysts were used in the study of chloramphenicol utilization problems [7,8,9,10,11]. Moreover, although catalysts with an active ingredient based on silver have proven themselves well [12], the search for active compositions with cheaper components is in progress. Titanium oxides can be considered promising in this regard [3, 8, 9, 13, 14].

Due to a number of disadvantages of existing titanium (low activity in the visible light, use in the form of a solution, etc. [15, 16]) one of the main issues is the structure and composition of existing titanium photocatalysts.

Given the above, we can assume that the most optimal designs of photocatalysts for operation under irradiation conditions will be supported systems [8, 17, 18]. In addition, an important factor is the dimensionality of the structure. It is shown that nanoscale structures achieve a significant effect in catalysis [7, 9, 11, 19, 20].

Therefore, to obtain effective photocatalysts, it is necessary to determine the preparation technology and composition of the supported system.

Supports from metallic foil have advantages compared with glass, ceramics, etc. They are strong, stable in many environments, conduct heat well, and durable. In addition, their plasticity allows to creating of catalysts of almost any shape.

As a method of synthesis supported catalysts, ion-plasma technologies have a number of advantages [19, 21,22,23]. In particular, ionic implantation technology is attractive for the treatment of catalytic carriers [24,25,26]. It permits to obtain a thin surface layer active component due to its bombardment by target ions with significant energies. Due to the emission of surface atoms and mixing with implanted ions, new compounds are formed and the surface layer of the sample is strengthened. In contrast to the traditional applied layers, the obtained modified surface has significant strength and heat resistance. Therefore, the structural properties of implants obtained by implanting titanium ions in steel and aluminum were studied. Some samples were oxidized at different temperatures and investigated in the reaction of chloramphenicol photodegradation.

2 The Experimental Part

The detail of synthesis technology of nanoscaled modified layers is described in [19, 27]. Stainless steel foil (100 μm) and aluminum foil (50 μm) were treated by titanium ions according to this method. The samples are marked: Ti/SS and Ti/Al accordingly. After implantation, some of the samples were calcinated on air at different temperatures (200, 300, 400, 500, 600 °C). Calcination time of the sample at each temperature was equal to two hours.

Methods SEM (scanning electron microscopy) and EDXS (energy-dispersive X-ray spectroscopy) were used to determine the qualitative and quantitative composition of the samples. The research was performed using scanning electron microscope Tescan Vega3 LMU and an energy-dispersive X-ray microanalyzer (Oxford Instruments Aztec ONE with X-MaxN20 detector) at the Center for Collective Use “Laboratory of Materials Science of Intermetallic Compounds” at Lviv National University named after Ivan Franko.

Scanning of the surface of the samples (sections) was carried out using an electron beam (generated by a gun W-thermocathode) with a diameter of several nanometers and accelerated voltage of ~25 kV. The maximum resolution reaches 30.0 Å at high vacuum and voltage of 30 kV (increase ~1,000,000 times). The operating distance from the gun to the sample in the SEM method varies from the required increase, for sections of metal alloys is 15–20 mm. The microscope is designed to study samples in high and variable vacuum. At high vacuum (9.9–10–3 Pa), it is possible to investigate conductive samples (typical alloys of intermetallics), partially conductive samples (semiconductor alloys, films, crystals) or non-conductive samples (polymers, objects of biological origin, etc.) with a sprayed layer of conductive coatings (such as carbon or gold). Variable vacuum is more often used in the study of nano-objects with a developed surface. The microscope is equipped with two detectors SE and BSE. In the SE-detector mode (“secondary electrons”), the surface condition (topographic contrast) of the sample can be estimated, and in the BSE-detector mode (“reflected secondary electrons”) phases can be identified based on the contrast by the average atomic number (the phase with more electrons will be colored lighter than the phase based on elements with a smaller sequence number). The range of quantitative determination of elements is from Be to Cf. The optimal working distance from the gun to the sample in EDRS methods is 15–17 mm for conductive samples.

Arrays of experimental intensities and angles from the studied samples were obtained on an automatic diffractometer STOE STADI P (manufactured by STOE & Cie GmbH, Germany). It is equipped with a linear position-precision PSD detector according to the scheme of modified Guine geometry and the method of passing bending (CuKα1 radiation; concave Ge monochromator (111) of Johann type; range of angles 2θ was 4.000 ≤ 2θ ≤ 99.985° with a step of 0.015° 2θ; step of the detector was equal to 0.480° (2θ).

The detail of the samples study by SAXS and XPS methods was reported in [19, 27, 28]. The procedure of determination of elements distribution in surface layer by XPS method was described in [27].

The photocatalytic properties of the samples in degradation of chloramphenicol (50 threshold limit values (TLV)) was determined under visible and UV irradiation. The study was carried out in a cylindrical reactor (9 cm diameter) with a wall-placed 10 cm height sample (implantation on both sides of the foil) and immersed thermostatically controlled radiation source. The source of radiation (high-pressure mercury or sodium lamps were used) was placed in reactor center, which permits to implement the investigation in both UV and visible range. The reaction products were analyzed on a SelmiChrom-2 gas chromatograph equipped with a FID on a stainless steel column (length 1 m, diameter 3 mm) filled with Porapak Q.

