**5. Environmental applications**

#### **5.1. Water treatment**

The resultant GO/TiO2

between GO and TiO2

**4.4. Heterojunction formation**

114 Graphene Oxide - Applications and Opportunities

conductor [39]. GO/TiO2

electron-hole pairs compared with that of TiO2

**4.5. Coupling multiple active sites**

response properties under solar light irradiation [41].

**Figure 4.** p–n heterojunction formation at the interface between GO and TiO2.

TiO2

known rhodamine B dye. In comparison with commercial P25 TiO2

showed a three time faster degradation rate due to the enhanced electronic combination

Incorporating GO with metal-containing semiconductors can initiate a p-n junction, which considerably improves the separation of photo-generated charges. This is a possible way to fabricate GO/semiconductor composites with different properties by using a tunable semi-

composites were prepared by using TiCl3

 semiconductors functioned as the separator for the photo-generated electron-hole pairs, **Figure 4**. These semiconductors could be excited by visible light with wavelengths longer than 510 nm for the degradation of methyl orange. Also, the integration of GO with TiO<sup>2</sup>

[40]. Similar to TiO2

Again, the concentration of GO in starting solution played an important role in the photocatalytic performance of the composites. The heterojunction between p-type GO and n-type

significantly increase the photovoltaic response and significantly prolong its mean life-time of

heterojunction with GO for visible light absorption. Quantum dot sized ZnO nanoparticles deposited on graphene sheets with a p-n heterojunction interface were demonstrated by a change of photocurrent direction at different bias potential that significantly enhanced photo-

GO can act as a common platform for more than one active site to produce enhanced heterostructure for photocatalytic activity. For example, ZnS-CdS/GO shows a twice activity toward photocatalytic hydrogen generation compared with ZnS-CdS standalone heterostructures [28].

in addition to the remarkable higher gross surface area.

hybrids were tested in the photocatalytic degradation of the well-

, the prepared hybrids

and GO as reactants.

, ZnO also can form a p-n

will

The contamination problem of natural water resources with pollutants of different forms is a problem that threatens public health. The photocatalysis is expected to play a major role in the water purification process because it has a great ability to exploit solar energy in pollutants degradation in the moderate temperature range. Visible light-responsive photocatalysis has been widely investigated for the treatment of inorganic, organic, and biological contaminated water. However, the application of photocatalysis in water treatment is still in the research stage.

### *5.1.1. Degradation of organic pollutants*

Since organic dyes pharmaceuticals are usually leakage with a significant part to the industrial wastewater during manufacture processes; it has received a lot of attention in terms of treatment processes, including photocatalysis. Because of the easy tracing of dye decolonization process, it has left a great scientific legacy of published scientific papers. In general, when the photocatalyst is irradiated with photon with energy compatible with the band gap energy (Eg), an electron is transferred from the VB to the CB, leaving behind a hole. Accordingly, the produced electron-hole pairs are involved in a series of chain oxidative-reductive reactions, Eqs. (1)–(10) [42].

$$\text{Photocatalyst} \star h\nu \longrightarrow \text{h}^{\star} \text{-} \text{e}^{\cdot} \tag{1}$$

$$\rm h^{+}\rm H\_{2}O \longrightarrow \rm {}^{\bullet}OH + \rm H^{+} \tag{2}$$

$$\mathrm{h}^{\ast}\mathrm{+OH}^{\cdot}\longrightarrow\mathrm{\mathrm{\mathrm{\mathrm{\mathrm{\mathrm{\mathrm{\mathrm{\mathrm{\cdot}}}}}}}}\mathrm{\mathrm{\mathrm{\mathrm{\cdot}}}}}\mathrm{\mathrm{\mathrm{\cdot}}}\tag{3}$$

h+ + pollutant ⟶ (pollutant)+ (4)

$$\text{e}^- \text{+} \text{O}\_2 \longrightarrow \text{"O}\_2^- \tag{5}$$

$$\rm O\_2^{\cdot +} + H^{\cdot} \longrightarrow \rm \rm \rm OOH \tag{6}$$

$$\text{2.2'OOH} \longrightarrow \text{O}\_2 \star \text{H}\_2\text{O}\_2 \tag{7}$$

polysulfone membrane over pristine polysulfone membrane have been identified, including the effective photodegradation of methylene blue under UV (about 60–80% faster) and sunlight (3–4 times faster) beside improved membrane flux. After that many attempts have been carried out to construct and utilized photocatalytic membrane for water and salty water purification [47–51]. In the next-generation of water treatment photocatalytic membranes, the antimicrobial character was also included. In situ implementation of Ag nanoparticles onto

