**1. Introduction**

The development of new nanocrystals made from the doping of ions in semiconductors creates interesting physical–chemical properties and biological effects. The nanopowders are aiming at agricultural applications, and doped nanocrystals embedded in the glass system can be used in spintronics applications.

Bacterial diseases of plants occur in every place that is reasonably moist or warm, and they affect all kinds of plants. Bacterial diseases are prevalent and severe in the humid tropics, but they may be extremely destructive anywhere under favorable environmental conditions [1]. Control bacterial diseases in agriculture are complex because the few registered chemical products and the nanoparticles or nanocrystals emerge as an innovative method in disease management. Zinc-oxide (ZnO) nanoparticles or nanocrystals are among the most commonly used [2–5].

ZnO, ZnS, or MgO nanoparticles have previously been used to control plant diseases caused by *Liberibacter crescens* [6]. *Xanthomonas alfalfae subsp. citrumelonis* and *Pseudomonas syringae* [7], *Xanthomonas perforans* [8], *Xanthomonas campestris pv. Campestris* [9], *Pantoea ananatis* [10, 11]*, Xanthomonas axonopodis pv. Citri* [12], *Xanthomonas oryzae pv. Oryzae* [13], and *Xanthomonas citri subsp. Citri* [14]. ZnO nanocrystals (NCs) may be doped with various elements, such as noble metals or transition metals, to increase their bactericidal effect. Doping is a process that consists of adding new elements to the nanoparticle's structure and changing their chemical characteristics [2]. Therefore, in this chapter book, we will show the results of ZnO NCs doped with silver (Ag), gold (Au), and magnesium (Mg) ions to control bacterial diseases in agriculture.

The fruit fly *Drosophila melanogaster* is a well-established model organism in various areas of science, including nanotoxicology [15]. The fruit fly also has 77% of the conserved genes related to human diseases [16] and considerable similarities with humans in different physiological mechanisms [17].

Several mutant lines for a broad range of human diseases are available in this model, besides its low cost and easy maintenance in the laboratory, in addition to a short life cycle, when compared to other model organisms such as fishes and mammals. Taken together, these characteristics make *Drosophila* a valuable model for studies that evaluate long-term and developmental effects in nanotoxicology [15]. Here we present results regarding the biocompatibility analysis of the pure and Ag-doped Na2Ti3O7 nanocrystals in *Drosophila*.

The doped nanocrystals can be embedded in glassy systems, allowing for various applicability in devices. Zn1-xAxTe (A = Cr; Cu) nanocrystals (NCs) have been one investigated diluted magnetic semiconductor (DMS) system, due mainly to their strengthening *sp*-*d* exchange interactions with increasing A-doping concentration [18]. Cr and Cu-doped NCs simultaneously exhibit semiconductor and magnetic properties that may allow more diverse technological applications than undoped semiconductors [19, 20]. In this context, we present a very effective method for the growth of Cr2+ and Cu2+ ions-doped ZnTe NCs in a glass system (65P2O5 · 14ZnO · 1Al2O3 · 10BaO · 10PbO (mol %), named PZABP) using the fusion nucleation method, as descriptions in Refs. [21, 22].

Bi2Te3 semiconductors at the nanoscale are highly performing materials for thermoelectric and promising applications as topological insulators [23]. These nanosemiconductors' physical and chemical properties can enhance and perform new features based on quantum behavior and the electronic structure's doping [24–26]. The synthesis of Bi2Te3 NCs in diamagnetic host glasses allows the samples' high chemical stability. During fusion, Cr ions can incorporate into these systems allowing possible applications in the manufacture of magneto-optical devices [25–27]. Therefore, the long-range magnetic properties generated by the domain of the Cr ion doping spins, in addition to the insulating topological states of the Bi2Te3 semiconductor NCs, have aroused great interest in the scientific community for the development of spintronic nanodevices [24, 27, 28]. Thus, we will show some results of Cr doped Bi2Te3 NCs.

Therefore, in this chapter, we show doped nanocrystals' results in powdered or embedded glass systems aiming at several applications.

