**5. Special measures for practical on-site application**

SERS is a promising trace analytical technique. However, we have noted that among thousands of the reported SERS researches, most are limited on conceptual or laboratorial uses. The out‐ room or on‐site SERS analysis that required special instruments such as portable SERS device is also important to make such ideas into real application. In this part, we mainly focus on special measures for real application, including specially designed SERS substrates and the newly reported SERS‐based devices that are designed with the goal of real application with facile sample preparation, fast signal readout and also ability for online sensitive quantifica‐ tion.

#### **5.1. Special SERS substrates matching with miniaturized (portable) Raman instrument**

Concerning to infield detection or fast signal readout, portable Raman instrument is no doubt more favorable, but unfortunately, most commonly used nanoparticle‐based substrates are not suitable on portable Raman instrument because of the high demands of focus position (partly due to low reproducibility from Brownian movement and uncontrollable aggregation). The assembled or encapsulated substrates have been successfully applied in developing SERS detection system combined with portable instruments. For example, the PVA hydrogel‐based substrate was applied into the trace antibiotics detection form the real polluted water with portable Raman spectrometer [45]. Recently, a portable SERS kit was demonstrated for rapid and reliable detection of trace drugs from environmental samples [90]. The whole detection procedure included a 3‐min pretreatment for target extraction and a handheld Raman detection with highly reproducible assembled gold nanorod array as substrate (the sample preparation and detection process are shown in **Figure 7a**). The portable kit was successfully used for detecting methamphetamine, 3,4‐methylenedioxymethamphetamine and methca‐ thinone from real urine samples, showing great prospective toward public safety and healthcare [90].

**Figure 7.** (a) Illustration of a portable kit for rapid SERS detection of drugs in real human urine. Reproduced with the permission from Ref. [90]. (b) Schematic diagram of the fabrication of the aptamer‐based SERS microfluidic sensor for the detection of PCB77. Reproduced with the permission from Ref. [52].

#### **5.2. Microfluidic SERS device**

**5. Special measures for practical on-site application**

tion.

344 Raman Spectroscopy and Applications

healthcare [90].

SERS is a promising trace analytical technique. However, we have noted that among thousands of the reported SERS researches, most are limited on conceptual or laboratorial uses. The out‐ room or on‐site SERS analysis that required special instruments such as portable SERS device is also important to make such ideas into real application. In this part, we mainly focus on special measures for real application, including specially designed SERS substrates and the newly reported SERS‐based devices that are designed with the goal of real application with facile sample preparation, fast signal readout and also ability for online sensitive quantifica‐

**5.1. Special SERS substrates matching with miniaturized (portable) Raman instrument**

Concerning to infield detection or fast signal readout, portable Raman instrument is no doubt more favorable, but unfortunately, most commonly used nanoparticle‐based substrates are not suitable on portable Raman instrument because of the high demands of focus position (partly due to low reproducibility from Brownian movement and uncontrollable aggregation). The assembled or encapsulated substrates have been successfully applied in developing SERS detection system combined with portable instruments. For example, the PVA hydrogel‐based substrate was applied into the trace antibiotics detection form the real polluted water with portable Raman spectrometer [45]. Recently, a portable SERS kit was demonstrated for rapid and reliable detection of trace drugs from environmental samples [90]. The whole detection procedure included a 3‐min pretreatment for target extraction and a handheld Raman detection with highly reproducible assembled gold nanorod array as substrate (the sample preparation and detection process are shown in **Figure 7a**). The portable kit was successfully used for detecting methamphetamine, 3,4‐methylenedioxymethamphetamine and methca‐ thinone from real urine samples, showing great prospective toward public safety and

**Figure 7.** (a) Illustration of a portable kit for rapid SERS detection of drugs in real human urine. Reproduced with the permission from Ref. [90]. (b) Schematic diagram of the fabrication of the aptamer‐based SERS microfluidic sensor for

the detection of PCB77. Reproduced with the permission from Ref. [52].

In recent years, applications of microfluidic system (or lab‐on‐a‐chip) to environmental analysis have attracted much attention because of the notable advantages such as low sample consumption, rapid analysis, online analysis and incorporation of separation, concentration and quantification process [6]. The combination of microfluidic device with SERS technique not only makes use of these advantages, but also benefits a lot for the sensitive and fast online or infield detection. A microfluidic chip was developed for the trace detection of polychlori‐ nated biphenyls [52]. The targets were selectively captured into the detection zone in the channel with aptamer functionalization, and then detected with Ag nanocrown array as enhancing substrate (illustration for the microchip is shown in **Figure 7b**). The detection concentration down to 1.0 × 10−8 mol L−1 demonstrates such smart chip can be utilized for sensitive detection of pollutants in the environment [52]. Similarly, by mixing the confluent streams of Ag colloids and trace analytes in the channel through triangular structure, the trace detection of cyanide was accomplished in an alligator teeth‐shaped microfluidic channel [91]. An integrated real‐time sensing system by making use of a portable Raman spectrometer and a micropillar array chip was developed for the field analysis of two pollutants dipicolinic acid and malachite green, and the observed LOD was estimated to be 200 and 500 ppb, respectively, and further exhibited the capability of microfluidic‐SERS ship for environmental detection in the field [92].