According to national ambient air quality standards (NAAQS) carbon monoxide (CO), ozone

considered harmful to public health and the environment. Unfortunately, gases such as NOx,

, and CO are difficult to oxidize and remove. Hence, the role of photocatalysis as an effective economic alternative to oxidize the aforementioned gases to products, which are harm-

and CO has been reported [53]. The cobalt-imidazole functionalized GO incorporat-

to visible light irradiation. Experimental results revealed a high percentage deterioration of

with the ability of GO to modify its band gap with the exploitation of cobalt to form complex

emitted into the atmosphere as a major product of combustion operations. Unfortunately,

the exploitation of solar energy as an energy source represents an opportunity for two birds with one stone, that is, the energy harvesting/storage and environmental issues. Superior

aspects [54]: (i) prevent carrier recombination, (ii) increasing specific surface areas, (iii) strong

chemical stability, (v) improving nanoparticles (NPs) dispersion, and (vi) enhancing light

research was not limited to use GO standalone, but there is a growing effort to improve using

spread over the surface of the GO. For instance, GO doped oxygen-rich TiO2

Since GO could act as an active photocatalyst, it was used as a photocatalyst for CO2

NOx (51%) and CO (46%). This photocatalyst reflects the ability of TiO<sup>2</sup>

neous solar energy harvesting. Side-by-side to exploit CO2

advantages of the graphene-based photocatalyst for CO2

π-π interaction between graphene and CO<sup>2</sup>

nol conversion. The photo-reduction of CO2

achieve six-fold higher than the pure TiO2

nanocomposite membrane assemblies, allowing for simultaneous fil-

/GO functionalized with a cobalt complex for significant degradation

result in a notable decrease of the band gap and increased the sensitivity

gas needs high energy. Therefore, the existence of some processes related to

, *<sup>x</sup>* <sup>=</sup> <sup>1</sup> or 2), sulfur dioxide (SO2

Immobilization Impact of Photocatalysts onto Graphene Oxide

http://dx.doi.org/10.5772/intechopen.78054

) to hydrocarbons represents a perfect example of simulta-

), and lead (Pb)

117

to act as photocatalyst

, the main cause of global warming,

reduction was categorized into six

to metha-

hybrid

, (iv) enhancing photocatalyst mechanical and

to methanol conversion rate on modified GO

under 300-watt halogen lamp irradiation [55]. The

the surface of GO/TiO2

less to public health.

Recently, novel TiO2

formation with pollutant gases.

Reduction of carbon dioxide (CO2

 **reduction**

ing with the TiO2

(O3

SO2

of NOx

**5.3. CO2**

exploiting CO2

absorption.

TiO2

tration, and disinfection [52].

**5.2. Air pollutants removal**

), particulate matter, nitrogen oxides (NO<sup>x</sup>

$$\rm H\_{2}O\_{2} + 2\cdot O\_{2}^{-} \longrightarrow \rm \rm \rm OH + OH^{-} + O\_{2} \tag{8}$$

$$\mathrm{H}\_{2}\mathrm{O}\_{2} \star \hbar \nu \longrightarrow 2\,\mathrm{^{\bullet}OH} \tag{9}$$

$$\text{pollutant} \star \text{(}^\bullet \text{OH,h} \text{; }^\bullet \text{OOH or } ^\bullet \text{O}\_2^- \text{)} \longrightarrow \text{degradation product} \tag{10}$$

Recently, enhanced photocatalytic ZnO/GO nanocomposite was introduced for the degradation of methyl orange under UV irradiation [43]. The reaction proceeds for 2 h to achieve 95% degradation from the initial dye concentration of 10 mg/L. Pseudo-first-order kinetics were recorded with respect to methyl orange with an apparent reaction rate constants in the range of 0.009–0.030 min−1. Moreover, the aforementioned ZnO/GO photocatalyst passed the stability and reusability test.

