Synthesis and Characterization of Large-Scale (

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Synthesis and characterization of large scale, (< 2 nm) chitosan decorated copper nanoparticles and their application in anti-fouling coating Tamilselvan Abiraman, and Sengottuvelan Balasubramanian Ind. Eng. Chem. Res., Just Accepted Manuscript • DOI: 10.1021/acs.iecr.6b04692 • Publication Date (Web): 17 Jan 2017 Downloaded from http://pubs.acs.org on January 23, 2017

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Industrial & Engineering Chemistry Research

Synthesis and characterization of large scale, (< 2 nm) chitosan decorated copper nanoparticles and their application in anti-fouling coating

Tamilselvan Abiraman, and Sengottuvelan Balasubramanian* Department of Inorganic Chemistry, University of Madras, Chennai-600025, India.

ABSTRACT: The sub 2 nm size chitosan decorated copper nanoparticles were synthesized in large scale (5.2g, 98%) by green chemical reduction method. The reduction of copper(II) salt by L-ascorbic acid (green reducing agent) in water medium in the presence of chitosan (green capping agent) at 85°C, resulted in the formation of chitosan decorated copper nanoparticles (CDC NPs). The chitosan decorated copper nanoparticles were characterized by spectral (DRS, FT-IR, XPS, FESEM, HRTEM) and thermal (TGA) studies. The CDC NPs were mixed with polyurethane clear and white and acrylic emulsion paint and coated on to mild steel, cement slab and wood panels. The measurement of water contact angle and hydration free energy of uncoated and CDC nanopaint coated panels were indicated the extent of hydrophilicity. The antifouling activity of CDC NPs coated panels were examined against marine (Amphora) and green (Arthrospira, Chlorella) algae. The copper leached out from the surface of CDCNP coated panels are near null, which is confirmed by the measurement of Inductively Coupled Plasma (ICP) spectrometry. The CDC NPs show ~80-95% antifouling efficiency against the growth of algae. Key words: Large scale synthesis, sub 2 nm copper nanoparticles, chitosan, L-ascorbic acid, anti-fouling, green and marine algae.

ACS Paragon Plus Environment


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1. INTRODUCTION The accumulation of marine organisms such as algae, bacteria, mollusks and animals on structures submerged in seawater is known as fouling or bio-fouling.1 Nearly four thousand biofouling organisms have been found globally such as barnacles, bryozoans, tubeworms, bacteria, algae spores, mussels and diatoms.2 The temperature, surface energy of the substrate, roughness, porosity, salinity, nutrient level flow rate and the intensity of solar radiation3 are some of the factors which cause the deposition of marine bio-fouling organisms on any surface. The settlement of unwanted biological organisms on to natural or synthetic surfaces creates several problems in the naval industry, such as corrosion of the surfaces, increased fuel consumption, increased roughness, increased hydrodynamic drag, higher corrosion rate, blocking of valves and pipes of seawater conducting installations, greenhouse gas emission and hampering. The marine industry will be consuming more than half a billion tons of fuel per year by the end of this decade and will be releasing hundreds of million tons of CO2 and other pollutant gases and harmful particles to the atmosphere.4 The attempts to active more effective antifouling defense will result in saving worldwide over $150/p.a. in 2020,4 without including indirect costs resulting from hull repairs, transport delays, sunk vessels due to bio-corroded hulls. The antifouling coatings have been established to avoid the accumulation of bio-fouling organisms in the hull of the ship, cement slab and wood construction in the aqueous environment. The modern antifouling coatings can be classified into (i) nontoxic coatings and (ii) chemically active coatings. The earliest techniques employed made use of wax, tar, pitch, toxic lead or arsenic-based coatings and tri butyl tin (TBT-based compounds) as antifouling agents. The earlier studies indicated that this type of biocide compounds have adverse effect on marine life due to their persistence and toxic behavior. The International Maritime Organization issued


