João F.C.B. Ramalho

University of Aveiro | UA · Division of Physics

Quick Response (QR) codes are a gateway to the Internet of things (IoT) due to the growing use of smartphones/mobile devices and its properties like fast and easy reading, capacity to store more information than that found in conventional codes, and versatility associated to the rapid and simplified access to information. Challenges encompass the e...

The general use of smartphones assigns additional relevance to QR codes as a privileged tool to the Internet of Things (IoT). Crucial for QR codes is the evolution to IoT-connected smart tags with enhanced storage capacity and secure accesses. Using the concept of super-modules (s-modules) built from adjacent spatial multiplexed modules with regula...

Sensors play a key role on the Internet of Things (IoT), providing monitoring inside and outside the networks in a multitude of parameters. A fundamental parameter to sense is temperature, being essential to acquire knowledge on the best way to include thermal sensing into the communications networks. Despite that the temperature measurement in the...

Sensors play a key role on the Internet of Things (IoT) providing monitoring inside and outside the communication networks in a multitude of parameters. Challenges towards IoT lie in the lack of affordable strategies able to convert sustainably a signal from an optical sensors network into a digital data sequence. The coupling of optical sensors to...

The need to sense and track in real time through sustainable and multifunctional labels is exacerbated by the COVID‐19 pandemic, where the simultaneous measurement of body temperature and the fast tracking of people is required. One of the big challenges is to develop effective low‐cost systems that can promote healthcare provision everywhere and f...

Given the rapid expansion of the Internet of Things and because of the concerns around counterfeited goods, secure and resilient cryptographic systems are in high demand. Due to the development of digital ecosystems, mobile applications for transactions require fast and reliable methods to generate secure cryptographic keys, such as Physical Unclon...

Optical Sensors The coupling of optical sensors to smartphones appears as a strategy for the new generation of mobile optical sensing and the Internet of Things (IoT). Healthcare services standout and the concepts of eHealth and mHealth emerge, being more and more explored towards the development of effective low‐cost and sustainable systems that p...

Nowadays, the Internet of Things (IoT) has an astonishingly societal impact in which healthcare services stand out. Amplified by the COVID-19 pandemic scenario, challenges include the development of authenticatable smart IoT devices with the ability to simultaneously track people and sense in real-time human body temperature aiming to infer a healt...

Sintered transparent ceramics, presenting extraordinary resistance to thermal shocks, incomparably larger than glasses, glass ceramics, and single crystals, maybe valuable luminescence thermometers especially for high-temperature applications. The literature on that subject is, however, very much limited at present. In this paper, the performance o...

Having proven that the temperature range of luminescent thermometers can be greatly widened by combining the intra‐ and interconfigurational transitions of the Pr3+, the possibility to manage important thermometric parameters by bandgap engineering and variation of energy of excitation photons are examined. Partial replacement of Ge with Si to form...

Luminescence thermometry and 2D imaging by means of luminescence thermometric phosphors are of growing interest as these non-contact and almost non-invasive techniques may possibly offer important advantages in some areas of applications. The requirements such thermometers have to fulfill are quite dependent on considered application. It is obvious...

For years, various contact techniques were used to measure temperature. Development of novel and evolving technologies raised the interest in elaboration of non-contact thermometry. Nowadays, this is radiation pyrometry which is the method of choice for such purposes. Yet, it has important limitations – sensitivity to stray light or reflected radia...

QR (Quick Response) codes are two-dimensional barcodes composed of special geometric patterns of black modules in a white square background that can encode different types of information with high density and robustness, correct errors and physical damages, thus keeping the stored information protected. Recently, these codes have gained increased a...

In this study, it is shown how the temperature range of luminescent thermometers can be widened in an unprecedented way by combining the intra- and interconfigurational transitions of the Pr³⁺ ion in a single material. Using Sr2GeO4:Pr³⁺ crystalline powders as an illustrative example, the implementation of luminescence thermometry is reported in th...