#### *5.1.2. Stalemate of inorganic pollutants*

Chromium is one of the common cationic pollutants in wastewater. Chromium exists in two main oxidation states in the environment, Cr(VI) and Cr(III). Compared with Cr(III), Cr(VI) is more toxic [44]. Hexagonal nanoflowers of Tin(IV) sulfide/GO was synthesized by hydrothermal method [45]. The composite showed a high photocatalytic activity toward the oxidation of hexavalent chromium upon contact with the SnS2 /GO under visible light irradiation, Eqs. (11)–(13).

$$\text{SnS}\_2/\text{GO} + \hbar\nu \longrightarrow \text{h}^+ + \text{e}^- \tag{11}$$

$$2\,\mathrm{h}^\* \star \mathrm{H}\_2\mathrm{O} \longrightarrow \,\vee \mathrm{O}\_2 \star 2\,\mathrm{H}^\* \tag{12}$$

$$\rm{CrO\_4^{2-}} + 8 \, H^+ + 3 \, e^- \longrightarrow \rm{Cr^{3+}} + 4 \, H\_2O \tag{13}$$

#### *5.1.3. Membrane purification*

Membrane fouling and poor water flux are the main problems facing water treatment by membrane technique. However, incorporation of photocatalysis onto the membrane surface is expected to increase the water flux as result of the photo-enhanced hydrophilicity and contaminant degradation. Surface modification by photocatalyst grafting provides a very promising route to the fabrication of high-performance photocatalytic membranes for sustainable water treatment.

Deposition of TiO2 and GO nanosheets on the polysulfone-base membrane was one of the first attempts to construct a photocatalytic membrane [46]. Several properties of the TiO2 /GO/

polysulfone membrane over pristine polysulfone membrane have been identified, including the effective photodegradation of methylene blue under UV (about 60–80% faster) and sunlight (3–4 times faster) beside improved membrane flux. After that many attempts have been carried out to construct and utilized photocatalytic membrane for water and salty water purification [47–51]. In the next-generation of water treatment photocatalytic membranes, the antimicrobial character was also included. In situ implementation of Ag nanoparticles onto the surface of GO/TiO2 nanocomposite membrane assemblies, allowing for simultaneous filtration, and disinfection [52].

#### **5.2. Air pollutants removal**

2 •OOH ⟶ O2 + H<sup>2</sup> O2 (7)

H<sup>2</sup> O2 + *h* ⟶ 2 •OH (9)

Recently, enhanced photocatalytic ZnO/GO nanocomposite was introduced for the degradation of methyl orange under UV irradiation [43]. The reaction proceeds for 2 h to achieve 95% degradation from the initial dye concentration of 10 mg/L. Pseudo-first-order kinetics were recorded with respect to methyl orange with an apparent reaction rate constants in the range of 0.009–0.030 min−1. Moreover, the aforementioned ZnO/GO photocatalyst passed the stabil-

Chromium is one of the common cationic pollutants in wastewater. Chromium exists in two main oxidation states in the environment, Cr(VI) and Cr(III). Compared with Cr(III), Cr(VI) is more toxic [44]. Hexagonal nanoflowers of Tin(IV) sulfide/GO was synthesized by hydrothermal method [45]. The composite showed a high photocatalytic activity toward the oxida-

SnS2 /GO + *h* ⟶ h+ + e<sup>−</sup> (11)

2 h+ + H<sup>2</sup> O ⟶ 1⁄<sup>2</sup> O2 + 2 H<sup>+</sup> (12)

Membrane fouling and poor water flux are the main problems facing water treatment by membrane technique. However, incorporation of photocatalysis onto the membrane surface is expected to increase the water flux as result of the photo-enhanced hydrophilicity and contaminant degradation. Surface modification by photocatalyst grafting provides a very promising route to the fabrication of high-performance photocatalytic membranes for sustainable

first attempts to construct a photocatalytic membrane [46]. Several properties of the TiO2

, •OOH or •O2

<sup>−</sup> ⟶ •OH + OH− + O2 (8)

<sup>−</sup> ) ⟶ degradation product (10)

/GO under visible light irradiation,

/GO/

<sup>2</sup><sup>−</sup> + 8 H<sup>+</sup> + 3 e<sup>−</sup> ⟶ Cr3+ + 4 H<sup>2</sup> O (13)

and GO nanosheets on the polysulfone-base membrane was one of the

H<sup>2</sup> O2 + •O2

116 Graphene Oxide - Applications and Opportunities

•OH, h+

tion of hexavalent chromium upon contact with the SnS2

pollutant + (

ity and reusability test.

Eqs. (11)–(13).