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an order prohibiting the use of such type of biocide in the production of antifouling paints in 2003.5 The alternative solution for antifouling agents several materials such as V2O5 NPs, Polysulfone-PANI/TiO2 ultrafiltration nanocomposite membranes, carbon nanotube hollow fiber membranes, silver NPs modified surfaces, HPEI-GO/PES ultrafiltration membrane, halloysite nanotubes loaded with Cu2+ ion as well as Ag NPs which are incorporated in polyethersulfone ultrafiltration hybrid membrane, copper nanoparticle/halloysite nanotube nanocomposites,6-11 nanocomposite of Ag NPs and poly (vinylidene fluoride), hybrid polymer/Au NPs and CNTs/Al2O3 membrane,12-14 polyelectrolyte, polyisoprene-based coatings, poly(ethylene glycol) nanofibrous mesh, polyglycerol-grafted poly(ether sulfone), polyvinylidene fluoride hollow fiber membranes and zwitterionic poly(serine methacrylate) have also been employed as antifouling agents.15,16 Co-biocides such as tebuconazole and propiconazole also called as boosters have been used to enhance the antifouling activity. However, it was found that the material cost and their preservation are high. Hence the development of new materials which act as good antifouling agents is essential. The copper and copper based compounds have been used for a very long time for the protection of underwater hulls. Chapman et al have reported the use of large particle size (50-100 nm) copper NPs as antifouling agent.17 Chitosan is a biodegradable polymer and it was used for the reduction of particle size as well as shape and prevention of agglomeration. Wang et al used chitosan as an antimicrobial agent.18 L-ascorbic acid, which is a naturally occurring substance, is capable of acting as an antioxidant, mild reducing as well as capping agent.19 Nanotechnology is one of the fastest growing fields since it produces materials which possess unique physical, chemical and biological properties. The transition metal NPs such as



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Au, Ag and Cu find application in various fields such as catalysis, optical, chemical, electronic devices, biological, sensor, dye-sensitized solar cells, environmental technology and medicine. Copper NPs are considered as better replacement for both Au and Ag NPs because of their easy availability, low cost and good thermal conductivity. Several approaches are available for the preparation of Cu NPs which include chemical reduction, electrochemical, thermal decomposition, sonochemical, micro emulsion and laser ablation methods as well as polyol and reverse micelle processes.20-22 The chemical reduction method is fast and easy to manage for the preparation of metal NPs. The synthesis of copper nanoparticles is very dificult under normal atmosphere because copper is easily oxidized in air. Generally copper NPs have been synthesized by using toxic reducing as well as capping agents such as sodium borohydride, sodium hypophosphite, hydrazine hydrate and PVP besides maintaining inert atmosphere and relatively high temperature.23 Basically, the surface area of nanoparticles are inversily propotional to their particle size. The major issue in the synthesis of nanoparticles is scaling up of particles with small size, because the particles are easily aggregated during scaling up. There are only few reports on the synthesis of copper NPs with 2 nm size copper NPs without any impurities like Cu2O, which was confirmed by the absence of peak at ~460 nm.

Figure 2. FT-IR spectra of chitosan (a) and CDC NPs (b).


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The FT-IR spectral study has been employed to determine the nature of the functional groups and the interaction between chitosan and copper NPs. The FT-IR spectra were obtained in the range of 4000-400 cm-1 using KBr. shows The FT-IR spectrum of chitosan biopolymer is reproduced in figure 2a. The 3361 cm-1 band is attributed to -OH and -NH stretching vibrations. The bands at 2878 and 2134 cm-1 are due to aliphatic -C-H symmetric and asymmetric stretching vibrations respectively. The -NH2 bending vibrations are observed at 1654 and 1593 cm-1. The -C-H bending frequencies are observed at 1421, 1378 and 1317 cm-1 and -C-O-C- skeletal frequency is observed at 1079 cm-1.37 Figure 2b shows the absorbance bands of CDC NPs. The shift and the shape changes of all the bands (mainly -OH and -NH at 3446 cm-1) occurred due to the contribution from the reduction and stabilization of copper NPs. The FT-IR spectra (Figure S2) clearly show the absence of other peaks due to impurities such as CuO or Cu2O in the region 430-630 cm-1 indicating that the copper NPs are well decorated by the chitosan biopolymer.38 The composition of CDC NPs was analysed by high resolution XPS. Figure 3a shows the survey spectum of CDC NPs which indicates the presence of the elements such as Cu, C, N and O. The two peaks observed at 932.7 and 952.6 eV are attributed to the core levels of Cu 2P3/2 and Cu 2P1/2 in the copper core level peak fitting spectum. This observation confirms the formation of zero valent Cu NPs (Figure 3b).39 The additional three shake up satellite peaks at 936.4, 946.3 and 955.7 eV suggest that chitosan is very strongly bound to copper NPs. The full width half maximum values for CuO and Cu2O are 2.7 eV and 1.9 eV respectively, but the FWHM for CDC NPs is 1.0 eV indicating the absence of impurities such as Cu2O and CuO. Figure 3c shows the C 1s peak fitting spectrum with a binding energy at 284.8 eV which is attributed to C-C/C-H.



