**2. Conventional SERS substrate fabrication methods**

Conventional SERS substrate types are nanostructures covered by metallic nanoobjects (NS/PLA), including nanoparticles or colloids. The fabrication methods of that substrate are briefly summarized below.

The SERS substrates in a type of nanostructures covered by metallic nanoobjects (NS/PLA) are produced by the application of the physical vapor deposition (PVD) technique of thin discontinuous metallic layers on nanostructures [30], using lithographic techniques (photolithography, electron or ion beam lithography) [31], nanoprinting or lithography supported by a template (matrices of porous polymers or shadow lithography—nanosphere lithography (NSL)) [31]. However, the methods listed above are relatively expensive and time-consuming for areas larger than the range of mm2 [32]. The limitation of using lithography method in SERS substrate production is connected with fabrication cost of nanostructures on large area [33] and resolution [34] of this technique. Below, in **Table 1**, the main disadvantages of that approach are presented.

The use of Au, Ag, or Cu metal colloids, with a diameter in the range of 10–80 nm, which are produced by chemical reduction, requiring the use of expensive chemical reagents, but the largest enhanced SERS (up to 1014), is shown for highly aggregated colloids [31]. The biggest disadvantages of using colloids are storage (usually they should be used immediately after preparation), difficulties in use in portable spectrometers, high cost, problems with repeatability, and the limited range of materials that can be determined due to colloids' dimensions. The use of colloidal metallic particles or nanowires on a glass substrate ensures a relatively homogeneous size of nanoobjects; however, their placement on the substrate is random and unique.

Since few years, the interest on new kind of flexible SERS substrates grows linearly. The new interesting group of SERS substrates constitutes flexible and highly sensitive multiparticle complexes. They are mainly based on metal nanoparticles


**65**

*An Overview of Anodic Oxides Derived Advanced Nanocomposites Substrate for Surface...*

combined with different kinds of fibers, thanks to which they possess new properties. To prepare that kind of SERS substrate, many approaches are taken under consideration, including the use of polymer nanofabric [35, 36], cellulose [37, 38], or flexible piezoelectric-modulated layer [39] decorated by silver or gold nanoparticles or nanowires. Few of these substrates can find its application in food industry, especially for pesticide detection [37, 38, 40], and others in explosive materials detection [41]. Despite many unquestionable advantages, such as high sensitivity, that kind of substrates can be temperature and humidity sensitive as well as still has short lifetime. In this chapter other issues related to this type of SERS substrate will not be addressed.

There are several commercially available SERS substrates. They are manufactured based on silicon etching and metal deposition techniques (Klarite substrates (discontinued), Renishaw), colloid distribution on cellulose fiber substrate (Ocean Optics substrate), or ion etching (Silmeco substrates). For more information on these solutions, see **Table 2**. All data were taken from the companies' websites.

> • High repeatability of microstructures

• Durable substrates • Restrictions on use in the excitation wavelength and laser

power range • Single-use medium • Gain up to 106

analyte

sensitivity

• Single-use

sensitive

• Reusable

range

production

• SERS enhancement was not high

• Temperature and humidity

• Durability 1–1.5 months • Temperature and humidity

• Restrictions in the excitation wavelength and laser power range

• Durability up to 6 months • Restrictions in the excitation wavelength and laser power

• Laser power restrictions • Relatively high cost of substrate

**Features Price/active area**

depending on the

Around 75 EUR/ piece (4 × 4 mm)

175\$/ 25pieces (0.25 inch)

64\$/piece (cellulose/Au) 62\$/piece (cellulose/Ag) (5.5 mm)

80\$/piece, Au or Ag nanosponge (4 × 4 mm)

350\$/5pieces (4 × 4 mm)

*DOI: http://dx.doi.org/10.5772/intechopen.92811*

**3. Commercially available SERS substrate**

**Fabrication technology**

Silicon etching and coating of 300–500 nm Au

Colloidal Ag nanoparticles deposited on cellulose fibers, printed

Colloidal Ag nanoparticles deposited on cellulose fibers—printing

Metallic Au or Ag nanosponges

Si nanostructures coated by Ag or Au, ion digestion and vapor deposition, solution deposition or

incubation

**Company name/SERS substrate name**

Diagnostic anSERS Inc., USA

Ocean Optics Inc., USA

Ocean Optics Inc., USA

Silmeco ApS, Denmark

Renishaw-Klarite substrate (production terminated)

#### **Table 1.**

*Main positive and negative features of using lithography methods in SERS substrate production.*

*An Overview of Anodic Oxides Derived Advanced Nanocomposites Substrate for Surface... DOI: http://dx.doi.org/10.5772/intechopen.92811*

combined with different kinds of fibers, thanks to which they possess new properties. To prepare that kind of SERS substrate, many approaches are taken under consideration, including the use of polymer nanofabric [35, 36], cellulose [37, 38], or flexible piezoelectric-modulated layer [39] decorated by silver or gold nanoparticles or nanowires. Few of these substrates can find its application in food industry, especially for pesticide detection [37, 38, 40], and others in explosive materials detection [41]. Despite many unquestionable advantages, such as high sensitivity, that kind of substrates can be temperature and humidity sensitive as well as still has short lifetime. In this chapter other issues related to this type of SERS substrate will not be addressed.