*5.1.2. Stalemate of inorganic pollutants*

CrO4

*5.1.3. Membrane purification*

water treatment.

Deposition of TiO2

According to national ambient air quality standards (NAAQS) carbon monoxide (CO), ozone (O3 ), particulate matter, nitrogen oxides (NO<sup>x</sup> , *<sup>x</sup>* <sup>=</sup> <sup>1</sup> or 2), sulfur dioxide (SO2 ), and lead (Pb) considered harmful to public health and the environment. Unfortunately, gases such as NOx, SO2 , and CO are difficult to oxidize and remove. Hence, the role of photocatalysis as an effective economic alternative to oxidize the aforementioned gases to products, which are harmless to public health.

Recently, novel TiO2 /GO functionalized with a cobalt complex for significant degradation of NOx and CO has been reported [53]. The cobalt-imidazole functionalized GO incorporating with the TiO2 result in a notable decrease of the band gap and increased the sensitivity to visible light irradiation. Experimental results revealed a high percentage deterioration of NOx (51%) and CO (46%). This photocatalyst reflects the ability of TiO<sup>2</sup> to act as photocatalyst with the ability of GO to modify its band gap with the exploitation of cobalt to form complex formation with pollutant gases.

#### **5.3. CO2 reduction**

Reduction of carbon dioxide (CO2 ) to hydrocarbons represents a perfect example of simultaneous solar energy harvesting. Side-by-side to exploit CO2 , the main cause of global warming, emitted into the atmosphere as a major product of combustion operations. Unfortunately, exploiting CO2 gas needs high energy. Therefore, the existence of some processes related to the exploitation of solar energy as an energy source represents an opportunity for two birds with one stone, that is, the energy harvesting/storage and environmental issues. Superior advantages of the graphene-based photocatalyst for CO2 reduction was categorized into six aspects [54]: (i) prevent carrier recombination, (ii) increasing specific surface areas, (iii) strong π-π interaction between graphene and CO<sup>2</sup> , (iv) enhancing photocatalyst mechanical and chemical stability, (v) improving nanoparticles (NPs) dispersion, and (vi) enhancing light absorption.

Since GO could act as an active photocatalyst, it was used as a photocatalyst for CO2 to methanol conversion. The photo-reduction of CO2 to methanol conversion rate on modified GO achieve six-fold higher than the pure TiO2 under 300-watt halogen lamp irradiation [55]. The research was not limited to use GO standalone, but there is a growing effort to improve using TiO2 spread over the surface of the GO. For instance, GO doped oxygen-rich TiO2 hybrid (GO-OTiO2 ) was synthesized through the wet chemical impregnation technique [56]. The photocatalytic performances were evaluated through the photoreduction of CO2 under the irradiation of low-power energy-saving daylight bulbs. GO extent the reactivity of doped oxygen-rich TiO2 to 95.8% even after 6 h of light irradiation. This observation firmly established the role of GO as an effective catalyst support. The composite with 5 wt%, GO has a CH<sup>4</sup> yield of 1.718 μmol g−1cat. after 6 h of reaction, that is, 14.0 folds comparison to commercial Degussa P25.

recombination. Under UV-vis irradiation, the GO-MnTPP hybrid demonstrates considerable

Photoelectrochemical sensors based on materials with photoelectric properties, such as TiO2 have drawn attention in bioanalysis, medical diagnoses, and pollutant monitoring. A density

construction of a blue-light photoelectrochemical sensor based on nickel tetra-amine phthalocyanine-GO for the detection of erythromycin [65]. The prepared composite was fixed on the surface of the indium tin oxide coated glass electrode. When the light was incident on the surface of the material the electron-hole pairs generation process started with a photocurrent response. The erythromycin suppresses electron/hole recombination resulted in changes in the photocurrent with a linear response for erythromycin concentrations ranging from 0.40 to 120.00 μmol L−1.