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Figure 3. XPS images of CDC NPs: survey spectrum of all elements (a), peak fitting spectra of (b) Cu 2P3/2, (c) C 1s, (d) O 1s and (e) N 1s.


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The minor shift observed around 0.6 eV is due to the presence of amine group and the signals from C-N and C-H/C-C overlap with each other. The two peaks appearing at 288 and 291.7 eV are attributed to C-OH/C-N and -C-O-C- of chitosan respecively.40 The O 1s peak fitting spectrum exhibits different contributions of oxygen with binding energy at 528.7, 530.3 and 535 eV due to (Cu…OH), (C-OH) and (O-C-O) respectively (Figure 3d). The peak fitting spectum of N 1s (Figure 3e) indicates the binding energy at 402 eV which confirms that amine groups are chelated to copper NPs.41 The strong chemisorption of chitosan on the surface of copper NPs is indicated in the Figure 3. This interface takes place in chitosan preceding to the nucleation process. The copper NPs oxidation and particle growth is effectively prevented by the chemically adsorbed chitosan.

Figure 4. FESEM images of Cu NPs-loaded chitosan microspheres (low (a) and high (b) magnification). The FESEM analysis shows the morphology of Cu NPs-loaded chitosan. The low magnification image (Figure 4a) shows that the Cu NPs-loaded chitosan are uniformly formed as microspheres without any aggregation which is observed only in the optimized reaction



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condition (Figure S3a). The Figure 4b shows the high magnification image of Cu NPs-loaded microsphere chitosan surfaces which clearly indicates the absence of Cu NPs on the outer surface. This is attributed to the size of Cu NPs which is sub 2 nm and also the resolution limit of FESEM instrument. Figure S3b shows the high magnification image of aggregated Cu NPsloaded chitosan microsphere surfaces which clearly indicates that the aggregated Cu NPs are uniformly distributed on the chitosan matrix. The FESEM images demonstrate the formation of small size (< 2 nm) Cu NPs, however their morphology is not clearly understood.

Figure 5. HRTEM image (a) and SAED pattern of CDC NPs (b). The shape and size of the CDC NPs were analyzed by HRTEM. Figure 5a shows, the high magnification HRTEM image of CDC NPs. The dark region is surrounded by white features which confirm that Cu NPs are uniformly decorated by chitosan. The HRTEM image did not show clearly the particle size because the particles are > 2 nm which surpasses the resolution limit of HRTEM instrument. The HRTEM image provides a clear indication that Cu NPs are distributed without any aggregation which is observed only in the optimized reaction condition (Figure S4). The average particle size is predicted to be around 1.5 ± 0.2 nm using


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image J software. Based on the results of DRS and HRTEM studies, the Cu NPs were found to be spherical in shape with < 2 nm size. The selected area electron diffraction (SAED) arrangement of CDC NPs confirms the formation crystalline CDC NPs with fcc structure (Figure 5b).42

Figure 6. Thermograms of chitosan (a) and CDC NPs (b). The thermal behavior of chitosan and CDC NPs was determined by thermo gravimetric analysis. Chitosan exhibits a gradual weight loss in the range 35 to 150°C in the first stage, which is attributed to loss of water (Figure 6a). The rapid decomposition of chitosan occurs in the temperature range of 260-350°C, due to the decomposition of acetylated and deacetylated groups of chitosan.43 The maximum decomposition temperature of chitosan is observed at 305°C. The different stages of weight loss and gain by CDC NPs have been observed (Figure 6b). The weight loss between 50-250°C is attributed to residual water evaporation. The nanoparticles then gain 4% weight at 284°C, which corresponds to the oxidation of Cu to Cu2O. Then the loss of chitosan (0.4 %) occurs at 318°C. The 14.6 % weight gain observed at 396°C



