Primers

This Primer offers a practical and rational introduction to macromolecular crystallography, whether to engage directly with or to critically assess results, with a focus on understanding the diffraction data, solving the phase problem, building and refining the atomic model, and interpreting the resulting atomic structure.

Laser-driven ultrafast tranmission electron microscopy (UTEM) approaches such as stroboscopic UTEM enable the study of ultrafast reversible processes at time resolutions at the femtosecond scale and beyond. This Primer focuses on stroboscopic UTEM, describing its experimental set-up and variants, and covers the various applications of this technique in condensed matter physics, including imaging structural dynamics, photo-induced near-field electron microscopy, attosecond-scale imaging, dark-field imaging and beyond.

This Primer highlights the key principles and recent advancements of flow biocatalysis, covering essential reactor designs, immobilization strategies and analytics. Practical industrial examples and guidelines for reproducibility are emphasized, providing newcomers and experts with actionable insights to design, optimize and effectively implement continuous biocatalytic processes.

This Primer explores metal–organic chemical vapour deposition (MOCVD) as a transformative technique for synthesizing wafer-scale 2D dichalcogenides. The MOCVD apparatus, the growth mechanism, process conditions, current applications across next-generation 3D integration, photonics, optoelectronics, flexible electronics and the future potential of MOCVD are discussed.

This Primer provides a comprehensive road map into the experimental design, theory, data collection and interpretation of time-domain thermoreflectance (TDTR) experiments and variants for measuring the thermal properties of materials. The applications of TDTR are discussed, along with its inherent limitations, and future research directions for nanoscale thermal property measurements are presented.

Kelvin probe force microscopy is an extension of atomic force microscopy used to measure electrical properties of materials such as conductive and semiconductive samples, including surface potential, work functions and surface charge. These are retrieved at the same time as topographical information.

Diversity oriented clicking (DOC) is an approach for creating a diverse range of molecules from click chemistry-reactive connective hubs. This Primer by Wang et al. covers the concepts behind DOC, the hubs and click chemistries available for DOC strategies, and the application of DOC-generated structures with a focus on the generation of molecular probes and bioactive molecules for drug discovery.

Surface plasmon resonance sensing enables the label-free detection of molecular interactions at metal surfaces and highly sensitive measurements of film thickness. Refractive index changes caused by changes in the environment around a metal–dielectric interface cause variations in the interface optical response, which enable highly sensitive and time-resolved measurements.

Acoustic tweezers use ultrasound waves for non-contact manipulation of particles and cells, offering high biocompatibility and safe handling of samples. Their various configurations enhance functionality across scales, granting a great versatility, whereas addressing current reproducibility and technological limitations will promote wider applications in biomedical fields and precision medicine.

Flow chemistry is a synthesis technique that uses pumps, tubing and connectors to control reactions spatially rather than temporally. This spatial control enables faster reaction times, better temperature regulation and higher yields over traditional batch processes, making it advantageous for the synthesis of pharmaceuticals, agrochemicals and advanced materials.

Colloidal quantum dots are nanometre-sized semiconductors with unique, size-dependent, optoelectronic properties owing to quantum confinement. This Primer discusses various synthetic methods and chemical compositions of quantum dots, emphasizing their applications in optical devices such as solar cells, colour converters, light-emitting diodes and quantum optics.

Size-exclusion chromatography coupled with multi-angle static light scattering allows for the separation of macromolecules or colloids in suspension and the determination of the molar mass of the components. This Primer covers the equipment, sample preparation and controls needed for a size-exclusion chromatography with multi-angle static light scattering experiment; data processing, applications, limitations and workarounds; and concludes with a review of the applications and challenges in the field.

Optical coherence elastography (OCE) is a technique that uses tomographic scans of tissue to retrieve information on its mechanical properties. By measuring shear and Young’s moduli, the elasticity of the sample can be mapped in two or three dimensions, making OCE a useful tool in fields such as oncology, ophthalmology and mechanobiology.

Photoluminescence microscopy can give information on the electronic properties of optoelectronic materials and thus the performance of optoelectronic devices. In this Primer, Wei et al. cover experimental set-ups for photoluminescence microscopy, including widefield and confocal configurations, and considerations for data acquisition and analysis.

Photo-induced force microscopy enables nanoscale chemical imaging by detecting optically induced forces between a probe and a sample with sub-nanometre spatial resolution. Photo-induced force microscopy directly senses the light-induced dipolar force with uses in molecular nanoscopy, nanophotonics, polymer science, biology and surface chemistry.

Mechanochemistry is a method of forming chemical products through physical collisions between the milling media — such as small steel balls — and the reactants. Although small amounts of liquid can be added to modify the rheology of the reaction, mechanochemistry is typically a solventless technique, greatly reducing the amount of waste generated compared with traditional solvent-rich reaction conditions. This Primer describes variations in setting up a mechanochemical reaction, methods for measuring reaction progress in situ and recent applications — such as pharmaceutical production — in which mechanochemistry aims to serve as a greener alternative to traditional chemical manufacturing.

In vivo microelectrode arrays allow the measurement of action potentials from individual neurons in awake animals to better understand the function of the brain and the peripheral nervous system. In this Primer, Williams et al. cover the different designs, experimental set-ups and applications of this technology and discuss data processing steps for electrophysiological data.

X-ray magnetic circular dichroism is an element-specific technique that uses circularly polarized X-rays to probe the spin and orbital magnetic moments of materials and explore their magnetic structures, including spin textures and dynamic behaviours. This Primer looks at the fundamental principles of X-ray magnetic circular dichroism, its application in advanced imaging methods and in investigating a wide array of magnetic phenomena.

Droplet-based bioprinting (DBB) enables the fabrication of three-dimensional structures from biomaterials. In this Primer, Gupta and colleagues describe the various DBB modalities and their applications, considerations for the selection of bioinks and substrates, methods to assess printability, the limitations of DBB and their solutions, and potential advances that might be brought about by incorporating new technologies.

Interferometric scattering microscopy (iSCAT) is a label-free imaging technique that enables detection of nanoscale objects. This Primer provides an overview of the principles of iSCAT detection and imaging, factors that affect its performance, its applications in the laboratory and potential avenues for advancing the technique further.