Towards integrated surface-enhanced Raman spectroscopy of anionic pollutants in water

Abstract

Computers and the internet have changed the way we understand and interact with the world that surrounds us. The 21st century is known as the information age. In 2019, the International Telecommunications Union (ITU) estimated that more than 51% of the world´s population had access to an internet connection [1]. Internet traffic is in continue growthevolving from 100 GB of data per day in 1992 to a forecast of 1671 TB of data per second in 2030 [2, 3] considering only internet mobile traffic. Microprocessorstraditionally used in computersare now incorporated in many of the devices that we use and carry daily. In 2020, 51% of the total microprocessors sold were incorporated to tablets, cell phones and appliances [4]. By 2030, the number of devices connected to the internet will be more than 2.8 times the global population (i.e., there will be an estimated number of 24.1 billion devices connected to the internet). We live in a hybrid world, where an unpreceded, distributed and itinerant network of microcontrollers and microprocessors, operating in the digital domain and interconnected using broadband telecommunication networks, can analyze the parameters of our analog world and help us take decisions in a fraction of a second. Sensors and actuators are the bridge that allows the interconnection of both our analog and digital realities.However, technological progress also brings some challenges to our society. The world population is in continuous increase, with a number of 7.9 billion persons in 2021 and an estimated increase of 1.8 billion persons by 2050 [5]. In developed economies, 81% of the population is concentrated in big cities [6]. The high population density in the city is a threat for the sustainability of modern human activity. The concept of smart cities pursues the improvement of the efficiency of traditional networks and services by the usage of digital technologies for the benefit of its citizens. A smart city includes improved ways of transportation, upgraded water distribution and waste disposal facilities and more efficient heating and lighting of buildings. A smart city also includes a more responsive administration that is able to face the challenges of the increasing population and meet the needs of present and future generations [7].Water is one of the nine top sectors supported by the Dutch government through the Top Consortium for Knowledge and Innovation (TKI) [8].Ensuring the quality of water reserves is essential to guarantee not only the safety of the citizens of a country but also the prosperity of the nation. At the Finally, infrared absorption spectroscopy is a complementary technique to Raman spectroscopy. In this technique, a low energy (infrared) light-source is used to excite molecules causing direct transitions between vibrational states. The drop of the light intensity at different wavelengths composes the infrared absorption spectrum, which has direct relation to the structure and composition of the molecules under study. A different selection rule applies for vibrational mod...