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corresponds to the oxidation of Cu2O to CuO.44 From the TGA results, clearly indicate that the copper NPs are well decorated by chitosan and it has been observed that the decomposition temperature of CDC NPs slightly increases compared to that of chitosan which indicates that CDC NPs are thermally more stable. In general, the bio-fouling depends on hydrophilicity (or) hydrophobicity, porosity and roughness of any surfaces. The bio-fouling decreases by increasing hydrophilic nature of CDCNP coated panels when compared to uncoated panels, which is confirmed by the measurement of water contact angle. Figures 7a, b & c show, the water contact angle images of CDCNP coated panels, the values for W (69°), CS (60°) and MS (49°) panel surfaces which clearly show that all the coated panels are hydrophilic in nature. Figures 7d & e show, the contact angle of uncoated MS (90.7) and CS (100.2) panel surfaces which indicate that both panels are hydrophobic in nature.

Figure 7. The water contact angle images of CDCNP coated panels (a-c) and uncoated panels (d & e).


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The recent reports suggest that the hydrophilicity of NPs can be increased by blending them with polymeric material.45-47 The hydrophilicity and free energy of hydration values of CDCNP coated and uncoated panel surfaces are shown in Table. 1, which clearly indicates that CDCNP coated panel surfaces are more hydrophilic and the free energy of hydration values are higher than that of the uncoated panel surfaces, which is the typical behavior exhibited by hydrophilic materials ( ∆Gsw ≤ -113 mJ m-2 ).48 The increase in hydrophilicity and free energy of hydration values of CDCNP coated panel surfaces result in increased antifouling activity. The measurement of contact angle for uncoated W panel surface has not been carried out, because it has lot of pores on its surface and hence the water drops are completely absorbed. The free energy of hydration of the CDCNP coated panel surfaces (-∆Gsw) was found out from the water contact angle data by the following Young-Dupre equation.

where, (γwTOT) is the total surface tension of water. Table 1. Water contact angle and free energy of hydration values of CDCNP coated and uncoated panels Water contact -∆Gsw (mJ m-2)

Panels Angle (ɵ) Coated (W)

49

119.18

Coated (MS)

60

107.95

Coated (CS)

69

97.76

Uncoated (MS)

90.2

71.10

Uncoated (CS)

100.2

59.22



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The surface smoothness of CDCNP coated and uncoated MS panels were measured by AFM analysis. Figure. 8a shows the AFM image of uncoated MS panel surface, which clearly indicates that the RMS roughness (Rq) of uncoated MS panel surface is 58.2 nm. The Rp-p values which is the difference between lower and higher points on the surface is near 265 nm. In the case of CDCNP coated panel surface, the RMS roughness (Rq) is found to be 4.4 nm and Rpp is found to be 6 nm (Figure 8b).49 The AFM values are undoubtedly lower when compared to the uncoated MS panel surface. Based on the AFM result, it can be concluded that the surface of CDCNP coated panel is very smooth when compared to uncoated MS panel.

Figure 8. AFM images of (a) uncoated and CDCNP coated MS panels. 3.2. Antifouling behavior of CDCNP. The roughness of any surface is considered as one of the major causes which affect the growth of algae. The free growth of algae is facilitated by the rough surface of the panel. Figures 9a & b show the visual images of CDCNP coated and uncoated panel surfaces prior to growth of algae and they clearly indicate the difference in surface characteristics among the CDCNP coated


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and uncoated panels. The CDCNP coated panel surfaces are homogeneous and very smooth, but in the case of uncoated panel the surfaces are very rough.