Incorporation of GO with different semiconductor, metal nanostructures, and complexes allows the design of many generations of photocatalyst systems. In addition, great opportunities still exist in the exploitation of novel GO base hybrids and composites photocatalyst. Dual function photocatalysis that can perform multitasks simultaneously represents the greatest future trend along with the discovery of new materials. This is not a fantasy; previously a

of organic pollutants [66]. The positive effect of GO on the dual photocatalytic activity was

Photocatalysts alone almost showed a very low photocatalytic activity because of the rapid recombination of CB electrons and VB holes. The chemical bonding and associated charge transfer at the interface between the photocatalyst and GO support can be used to fine-tune the electronic and chemical properties of the active sites. GO can act as a common platform for more than one active site to produce enhanced heterostructure for photocatalytic activity. GO is an excellent supporting material due to its high specific surface area and superior electron mobility. GO plays the role of an electron acceptor that accelerates the interfacial electron-transfer process from photocatalysts materials, which strongly hindering the recombination of charge carriers and thus improving the photocatalytic activity. The spread of the oxygenated functional

groups on its surface facilitates the process of planting photoactive spots on its surface.

dual-functional photocatalysis was introduced based on a ternary hybrid of TiO2

interaction with pristine and

modified

gas sensor [64]. Another example the

http://dx.doi.org/10.5772/intechopen.78054

119

Immobilization Impact of Photocatalysts onto Graphene Oxide


evolution.

functional theory (DFT) study was carried out to model the NO2

/GO nanocomposites for a promising NO2

photocatalytic activity for H<sup>2</sup>

**5.5. Sensing applications**

**6. Future perspectives**

**7. Conclusion**

with GO along with Pt and fluoride for both H<sup>2</sup>

observed only when Pt and surface fluoride were co-present.

N-doped TiO2

Besides TiO2 , other semiconductors, clusters, nanoparticles, and complexes immobilized onto GO has also been investigated for CO2 reduction to hydrocarbon. Hexamolybdenum cluster compound was used for the modification of GO for visible light absorption [57]. After 24 h of visible light illumination, the yield of methanol was found to be 1644 and 1294 μmol g−1cat. for GO/Cs2 Mo<sup>6</sup> Bri 8 Bra x and GO/(TBA)2 Mo<sup>6</sup> Bri 8 Bra x (TBA = tetrabutylammonium), respectively. These values are much higher than GO alone (439 μmol g−1cat.). Halide perovskite quantum dots (CsPbBr3 QD/GO) was utilized for the photochemical conversion of CO2 [58]. These materials primarily regarded as optoelectronic materials for light emitting diode (LED) and photovoltaic devices. Compared to the individual CsPbBr3 QDs, the rate of electron consumption improved from 23.7 to 29.8 μmol g−1cat. after the incorporation with the GO. As an example of nanoparticles decorated GO with a series of Cu-nanoparticles were utilized to reduce CO2 to hydrocarbon fuels under visible light irradiation [59]. Cu-NPs (10 wt%) effectively tune the work function of GO 60 times higher. A ruthenium trinuclear polyazine complex was also immobilized onto GO functionalized with phenanthroline ligands [60]. Using a 20 W white cold LED flood light, in a dimethyl formamide-water mixture sacrificing agent, the yield of methanol was found to be 3977.57 ± 5.60 μmol g−1cat. after 48 h.

#### **5.4. Water splitting**

Water splitting with hydrogen evolution based on photocatalytic process represents a renewable energy production with no reliance on fossil fuels and no CO2 emission. The role of GO in photocatalytic water splitting was perfectly reviewed [61]. GO itself as a photocatalyst steadily catalyzes H<sup>2</sup> generation from 20 vol% aqueous methanol solution and pure water under irradiation with UV or visible light [62]. Concurrently with the photocatalytic reaction, the CB of GO with an excessive overpotential associated with the level for H<sup>2</sup> generation reveals fast electron injection from the excited GO into the solution. On the other hand, the holes in the VB of GO do not interact with the water molecules for O<sup>2</sup> generation but are disabled to the hole scavenger (methanol) alternatively.

The GO band gap decrease during the photocatalytic reaction because of GO reduction. However, the H<sup>2</sup> evolution remained unchanged, indicating that the involved oxygenated sites remain accessible to protons in the liquid phase.

Recently, GO sheets covalently functionalized with (5, 10, 15, 20-tetraphenyl) porphinato manganese(III) (MnTPP) GO-MnTPP and tested for water splitting under UV-vis light irradiation [63]. The dye moiety acted as a sensitizer while GO moiety acted as a supporting matrix, electron mediator, enhancing photoexcited electrons transfer, and suppressing charges recombination. Under UV-vis irradiation, the GO-MnTPP hybrid demonstrates considerable photocatalytic activity for H<sup>2</sup> evolution.