3 Results and Discussion

The data obtained by XRD method (Figs. 1 and 2) demonstrate the presence of (111) (200) and (220) planes austenite reflexes (initial stainless steel) in diffractograms of all synthesized samples with implanted titanium. This fact coincides with the results obtained in the work [27].

Fig. 1
figure 1

Data of XRD analysis for initial SS foil, Ti/SS, and Ti/SS oxidized at 300 °C

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Fig. 2
figure 2

data of XRD analysis for Ti/SS oxidized at 400, 500, and 600 °C

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A similar situation is observed for samples on aluminum foil (Figs. 3, and 4).

Fig. 3
figure 3

Data of XRD analysis for initial Al foil, Ti/Al, and Ti/Al oxidized at 200 °C

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Fig. 4
figure 4

Data of XRD analysis for Ti/Al oxidized at 300, 400, and 500 °C

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The lack of reflexes other than the original ones can be explained by the fact that ionic implantation does not create distinct crystalline structures in the surface layer.

From the SEM data (cross section) [19, 27], it is known that the stainless steel surface after titanium implantation has the new layer (thickness of this layer is near to 80 nm).

The results of XPS study demonstrate the presence of titanium (target ions), oxygen (from air), and nitrogen (from plasma of the ion source) in this nanolayer [27] and the formation of amorphous titanium oxynitride and nitride of titanium in this layer on stainless steel surface as result of titanium implantation. It was shown [27] that treatment of this sample at 600 °C led to formation of titanium oxide in this surface layer. The influence of other temperatures of the sample treatment on its properties was not studied. Therefore, an elemental analysis and morphology of the surface layer was performed using SEM and EDXS.

The results (Fig. 5) of the study of morphology (SEM) show that the treatment of the steel sample with titanium ions leads to the severity of the relief. Smaller formations are smoothed, and larger ones are enlarged. After annealing of the samples, the microgeometry changes again—there is a smoothing and averaging of defects. With increasing of the treatment temperature, this effect increases.

Fig. 5
figure 5

Data of SEM investigation of initial steel SS (a), sample Ti/SS (b) and after its temperature treatment under 300 °C (c) and 400 °C (d)

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On initial sample of aluminum foil (Fig. 6), the defects are visible in the form of stripes, which is the result of production technology. After implantation of titanium, as well as for steel foil, there is an expression of a relief, which is smoothed at oxidation, leaving only technological strips.

Fig. 6
figure 6

Data of SEM investigation of initial foil Al (a), sample Ti/Al (b), and after its temperature treatment under 200 °C (c) and 300 °C (d)

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The similarities in the behavior of implants on different media confirm the results of EDXS.

EDXS analysis of aluminum-based implants (Fig. 7) shown in the original sample only the components that must be according to the production technology. After implantation, the amount of oxygen in the samples increases and nitrogen appears which enters with the ion stream from the ion source plasma.

Fig. 7
figure 7

Data of EDXS analysis of initial foil Al (a), sample Ti/Al (b), and after its temperature treatment under 500 °C (c)

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It is determined that after oxidation with a temperature of 500 °C (Fig. 7c) only the ratio of nitrogen–oxygen changes in favor of the latter.

Similarly, the composition of the sample synthesized by processing steel foil is changed (Fig. 8).

Fig. 8
figure 8

Data of EDXS analysis of initial foil SS (a), initial sample Ti/SS (b), and after its temperature treatment under 500 °C (c)

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The original sample (Fig. 8a) corresponds to the standard composition of the components.

During processing, it receives oxygen (Fig. 8b), which the amount increases after oxidation (Fig. 8c).

The obtained results of the samples investigation and the literature data [19, 27] show the perspective of the study of the synthesized implants in the reaction of chloramphenicol (CAP) decomposition (Fig. 9).

Fig. 9
figure 9

Photocatalytic degradation of the chloramphenicol on the Ti/SS sample treated at 200 °C

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The obtained results of photocatalytic activity of implants with titanium ions demonstrate that the chloramphenicol degradation at UV irradiation (all samples were inactive in visible light irradiation) proceed with an offset toward the visible range. Moreover, the magnitude of this shift depends on the exposure time of the sample (Fig. 9). So, it is possible to suppose that photocatalytic activity of the catalysts prepared by ionic implantation of titanium on stainless steel depend on surface composition and morphology, which allows the selection of the appropriate catalyst.

4 Conclusions

The samples were synthesized on aluminum and steel carriers by ion implantation. It is shown that there are no newly formed crystalline structures in the surface layer of the support samples and this state is observed for oxidized carriers as well. The formation of surface nanolayer of implanted titanium was established.

It was found that the samples synthesized on stainless steel by ionic implantation change their morphology during oxidation in the same way as the samples on aluminum foil. It is shown that the nature of changes in surface composition for samples on different supports is similar. It was found that the implants show some photocatalytic activity in the decomposition reaction of chloramphenicol.

Thus, ionic implantation has significant potential as a technology for the synthesis of photocatalysts, which is relevant for environmental catalysis, energetics, pharmaceutical industry and more.