Figure 9. The visual images of uncoated (a) and CDCNP coated panel surfaces (b)-before the algal growth. Figures 10a & c show the visual images of CDCNP coated panel surfaces, after the algal growth. The green Arthrospira and Chlorella algae50 were found to grow only partially on the CDCNP coated panel surface areas. But, Figures 10b & d show that the uncoated panel surfaces were completely covered by the algal growth. In the case of NPs, the particle size is inversely proportional to their efficiency and hence the CDC NPs with < 2 nm are more efficient. The chitosan also exhibits good antimicrobial property. When copper NPs and chitosan were employed together, their efficiency was found to be higher when compared to that of their individual application. The antifouling behavior of CDC NPs is high and hence the panels are not completely affected by the algae.



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Figure 10. The visual images of CDCNP coated (a, c & e) and uncoated panel surfaces (b, d & f)–after the algal growth.


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Figures 10e & f show the visual images of uncoated and CDCNP coated panel surfaces and they clearly indicate the difference in algal growth between uncoated and CDCNP coated panels against the marine Amphora algae. The uncoated panels are completely affected by the algae, however only partial growth of the algae was found on the CDCNP coated panel surfaces, because the CDCNP is more hydrophilic and it prevents the growth of algae on the coated surface areas. The panels coated without any nanoparticles are also completely affected by the algal growth (Figure S5). The above results clearly show that the growth of algae was completely prevented only in the presence of CDC NPs and not by commercial paints. Therefore, the CDC NPs effectively act as good antifouling agent in both fresh and marine algae environment. The algal growth was measured via cell counts and Chlorophyll-a concentration and it is discussed below: Generally the algae growth occurs in four stages. The first two are: (i) lag phase (ii) log phase and the later phases are: (iii) stationary phase and (iv) death phase. In lag phase, the algal growth is initiated and hence the growth of algae is slow. However, in the log phase, the growth of algae is very high, because of the high cell multiplication of the algae. In the stationary phase also the growth of algae is found to the similar to that of the previous phase. The nutrient deficiency results in the decrease in the growth of algae during the death phase. The comparison of antifouling performance of uncoated and CDCNP coated panel surface of the all the three substrates against the marine Amphora and green Arthrospira, Chlorella algae were analyzed by the measurement of Chlorophyll-a concentration for Arthrospira and cell counts for Chlorella and Amphora algae during 0-30 days with an interval of 10 days are indicated in Figure 11.



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Figure 11. Chlorophyll-a concentration of CDCNP coated and uncoated panels in tank-1(a & b), Cell counts of CDCNP coated and uncoated panels in tanks-2 & 3 (c & e) and Cell counts of CDCNP coated and uncoated panels in tanks-2 & 3(d & f).


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Figures 11b, d & f show the cell counts and Chlorophyll-a concentration on the surface area of uncoated panels. The cell counts and Chlorophyll-a concentration increase rapidly in the lag phase (0-10days) on the uncoated panel surface areas. After the lag phase, because of cell multiplication, there is a rapid increase in algal growth (log phase 10-20days) on the uncoated panel surface areas. After 20 days, the algal growth increases gradually, because it is close to stationary phase. But, the cell counts and Chlorophyll-a concentration of CDCNP coated panel surface areas increase extremely slowly during 0-20 days in spite of higher cell multiplication of the algae and spread of algae throughout the tank by aeration. The presence of some algae on the CDCNP coated panel surface is noticed. After the log phase (>20), the cell counts and Chlorophyll-a concentration were found to decrease since the panel surface areas were well protected by the CDCNP. Hence, the deposited algae were destroyed by the CDC NPs (Figure 11a, c & e). The antifouling behavior of the CDC NPs against three different algae in three different surfaces was found to vary in the following order: Arthrospira – [Wood (~95%) > Mild steel (~93%) > Cement slab (~90%)] > Amphora – [Wood (~90%) > Mild steel (~88%) > Cement slab (~85%)] > Chlorella – [Wood (~85%) > Mild steel (~83%) > Cement slab (~80%)]. 3.3. The algal growth analysis in all the three tanks. Some of the major disadvantages by the use of commercial antifouling paints in the marine environment are; they leach out easily from the surface of the substrate as well as they kill the other untargeted algae. The Figure 12 shows the algal growth in all the three tanks, which clearly indicate that the cell counts and Chlorophyll-a concentration are gradually increase till the end of the analysis (0-30 days). The above result and ICP analysis demonstrate, that the amount of leached out CDCNP from the coated panel surface is insignificant and it does not reduce the growth of algae in all the three



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tanks. The stronger adhesion of CDCNP on the panel surface is due to the bare coating and it prevents the leaching of nanoparticles from the surface of the coated panels. It has been found that the CDC NPs with less than 2 nm size act as a good antifouling agent against the bio-fouling organisms.

