# Effect of h-BN Support on Photoluminescence of ZnO Nanoparticles: Experimental and Theoretical Insight

^{1}

^{2}

^{3}

^{*}

## Abstract

**:**

## 1. Introduction

## 2. Materials and Methods

#### 2.1. Materials

_{3}COO)

_{2}Zn × 2H

_{2}O) was acquired from Lenreaktiv (St Petersburg, Russia). Sodium hydroxide (NaOH) and isopropyl alcohol (IPA) were purchased from PrimeChemicalGroup (Mytishchi, Russia).

#### 2.2. Synthesis

_{3}COO)

_{2}Zn × 2H

_{2}O was dissolved in 25 mL IPA and then added to 125 mL IPA cooled to 0 °C. Then, the cooled NaOH solution was added slowly with gently stirring. The resulting solution was placed in a thermostat heated to 65 °C and kept for 1 min. After that, 50 mL of the sonicated suspension of h-BN in IPA was added. The resulting suspension was cooled in a thermostat for 1.5 h at a cooling rate of 0.7 °C/min. The heterostructures were subtracted by vacuum filtration using a cellulose acetate filter (d = 0.2 µm) and washed with IPA.

#### 2.3. Characterization

#### 2.4. Quantum-Chemical Calculations

## 3. Results

#### 3.1. TEM

#### 3.2. XRD and FTIR

^{−1}. The presence of these peaks is associated with out-of-plane B-N-B bending and in-plane B-N stretching vibrations, respectively. The FTIR spectra of ZnO/h-BNμm and ZnO/h-BNnm composites show an additional peak approximately at 450 cm

^{−1}, which is a characteristic of Zn-O stretching vibration. Since no (-COOH) related peaks in the range of 1100–1700 cm

^{−1}are seen, it is reasonable to conclude that the obtained ZnO/h-BN heterostructures do not contain residual acetate precursor or additional functional groups.

#### 3.3. Photoluminescence

_{i}) to the top of the valence band (VB). The green emission is usually associated with oxygen vacancies (V

_{o}). A more detailed description of the origin of each peak, with references to literature data, is given in Table 1.

## 4. Discussion

^{++}, it is necessary to activate a single positively charged oxygen vacancy (Vo

^{+}). This requires that a hole trapped in surface defects tunnels to Vo

^{+}, forming Vo

^{++}. This process is faster than the exciton recombination responsible for the NBE, but if the local electronic structure of the ZnO surface is changed with a dielectric, there will be a decrease in the number of surface traps due to the screening effect, which will weaken the DLE and enhance the NBE. Since the surface of ZnO NPs is passivated because the contacting material has a different dielectric constant, it may be the difference in dielectric constant between h-BNnm and h-BNµm that caused the effect we observed. The dielectric constant, in turn, can depend on the thickness of h-BN particles [33], which in our case is an order of magnitude larger for h-BNµm compared to h-BNnm, as evidenced by the results of SEM analysis and an increase in the intensity of the Raman peak [34] (Figure 6).

## 5. Conclusions

## Author Contributions

## Funding

## Institutional Review Board Statement

## Informed Consent Statement

## Data Availability Statement

## Conflicts of Interest

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**Figure 2.**Characteristic STEM micrographs and ZnO NPs size distributions of ZnO/h-BNμm (

**a**,

**c**) and ZnO/h-BNnm (

**b**,

**d**) heterostructures.

**Figure 3.**HADF-STEM image (

**a**) with corresponding spatially resolved B, N, O and Zn EDXS elemental maps (

**c**) and HRTEM image (

**b**) of ZnO/h-BNnm sample. Insets in (

**b**) show FFT pattern obtained from the framed area.

**Figure 4.**(

**a**) XRD patterns and (

**b**) FTIR spectra of h-BNμm, h-BNnm, ZnO/h-BNμm and ZnO/h-BNnm samples.

**Figure 7.**1L-h-BN/wZnO (

**a**) and 4L-h-BN/wZnO (

**b**) heterostructures and corresponding densities of states. Red, large grey, small grey, green, and pink cycles show oxygen, zinc, boron, nitrogen, and hydrogen atoms.

**Figure 8.**Charge difference distribution between h-BN and wZnO for (

**a**) 1L-hBN/wZnO and (

**b**) 4L-hBN/wZnO heterostructures. Yellow and blue clouds show the accumulation and loss of electrons. The isosurface level is 5 × 10

^{−5}e/Å

^{3}.

**Figure 9.**Dependence of the extinction coefficient of h-BN/wZnO heterostructures on the irradiation wavelength in (

**a**) transverse and (

**b**) perpendicular directions to the surface.

**Figure 10.**Dependence of the extinction coefficient of individual components of wZnO/h-BN heterostructures on the irradiation wavelength in (

**a**) transverse and (

**b**) perpendicular directions to the surface.

**Figure 11.**Schematics of band gap arrangement of freestanding 1L-h-BN and 4L-h-BN relative to wZnO slab.

nm(eV) | Electron Transition | References |
---|---|---|

~363(~3.4) | CB ^{1}→VB | [27,28] |

~375(~3.3) | [29] | |

~383(~3.2) | [30,31] | |

~425(~2.9) | Zn_{i}→VB | [5] |

~445(~2.8) | V_{Zn}^{++ 2}→VB | [32] |

~545(~2.3) | CB→V_{O}^{++ 3} | [29] |

^{1}CB—conduction band.

^{2}V

_{Zn}

^{++}—ionized zinc interstitials.

^{3}V

_{O}

^{++}—double positively charged oxygen vacancy.

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**MDPI and ACS Style**

Barilyuk, D.V.; Sukhanova, E.V.; Popov, Z.I.; Korol, A.A.; Konopatsky, A.S.; Shtansky, D.V.
Effect of *h*-BN Support on Photoluminescence of ZnO Nanoparticles: Experimental and Theoretical Insight. *Materials* **2022**, *15*, 8759.
https://doi.org/10.3390/ma15248759

**AMA Style**

Barilyuk DV, Sukhanova EV, Popov ZI, Korol AA, Konopatsky AS, Shtansky DV.
Effect of *h*-BN Support on Photoluminescence of ZnO Nanoparticles: Experimental and Theoretical Insight. *Materials*. 2022; 15(24):8759.
https://doi.org/10.3390/ma15248759

**Chicago/Turabian Style**

Barilyuk, Danil V., Ekaterina V. Sukhanova, Zakhar I. Popov, Artem A. Korol, Anton S. Konopatsky, and Dmitry V. Shtansky.
2022. "Effect of *h*-BN Support on Photoluminescence of ZnO Nanoparticles: Experimental and Theoretical Insight" *Materials* 15, no. 24: 8759.
https://doi.org/10.3390/ma15248759