Zn ch3coo 2 2h2o

The various metabolites secreted by bacterial strain NMJ15 were used as a reducing agent for zinc acetate dihydrate (Zn(CH₃COO)₂·2H₂O) (Sigma Aldrich, Munich, Germany) as a precursor for ZnO-NPs. The bacterial strain was inoculated into nutrient broth media (pH 7) and incubated for 72 h at 35 ± 2 °C under shaking conditions (150 rpm). After an incubation period, the bacterial cells were harvested by centrifugation at 10,000 rpm for 5 min, followed by washing the collected cells thrice by distilled H₂O to remove the attached medium components. Approximately 10 g of the collected bacterial cells were mixed with 100 mL distilled H₂O and incubated at 35 ± 2 °C for 48 h. At the end of the incubation period, the previous mixture was subjected to centrifugation at 10,000 rpm for 5 min and we collected the supernatant or cell-free filtrate (CFF), which was used for biosynthesis of ZnO-NPs as follows: 100 mL of CFF (pH 8.5) was mixed with Zn(CH₃COO)₂·2H₂O to get 2 mM as a final concentration and incubated at 35 ± 2 °C for 24 h under shaking condition. The formed creamy, white precipitate was harvested, washed twice with distilled H₂O, and subjected to oven-drying (GESTER, 850W, Quanzhou, China) at 150 °C for 24 h. [27 (link)].

All reagents used in this experiment were commercially available without further purification. ZnO NWs were synthesized via the hydrothermal method [3 ]. The detailed process is given as follows: a ZnO seed solution was prepared by adding 10 mM Zn(CH₃COO)₂·2H₂O (99.9% Sigma Aldrich Corp., St. Louis, MO, USA) into ethanol (200 prove, Fisher Scientific Inc., Hampton, NH, USA) and stirred at 58 °C for 2 h. The mixed solution was spin-coated onto a cleaned glass or Si substrate (25 by 25 mm in size) multiple times at room temperature. The substrate was then kept at 150 °C for 1 h to promote the adhesion of the seed particles to the substrate. The growth solution was composed of 25 mM Zn(NO₃)₂·6H₂O (Sigma Aldrich) and 25 mM hexamethylenetetramine (HMTA, Sigma Aldrich). Prior to the synthesis, the growth solution was preheated in a convection oven at 90 °C for 1 h to achieve a thermal equilibrium. The substrate was then immersed into the solution at 90 °C for 6 h for ZnO NW growth. After removal from the solution, the substrate with ZnO NWs was thoroughly rinsed by DI water and blown dry. A 3-h-long dehydration step at 60 °C was carried out for the substrate afterwards.

Analytical chemicals, including NaOH (98%), Zn(CH₃COO)₂·2H₂O (98%), and C₂H₅OH (99%) were purchased from Sigma-Aldrich Chemicals (Merck KGaA, Darmstadt, Germany). P. aeruginosa and S. aureus were isolated and cultured in the Biochemical Department, Chemical Institute, Vietnam Academy of Science and Technology.

ZnO NW and
NF thin films have been prepared via chemical bath deposition (CBD)
as described in our earlier reports.^{34 (link),45 (link)} ZTO and CIGS/InS
layers have been deposited on the ZnO nanostructured thin films via
ultrasonic spray pyrolysis.^{46 (link)−49 (link)} For the ZTO layer, 25 mM zinc acetate dihydrate (Zn(CH₃COO)₂·2H₂O, Sigma-Aldrich, 99%)
and 75 mM tin(IV) chloride pentahydrate (SnCl₄·5H₂O, Sigma-Aldrich, 98%) were dissolved in methanol–deionized
water (v/v = 3:1) and sprayed on the ZnO thin films with a 20 pass
number, 48 kHz at 200 °C. The ZTO layer was then annealed at
550 °C for 2 h for complete transformation of the ZnSn(OH)₆ phase to ZTO. CIGS and In₂S₃ layers
were deposited as described in the literature.^{44 (link)} The thin-film electrode preparation route is schematically
summarized in Figure 1.

All the chemicals are of analytical grade and used without further purification. A ZnO NW array was synthesized via the hydrothermal method as previously described [28 (link)]. In the first step, 10 mM Zn(CH₃COO)₂·2H₂O (99.9% Sigma-Aldrich) was dissolved in methanol (Fisher Scientific). After vigorous stirring at 60 °C for 2 h, the mixed solution was spin-coated onto a glass substrate at 1000 rpm for 30 s. Prior to the seed deposition, the glass substrate was cleaned by acetone, isopropanol alcohol, and deionized (DI) water, consecutively. The seeded glass substrate was heated to 150 °C for 1 h for dehydration. The growth solution of 25 mM Zn(NO₃)₂·6H₂O (Sigma-Aldrich) and 25 mM hexamethylenetetramine (HMTA, Sigma-Aldrich) was prepared and preheated in a convection oven at 90 °C for 1 h to achieve thermal equilibrium. The annealed substrate was then immersed into the growth solution at 90 °C for 6 h. Consequently, a vertically grown ZnO NW array was obtained on the glass substrate after thoroughly rinsing by DI water.