Figure 12. Algal growth in the entire tank. 3.4. Measurement of the amount of copper released from CDCNP coated panel surfaces (tank-3). The amount of copper released from the CDCNP coated panel surfaces was measured by ICP spectrometry from 0 to 30 days. The Figure 13 shows the concentration of Cu2+ ion in the bulk solution (tank-3), which indicates that there is no difference in Cu2+ ion concentration during zero to thirty days in the bulk solution. The ICP values confirm the absence of additional copper(II) ions which clearly indicate that the originally added nutrient of copper(II) salts for the algal growth was only present in tank-3. The ICP results also suggest that


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the copper NPs were not leached out from the coated panels and the CDC NPs adhere strongly on to the surface of the panels.

Figure 13. The concentration of copper(II) ion from the bulk solution( tank-3). 3.5. Identification of copper species in the solution. 2 L of the solution from tank-3 was taken and concentrated to 50 mL. The concentrated bulk solution (CBT-3S) was used for the additional confirmation test for the absence of leached out copper NPs in the bulk solution (tank3). The CDC NPs were not leached out from the coated panel surfaces and only added nutrient of copper(II) salts for the algae growth was present in the bulk solution, which is confirmed by the following experiments:



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The equation(1) represents general confirmation test for copper metal. The same experiment was carried out with CBT-3S and no brown color NO2 gas was observed (eq2) which suggests the absence of metallic copper in CBT-3S. Equations (3) & (4) represent the confirmation test for copper(II) ion. The copper(II) ion is converted to copper nitrate and nitric oxide by reaction with conc.HNO3. The nitric oxide generated subsequently reacts with the added ferrous salt to form mono nitrosyl penta aqua iron(II) complex, which is confirmed by the


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formation of brown ring. The same experiment was carried out with CBT-3S and the appearance of brown ring (eq5 & 6) confirms that only Cu2+ ions are present in the bulk solution, which was originally added for the algal growth in tank-3. The above results indicate that the CDCNP adheres strongly on to the surface of the panels and hardly any copper NPs are released from the panel surfaces. 3.6. Antibacterial activity of metal NPs and capping agent. The antibacterial activities of copper NPs and chitosan were investigated by Agar well diffusion method. The antibacterial activity was tested with Gram positive (S. aureus) as well as Gram negative (S. typhimurium) bacterial strains. Figure 14. shows the zone of inhibition around (plate#1) chitosan and (plate#2) copper NPs against both Gram positive (S. aureus) and Gram negative (S. typhimurium) bacterial strains. The negative control 10% DMSO did not show any inhibition (e) and 25 µg Streptomycin as positive control (d) in both the plates (#1 and #2) show that DMSO and Streptomycin do not exhibit any antibacterial behavior against the tested bacterial strains. However, chitosan and copper NPs inhibited the growth of both Gram (+ve) and Gram (-ve) bacteria. The bacterial growth inhibition of chitosan and copper NPs were proportional to their concentration.



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Figure 14. Antimicrobial activities of (1) chitosan and (2) copper NPs against both Gram (+ve) (S. aureus) and Gram (-ve) (S. typhimurium) bacteria strains. (a) 50 µg, (b) 100 µg,

(c) 150 µg,

(d) 25 µg standard (Streptomycin – Positive control) and (e) 10 % DMSO (Negative control).


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Table 2. Antibacterial activity of copper NPs and chitosan

Gram (+ve) bacteria

Gram (-ve) bacteria

(S. aureus)

(S. typhimurium )

Pathogens

Sample

(a)

(b)

(c)

(d)

(e)

(a)

(b)

(c)

(d)

(e)

Chitosan

0.5

2.5

5.5

7

-

1.0

3.5

7

9

-

Copper NPs

0.5

3.5

6.5

8

-

0.5

4.5

8.0

10

-

The average diameters of inhibition zones of copper NPs and chitosan were determined and listed in Table-2. These values indicate that the inhibition zone increases with increase in the concentration of copper NPs and chitosan (a-d). The present study clearly shows that both copper NPs and chitosan are solely responsible for the antibacterial activity against both Gram (+ve) (S. aureus) and Gram (-ve) (S. typhimurium) bacteria.51 The antibacterial mechanism of samples can be attributed to the formation of reactive oxygen species (ROS), which results in cell death. It has been reported52 that the rupture of bacterial outer membrane can weaken the cells, which is caused by interaction of sample surface with bacterial membrane.

