The literature has shown that there is no consensus regarding the best resin composite photoactivation protocol. This study evaluated the efficiency of the conventional, soft-start, pulse-delay and exponential protocols for photoactivation of resin composites in reducing the shrinkage stress and temperature variation during the photopolymerisation. The photoactivation processes were performed using a photocuring unit and a smartphone app developed to control the irradiance according each photoactivation protocol. These photoactivation methods were evaluated applying photoactivation energies recommended by the resins manufactures. Three brands of resin composites were analysed: Z-250, Charisma and Ultrafill. The cure effectiveness was evaluated through depth of cure experiments. All results were statistically evaluated using one-way and multi-factor analysis of variance (ANOVA). The use of exponential and pulse-delay methods resulted in a significant reduction of the shrinkage stress for all evaluated resins; however, the pulse-delay method required too long a photoactivation time. The increases on the temperature were lower when the exponential photoactivation was applied; however, the temperature variation for all photoactivation protocols was not enough to cause damage in the restoration area. The evaluation of the depth of cure showed that all photoactivation protocols resulted in cured resins with equivalent hardness, indicating that the choice of an alternative photoactivation protocol did not harm the polymerisation. In this way, the results showed the exponential protocol as the best photoactivation technique for practical applications.

Teaching and learning strategies that use innovating technologies, such as the development of software or an understanding of the theoretical concepts of analytical equipment, can be essential tools for the construction of knowledge. In this way, this work describes the construction of an innovative and low-cost colorimeter using a RGB LED and a microcontroller board as a guide for teachers of undergraduate classes to prepare pedagogical activities using the proposed device as a learning object. The device was applied in experiments using methylene blue (MB), methylene orange (MO) and cobalt chloride (CC) aqueous solutions of different concentrations. Each one of these solutions has absorption peaks near the RGB colors. The results demonstrated that this low-cost device was able to identify unambiguous absorption peaks in the expected range of the MB, MO and CC absorption spectrums, allowing us to determine a feasible calibration curve for each tested solution.

The global prevalence of counterfeit and low-quality pharmaceuticals poses significant health risks and challenges in medical treatments, creating a need for rapid and reliable drug screening technologies. This study introduces a cost-effective electrochemical paper-based device (ePAD) modified with functionalized bamboo-derived biochar (BCF) for the detection of paracetamol in substandard medicines. The sensor was fabricated using a custom 3D-printed stencil in PLA, designed for efficient production, and a 60:40 (m/m) graphite (GR) and glass varnish (GV) conductive ink, resulting in a robust and sensitive platform. The electroactive area of the ePAD/BCF sensor was determined as 0.37 cm². Characterization via SEM and cyclic voltammetry (CV) verified its structural and electrochemical stability. The sensor demonstrated linear detection of paracetamol from 5.0 to 60.0 µmol L⁻¹ with a detection limit of 3.50 µmol L⁻¹. Interference studies showed high selectivity, with recoveries of over 90%, and the sensor successfully quantified paracetamol in commercial analgesic and anti-flu samples. This sustainable, bamboo-based ePAD offers a promising solution for rapid on-site pharmaceutical quality control, with significant potential to enhance drug screening accuracy.

O ensino de conceitos físicos abordando o tema ondas eletromagnéticas é um dos grandes desafios para os professores de Ciências da Natureza no ensino fundamental, uma vez que esses professores geralmente são graduados em curso de Ciências Biológicas. Nesse contexto, o objetivo deste trabalho é apresentar um aprimoramento do objeto educacional conhecido como caixa de cores, no qual a fonte de luz é capaz de emular todo o espectro eletromagnético visível em função do comprimento de onda. É esperado que, com o uso desse objeto educacional, o estudante do ensino fundamental possa perceber que o espectro eletromagnético visível é contínuo e que cada comprimento de onda está associado a uma cor desse espectro. A caixa de cores foi construída utilizando um microcontrolador e componentes eletrônicos de baixo custo. O aparato proposto foi capaz de emular o espectro eletromagnético visível (de 400 nm até 700 nm), o que o torna inovador frente às propostas de caixa de cores já reportadas na literatura. O uso do objeto educacional permite a proposição de atividades didáticas abordando conceitos de ondas eletromagnéticas, assim como estudar padrões de absorção e reflexão dessas ondas por objetos de diferentes cores.

Low-cost and portable analytical devices are increasingly relevant for decentralized measurements, in situ monitoring, and educational applications. This study presents the design, construction, and validation of a low-cost, portable colorimeter for the indirect determination of ethanol in aqueous solutions via dichromate oxidation. Built with accessible components, including an Arduino microcontroller, an RGB LED, and a light-dependent resistor (LDR) photodetector, the device provides a simple open-hardware platform for visible-range colorimetric measurements without the need for optical filters. Ethanol concentration is determined through oxidation in an acidic medium, generating an optical response proportional to the analyte concentration. Data processing is performed using open-source Python scripts combined with Gaussian fitting for signal extraction and calibration. The main novelty of the system lies in integrating simplified optical components, open-hardware architecture, and computational signal processing to obtain reliable analytical responses in a portable, accessible format. The device’s performance was compared with a commercial UV–Vis spectrophotometer, showing linear behavior over 0.5–1.5% (v/v) ethanol (R² = 0.99) and relative errors below 11% for beverage samples. These results demonstrate that the proposed system is a reliable and cost-effective alternative for rapid ethanol analysis in relatively simple alcoholic matrices.