### **5.5. Sensing applications**

(GO-OTiO2

CH<sup>4</sup>

oxygen-rich TiO2

Besides TiO2

for GO/Cs2

dots (CsPbBr3

**5.4. Water splitting**

steadily catalyzes H<sup>2</sup>

However, the H<sup>2</sup>

mercial Degussa P25.

Mo<sup>6</sup> Bri 8 Bra x

GO has also been investigated for CO2

118 Graphene Oxide - Applications and Opportunities

and GO/(TBA)2

methanol was found to be 3977.57 ± 5.60 μmol g−1cat. after 48 h.

able energy production with no reliance on fossil fuels and no CO2

holes in the VB of GO do not interact with the water molecules for O<sup>2</sup>

disabled to the hole scavenger (methanol) alternatively.

sites remain accessible to protons in the liquid phase.

tovoltaic devices. Compared to the individual CsPbBr3

) was synthesized through the wet chemical impregnation technique [56]. The

to 95.8% even after 6 h of light irradiation. This observation firmly estab-

, other semiconductors, clusters, nanoparticles, and complexes immobilized onto

reduction to hydrocarbon. Hexamolybdenum cluster

(TBA = tetrabutylammonium), respectively.

QDs, the rate of electron consumption

under the

[58]. These mate-

emission. The role of

generation but are

generation

photocatalytic performances were evaluated through the photoreduction of CO2

Mo<sup>6</sup> Bri 8 Bra x

irradiation of low-power energy-saving daylight bulbs. GO extent the reactivity of doped

lished the role of GO as an effective catalyst support. The composite with 5 wt%, GO has a

compound was used for the modification of GO for visible light absorption [57]. After 24 h of visible light illumination, the yield of methanol was found to be 1644 and 1294 μmol g−1cat.

These values are much higher than GO alone (439 μmol g−1cat.). Halide perovskite quantum

rials primarily regarded as optoelectronic materials for light emitting diode (LED) and pho-

improved from 23.7 to 29.8 μmol g−1cat. after the incorporation with the GO. As an example of nanoparticles decorated GO with a series of Cu-nanoparticles were utilized to reduce CO2 to hydrocarbon fuels under visible light irradiation [59]. Cu-NPs (10 wt%) effectively tune the work function of GO 60 times higher. A ruthenium trinuclear polyazine complex was also immobilized onto GO functionalized with phenanthroline ligands [60]. Using a 20 W white cold LED flood light, in a dimethyl formamide-water mixture sacrificing agent, the yield of

Water splitting with hydrogen evolution based on photocatalytic process represents a renew-

GO in photocatalytic water splitting was perfectly reviewed [61]. GO itself as a photocatalyst

under irradiation with UV or visible light [62]. Concurrently with the photocatalytic reaction,

reveals fast electron injection from the excited GO into the solution. On the other hand, the

The GO band gap decrease during the photocatalytic reaction because of GO reduction.

Recently, GO sheets covalently functionalized with (5, 10, 15, 20-tetraphenyl) porphinato manganese(III) (MnTPP) GO-MnTPP and tested for water splitting under UV-vis light irradiation [63]. The dye moiety acted as a sensitizer while GO moiety acted as a supporting matrix, electron mediator, enhancing photoexcited electrons transfer, and suppressing charges

the CB of GO with an excessive overpotential associated with the level for H<sup>2</sup>

generation from 20 vol% aqueous methanol solution and pure water

evolution remained unchanged, indicating that the involved oxygenated

QD/GO) was utilized for the photochemical conversion of CO2

yield of 1.718 μmol g−1cat. after 6 h of reaction, that is, 14.0 folds comparison to com-

Photoelectrochemical sensors based on materials with photoelectric properties, such as TiO2 have drawn attention in bioanalysis, medical diagnoses, and pollutant monitoring. A density functional theory (DFT) study was carried out to model the NO2 interaction with pristine and N-doped TiO2 /GO nanocomposites for a promising NO2 gas sensor [64]. Another example the construction of a blue-light photoelectrochemical sensor based on nickel tetra-amine phthalocyanine-GO for the detection of erythromycin [65]. The prepared composite was fixed on the surface of the indium tin oxide coated glass electrode. When the light was incident on the surface of the material the electron-hole pairs generation process started with a photocurrent response. The erythromycin suppresses electron/hole recombination resulted in changes in the photocurrent with a linear response for erythromycin concentrations ranging from 0.40 to 120.00 μmol L−1.