4. CONCLUSIONS The sub 2 nm size chitosan decorated copper nanoparticles were synthesized in large scale (5.2g, 98%) by a simple green chemical reduction method. The L-ascorbic acid and chitosan were used as green reducing and capping agent respectively. The DRS, FT-IR, XPS, FESEM, HRTEM and TGA studies were carried out for the characterization of CDC NPs. The nanoparticles were



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mixed with polyurethane clear, polyurethane white and acrylic emulsion paints and coated on to the surface of W, MS and CS panels. The resulting CDCNP coatings exhibit higher hydration free energy, lower water contact angle and enhanced hydrophilicity as a result of which a significant antifouling effect (80-95%) was observed against the green and marine algal growth in both sea and freshwater environments. The IPC spectrometry was used to study the stability of CDCNP on the panel surface. The analysis of tank-3 solution by ICP spectrometry clearly demonstrates that copper NPs strongly adhere to the surface of the coated panels and they are not leached out even after 30 days. The present investigation confirms the potential for developing simple and less toxic surfaces containing CDC NPs which can successfully contain bio-fouling by direct coating on the panel surfaces. It is expected that such CDC NPs formulation can provide environmentally friendly antifouling coatings. ASSOCIATED CONTENT Supporting information UV-Visible spectroscopy of CDC NPs (Figure S1), FT-IR spectrum of CDC NPs containing Cu2O and CuO NPs (Figure S2), FESEM image of CDC NPs (pH>9) (Figure S3), HRTEM image of CDC NPs (pH>9) (Figure S4), The visual images of commercial paint (without CDC NPs) coated wood, mild steel and cement slab panels after the algal growth (a, b) c) - (tank-2). (Figure S5). AUTHOR INFORMATION Corresponding Author E-mail: [email protected]


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ACKNOWLEDGMENTS The authors thank the University of Madras for the financial support (UGC, NON-NET). The NCNSN, University of Madras is gratefully acknowledged for the XPS, FESEM and HRTEM studies. The authors also wish to thank Dr. Aruna Dhathathreyan, CLRI for the water contact angle measurements. REFERENCES (1) Lejars, M., Margaillan, A., Bress, C. Fouling Release Coatings: A Nontoxic Alternative to Biocidal Antifouling Coatings. Chem. Rev. 2012, 112, 4347-4390. (2) Qian, P., Li, Z., Xu, Y., Li, Y., Fusetani, N. Mini-review: Marine natural products and their synthetic analogs as antifouling compounds: 2009-2014. Biofouling. 2014, 31, 101-122. (3) Rana, D., Matsuura, T. Surface Modifications for Antifouling Membranes. Chem. Rev. 2010, 110, 2448-2471. (4) Banerjee, I., Pangule, R. C., Kane, R. S. Antifouling Coatings: Recent Developments in the Design of Surfaces That Prevent Fouling by Proteins, Bacteria, and Marine Organisms. Adv. Mater. 2011, 23, 690-718. (5) Al-Naamani, L., Dobretsov, S., Dutta, J., Burgess, J. G.Chitosan-zinc oxide nanocomposite coatings for the prevention of marine biofouling. Chemosphere. 2017, 168, 408-417. (6) Jingyi, Z., Zhang, Y., Chen, Y., Du, L., Zhang, B., Zhang, H., Liu, J., Wang, K. Preparation and Characterization of Novel Polyethersulfone Hybrid Ultrafiltration Membranes Bending with Modified Halloysite Nanotubes Loaded with Silver Nanoparticles. Ind. Eng.Chem. Res. 2012, 51, 3081-3090.



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Synthesis and Characterization of Large-Scale (

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