#### **2. Nanocrystals in powder or embedded in glass systems**

Depending on how these nanocrystals are, for example, powdered or embedded in glass systems, the applicability is diverse. Thus, in applications in agronomy, dental, or biology, these doped nanocrystals must be in powder to be dispersed or not in solutions. In applications such as spintronics, the doped nanocrystals must be embedded in

**143**

*Doped Semiconductor Nanocrystals: Development and Applications*

a thermally and chemically stable system, such as a glass system. We will comment on these peculiarities and advantages of each doped nanocrystal in the following sections.

The pure and doped ZnO NCs were synthesized by coprecipitation by reference [29]. Pure and doped sodium titanate (Na2Ti3O7) were synthesized by reference [30].

The PZABP glass matrix with a nominal composition of 65P2O5 · 14ZnO · 1Al2O3 · 10BaO · 10PbO (mol %) adding 2Te (wt %), and Cr or Cu at doping *x* content varying with Zn content from 0 to 10 (wt %), were synthesized by fusion in alumina crucibles at 1300 °C for 30 minutes. These melted mixtures were quickly cooled to room temperature forming a glass system doped with the precursor ions needed for nanoparticle growth. Next, the glass samples were thermally annealed at 500 °C for 10 hours to enhance the diffusion of Zn2+, Cr2+ or Cu2+ and Te2− ions throughout the host PZABP matrix and induce the growth of Zn1-xCrxTe/Zn1-xCuxTe NCs. The physical properties of the glass samples were studied by optical absorption (OA), recorded with a model UV-3600 Shimadzu UV–VIS–NIR spectrometer, operating between 190 and 3300 nm; XRD patterns were recorded using a XRD-6000 Shimadzu diffractometer equipped with monochromatic CuKa1 radiation (k = 1.54056 Å) and set to a resolution of 0.02; Transmission electron micrographs (TEM JOEL, JEM-2100, 200 kV) and EPR measurements at temperature of 10 K were performed with a high sensitivity Bruker-EMX spectrometer operating at X-band (9.4 GHz) microwave frequency.

**2.1 Synthesis of Nanopowders and nanocrystals embedded in glassy** 

*2.1.2 Synthesis of Cr or Cu-doped ZnTe nanocrystals embedded in glass matrix*

*2.1.3 Synthesis of Cr-doped Bi2Te3 nanocrystals embedded in glass matrix*

temperature, permitting the formation of Cr-doped Bi2Te3 NCs.

temperature, permitting the formation of Cr-doped Bi2Te3 NCs.

*2.1.5 Nanocrystals for the control plant bacterial disease*

*2.1.4 Synthesis of Cr-doped Bi2Te3 nanocrystals embedded in glass matrix*

matrix with the following nominal composition: SNAB–45SiO2·30Na2CO3·

matrix with the following nominal composition: SNAB–45SiO2·30Na2CO3·

Bi2-xCrxTe3 NCs were synthesized by the fusion method in a borosilicate glass

5Al2O3·20B2O3 (mol %), 2% (of the weight of the glass matrix) of Te and Bi2O3, with nominal Cr content of x (x = 0.00, 0.01, and 0.05) as a function of bismuth concentration. The powdered glass and NC precursors were mixed together and melted in an alumina crucible at 1200 °C for 30 min and then rapidly cooled to room

Bi2-xCrxTe3 NCs were synthesized by the fusion method in a borosilicate glass

5Al2O3·20B2O3 (mol %), 2% (of the weight of the glass matrix) of Te and Bi2O3, with nominal Cr content of x (x = 0.00, 0.01, and 0.05) as a function of bismuth concentration. The powdered glass and NC precursors were mixed together and melted in an alumina crucible at 1200 °C for 30 min and then rapidly cooled to room

To evaluate the growth inhibition zone of *Xanthomonas campestris pv. campestris in vitro,* a basic layer of 2% agar-water medium and semi-solid nutrient medium (0.8%)

*DOI: http://dx.doi.org/10.5772/intechopen.96753*

**matrices**

*2.1.1 Synthesis of Nanopowders*

a thermally and chemically stable system, such as a glass system. We will comment on these peculiarities and advantages of each doped nanocrystal in the following sections.
